&R T Bulletin 3-47
Guide for Sea Trials (Progressive Speed, Maneuvering, and Endurance) Technical and Research Program The Society of Naval Architects and Marine Engineers 99 Canal Center Plaza, Ste 310, Alexandria, VA 22314 www.sname.org
SNAME Technical and Research Bulletin 3-47 (2015) Guide for Sea Trials
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SNAME Technical and Research Bulletin 3-47 (2015) Guide for Sea Trials
TECHNICAL AND RESEARCH BULLETIN 3-47 (2015)
GUIDE FOR SEA TRIALS (PROGRESSIVE SPEED, MANEUVERING, AND ENDURANCE) Prepared by
Ship Production and Machinery Committee Working Groups In conjunction with the
SHIPS MACHINERY COMMITTEE August 2015
Published by
The Society of Naval Architects and Marine Engineers 99 Canal Center Plaza, Alexandria, Virginia 22314 Copyright 2015 by the Society of Naval Architects and Marine Engineers with rights reserved.
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SNAME Technical and Research Bulletin 3-47 (2015) Guide for Sea Trials
This Bulletin was prepared under direction from the Ships Machinery Committee for
THE SOCIETY OF NAVAL ARCHITECTS AND MARINE ENGINEERS TECHNICAL AND RESEARCH PROGRAM Prepared by a Working Group of Ship Production and Machinery Committee Working Groups and Volunteers Mr. Frederick (“Rick) H. Ashcroft, Working Group Chair Mr. Roderick Barr Mr. Robert Behr Mr. Jeffrey Bohn Mr. Karl Briers Mr. Christopher Cable Mr. Bruce Cowper Mr. Brice Fuchs Mr. Soren Hanson Dr, Wei-Yuan Hwang Captain Tom Knierim Mr. Darrell Milburn
Mr. Jan Otto de Kat Mr. Frans Quadvlieg Mr. J. Ryan Roberts Mr. Eugene Van Rynbach Mr. Mark Shanks Mr. Gene Shuck Mr. Malcolm Whitford
Reviewed and Approved by:
SHIPS MACHINERY COMMITTEE Mr. Richard Delpizzo, Committee Chair
Mr. Robert J. Bazzini Mr. Robert S. Behr Mr. John W. Boylston Mr. William G. Bullock Mr. Hannon Marshal Burford Mr. Allen Chin Mr. Joseph H. Comer Mr. W. Mark Cummings Mr. John J. Dumbleton Mr. Jose Femenia Mr. Earl W. Fenstermacher Mr. Robert M. Freeman Mr. Joseph D. Hamilton Mr. Richard W. Harkins Mr. John F. Hennings Mr. Richard D. Hepburn
Mr. Bahadir Inozu Mr. Charles A. Narwicz Mr. Mark F. Nittel Mr. Michael G. Parsons Mr. Kevin Prince Mr. Michael J. Roa Mr. David R. Rodger Mr. Alan L. Rowen Mr. Peter George Schaedel Mr. John Thomas Schroppe Mr. William J. Sembler Mr. Tony Teo Mr. Richard P. Thorsen Mr. Andrew Szypula Mr. Ivan Zgaljic
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SNAME Technical and Research Bulletin 3-47 (2015) Guide for Sea Trials
Abstract This guide covers progressive speed, maneuvering, and endurance sea trials of self-propelled surface ships displacing 300 tonnes or more, powered by hydrocarbon fuels such as petroleum, natural gas or bio fuel, and driven by diesel or Otto cycle engines, gas turbine, or electric motors. References are made to applicable international standards. This Bulletin does not cover dock trials, tests, or demonstrations that can be conducted dockside, which are covered in SNAME T&R Bulletin 3-39, Guide for Shop and Installation Tests. This Guide is intended to assist users in applying IMO maneuvering standards and to allow the owner, designer and builder to rate the vessel’s maneuvering performance relative to statistical data of vessel maneuvering characteristics. The Guide summarizes the procedures to be used in assessing a vessel’s maneuvering performance. SNAME welcomes comments and suggestions for improvement of this Guide. Comments or suggestions can be sent electronically to
[email protected].
SNAME Technical and Research Bulletin 3-47 (2015) Guide for Sea Trials
Preface This document evolved from the worldwide use of The Society of Naval Architects and Marine Engineers' (SNAME) Code for Sea Trials - 1973 (Technical and Research Code C-2) dealing with sea trials. The Ships' Machinery Committee of the Society's Technical and Research Program assigned the initial expansion and update of the document to Panel M-19 (Ship Trials) with the assistance of Panel H-10 (Ship Controllability). At that time the document was altered from being a "code" to being a "guide". The resulting Guide was published in 1989. Continuing its popularity and frequency of citation in ship specifications, the National Shipbuilding Research Program (NSRP) provided support for the 2015 update of the guide. While the basic guidelines remain solid, updates were long overdue in recognizing technological advances in sea trial instrumentation, the change from steam propulsion to diesel and other modern propulsion systems, recognition of other technological advances and updates of the International Maritime Organization (IMO) and other standards organizations regarding a number of areas including ship maneuverability, instrumentation, and environmental issues. Representatives from the SNAME’s Ship Production Committee., NSRP, and volunteers including senior marine engineers and naval architects from all fields of interest provided comments. The consensus of these efforts were included in the guide as approved and issued. The final draft was reviewed by the Ships' Machinery Committee with plans to undergo a periodic updating process that would provide for regular updating and improvements to the guide. The basic concept followed in this guide is to provide information on a sufficient variety of sea trials and tests to enable an owner or acceptance authority to choose those suitable for the type of ship and operation involved. Positive contractual invocation of specific individual trials is recommended rather than having them invoked as a package without proper consideration. This avoids burdening the industry with expensive trials not needed by the owner. The guide provides a list of those trials recommended as necessary to demonstrate that the ship as built and delivered will perform as specified. Absence of an at-sea test or trial from those recommended does not imply a negative recommendation by the Society, but merely that the primary objective of such a test or trial is to provide design data to meet some other important objective, rather than to prove the ship under trial. Similarly, the omission of requirements is not intended to negate the value of the efforts which are directed to verifying design standards, scale factors, and margins rather than the acceptability of the ship. Some examples of omitted requirements are the extensive processing of trial data and the correcting of trial data to a design baseline when the data obtained clearly indicate that the ship is satisfactory. Such tests, trials, data processing, and data correcting should be separately and specifically invoked when desired. Trial recommendations are based on the assumption that all operability testing and machinery checkouts have been previously conducted at the dock insofar as conditions at the shipbuilder's plant permit. Methods of analysis of results from trials are not included herein, in general, but may be found in the technical literature and in other guides of the Society. Section 1 of the guide includes general remarks applicable to any sea trial and provides a basic recommendation for trials to be conducted. Sections 2, 3, and 4 provide instructions for sea tests and trials. Section 5 provides a brief description of instruments used for trials and a bibliography of publications which can be consulted for detail. It also includes instructions for instrumentation peculiar to trials, in particular, torsionmeters. Section 6 establishes a format and provides illustrative
SNAME Technical and Research Bulletin 3-47 (2015) Guide for Sea Trials
forms for the presentation of sea trial reports. Appendices include definitions of terms peculiar to sea trials as they are employed in the guide and a procedure for adjusting turning circle test data for drift.
Disclaimers This guide is intended to be advisory only. There is no implication of warranty by SNAME that successful performance of the recommended trials will ensure that a ship will comply with the requirements of the contract specifications, regulatory bodies or classification societies, or that it will perform satisfactorily and safely in service. The opinions or assertions of the authors are not to be construed as official or reflecting the views of SNAME or any government agency. It is understood and agreed that nothing expressed herein is intended or shall be construed to give any person, firm, or corporation any right, remedy, or claim against SNAME or any of its officers or members.
Acknowledgements The Committee gratefully acknowledges the contributions of the members of the Society, industry, and government who have been generous in assisting the working group in accomplishing its task. The National Shipbuilding Research Program (NSRP) is recognized for providing funding that allowed for active involvement of shipbuilding professionals and completion of this update in a timely and meaningful manner. The American Bureau of Shipping is recognized for allowing a number of figures from their publications available for the update. Student Samantha Adornati from Stevens Institutes under the direction of Professor Raju Datla is recognized for drafting and/or revising figures in the guide.
It is understood and agreed that nothing expressed herein is intended or shall be construed to give any person, firm, or corporation any right, remedy, or claim against SNAME or any of its officers or members. i
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TABLE OF CONTENTS Abstract .................................................................................................................................................... Preface ...................................................................................................................................................... Disclaimers .............................................................................................................................................. i Acknowledgements ................................................................................................................................. i TABLE OF CONTENTS ...................................................................................................................... iii LIST OF FIGURES ............................................................................................................................... ix LIST OF TABLES ................................................................................................................................ ix 1.0 INTRODUCTION ............................................................................................................................ 1 1.1 SUPERSESSION ......................................................................................................................... 1 1.2 ORIGIN ........................................................................................................................................ 1 1.3 PURPOSE .................................................................................................................................... 1 1.4 SCOPE.......................................................................................................................................... 1 1.5 TRIAL OBJECTIVES .................................................................................................................. 1 1.5.1 Demonstration of Operability ................................................................................................ 1 1.5.2 Demonstration of Performance.............................................................................................. 2 1.5.3 Demonstration of Endurance ................................................................................................. 2 1.5.4 Demonstration of Economy ................................................................................................... 2 1.5.5 Demonstration of Energy Efficiency Design Index (EEDI) .................................................. 2 1.5.6 Demonstration of Controllability........................................................................................... 2 1.5.7 Establishment of Operating Performance Baseline ............................................................... 2 1.5.8 Provision of Forensic Data .................................................................................................... 2 1.5.9 Provision of Design Data....................................................................................................... 2 1.5.10 Classification and Safety Requirements .............................................................................. 3 1.6 SHIP AND ENVIRONMENTAL CONDITIONS ....................................................................... 3 1.6.1 Sea Trial Loading Conditions ................................................................................................ 3 1.6.2 Water Depth........................................................................................................................... 3 1.6.3 Wind, Waves, and Currents ................................................................................................... 4 1.7 LIST OF TRIALS AND SELECTION ........................................................................................ 4 1.8 RECOGNITION OF UNCERTAINTY ....................................................................................... 6 1.9 PLANNING.................................................................................................................................. 6 1.9.1 Design Accommodation ........................................................................................................ 6 iii
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1.9.2 Pre-Arrangements .................................................................................................................. 7 1.10 PRE-TRIAL CHECK LIST ........................................................................................................ 8 1.11 BUILDERS' TRIALS ................................................................................................................. 8 2.0 PROPULSION PLANT TRIALS..................................................................................................... 9 2.1 GENERAL ................................................................................................................................... 9 2.1.1 Scope of This Section ............................................................................................................ 9 2.1.2 Specific Objectives ................................................................................................................ 9 2.1.3 Pre-Trial Agreements ............................................................................................................ 9 2.1.4 Trial Preparations .................................................................................................................. 9 2.1.5 Trial Duration ...................................................................................................................... 10 2.2 PROPULSION PLANT ECONOMY TRIALS ......................................................................... 13 2.2.1 Purpose ................................................................................................................................ 13 2.2.2 Operating Conditions........................................................................................................... 13 2.2.3 Frequency of Observations .................................................................................................. 13 2.2.4 Communication ................................................................................................................... 13 2.2.5 Measurements and Instrumentation ..................................................................................... 13 2.2.6 Fuel Rate Data Required ..................................................................................................... 14 2.2.7 Trial Report ......................................................................................................................... 15 2.3 PROPULSION PLANT AHEAD ENDURANCE TRIALS ...................................................... 15 2.3.1 Purpose ................................................................................................................................ 15 2.3.2 Measurements and Instrumentation ..................................................................................... 15 2.3.3 Trial Report ......................................................................................................................... 16 2.4 PROPULSION PLANT ASTERN TRIAL ................................................................................ 16 2.4.1 Purpose and procedure ........................................................................................................ 16 2.4.2 Measurement and Instrumentation ...................................................................................... 16 2.4.3 Trial Report ......................................................................................................................... 16 2.5 SPECIAL CONSIDERATIONS FOR DIESEL AND OTTO CYCLE ENGINE PROPULSION PLANT TRIA LS .................................................................................................................... 16 2.5.1 Auxiliary Components......................................................................................................... 16 2.5.2 Revolutions .......................................................................................................................... 17 2.5.3 Fuel Measurements .............................................................................................................. 17 2.5.4 Fuel Rate Data Required ..................................................................................................... 17 2.5.5 Power ................................................................................................................................... 17 2.5.6 Fuel Switching ..................................................................................................................... 18 2.5.7 Daily Fuel Consumption and Ship’s Overall Fuel Rate ...................................................... 18 2.5.8 Trial Data and Report .......................................................................................................... 18 iv
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2.6 SPECIAL CONSIDERATIONS FOR GAS TURBINE PROPULSION PLANT TRIALS ...... 18 2.6.1 Auxiliary Components......................................................................................................... 18 2.6.2 Fuel Rate Data Required ..................................................................................................... 18 2.6.3 Power ................................................................................................................................... 19 2.6.4 Trial Data and Report .......................................................................................................... 19 2.7 SPECIAL CONSIDERATIONS FOR ELECTRIC DRIVE PROPULSION PLANT TRIALS 19 2.7.1 Auxiliary Components......................................................................................................... 19 2.7.2 Power ................................................................................................................................... 19 2.7.3 Trial Data and Report .......................................................................................................... 19 2.8 CENTRALIZED PROPULSION CONTROL SYSTEM TEST ................................................ 20 2.8.1 Purpose ................................................................................................................................ 20 2.8.2 Procedure ............................................................................................................................. 20 2.8.3 Trial Report ......................................................................................................................... 20 3.0 MANEUVERING AND SPECIAL TESTS ................................................................................... 23 3.1 SELECTION OF TESTS ........................................................................................................... 23 3.2 PREPARATION ........................................................................................................................ 24 3.3 REPORTS .................................................................................................................................. 24 3.4 AHEAD STEERING .................................................................................................................. 24 3.5 ASTERN STEERING ................................................................................................................ 27 3.6 AUXILIARY MEANS OF STEERING..................................................................................... 27 3.7 TURNING CIRCLES ................................................................................................................. 27 3.8 "Z" MANEUVER*..................................................................................................................... 32 3.9 INITIAL TURNING TESTS ...................................................................................................... 35 3.10 PULLOUT TESTS ................................................................................................................... 37 3.11 THE DIRECT SPIRAL TEST.................................................................................................. 40 3.12 THE REVERSE SPIRAL TEST .............................................................................................. 43 3.13 THRUSTER TESTS................................................................................................................ 46 3.13.1 Bow Thruster Tests............................................................................................................ 46 3.13.2 Other Thrust Devices ......................................................................................................... 48 3.13.3 Special Thruster Tests ....................................................................................................... 48 3.14 QUICK REVERSAL FROM AHEAD TO ASTERN (“CRASH ASTERN” STOPPING TESTS) .................................................................................................................................... 48 3.15 QUICK REVERSAL FROM ASTERN TO AHEAD .............................................................. 51 3.16 LOW SPEED CONTROLLABILITY MANEUVERS ............................................................ 51 3.17 SLOW STEAMING ABILITY ................................................................................................ 53 3.18 EMERGENCY PROPULSION SYSTEMS............................................................................. 53 v
SNAME Technical and Research Bulletin 3-47 (2015) Guide for Sea Trials
3.19 NAVIGATION EQUIPMENT ................................................................................................. 53 4.0 STANDARDIZATION TRIALS ................................................................................................... 54 4.1 PURPOSE .................................................................................................................................. 54 4.2 GENERAL PLAN ...................................................................................................................... 54 4.3 TRIAL AREA ............................................................................................................................ 54 4.3.1 GNSS ................................................................................................................................... 54 4.3.2 Depth of Water .................................................................................................................... 54 4.4 WIND AND SEA ....................................................................................................................... 54 4.5 NUMBER OF SPEED POINTS ................................................................................................. 55 4.6 COURSE SELECTION.............................................................................................................. 55 4.6.1 Length of Runs .................................................................................................................... 55 4.6.2 Number of Runs .................................................................................................................. 55 4.7 OPERATION OF THE SHIP ..................................................................................................... 55 4.8 DATA REQUIREMENTS ......................................................................................................... 56 STANDARDIZATION RESULTS ................................................................................................................ 57 4.9 ORGANIZATION OF OBSERVERS ....................................................................................... 58 4.10 INSTRUMENTATION FOR STANDARDIZATION DATA ................................................ 58 4.11 COORDINATION PROCEDURE ........................................................................................... 58 4.12 TOLERANCES AND LIMITS ................................................................................................ 58 4.13 DATA REDUCTION ............................................................................................................... 59 4.14 CORRECTIONS ...................................................................................................................... 59 5.0 INSTRUMENTS AND APPARATUS FOR SHIP'S TRIALS ...................................................... 60 5.1 GENERAL ................................................................................................................................. 60 5.1.1 Introduction ......................................................................................................................... 60 5.2 TEMPERATURE MEASUREMENTS ..................................................................................... 60 5.2.1 Types of Instruments ........................................................................................................... 60 5.2.2 Thermowells and Temporary Installations .......................................................................... 60 5.2.3 Adapters for Sensing Elements............................................................................................ 61 5.2.4 Instrument compatibility ..................................................................................................... 61 5.2.5 Calibration and Sea Trials ................................................................................................... 61 5.2.6 Special Thermocouples ....................................................................................................... 61 5.3 PRESSURE MEASUREMENTS............................................................................................... 61 5.3.1 Types of Instruments ........................................................................................................... 61 5.3.2 Proper Connections and Protection ..................................................................................... 61 5.3.3 Zero Adjust for Elevation .................................................................................................... 62 5.3.4 Calibration and Sea Trials ................................................................................................... 62 vi
SNAME Technical and Research Bulletin 3-47 (2015) Guide for Sea Trials
5.3.5 Barometers........................................................................................................................... 62 5.3.6 Manometers ......................................................................................................................... 62 5.3.7 Manometers for Flow Measurement.................................................................................... 63 5.3.8 Liquid Columns ................................................................................................................... 63 5.3.9 Zimmerli Gage..................................................................................................................... 63 5.3.10 Absolute Pressure Gages ................................................................................................... 63 5.3.11 Gage Protection from Pressure Pulsation .......................................................................... 63 5.3.12 Further Information ........................................................................................................... 63 5.4 FLOW MEASUREMENTS ....................................................................................................... 63 5.4.1 Types of Instruments ........................................................................................................... 63 5.4.2 Positive Displacement Flow Meters .................................................................................... 63 5.4.3 Meter Installation for Precise Measurements ...................................................................... 64 5.4.4 Orifice Plate, Flow Nozzle, and Venturi Tube .................................................................... 64 5.4.5 Indicating and Recording Mechanism for Orifice Plate, Flow Nozzle, and Venturi Tube . 64 5.5 TORQUE AND POWER MEASUREMENTS.......................................................................... 65 5.5.1 Power Determined Indirectly............................................................................................... 65 5.5.2 Power Determined From Torque Measurements................................................................. 65 5.5.3 Shaft Torsionmeters............................................................................................................. 65 5.6 SHAFT-POWER METERS ....................................................................................................... 66 5.7 SHAFT THRUSTMETERS ....................................................................................................... 66 5.7.1 Purpose of Thrustmeter ....................................................................................................... 66 5.7.2 Useful Installations .............................................................................................................. 66 5.7.3 Types of Instruments ........................................................................................................... 66 5.8 SHAFT SPEED MEASUREMENTS......................................................................................... 66 5.8.1 Propeller Revolution Counters ............................................................................................ 66 5.8.2 Portable Tachometers and Speed Indicators ........................................................................ 67 5.8.3 Additional 'Information ....................................................................................................... 67 5.9 FLUE AND EXHAUST-GAS ANALYSES ............................................................................. 67 5.9.1 Orsat Analyzer ..................................................................................................................... 67 5.9.2 Manual and Automatic Types of Flue Gas Analyzers ......................................................... 69 5.9.3 Additional Information ........................................................................................................ 69 5.10 VISCOSITY MEASUREMENTS............................................................................................ 69 5.11 ELECTRICAL MEASUREMENTS ........................................................................................ 69 5.11.1 Measuring Devices ............................................................................................................ 69 5.11.2 Calibration ......................................................................................................................... 69 5.11.3 Additional Information ...................................................................................................... 69 vii
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5.12 WIND SPEED AND DIRECTION MEASUREMENTS ........................................................ 70 5.12.1 Cup Anemometer............................................................................................................... 70 5.12.2 Indicators ........................................................................................................................... 70 5.12.3 Biram Anemometer ........................................................................................................... 70 5.12.4 Direct-Reading Anemometer ............................................................................................. 70 5.12.5 Deflecting-Vane Anemometer ........................................................................................... 70 5.12.6 Wind Direction Indicator ................................................................................................... 70 5.12.7 Combination Indicators ..................................................................................................... 71 5.12.8 Locating Sensors ............................................................................................................... 71 5.12.9 Ultrasonic Wind Sensors ................................................................................................... 71 5.13 TRACKING SYSTEMS .......................................................................................................... 71 5.14 TIME MEASUREMENTS....................................................................................................... 71 5.14.1 Types of Instruments ......................................................................................................... 71 5.14.2 Synchronizing Clocks ........................................................................................................ 71 5.14.3 Stop Watches ..................................................................................................................... 71 5.14.4 Electric Timers and Clocks ............................................................................................... 71 5.14.5 Recorders ........................................................................................................................... 72 6.0 TRIAL DATA AND REPORT ...................................................................................................... 73 6.1 GENERAL ................................................................................................................................. 73 6.2 DATA PLAN ............................................................................................................................. 73 6.3 DATA CREW TRAINING ........................................................................................................ 73 6.4 MANEUVERING TRIALS AND SPECIAL TESTS ................................................................ 74 6.5 STANDARDIZATION TRIALS ............................................................................................... 74 6.6 FUEL ECONOMY AND ENDURANCE TESTS ..................................................................... 74 6.7 PROPULSION PLANT TRIALS............................................................................................... 77 6.8 TRIAL REPORT ........................................................................................................................ 78 6.8.1 Introduction ......................................................................................................................... 78 6.8.2
Ship's Characteristics .................................................................................................... 78
6.8.3 Trial Data ............................................................................................................................. 79 6.8.4 Other Data ........................................................................................................................... 79 6.8.5 Appendices - As Elected ..................................................................................................... 79 REFERENCES ..................................................................................................................................... 87 APPENDIX A DEFINITIONS............................................................................................................. 89 A.1 GENERAL TERMS .................................................................................................................. 89 A.2 PROPULSION PLANT TRIALS .............................................................................................. 90 A.3 MANEUVERING AND SPECIAL TESTS .............................................................................. 91 viii
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A.4 STANDARDIZATION TRIALS .............................................................................................. 91 A.5 INSTRUMENTATION ............................................................................................................. 92 APPENDIX B CORRECTING TURNING CIRCLE PLOTS FOR DRIFT........................................ 93 B.1 PRINCIPLE ............................................................................................................................... 93 B.2 PLOTTING OVERGROUND TRACK .................................................................................... 93 B.3 DETERMINATION OF DRIFT ................................................................................................ 93 B.4 DETERMINATION OF DRIFT RATE .................................................................................... 94 B.5 PLOTTING THE DRIFT CORRECTED TURNING CIRCLE ................................................ 94 B.6 DETERMINATION OF TURNING CIRCLE DIMENSIONS ................................................ 94 B.7 CALCULATION OF DRIFT RATE IN KNOTS ..................................................................... 94
LIST OF FIGURES Figure 1 Turning Circle Definitions (Courtesy of ABS) ...................................................................... 29 Figure 2 Turning Circle Test ............................................................................................................... 30 Figure 3 "Z" Maneuver Test (Courtesy of ABS) .................................................................................. 33 Figure 4 Initial Turning Test, Change of Heading Plot ....................................................................... 36 Figure 5 Initial Turning Test, Plot of Change of Turning Rate ........................................................... 36 Figure 6 Pullout Test (Courtesy of ABS) ............................................................................................ 38 Figure 7 Direct Spiral Test .................................................................................................................. 43 Figure 8 Reverse Spiral Test (Courtesy of ABS) ................................................................................ 44 Figure 9 Crash Stop Test (Courtesy of ABS ....................................................................................... 49 Figure 10 Typical Standardization Course .......................................................................................... 56 Figure 11 Sample Plot Illustrating Correction of Turning Circle for Drift ......................................... 95
LIST OF TABLES Table 1 Recommended Trials ................................................................................................................ 5 Table 2 Recommendations for Internal Combustion Propulsion Plant Trials ...................................... 11 Table 3 Recommendations for Gas Turbine Propulsion Plant Trials .................................................. 12 Table 4 Centralized Control System Tests .......................................................................................... 21 Table 5 Steering Tests ......................................................................................................................... 26 Table 6 Turning Circle Test Data ........................................................................................................ 31 Table 7 "Z" Maneuver Test Data ......................................................................................................... 34 Table 8 Initial Turning Test Data ........................................................................................................ 37 Table 9 Pullout Test Data .................................................................................................................... 39 Table 10 Direct Spiral Test.................................................................................................................. 41 Table 11 Reverse Spiral Test Data ...................................................................................................... 45 Table 12 Thruster Test Data ................................................................................................................ 47 Table 13 Crash Stop Test Data ............................................................................................................ 50 ix
SNAME Technical and Research Bulletin 3-47 (2015) Guide for Sea Trials
Table 14 Low Speed Controllability Maneuvering Test Data ............................................................. 52 Table 15 Slow Steaming Ability ......................................................................................................... 53 Table 16 Standardization Trials Data .................................................................................................. 57 Table 17 Standardization Trial Tolerances and Limits ....................................................................... 58 Table 18 Internal Combustion engine Propulsion Plant Economy Test ............................................... 75 Table 19 Gas Turbine Plant Economy Test Data ................................................................................ 76 Table 20 Propulsion Plant Data (Includes 10 Data Sheets) ................................................................. 80 Table 21 Propulsion Plant Data - Sheet 2 Diesel................................................................................. 81 Table 22 Propulsion Plant Data - Diesel (Cont2) ................................................................................ 83 Table 23 Propulsion Plant Data - Electric Drive ................................................................................. 84 Table 24 Propulsion Plant Data - Gas Turbine .................................................................................... 84 Table 25 Propulsion Plant Data - Gas Turbine (Cont) ........................................................................ 86
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1.0 INTRODUCTION 1.1 SUPERSESSION This Society of Naval Architects and Marine Engineers (SNAME) T&R Bulletin 3-47(2015) "Guide for Sea Trials (Progressive Speed, Maneuvering, and Endurance)" supersedes T&R Bulletin 3-47 Guide for Sea Trials 1989.
1.2 ORIGIN This Guide was developed by updating the 1989 Guide for Sea Trials-1989 that was produced by SNAME Panel M-19 (Ship Trials) with assistance from Panel H-10 (Ship Controllability) and approved by the Ships’ Machinery Committee of SNAME. This update effort was supported by funding from the National Shipbuilding Research Program. Those contributing to the update include a variety of volunteers from organizations including shipbuilders, ship owners, ship designers, operators, Classification Society, Government organizations and others. Publications of other SNAME Technical Panels, Classification Societies, and international standards organizations were consulted to check compatibility and various sources in the technical literature were researched for advances and current trends. The recommendations include incorporation of ISO 15016.2 Guidelines for the assessment of speed and power performance by analysis of speed trial data and IMO Resolution MSC.137 (76), Standards for Ship Maneuverability.
1.3 PURPOSE The purpose of the Guide is to provide ship owners, designers, operators, and builders with definitive information on ship trials to form a basis for contractual agreement.
1.4 SCOPE The Guide covers sea trials of self-propelled surface ships, commercial or naval, displacing 300 tonnes or more, powered by hydrocarbon fuels such as petroleum, natural gas and bio fuels and driven by diesel or Otto cycle engines, gas turbine, or electric motors. It does not cover dock trials, tests or demonstrations that can be conducted dockside. For these type of tests refer to SNAME Technical and Research Bulletin 3-39, Guide for Shop and Installation Tests-1985. Nothing in this Guide should be construed to delete or modify requirements of specified regulatory bodies.
1.5 TRIAL OBJECTIVES A sea trial may have one or more of the following objectives depending on the position of the ship in its class, the innovative content of its design, and the needs or desires of its owners.
1.5.1 Demonstration of Operability The ship propulsion and control systems can be shown to operate in their design modes only at sea, and the shipbuilder and customer both benefit from a demonstration of proper operation that verifies the correctness of construction, manufacture, and installation.
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1.5.2 Demonstration of Performance The attainment of maximum contract levels of power or speed is particularly important for the first ship of a class to verify the adequacy of the design of the propulsion plant and its supporting auxiliaries.
1.5.3 Demonstration of Endurance Demonstration of ability to maintain maximum power and speed for sufficient time to develop equilibrium conditions and to operate at those conditions for the prescribed period without failure of system components is important for every ship. It is assumed that the ability to operate in this manner indefinitely, or for the design life, will thereby have been demonstrated, since any functional inadequacies will have been made evident by this and other trial operations.
1.5.4 Demonstration of Economy Demonstration of the contract specific fuel consumption is mandatory when there is a penalty involved or when required by the ship's specifications. Attainment of the best possible fuel consumption is important when there is a bonus involved. When neither are involved it is still required to determine fuel rate for the first of a class to verify design and for subsequent ships to verify proper operability of the energy conversion system.
1.5.5 Demonstration of Energy Efficiency Design Index (EEDI) Demonstration of the vessel's EEDI characteristics is important to verify its relative rating of energy efficiency (see ISO 15016.2 for details on EEDI).
1.5.6 Demonstration of Controllability Demonstration that a vessel has maneuvering qualities permitting course keeping, turning, checking turns, operating at acceptably slow speeds, and stopping in a satisfactory manner is important for safe operations of a ship in open and restricted areas.
1.5.7 Establishment of Operating Performance Baseline It is desirable to establish a performance baseline (in the form of data sets) for a new class of ships and to a lesser degree for individual ships so that ship operators will have a standard with which to compare current operating data enabling monitoring of plant performance and operational capabilities. Performance baseline data is also important for populating onboard performance monitoring systems used in optimizing vessel operations. Ship pilots as well as operators also need to know the controllability characteristics of the vessel. Properly developed ship trial test data reported according to the comprehensive guidelines of IMO Resolutions A.751 and A.601 (15) (see for instance the ABS Guide for Vessel Maneuverability) provide such data in a standard format for operator use.
1.5.8 Provision of Forensic Data It is increasingly important for ship operators to have available certifiable data on the ship's maneuvering capabilities in the event the ship is involved in legal action for collision damage. Data from other ship systems may be pertinent to litigation involving habitability, safety or pollution responsibilities.
1.5.9 Provision of Design Data All trial data augments the bank of design data on which naval architects and marine engineers draw upon. This allows greater predictability during the design process permitting the required performance characteristics to be delivered with greater confidence. Special data to verify the success 2
SNAME Technical and Research Bulletin 3-47 (2015) Guide for Sea Trials
of innovative features or to advance the state of the shipbuilding art may be called for. In such cases it is important that the design authorities who will use the data specify requirements in detail, including instrumentation, operating conditions, and procedures. The IMO, for instance, gathers data on ship maneuverability in its developing and refining of standards and has detailed specific maneuvers that are included herein.
1.5.10 Classification and Safety Requirements Classification societies and safety authorities often require demonstration of equipment and systems which affect safety of the ship, its cargo or its crew.
1.6 SHIP AND ENVIRONMENTAL CONDITIONS Proper ship and environmental conditions during trials are often critical for achieving useful results.
1.6.1 Sea Trial Loading Conditions Where possible, trials will be carried out in the design load draft condition. However, due to limitations in ballast capacity, Contractor's Sea Trials will frequently be performed at other drafts. Separate trials in the ballast condition may be required. For uniformity in selecting ballast drafts for oil tankers, consideration should be given to those specified by IMO 73/78 MARPOL for designed ballast draft capability for tankers. In all cases, the fore and aft drafts at the time of the trial must be recorded. For ships not provided with full draft capability via ballasting, trial drafts will not approximate maximum design draft, and demonstrations of capabilities that are draft dependent, such as ship's speed and maneuverability, are of limited value. In such cases it is advisable to specify model tests at anticipated trial drafts as well as maximum design draft, as without such tests, extrapolation of trial results depends on uncertain estimates. Trials should be conducted at drafts as close as practicable to the model test conditions. In the absence of model test data as a reference point, standardization results at other than the maximum design draft is not recommended.
1.6.2 Water Depth The most demanding operational requirements for many ships are met in shallow water during coastal and port navigation. Unfortunately, the usual practice is to perform ship trials in deep water for standardization and comparative purposes. The adequacy of a ship's capabilities in shallow water, particularly maneuvering characteristics, must usually be inferred or predicted based on its success in deep water, and from comparison of its deep water characteristics relative to other vessels. Ships interact with the bottom, with banks, and with other vessels in restricted waters with very significant effects on ship movement. Trials should therefore always be made in deep unconfined waters where possible. To minimize the possibility of such effects on the underway performance trial results of the ship, water depth, other than for special trials to investigate shallow water capabilities, should always exceed five times the mean draft of the ship. During speed trials additional depth is needed based on speed and vessel midship section area: H > 5.0 (Am)1/2 H > 0.4 V2 where:
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H = Water Depth (m) Am = Midship Section Area (m2) V = ship's Speed (m/sec)
1.6.3 Wind, Waves, and Currents The uncontrollable environmental conditions of wind, waves, and currents can significantly influence the results of all underway trials. These effects are also difficult to account for. Trials should thus be held in the calmest weather conditions available. Wind direction and speed should be noted at the start of each test, so that the effects can be studied and corrections applied. Currents, wave, and swell conditions and their change should also be noted. Sea State 4 with a significant wave height of up to 2.5 m, should be avoided. Sea State 3 with a significant wave height of up to 1.25 m, should be avoided for ships under 152.4 m (500 feet) in length. Wind speeds of more than 10 m/second (19.4 knots or nmi/hr) should be avoided. Maneuvering spiral tests and slow speed trials are particularly sensitive to wind and currents. Wind speed should not exceed around 5 m/second (9.7 knots) to assure useful results from such trials.
1.7 LIST OF TRIALS AND SELECTION Blanket invocation of this Guide is not intended. Sufficient trials and tests are included to enable the user to select a sea trial or test of any degree of complexity desired. Invocation of the total Guide, however, without regard to the objectives to be served or the utility of data obtained would result in excessive costs with little value. Users should study the Guide, and then when writing their ship’s specification specify by paragraph number in this guide the trials and tests required to meet their objectives. Lists of trials and tests recommended for first-of-a-class and follow-on ships are provided for convenience. If this Guide is invoked by contract, all of the recommended trials and tests are to be conducted except for those specifically deleted, and trials or tests marked "If Elected" are to be conducted only if specifically invoked. While some tests are required by international regulations or regulatory body requirements and must be run, other tests in this guide should be run if needed for specific demonstration of capabilities. Listed below are the names and tests covered in this Guide. The recommendation associated with the name of each test is provided to assist in developing a trials program. Further guidance on the purposes of each test and when it may be useful can be found in the column titled Guide Paragraph. The tests and recommendations are shown on Table 1.
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Table 1 Recommended Trials
Name
Recommendation
Economy Trials Endurance Trials Astern Trial Diesel Propulsion Gas Turbine Propulsion Electric Drive Centralized Propulsion Control System Ahead Steering Astern Steering Auxiliary Means of Steering Turning Circles Z Maneuver Initial Turning Pullout Direct Spiral Reverse Spiral Thruster Quick Reversal from Ahead to Astern Quick Reversal from Astern to Ahead Low Speed Controllability Slow Steaming Ability Emergency Propulsion Systems Navigation Equipment Standardization Trials
First of a Class only All Ships All Ships If Elected If Elected If Elected All Ships All Ships All Ships All Ships First of a Class only First of a Class only First of a Class only (1) First of a Class only First of a Class only If Elected (2) First of a Class only All Ships All Ships If Elected All Ships If Elected All Ships First of a Class only
Guide Paragraph 2.2 2.3 2.4 2.5 2.6 2.7 2.8 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 1.5, 2, 4
(1) Derived from paragraphs 3.7 and 3.8 (2) Alternative to "Direct Spiral"
It should be noted that some of these tests can be run concurrently. For twin screw ships, owners may want to consider running tests to examine the conditions of lost power to one shaft. Tests with one shaft in a locked or trailing mode can be run to examine effects on speed and maneuverability.
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Bulletin 3-47 does not address noise and vibration measurements which are generally not performed on sea trials. It is recommended that these tests, however, should be coordinated with related aspects of the sea trials program. Ahead endurance trials offer an opportunity for concurrent measurements for airborne noise.
1.8 RECOGNITION OF UNCERTAINTY Although ship designers, builders, and trial personnel may exercise greatest diligence in pursuing their art at the most advanced state, there is inherent in the measurement of ship performance an unavoidable uncertainty. No measurement is perfect and shipboard conditions preclude the use of the most precise techniques. Since the major ship performance parameters involve measurement of many fluctuating quantities, each with an element of uncertainty, the cumulative effect might be considerable. By applying probability techniques to the degree of fluctuation and the inherent precision of the instruments involved, including their calibration, it is possible to identify the degree of certainty with which a ship's performance can be determined. It is important that all parties to a ship construction program recognize the uncertainty of trial results and take it into consideration when establishing performance target/bonus/penalty levels. Knowledge of how much the precision of the individual measurements affects the performance determination and the range of precision available for the instruments involved enables the trial planner to make an intelligent and economic decision on instrumentation. The reader is referred to ISO 15016.2 Section 5.1 for a discussion on required accuracy for torque measurements.
1.9 PLANNING From award of a contract until delivery of the official trial report, sea trials require continual planning. Trial instrumentation requirements should be incorporated in design; prearrangements may be required for obtaining and calibrating trial instruments; trial readiness checks should be included in production planning; trial data acquisition, processing, and reporting systems should be developed, installed, and checked; instructions and procedures should be developed for trial operating and data crews; and these crews should be trained. A prerequisite to all planning is a clear understanding as to the tests and trials to be conducted, the depth of instrumentation and the data to be reported. If this Guide is properly cited in the ship's specifications, requirements should be clear. If the Guide is not cited or there remains an area of doubt, the shipbuilder, owner, and regulatory bodies involved, should reach agreement as soon as possible after the award of a contract, using this Guide as a basis for understanding. Presuming that agreement has been reached, the actions outlined below can be taken as applicable. References in this guide are made on occasion to other documents that provide additional useful information.
1.9.1 Design Accommodation (a) If a torsionmeter is to be installed, care should be taken in its location on the shafting with adequate clearance provided (ISO 15016.2 addresses various issues). If required, special surface finish and dimensional constraints should be imposed. If the shaft is hollow, the supplier of the rough machined unit should be alerted to provide precise internal diameter measurements. Mounting of signal transfer equipment or brush rigging should also be considered (current practice includes the use of wireless links from shaft mounted strain gages).
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(b) If special trial fuel meters are to be installed, systems should be designed to accommodate them. (c) If special gages, thermometers or orifices are to be installed, sensing points should be selected and the necessary fittings, wells, or flanges provided. (d) If fuel samples are to be taken during trials, a sampling connection or method should be provided.
1.9.2 Pre-Arrangements (a) If the shaft is to be calibrated, the shafting production schedule should be adjusted to provide for calibration availability; the torsionmeter should be requested if furnished by the government, or procured or overhauled if furnished by the contractor; the torqueing gear should be made ready, the calibration accomplished and the instrument factors established. Unless permanent torque meters are installed, this measurement is done using strain gages installed just prior to trials and calibrated using shunt resistors. Material properties of the shaft need to be provided by the manufacturer or assumed based on ISO 15016.2 (b) Plant operating conditions and modes; ship draft conditions; and shaft power levels should be established for each trial and the owner's concurrence obtained. (c) Plant operating and ship's ballasting and de-ballasting instructions should be prepared and distributed to trial crew supervisors. (d) Signal system should be designed and installed. (e) Correction factors should be obtained and the concurrence of owner’s technical representatives established. (f) Data instructions and station bill should be prepared and distributed. (g) Special trial instruments should be installed and all instruments which will provide trial data calibrated, “red line” settings made and “water legs” measured. Sensor calibration should include addressing remote or indirect means the sensor relies on for accuracy. (h) Data forms (paper or digital) should be prepared and the graphical interface checked against the ship as built, preferably by using them for Dock Trials to allow for proper data quality assurance. (i) Trial operating crew and data crew should be trained unless previously trained or experienced. (j) Calculation sheets or a data acquisition system (DAS) and computerized quality analysis (QA) sheets should be prepared, with dummy calculations and correction tables or plots provided. (k) GNSS tracking system, if to be aboard, including antenna should be installed and checked. (l) A sample of the fuel expected to be burned should be sent to a laboratory for gravity and heat content determination when fuel rates are to be calculated. (m) Trial agenda, procedures, and schedules should be prepared and furnished to the owners for comment. (n) Trial control and the data acquisition system should be planned and facilities installed, including appropriate communications and reference material. 7
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1.10 PRE-TRIAL CHECK LIST So many items are involved in determining readiness for sea trials that it is virtually necessary to use a check list. Such a list should include all machinery, equipment, and trials to be tested and pretests or other preparations necessary to perform the tests to assure readiness.
1.11 BUILDERS' TRIALS If builders' trials or runs are to be conducted, they should be specified. If data for any portion of the trial or runs is to be presented for acceptance, the owners, acceptance authorities, and involved regulatory bodies should be notified in advance. If builder’s trials are not specified, they are to be at the discretion of the builder for any purpose, including any of the following:
Checking the operation of the machinery installation and the trial equipment. Training the operating and trial personnel. Making adjustments to the propulsion plant to establish proper operation. Determination of ability to meet performance requirements.
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2.0 PROPULSION PLANT TRIALS 2.1 GENERAL 2.1.1 Scope of This Section This section contains recommendations for conducting internal combustion engine, gas turbine, and integrated electric propulsion plant trials with the ship underway under specified conditions. The propulsion plant is considered to include propulsion plant machinery, all auxiliaries and systems required for its operation and other such apparatus as are necessary for the operation of the ship under trial conditions. The instructions herein are intended to cover testing of the propulsion plant as an integrated system underway and do not cover ship or shop tests of individual equipment items, dock trials, or dockside tests required by specifications or regulatory bodies, unless prescribed herein as incidental to the trials. Specific requirements for these types of propulsion plants can be found beginning with paragraph 2.2.
2.1.2 Specific Objectives Specific objectives of propulsion plant trials may be one or more of the following:
To demonstrate satisfactory operation of the propulsion plant for a specified period of time at specified power, usually maximum design power. To determine the rate of fuel consumption of the plant when operating at specified shaft power and other specified operating conditions. To determine performance characteristics of the machinery plant or components thereof, as agreed. To demonstrate satisfactory operation of propulsion plant controls from all stations. To obtain propulsion plant data for future use in evaluating service performance.
Note that the power level of the propulsion plant may be specified in terms of revolutions per minute when trial draft or other conditions make full power unattainable within shaft speed limitations.
2.1.3 Pre-Trial Agreements Prior to the trials, there should be a clear understanding with respect to the following:
The specific objectives of the trials. The trial agenda and tentative schedule. Conditions and methods of operation during the trial. Corrections, if any, to be applied for deviations from specified conditions or specific standards. Measurement methods, temporary test equipment and instrumentation. Trial drafts. Duration of each trial run. Frequency of readings and measurements including digital sampling rates.
2.1.4 Trial Preparations Preparation for propulsion plant trials as, defined in this section should include the following:
Calibration of shafting to determine modulus of rigidity, or if the shaft is not to be calibrated, then an agreement on the modulus to be used. Installation and calibration of torsionmeter. 9
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Calibration of trial fuel meters. Where ship’s meters are used as trial or trial back-up instrumentation, they should also be calibrated. Calibration of special gages and meters. Records of calibrations should be available prior to trials and carried onboard during trials. Installation of trial equipment as required. Ascertaining that all machinery and equipment is in proper working condition. Preparation of the trial ballasting plan to provide the prescribed submergence of the propeller. Control and records of fuel onboard to provide for trials a homogeneous, known, supply. Analysis of the fuel to be burned including heating value, specific gravity, viscosity characteristics, and other pertinent properties.
2.1.5 Trial Duration Duration of each Propulsion Plant Trial should be as set forth in Table 2 and Table 3 unless otherwise specified or agreed. Unless otherwise agreed, any run, which has been interrupted by machinery casualties necessitating slowing down or stopping, should be entirely rerun. If the interruption of a run is due to operating error or maneuvering from the bridge due to traffic or other safety situations, only the disrupted portion of the run need be repeated.
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Table 2 Recommendations for Internal Combustion Propulsion Plant Trials
TRIAL
Ahead Endurancec
DURATION
4 hours
POWER LEVEL
Astern Endurance
Economy
30 Minutes
4 hours
Max Continuous Rating
Max Astern Continuous Rating b
CRITICAL MEASUREMENTS
Power
Torque/RPM
INTERVAL FOR CRITICAL MEASUREMENTS SUPPORTING DATA (As pertinent)
15 Minutes
10 Minutes
Specified Continuous Service Rating Power Level & Fuel Consumption 15 Minutes
Torque
Torque
RPM Prop Pitch PRPLS Motor KWd Rack Position Max Cylinder Firing Pressure
RPM Prop Pitch PRPLS Motor KWd Rack Position
Power or RPM
Torque RPM
PLANT CONTROL PARAMETER MEANS OF CONTROL
a
a
Same as Ahead Endurance Plus: Aux Load Fuel PRPLS Motor KWd Fuel sample for heating value analysis Air Intake Temps Power or RPM
Remote Control Remote Control Remote Control System System System a Endurance and economy Trials may be concurrent if power level is the same. If power levels differ, the duration of the Economy Trial may be reduced to two hours if it follows the Endurance Trial immediately (alternatively recommended). b
To be in accordance with Classification Society requirements. Endurance testing using an alternate fuel or secondary propulsion system may be required. d For electric drive ships. c
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Table 3 Recommendations for Gas Turbine Propulsion Plant Trials TRIAL DURATION
Ahead Endurance 4 hours a
Astern Endurance 30 Minutes
Economy 4 hours a
POWER LEVEL
Max Design a
Max Continuous b
Service a
CRITICAL MEASUREMENTS
Power
Torque/RPM
Power Level & Fuel Consump
INTERVAL FOR CRITICAL MEASUREMENTS
15 Minutes
10 Minutes
15 Minutes
SUPPORTING DATA (As pertinent)
Torque
Torque
RPM
RPM
Same as Ahead Endurance Plus: Aux Load
Prop Pitch PRPLS Motor KWc Exhaust Temp Plus Mfg's Lim
Prop Pitch PRPLS Motor KWc Exhaust Press Plus Mfg's Lim
Fuel PRPLS Motor KWc Air Intake Temps Plus 5%
Minus 2%
Minus 10%
Minus 5%
Plus 5%
Plus Mfg's Lim
Plus 5%
Minus 5%
Minus 20%
Minus 5%
PLANT CONTROL PARAMETER
Power or RPM
Torque RPM
Power or RPM
MEANS OF CONTROL
Remote Control System
Remote Control System
Remote Control System
DEVIATION OF CRITICAL MEASUREMENT AVERAGES FROM LEVEL SPECIFIED FLUCTUATION OF INDIVIDUAL DATA ITEM FROM AVERAGE FOR CRITICAL MEASUREMENT
a
Endurance and economy Trials may be concurrent if power level is the same. If power levels differ, the duration of the Endurance Trial may be reduced to two hours if it follows the Economy Trial immediately (alternatively recommended). b
To be in accordance with Classification Society requirements.
c
For electric drive ships.
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2.2 PROPULSION PLANT ECONOMY TRIALS 2.2.1 Purpose The primary purpose of Economy Trials is to determine fuel consumption. An ancillary purpose is to establish an RPM/SHP relationship under trial conditions.
2.2.2 Operating Conditions Uniform operating conditions should be maintained throughout each trial run. To establish steady operating conditions for economy measurements, a period of warming up or adjustments should be allowed prior to trial runs. Steady-state conditions should be proven prior to starting economy trials. Helm changes should be held to a minimum and course changes should be made with no more than 5 degrees rudder. The test director must be informed when ship navigation necessitates the change in ship’s speed or the use of more than 5 degrees rudder. An announcement should be made to suspend and/or resume affected measurements when under these conditions.
2.2.3 Frequency of Observations Unless otherwise agreed, observations and instrument readings should be taken at fifteen minute intervals. Readings of torque or shaft power should be taken as required for producing, as nearly as is practicable, a continuous record. Digital data acquisition should utilize appropriate data sampling techniques which will be averaged at 15-minute intervals. See Tables 2 and 3 for reading intervals for important data.
2.2.4 Communication Visual and audible signaling should be used onboard to announce and enable accurately marking the beginning and end of runs and to synchronize data taking. Hand-held radios and ship’s telephone or public address systems can be used, but should be controlled from a central station.
2.2.5 Measurements and Instrumentation (a) General. Trial observations should include all pertinent time intervals, pressures, temperatures, flow rates, levels, revolutions, combustion conditions, and other characteristics of operation, as may be required to satisfy the trial objectives. For information concerning trial instrumentation, see Section 5.0, Instruments and Apparatus for Ship's Trials. For data reporting forms listing recommended trial observations, see Section 6.0, Trial Data and Report. (b) Power. Method of determining shaft power should be as agreed before trials. Suitable measuring apparatus, methods of measuring, and methods of computing shaft power are given in Section 5.0, Instrumentation and Apparatus for Ship's Trials, but it is not intended to limit or restrict the use of the measuring equipment to types described therein.
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Measurements of auxiliary electric power should be made by ship’s instruments unless otherwise agreed. For major ampere loads, clamp type ammeters should be utilized to determine loads where ammeters are not fitted. For ships on which hotel loads are relatively large, provision for separate measurements of total auxiliary machinery loads and hotel loads is recommended. (c) Revolutions. Accurate and reliable trial shaft counters suitably interfaced with the trial signal system or data reduction system should be installed and checked out prior to the start of the sea trials. For details on shaft revolution counters, see Section 5.0, Instruments and Apparatus for Ship’s Trials. (d) Fuel Measurements. Measurements of fuel quantity should be made by flow rate meters, which should be calibrated before and after trials and the calibration correction applied to the observed trial data. For further details on the installation of trial fuel meters, refer to Section 5.0, Instruments and Apparatus for Ship’s Trials. (e) Other Measurements. Measurements of pressure and temperature which materially affect trial results should be obtained from calibrated test gages and thermometers installed for the trial. Data from ship's gages, thermometers and instruments may be used for trial purposes provided these instruments have been calibrated and set to read correctly in the operating range. Acceptable instruments for time measurements are described in Section 5.0, Instruments and Apparatus for Ship’s Trials. Measurements of water flow, when required, should be made with calibrated water meters installed for this purpose. Ship's installed meters may be used if calibrated. Modern engine electronic control systems are another resource of performance data onboard. Information from these systems can be useful during trials if high accuracy under trial conditions is known. Data points from sea trials can be used to verify the accuracy of these systems to assist the operator in optimizing performance.
2.2.6 Fuel Rate Data Required The fuel rate for all purposes should be expressed in grams per shaft power per hour or other agreed standard units for each trial run. See Tables 17 -18 of Section 4 Standardization Trials, for Data Sheets. The fuel rate should be determined from averages of readings recorded at fifteen (15) minute intervals and data obtained from other sources as indicated in the following: a) b) c) d) e)
Fuel meter readings at start and at end of each trial interval. Fuel meter correction from meter calibration curve. Fuel temperature at the meter. Gravity of fuel related to specific gravity of water at 60°F. (for liquid fuels) Table or plot of weight/volume for the range of metering temperature expected, applicable to the gravity of fuel being burned. (for liquid fuels) f) Higher heating value of fuel from laboratory tests or lower heating value as agreed or specified. g) Average shaft power (kW) for each trial interval. h) Fuel chemistry, if specified. 14
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Note: Fuel Properties should be determined by post trial analysis of a thorough mix of fuel samples taken at a minimum of four equally spaced intervals during the run. Also note that if Coriolis type meters are used, the fuel consumption rate can be obtained directly as mass per unit time so that d) and e) above are not required.
2.2.7 Trial Report See tables in Section 6.0, Trial Data and Report.
2.3 PROPULSION PLANT AHEAD ENDURANCE TRIALS 2.3.1 Purpose The primary purpose of Ahead Endurance Trials is to demonstrate satisfactory ahead operation of the propulsion plant at specified operating conditions as contractually required or agreed. This should include specific shaft power or revolutions per minute for a prescribed period of time. Since satisfactory operation and performance of the machinery plant is equally essential for endurance and economy trials, they may be conducted concurrently when specifications for both are the same for shaft power, period of run time, and fuel. For Endurance Trials the emphasis is on attaining and sustaining the required power level. Fuel rate is a secondary interest. For Economy Trials the fuel and power data are the essentials. Other data including possible auxiliary load levels are used to explain results to correct for off-standard conditions. Sometimes Endurance Trials are specified to include a demonstration of satisfactory operation of the propulsion plant under service conditions during a specified voyage of the ship. Such trials and the details thereof are subject to agreement between the parties involved and are not covered by this section. If the ship is designed to operate on more than one fuel, (HFO and MGO or Natural Gas, for instance), an endurance run may be required for each type of fuel to demonstrate capabilities and to demonstrate the ability to switch from one fuel to another.
2.3.2 Measurements and Instrumentation Economy Trial instrumentation and data systems are generally adequate for Endurance Trials. When both trials are specified, the requirements and discussions of paragraph 2.2 apply. When only Endurance Trials are specified, paragraph 2.2 is applicable, except that special fuel meter calibration may not be required and power level may be determined without use of a torsionmeter as discussed below. However, it is recommended that a torsionmeter be used for at least the first ship of a class so that corrections to the alternative methods discussed below can be developed both for future trials and for use in checking service performance. When a torsionmeter is fitted, power should be derived from the average torque and RPM for the trial period as set forth in paragraph 2.2. However, upon agreement or by specification, torsionmeters may be omitted and power approximated from one or more of the following: 1. Propeller revolutions per minute with model test data. 2. On ships with direct drive, prime mover parameters and conditions, and manufactu’er's shop test or design data. 3. On ships with electric drive, electrical input to the propulsion motor(s) with manufacturer's data on motor efficiency and power consumption of shaft-driven auxiliaries. Even when trial power is determined by use of a torsionmeter, a comparison should be made with power derived from engine data, particularly where a torsionmeter is not to be permanently fitted. 15
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2.3.3 Trial Report See tables in Section 6.0, Trial Data and Report.
2.4 PROPULSION PLANT ASTERN TRIAL 2.4.1 Purpose and procedure The primary purpose of the Astern Endurance Trial is to demonstrate satisfactory astern operation of the propulsion plant at specified operating conditions as contractually required or agreed. This should include specific shaft power or revolutions per minute for a prescribed period of time. An ancillary benefit is proving the adequacy of piping supports, and equipment under severe vibratory conditions. Difficulty in obtaining uniform propeller loading because of submergence variations due to ship pitch, wave impingement or the uncontrollable circular track generally followed when a single-screw ship is under sternway, often prevents steady propulsion plant operation. It is therefore advisable to establish limits to astern RPM and prime mover parameters. As a result, the average indicated shaft power for the astern run may be more or less than the target value. Some ship specifications will limit sternway to that speed where by maximum rudder movement from hard over will not result in rudder torque exceeding the maximum specified. In such cases the maximum astern speed should be established during the astern run by incrementally advancing propeller speed until steering engine pressures indicate the maximum rudder torque specified. Except as required for astern steering trials, the rudder should be held amidships during astern trials.
2.4.2 Measurement and Instrumentation Instrumentation and the data system should be the same as that for Ahead Endurance Trials.
2.4.3 Trial Report See tables in Section 6.0, Trial Data and Report.
2.5 SPECIAL CONSIDERATIONS FOR DIESEL AND OTTO CYCLE ENGINE PROPULSION PLANT TRIA LS This section addresses sea trial related tests which are peculiar to propulsion plants utilizing diesel and Otto cycle engines and amplifies some areas which are covered generally in paragraphs 2.2 through 2.4 above. A major purpose of the Economy and Endurance trials is to provide base-line operating data for the entire plant, and the sea trials should be planned and carried out with this in mind. Plants designed to operate on more than one fuel should be operated on each of the fuels during trials to obtain data appropriate for operation on each fuel.
2.5.1 Auxiliary Components The following are examples of auxiliary components which may be part of a diesel plant: a. Turbochargers, reciprocating or gear type blowers, or other sources of combustion or scavenging air pressure. b. Engine-driven lube oil, fuel or cooling fluid pumps. c. Independently driven generators, pumps or centrifuges. d. Power transmission elements including gears, couplings, clutches, etc. e. Waste heat boilers and/or auxiliary boilers. 16
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Special agreements should be made prior to trials for observing the performance of the auxiliary components mentioned above.
2.5.2 Revolutions Same as paragraph 2.2.5(c) except for installations having a reduction gear and/or a slip type coupling between the engine and the shaft. Then, both engine revolutions and shaft revolutions should be obtained.
2.5.3 Fuel Measurements Same as paragraph 2.2.5(d) except as follows: a) The fuel consumption of the main and auxiliary engines and any other fuel consuming equipment in operation should be measured separately. b) Systems that return fuel to the upstream side of the supply meter should have the return measured separately.
2.5.4 Fuel Rate Data Required Same as paragraph 2.2.5(e) except as follows: Include return fuel oil meter readings with other meter data. In addition, fuel rate corrections for variations of the following data from design conditions should be provided by the engine manufacturer: a) b) c) d) e) f)
Inlet air temperature. Inlet air pressure. Inlet air moisture content. Engine RPM. Exhaust pressure. Fuel oil heating value.
The purpose of these corrections is to properly evaluate diesel engine performance. Suitable test devices should be provided on trials to accurately measure these variables.
2.5.5 Power When torsionmeters are not required to be fitted, brake power for diesel engines may be estimated by the following methods: a) Rack Position - Brake power may be closely approximated by careful observations of fuel injection rack positions and comparison of these with data taken during shop tests where output is measured directly on a water or electric brake or equivalent. For maximum accuracy it is necessary that shop tests and ship's trials utilized comparable fuel. b) Slip Coupling - On installations using a slip type coupling, the torque transmitted can be closely approximated by comparing the engine RPM and shaft RPM with slip data supplied by the coupling manufacturer. c) Indicator Cards Indicator cards or equivalent may be taken on each cylinder, and the brake KW (BKW) may be computed with very good results for low or medium speed units. Engine efficiency data, other correlating data, or sample correction curves are also needed with the indicator card data to compute BKW. Each of the above methods may be used to determine brake power. An agreed allowance for gear or coupling losses must be applied to obtain shaft power, if these elements are in the power train. When a torsionmeter is fitted, the correlation between the shaft KW (SKW) determined from the torsionmeter and the BKW determined from engine data should be established during the trials. 17
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2.5.6 Fuel Switching When two or more types of fuel are specified for normal operation, such as inside and outside of an Emission Control Area (ECA), the switching from one fuel type to the other and then back again, are to be demonstrated at the highest power level possible to demonstrate the limits at which fuel switching can be carried out.
2.5.7 Daily Fuel Consumption and Ship’s Overall Fuel Rate If desired, a daily fuel consumption rate could be provided based on tonnes/day at a specified power, electrical load, etc. An overall fuel rate can possibly be developed to have meaning if tied carefully to specified operational conditions. Fuel consumption of various components such as auxiliary engines or boilers would need to be considered separately during the trials and then corrected to standard conditions. Use of different fuels would have to be analyzed and all values adjusted for fuel density and heating value. An overall ships fuel rate could then be computed by summing the components and dividing by some base reference number such as the propulsion shaft power.
2.5.8 Trial Data and Report See tables in Section 6.0, Trial Data and Report.
2.6 SPECIAL CONSIDERATIONS FOR GAS TURBINE PROPULSION PLANT TRIALS This section covers sea trial related items which are peculiar to gas turbine propulsion plants. This guide is written around the basic gas turbine propulsion unit consisting of a gas generating turbocompressor and independent free power turbine. It should not preclude trial modifications, however, which future gas turbine development may dictate.
2.6.1 Auxiliary Components The following are examples of auxiliary components which may be part of the gas turbine plant: a) b) c) d) e) f)
Precoolers, intercoolers, and after coolers. Reheaters, regenerators, and recuperators. Fuel conditioning equipment. Independently powered generators and pumps. Control equipment and safety devices. Power transmission elements including gears, clutch, shaft brake, coupling, controllable pitch propeller, etc. g) Waste heat or independently fired boilers. h) Anti-icing and bleed air systems. Special agreements should be made prior to sea trials for observing the performance of the auxiliary components mentioned above.
2.6.2 Fuel Rate Data Required Fuel rate corrections for variations from design values of the following should be provided by the gas turbine engine manufacturer: a) b) c) d)
Inlet air temperature. Inlet air moisture content. Power turbine RPM. Inlet air pressure. 18
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e) Exhaust pressure. These corrections are required to properly evaluate gas turbine performance. Suitable test devices should be provided on trials to provide the necessary data. Barometric pressure and relative humidity of the outside air should be recorded to permit evaluation of air inlet and exhaust duct systems. The shipbuilder, however, is responsible for designing the air inlet and exhaust systems to meet design turbine inlet and exhaust conditions, and no correction to the ship's overall fuel rate should be permitted for excessive pressure loss in these systems.
2.6.3 Power When torsionmeters are not fitted, brake power for gas turbine engines may be estimated from the engine RPM, internal gas pressures and temperatures and/or fuel oil flow with sufficient accuracy for endurance trial purposes. Sample reference curves and correction factors will be very useful to develop estimates. When torsionmeters are required to be fitted, a correlation should be established during trials between the power determined from the torsionmeter and the engine brake power as ascertained by the engine pressure, RPM, and temperature data.
2.6.4 Trial Data and Report See tables in Section 6.0, Trial Data and Report.
2.7 SPECIAL CONSIDERATIONS FOR ELECTRIC DRIVE PROPULSION PLANT TRIALS Electric drive propulsion as covered in this section consists of electrical power generating equipment and propulsion motor(s). Prime movers associated with the electric propulsion generators such as gas turbine, and diesel engines are covered in paragraphs above and are not repeated in this section.
2.7.1 Auxiliary Components The following are examples of auxiliary components which may be part of the electric drive propulsion plant: a) b) c) d) e) f)
Heat exchanger units. Independently powered pumps. Attached pumps. Independently powered fans Control equipment and safety devices. Power transmission elements including gears, clutches, shaft brakes, couplings, controllable pitch propeller, etc.
Special agreements should be made prior to trials for observing the performance of the auxiliary components listed above.
2.7.2 Power Power output from the propulsion motor can be determined from the torsionmeter when installed or from the instruments if not installed. Agreements should be made prior to trials regarding instrumentation to be used for power determination during trials.
2.7.3 Trial Data and Report See tables in Section 6.0, Trial Data and Report.
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2.8 CENTRALIZED PROPULSION CONTROL SYSTEM TEST 2.8.1 Purpose The purpose of the test is to demonstrate the ability of the system to control the propulsion plant in all design modes and to demonstrate satisfactory propulsion plant response during transient operation at specified rates and initial and final conditions.
2.8.2 Procedure Prior to sea trials the control system and its subsystems, sensing elements, valve and equipment operators, safety devices, alarms, and indicators should have been tested for proper installation and operation and should have been adjusted and timed to the values predicted to provide smooth and correct control of the ship at sea. Crewmen responsible for operations should be fully trained in the capabilities and operation of the control system prior to sea trials. Satisfactory integrated operation of the total control system should also have been demonstrated to the extent practicable. At the beginning of sea trials it is advisable to test the control system at reduced powers and make the indicated adjustments prior to demonstration of the full requirements. All required operations of the controls should be demonstrated under free route, maneuvering and emergency conditions in accordance with the sea trial agenda agreed to in advance. In addition to proper control in each mode, satisfactory transition between modes of control should be demonstrated. When the bridge control is demonstrated, there should be no assistance from the engine room watch. When centralized engine room control is demonstrated there should be no assistance from local equipment watchstanders unless such manual participation.is incorporated in the design. Safety features should be demonstrated at sea, if possible, without disrupting the adjustment of the control system or setting up conditions beyond the operating range of the propulsion system.
2.8.3 Trial Report See Table 4 for recording data and reporting results.
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Table 4 Centralized Control System Tests Ship Name
Trial Date
Sea State
Ship's Heading
Start Time Air Temperature oF/oC
Centralized Control Maneuvers
Position Ordered
Shaft RPM Response Time (sec)
Stop to Maximum Ahead (Stopping at each maneuvering speed position)
Maximum Ahead to Stop (Stopping at each maneuvering speed position)
Stop to Maximum Astern (Stopping at each maneuvering speed position)
Maximum Astern to Stop (Stopping at each maneuvering speed position)
Quick Reversal from Maximum Ahead to Maximum Astern Quick Reversal from Maximum Astern to Maximum Ahead Maximum Ahead to Stop Other Maneuvers (as specified)
Notes: 1. 2. 3. 4. 5.
Positions ordered may be in terms of RPM rather than telegraph position. Report any actuation of alarms and safety devices. Report any excursions in plant conditions or controls. The table will have to be adjusted for tests with controllable pitch propellers to include pitch and other considerations involving rpm. Speeds (maximum, full sea speed, etc.) to be tested need to be defined and agreed upon.
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3.0 MANEUVERING AND SPECIAL TESTS 3.1 SELECTION OF TESTS This section contains procedures for conducting maneuvering and other special trials and tests. Ship's specifications should include the owner's selection from the following tests: Ahead Steering (Section 3.4) Astern Steering (Section 3.5) Auxiliary Means of Steering (Section 3.6) Turning Circles (Section 3.7) "Z" Maneuver (Section 3.8) Initial Turning (Section 3.9) Pullout (Section 3.10) Direct Spiral (Section 3.11) Reverse Spiral (Section 3.12) Thruster (Section 3.13) Quick Reversal from Ahead to Astern (Section 3.14) Quick Reversal from Astern to Ahead (Section 3.15) Low Speed Controllability Maneuvers (Section 3.16) Slow Steaming Ability (Section 3.17) Emergency Propulsion Systems (Section 3.18) Navigation Equipment (Section 3.19) In selecting tests, consideration should be given to the requirements contained in IMO.137(76) "Standards for Ship Manoeuvrability" and to the purpose of the test. Some tests are essential to provide the information necessary to comply with IMO Resolution A601(15) "Provision and Display of Manoeuvring Information on Board Ships", which lists information to be available on the bridge in the Pilot Card, Wheelhouse Poster, and Manoeuvring Booklet. It is also essential to verify that the vessel has satisfactory basic course keeping and turning qualities. The data can also be useful in future designs. When possible, tests should be conducted to compare the ship's actual maneuvering performance with the designer's estimation. Maneuvering trials (covered in paragraphs 3.7 through 3.13) provide data that is applicable to all ships of a class, unless there has been a change in draft, rudder, or underwater appendages. In view of the large size of some modern vessels and the consequent greater disparity between their momentum and the forces available to change it, together with the potential for catastrophic pollution in the event of collision or grounding, owners should consider specifying maneuvering tests at other than the speeds and conditions prescribed herein. The objective should be to explore the maneuvering characteristics of each new class of ship to be able to provide the bridge with data applicable to all situations liable to be encountered. The speed for maneuvering tests should comply with the requirements of IMO Resolution MSC.137(76), for the tests listed in the Resolution. Section 4.2 of the Resolution states “the test speed used in the Standards is the speed of at least 90% of the ship’s speed corresponding to 85% of the maximum engine output.” If additional maneuvering tests are desired to demonstrate maneuvering characteristics at other speeds, additional tests at a different speed can be carried out. A general guideline for the test speed
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is the speed at which the ship may be expected to navigate in areas where maneuvers are normally required, and are not restricted by insufficient water depth or channel boundaries. In the case of slow, full form ships this speed may be close to design sea speed. For fast, fine-form ships on the other hand, it may be a much lower proportion of design speed. The following formula is suggested as a guide to selecting test speed: VT = CB x VD where:
VT = test speed VD = design speed CB = block coefficient at the design draught
This formula provides test speed values for bulk carriers and dry cargo/container ship types which are often used in general practice. Unless otherwise indicated tests should be commenced at the test speed.
3.2 PREPARATION Proper preparation is essential to obtain meaningful data and avoid aborting mandatory tests. Detailed instruction for performing each test, including maneuvering diagrams and data sheets where pertinent, should be prepared in advance. Test conductors and data takers should be instructed in their duties, shown their station, checked out on instruments, and have their understanding of the test verified.
3.3 REPORTS Reports should present the data in tabular or diagrammatic format. Sample diagrams and data sheets are shown in this Section and in Section 6. Reports should include, where pertinent, discussion of the significance of findings and an explanation of data anomalies. Reported information should be of sufficient detail to provide the data required to prepare the Pilot Card, Wheelhouse Poster, and Maneuvering Booklet described in IMO Resolution A.601(15) and the first order steering quality indices K and T.
3.4 AHEAD STEERING With the ship in the trial ballast condition and proceeding ahead at maximum trial shaft RPM, move the rudder at maximum rate as follows: 1. 2. 3. 4.
Midships to Hardover Right - Hold ten seconds. Hardover Right to Hardover Left - Hold ten seconds. Hardover Left to Hardover Right - Hold ten seconds. Hardover Right to Midships - Maneuver complete.
After ship's speed has been restored, use the other steering power unit and repeat the above rudder movements in opposite sequence. For rudder movement rate, use the average degrees per second for total time from start to 5 degrees before ordered angle. Throttle setting for single screw ships should not be changed during the test. For multi-screw ships, the throttle may be adjusted as necessary to correct unacceptable overspeed or overtorque. The following data should be recorded on Table 5 during the test: a) Time of test and base course. b) Time required for each rudder movement. c) Maximum rudder angles. 24
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d) Maximum oil pressure on ram. e) Servo pressure, replenishing pressure and pump stroke at maximum demand, if available from ship's instruments and indicators. f) Power unit in use and idle volts, amps and RPM. g) Steering gear motor minimum and maximum volts, amperes, and RPM for each rudder movement. h) Propeller shaft RPM at start and finish of test on each unit. i) Depth of water, sea condition, and wind direction. j) Steering station in control k) Trial drafts, fore and aft. The above test is appropriate for dual power unit electro-hydraulic systems. If a different system is installed, suitable adjustments to the requirements should be made. The ahead and astern steering tests demonstrate steering machinery capability.
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Ship Name
Table 5 Steering Tests Ahead Steering
Unit (P or S) Trial Date Time of Test Base Course Depth of Water Sea Condition Wind Direction Wind Velocity Trial Draft (Fwd) Trial Draft (Aft) Propeller RPM (beginning) Propeller RPM (end) Steering Station in Control Rudder Movement Time (Sec.) b
Maximum Rudder Angles
Max. Steady Motor Amps
Astern Steering Unit (P or S)
Auxiliary Steering (If demonstrated) Unit (P or S)
a
O-R
O-L
O-R
O-L
O-R
R-L L-R R-O O-R R-L L-R O-R R-L L-R R-O
L-R R-L L-O O-L L-R R-L O-L L-R R-L L-O
R-L L-R R-O O-R R-L L-R O-R R-L L-R R-O
L-R R-L L-O O-L L-R R-L O-L L-R R-L L-O
R-L L-R R-O O-R R-L L-R O-R R-L L-R R-O
a
Maximum Ram Pressure Max. Servo Press. (If Available) Max. Replenishment Press. (If Available) Max Pump Stroke (If Available) Idle Volts Idle Amps Idle RPM Minimum Motor Volts a. Rudder angles and rudder movement times as demonstrated. Time to secure normal steering mode and to activate emergency unit also to be recorded. b. Time from start is 5 degrees before ordered angle. c. Tables need to be expanded as needed to display data.
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3.5 ASTERN STEERING With the ship in the trial ballast condition and moving astern at maximum astern shaft speed, using either one of the main power units, move the rudder at maximum rate as follows: 1. 2. 3. 4.
Midships to Hardover Right - Hold ten seconds. Hardover Right to Hardover Left - Hold ten seconds. Hardover Left to Hardover Right - Hold ten seconds. Hardover Right to Midships - Maneuver complete.
Record data as described in paragraph 3.4 above.
3.6 AUXILIARY MEANS OF STEERING Where auxiliary power steering means is specified to control the rudder at reduced ship's speed, rate, and range of rudder movement, such operation should be demonstrated at sea. In addition to shaft RPM and time of rudder movements, the time necessary to secure normal mode and activate the auxiliary unit should be recorded. When the standby unit of a dual hydraulic steering gear is the specified auxiliary means of steering, it is tested under paragraph 3.4, and the test need not be repeated.
3.7 TURNING CIRCLES Turning circles should be performed to both right and left with 35 degrees rudder angle or the maximum design rudder angle permissible at the test speed. The essential information to be obtained from this maneuver consists of tactical diameter, advance, and transfer. Also of interest are the final ship speed and yaw rate in the "steady state" of the turning circle. A turning circle of at least 540 degrees should be completed to determine the main parameters of the maneuver and allow correction for any drift caused by a steady current or wind. Appendix B presents an acceptable method for correcting measurements for ship drift during the test. With the ship in the trial condition and proceeding ahead at the maximum trial shaft RPM, with either steering power unit, move the rudder at maximum rate and perform the following maneuvers: 1. 2. 3. 4.
Move rudder to Hardover Right and hold until ship's heading has changed 540 degrees. Resume a straight course and restore speed. Move Rudder to Hardover Left and hold until ship's heading has changed 540 degrees. Resume a straight course.
The throttle setting for single-screw ships should not be changed during the test. For multi-screw ships, the throttle may be adjusted as necessary to correct unacceptable overspeed or overtorque. If throttle adjustment has to be made during the turn, the maneuver should be repeated at a reduced approach RPM to determine the maximum speed at which a hard turn can be made without throttle adjustment. The following data should be recorded or derived and presented as shown in Table 6: a) b) c) d)
Time of test, and base course. Rudder angle. Compass reading to nearest degree every 10 seconds that ship is in the turning maneuver. Time elapsed and advance from start of rudder movement and clearing base course using GNSS data
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e) Ship's position at suitable intervals from GNSS equipment. If GNSS equipment is not installed, ship's track should be obtained by radar, shore station tracking, or visual observation of the wake. Observation intervals should coincide with heading data intervals. f) Shaft RPM at beginning and end of each circle. g) Depth of water and sea condition. h) Wind direction and velocity. i) Trial draft fore and aft. Turning circle tests may be specified at depths, drafts, speeds, and rudder angles other than those given if ship's maneuvering characteristics require further exploration. At the completion of each of the turning circle tests a pullout test may be performed to provide information on the ship's dynamic stability. For further information see paragraph 3.10. Turning circles should be plotted and tactical dimensions reported as illustrated in Figure 1 and Figure 2. Figure 1 shows the historic test resulting in measures of advance, transfer, and tactical diameter. Using today’s high precision position tracking systems, maximum ship advance and transfer measurements are included (see Figure 2). The entire swept path can also be depicted in the plot .
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Figure 1 Turning Circle Definitions (Courtesy of ABS)
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Figure 2 Turning Circle Test
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Table 6 Turning Circle Test Data Time (sec)
Heading from Base Course
NOTE: Representation of the ship should be a line scaled in length, oriented to and located on the circle such that the stern clearance track can be determined. Ship Name Test Data Time Test Began Base Course Rudder Angle Shaft RPM (Beginning) Shaft RPM (End) Depth of Water Sea Condition Wind Velocity Trial Draft (fwd) Trial Draft (aft) Maximum Drift Correction Distance Direction Tactical Diameter Final Diameter Time to Clear Base Course Advance to Clear Base Course Maximum Advance any Part of Ship Max. Departure from Base Course Drift Correction Direction
Rate
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3.8 "Z" MANEUVER* The "Z" Maneuver is shown in Figure 3 and may be identified as the Zig-Zag Maneuver or the Kempf Maneuver. With the ship in trial condition and proceeding ahead into the wind at the maximum trial shaft RPM, with either steering power unit, move the rudder at maximum rate and perform the following maneuvers: 1. Move the rudder from center to 10 degrees right - hold until ship's heading is 10 degrees to the right of the original course. 2. Move the rudder from 10 degrees right to 10 degrees left hold until ship's heading is 10 degrees to the left of the original course. 3. Move the rudder from 10 degrees left to 10 degrees right hold until the ship's heading is 10 degrees to the right of the original course. 4. Move the rudder from 10 degrees right to center hold until original heading is restored. Steady on original course. In some cases it may be desirable to modify the test so as to include a fifth rudder movement in order to collect additional data for other analysis. A pullout test may also be performed upon completion of the "Z” Maneuver. The standard type "Z" Maneuvers are the 10°/10° (which is a 10° rudder change and a 10° change of heading at next rudder execute, etc.) and the 20°/20° tests. Both the 10-10 and 20-20 maneuvers are specified in the IMO Standards, the latter primarily because of the large body of trials data available for this maneuver. The trials data base for evaluating results of the 20-10 maneuver is not large. Thus conducting this trial maneuver may not be that useful. There is a growing body of data, however, for 5-5 and 5-1 “Z” maneuvers because these maneuvers are more quickly accomplished than 10-10 or 20-20 maneuvers and they can clearly identify unstable ships and potentially eliminate or reduce the cost of time-consuming spiral maneuvers. At least one standard type "Z" Maneuver should be performed at the test speed. The 10°/10° test is preferred as it provides better discrimination between ship characteristics. The 20°/20° test should also be included to provide a comparison with data available from earlier tests. The 20°/10° tests are frequently performed in long towing basins, in narrow waters, and for reasons of special analysis. The essential information to be obtained for the "Z" Maneuver is the initial turning time, time to second execute, the time to check yaw, the angle of overshoot, and the magnitude of the overshoot. In addition an analysis of the "Z" Maneuver furnishes values of the steering indices K (gain constant) and T (time constant) associated with linearized steering theory (See "Analysis of Kempf's Standard Maneuver and Proposed Steering Quality Indices", First Symposium on Ship Maneuverability, David Taylor Model Basin Report 146, 1960 by K. Nomoto). The following data should be recorded or derived: a) b) c) d)
Time of test and base course. Time rudder is held at each position. Shaft RPM at beginning and end of test. Depth of water and sea condition.
Record data as shown on Table 7 and prepare a plot of rudder position and ship's heading changes during the maneuver. Indicate the tactical dimensional characteristics as illustrated in Figure 3. Tests may be specified at different ship speeds, depths of water, ballast conditions, and rudder angles if more data is required. 32
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Figure 3 "Z" Maneuver Test (Courtesy of ABS)
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Table 7 "Z" Maneuver Test Data Ship Name Test Date Time Test Began Base Course Shaft RPM (Beginning) Shaft RPM (End) Depth of Water Sea Condition Wind Direction Wind Velocity Trial Draft (fwd) Trial Draft (aft) Elapsed Time (sec)
Ship Heading
Departure from Course
Rudder Movement
Elapsed Time (sec)
1 Start 100 R Attain 100 R 2 Start 100 R Attain 100 3 Start 100 L to 100 R Attain 100 R 4 Start Center 5 Attain original course
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3.9 INITIAL TURNING TESTS The initial turning tests provide information on the transient heading condition between steady state approach and change of heading after application of the rudder as shown in Figure 4 and Figure 5. These tests should be performed with rudder angles of 10 degrees and 20 degrees. The time history of heading and yaw rate should be plotted. These tests may be performed in conjunction with turning circle tests and partially with "Z" Maneuvers, which are described in Sections 3.7 and 3.8, respectively. With the ship in the specified trial conditions and proceeding ahead at the designated speed and on a steady course, conduct the maneuver as follows for two separate tests, one at a rudder angle of 10 degrees and one at a rudder angle of 20 degrees. Lay the rudder over to the specified setting and hold until the ship has moved at least 2.5 ship lengths or until the turning becomes steady. IMO standards require initial turning performance only at 10 degrees rudder angle (10 degree change of heading angle when the ship has moved 2.5 ship lengths). The following data should be recorded on Table 8: (a) Before starting the test: 1) 2) 3) 4) 5)
Time of test and base course. Ship speed and corresponding RPM. Wind velocity and direction. Depth of water and sea condition. Trial draft.
(b) During the test: Rudder Angle. Both heading and rate of change of headings should be plotted for each rudder position.
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Figure 4 Initial Turning Test, Change of Heading Plot
Figure 5 Initial Turning Test, Plot of Change of Turning Rate
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Table 8 Initial Turning Test Data Rudder Angle Elapsed Time (sec)
Ship Name Heading Test Date Time Test Began Base Course Rudder Angle Shaft RPM (Beginning) Shaft RPM (End) Depth of Water Sea Condition Wind Direction Wind Velocity Trial Draft (fwd) Trial Draft (aft)
3.10 PULLOUT TESTS The pullout test gives a simple indication of a ship's dynamic stability on a straight course. The ship is first made to turn with a certain rate of turn in either direction, upon which the rudder is returned to amidship. If the ship is stable, then the rate of turn will decay to zero for turns to both left and right. If the ship is unstable, then the rate of turn will reduce to some residual rate of turn. The pullout tests must be performed to both left and right to show possible asymmetry. Normally, pullout tests are performed at the end of the turning circle tests, "Z" Maneuver, and initial turning tests, but they may be carried out separately. Each test consists of a left and right run as follows: 1. Attain a steady turning rate with a fixed rudder angle of approximately 15 degrees to 35 degrees. The engine control settings are kept constant. 2. Return rudder to amidships position, and record time. 3. Record heading, ship speed, and propeller RPM at 10 second intervals. These recordings should be continued for 12 readings, i.e., 120 seconds, past the interval in which steady state, i.e., a constant rate of turn, is obtained. 4. The resulting data should be captured as shown in Table 9 and then plotted as in Figure 6. This test is to be conducted at “a fixed rudder angle of approximately 15 to 35 degrees.” ISO specifies a rudder angle of 20 degrees. Running the test at other rudder angles may be useful.
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Figure 6 Pullout Test (Courtesy of ABS)
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Table 9 Pullout Test Data Time (sec)
Heading from Base Course
Speed (knots)
RPM
Ship Name Test Date Time Test Began Base Course Rudder Angle Shaft RPM (Beginning) Shaft RPM (End) Depth of Water Sea Condition Wind Direction Wind Velocity Trial Draft (fwd) Trial Draft (aft)
Condition
Initial Stbd
Final
Port
Stbd
Rudder Angle Rate of Turn (0/sec) Ship Speed (knots) RPM Instability in Degrees (Residual Rate of Change of Heading)
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3.11 THE DIRECT SPIRAL TEST The direct spiral test is an orderly sequence of turning tests to obtain a steady turning rate versus rudder angle relationship. This test can be a time consuming test to perform, especially for large and slow ships. The test is very sensitive to weather conditions and a significant amount of time and care is needed for the ship to obtain a steady rate of change of heading after each rudder angle change. The IMO requires a determination of the instability loop width for all unstable ships. As spiral tests are expensive to conduct, these tests probably do not need to be conducted if positive stability is clearly demonstrated from results of pullout tests or from a 5-5 or 5-1 “Z” maneuver. Where any question about stability exists a spiral test will be required. Ship's speeds most unfavorable to directional stability at trial draft should be estimated and specified for the test. Since this test may be adversely affected by the elements, it should be conducted only in relatively calm seas, i.e., sea state 3 or less, and winds of less than 10 knots. With the ship in the specified trial condition and proceeding ahead at the designated speed and on a steady course, using either steering power unit, conduct the maneuver as follows: 1. Turn the rudder 20 degrees to right and hold until the turning rate becomes steady. 2. Move the rudder to the following settings and hold at each until the turning rate in degrees per second becomes steady: 20oR, 15oR, 10oR, 5oR, 3oR, 1oR, 0o, 1oL, 3oL, 5oL, 10oL, 15oL, 20oL, 15oL, 10oL, 5oL, 3oL, 1oL,0o, 1oR, 3oR, 5oR, 10oR, 15oR, 20oR A steady turning rate is the difference between successive ship headings and should be noted as the test progresses. When these differences are reasonably constant for at least six consecutive readings, data is recorded and the rudder is ordered to the next setting. The following data should be recorded as indicated in Table 10: (a) Before starting the test: 1) 2) 3) 4) 5)
Time of test and base course. Ship speed and corresponding RPM. Wind velocity and direction. Depth of water and sea condition. Trial draft.
(b) During the test: 1) Rudder angle. 2) Gyro compass reading every 10 seconds to the smallest fraction of degree readable. Rate of change of headings should be plotted for each rudder position. For a stable ship the plot of turning rate versus rudder angle will appear as shown in Figure 7 (a). In cases where the ship is dynamically unstable the plot of the turning rate will appear as shown in Figure 7 (b). As the rudder angle is reduced the ship will continue to appear to be turning steadily in the original direction even after the rudder is turned to the opposite side. At a certain stage the yaw direction will abruptly change to the other side and the yaw rate versus rudder angle relation will not be defined by a single curve. Upon completion of the test the results will display the "hysteresis loop," as depicted in Figure 7 (b).
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Table 10 Direct Spiral Test Ship Name Test Date Time Test Began Base Course Rudder Angle Shaft RPM (Beginning) Shaft RPM (End) Depth of Water Sea Condition Wind Direction Wind Velocity Trial Draft (fwd) Trial Draft (aft) Data for Step No. Time (sec)
Ship Heading
Rudder Angle Change in Ship Heading
(Consistent for 6 consecutive readings)
Notes: A total of 6 readings of constant rate of heading change is needed to calculate average rate in Degrees/Second. This calculation is done for each step. Step
Rudder Angle
1 2 3 4 5 6 7 8 9 10 11
20 R 15 R 10 R 5R 3R 1R 0 1L 3L 5L 10 L
Constant Rate of Change in Ship Heading (Deg/Sec)
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12 13 14 15 16 17 18 19 20 21 22 23 24 25
15 L 20 L 15 L 10 L 5L 3L 1L 0 1R 3R 5R 10 R 15 R 20 R
Step
Yaw Rate (Deg/Sec)
1 2 3 4 5 6 7 8 9 10 11 12 13
1.0 R 0.8 R 0.6 R 0.4 R 0.2 R 0.1 R 0 0.1 L 0.2 L 0.4 L 0.6 L 0.8 L 1.0 L
Rudder Angle
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Figure 7 Direct Spiral Test
3.12 THE REVERSE SPIRAL TEST The reverse spiral test may provide a more rapid procedure than the direct spiral test in defining the instability loop as well as the unstable branch of the yaw rate versus rudder angle relationship. In the reverse spiral test the ship is steered at a constant rate of turn and the mean rudder angle required to produce this yaw rate is measured. Data is recorded and reported as shown in Table 11. Figure 8 shows the plot of the data gathered for an unstable ship. The necessary equipment is a properly calibrated rate of turn indicator and an accurate rudder angle indicator. Accuracy can be improved if a continuous recording of the rate of turn and the rudder angle are available for analysis. In certain cases the test may be performed with the automatic steering devices available onboard. Prior to the conduct of the test, the rate of turn indicator calibration may be checked by timing turns using the gyrocompass. If manual steering is used, the instantaneous rate of turn should be visually displayed to the helmsman, either on a recorder or on a rate of turn indicator. Points on the curve of yaw rate versus rudder angle may be recorded in any order using the reverse spiral test technique. The procedure for obtaining a point of the curve should be as follows: The ship is made to approach the desired rate of turn, by applying a moderate rudder angle. As soon as the desired rate of turn is obtained, the rudder is actuated such as to maintain this rate of turn as precisely as possible, using progressively decreasing rudder motions until steady values of speed and 43
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rate of turn have been obtained. Steady rate of turn should usually be obtained fairly rapidly since rate-steering is easier to perform than normal compass steering. The test should be performed at the following steady rates of turn in degrees per second: 1.0R, 0.8R, 0.6R, 0.4R, 0.2R, 0.1R, 0, 0.1L, 0.2L, 0.4L, 0.6L, 0.8L, and 1.0L. The following data should be recorded: (a) Before starting the test: 1. 2. 3. 4. 5.
Time of test and base course Ship speed and corresponding RPM Wind velocity and direction Depth of water and sea condition Trial drafts
(b) The average rudder angle associated with each associated steady state turn rate measurement point. This procedure should be repeated for a range of yaw rates until a complete yaw rate versus rudder angle relationship is established, e.g., between 20 degrees left to 20 degrees right rudders. The results of the spiral tests should be presented in accordance with the diagrams provided in Figure 8. The pronounced "S" shape on Figure 8 illustrates a ship with instability, and this instability provides a hysteresis loop like that illustrated in Figure 7 (b), Unstable Ship, for the rate of change of heading.
Figure 8 Reverse Spiral Test (Courtesy of ABS) 44
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Table 11 Reverse Spiral Test Data Ship Name Test Date Time Test Began Base Course Rudder Angle Shaft RPM (Beginning) Shaft RPM (End) Depth of Water Sea Condition Wind Direction Wind Velocity Trial Draft (fwd) Trial Draft (aft) Data for Step No. Time (sec)
Rudder Angle Change in Ship Heading
Ship Heading
(Consistent for 6 consecutive readings)
Notes: A total of 6 readings of constant rate of heading change is needed to calculate average rate in Degrees/Second. This calculation is done for each step. Step 1 2 3 4 5 6 7 8 9 10 11 12 13
Yaw Rate (Deg/Sec) 1.0 R 0.8 R 0.6 R 0.4 R 0.2 R 0.1 R 0 0.1 L 0.2 L 0.4 L 0.6 L 0.8 L 1.0 L
Rudder Angle
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3.13 THRUSTER TESTS 3.13.1 Bow Thruster Tests In addition to the performance test data of flow thrusters obtained during dock trials, tests of bow thrusters at sea demonstrate thruster effectiveness in turning the ship. With the ship in trial condition, conduct the maneuvers below. It should be noted that reduced thrust may result unless submergence of the thruster axis of at least 0.8 times the thruster diameter is provided. Bow thruster tests for dry cargo ships in the trial ballast condition are severely influenced by sea and wind and should be conducted only in protected areas or in the open sea when sea conditions are exceptionally smooth. With the ship dead-in-water and heading into the wind, operate the bow thruster at full thrust for 10 minutes or the time it takes to change the ship's heading 30 degrees to left of the original heading, whichever occurs first. Reverse the bow thruster and repeat. The following data should be recorded on Table 12 during the test: 1) 2) 3) 4) 5)
Time of test and base course Compass readings to nearest degree every 10 seconds Depth of water and sea condition Wind speed and direction Trial drafts
ISO prescribes tests to be conducted also at slow ahead and slow astern speeds. As thruster performance is highly speed dependent, it is recommended that tests be conducted at both zero and slow ahead (say, 2 to 3 knot) speeds. If slow ahead test results show a significant effect of forward speed it will be prudent to also conduct tests at a slow astern when it is anticipated that the thrusters will be used during astern operations.
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Table 12 Thruster Test Data Ship Name Time of Test Base Course Depth of Water Sea Condition Thruster Name
Elapsed Time (Min & Sec)
0 Knots
Thruster Only Hdg 0 10 20 30
a
Trial Date Wind Direction Wind Velocity Trial Draft (Fwd) Trial Draft (Aft)
Change in Ship Heading 3 Knots
Rudder Only
6 Knots
Change in Hdg 0o
Thruster & Full Rudder Hdg Change in Hdg 0o
30 o Left
30 o Left
30 o Left
30 o Left
30 o Left
0o
0o
0o
0o
0o
Hdg
Change in Hdg 0o
Thruster & Full Rudder Only Rudder Hdg Change in Hdg Change Hdg in Hdg o 0 0o
NOTES: 1. Ship is to be heading into the wind at the beginning of each test. 2. If elapsed time reaches 10 minutes prior to 30 o change in ship heading, terminate the test at this point. 3. If Thruster is effective at 6 knots, ship speed is to be increased at 3 knot intervals until thruster is no longer effective. a Reverse Thruster and/or Shift Rudder
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3.13.2 Other Thrust Devices Other thrust devices such as stern thrusters and active rudders may be tested similarly to the descriptions in paragraph 3.13.1. The data as indicated in Section 3.13.1 and Table 12 are suitable.
3.13.3 Special Thruster Tests For tankers or other similarly configured ships where deep trial drafts are possible, additional special tests may be conducted to better define the effectiveness of thrusters when the ship has forward motion. The following tests may be conducted and data should be recorded: (1)
Ship moving ahead at shaft RPM corresponding to 3 knots: a) With the ship moving into the wind, use the thruster and full rudder to change the ship's heading 30 degrees to the left of the original heading. b) Use the thruster and full rudder to swing the ship from left 30 degrees to the right of the original heading. c) Repeat (1) (a) and (b) above, using full rudder without the thruster.
(2) Ship moving ahead at shaft RPM corresponding to 6 knots: Repeat maneuvers in (1) (a) through (c) above. (3) Ship speeds above 6 knots: Repeat maneuvers (1) (a) through (c) above in increments of 3 knots above 6 knots until the thruster is no longer effective.
3.14 QUICK REVERSAL FROM AHEAD TO ASTERN (“CRASH ASTERN” STOPPING TESTS) With the ship at trial drafts and proceeding ahead at maximum trial shaft RPM and normal machinery operating conditions, signal "Full Astern" while maintaining the rudder in the amidships position. Reverse the throttle at maximum allowable rate or move the automatic control lever in one motion to the full astern position. See paragraph 2.8 for the centralized control test. When the ship gains sternway, continue with the scheduled tests. The following data should be recorded on data sheets like Table 13 during the test: 1) Time of test and base course. 2) Prime mover parameters immediately prior to "Full Astern" signal. 3) RPM, torque, and significant prime mover parameters at frequent intervals during the maneuver. 4) Time of issuing astern order. 5) Time when propeller stops prior to reversal. 6) Time shaft starts astern or the propeller pitch is positioned for astern way. 7) Time to stop ship "Dead-in-Water". 8) Time to reach required maximum astern shaft RPM. 9) Ship's position at suitable intervals from GNSS equipment, so that a diagram of the reversal maneuver showing track and heading may be plotted. 10) Depth of water and sea condition. 11) Wind direction and velocity. 12) Ship's drafts. 48
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For the purpose of obtaining operating data, additional stopping tests may be conducted from other initial speeds and using other stopping aids such as rudder cycling, as agreed. Figure 9 displays the plotted trajectory.
Figure 9 Crash Stop Test (Courtesy of ABS
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Table 13 Crash Stop Test Data
Ship Name Time to Test Base Course Shaft RPM (Beginning) Depth of Water Sea Condition Wind Direction Wind Velocity Trial Draft (Fwd) Trial Draft (Aft) Final Heading
Ahead to Astern Trial Date Time to Start Shaft Astern Time to Ordered RPM Astern Time to Stop Ship Ahead Reach Note: Also to be included are maximum excursions of RPM, torque, data for diesel or gas turbine plants, at frequent intervals during maneuver.
Elapsed Time (min and Sec)
Distance Traveled Between Markers (Feet)
Cumulative Distance Traveled (Feet)
Marker 1
Substitute plot of ship's track if GNSS equipment is in use
2 3 4
Time of Test Base Course Shaft RPM (Beginning) Depth of Water Sea Condition Wind Direction Wind Velocity
Astern to Ahead Trial Draft (Fwd) Trial Draft (Aft) Final Heading Time to Start Shaft Ahead Time to Ordered RPM Ahead Time to Stop Ship Maximum RPM Ahead Torque (If Available)
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3.15 QUICK REVERSAL FROM ASTERN TO AHEAD With the ship in the trial condition and moving astern at maximum specified RPM, signal "Full Ahead" while maintaining rudder in the amidships position. Reverse throttle at maximum allowable rate. When the ship has gained headway, continue with scheduled tests. The following data should be recorded on data sheets similar to Table 13 during the test: 1) Time of test and base course. 2) Prime mover parameters immediately prior to "Full Astern" signal. 3) RPM, torque, and significant prime mover parameters at frequent intervals during the maneuver. 4) Time of issuing astern order. 5) Time when propeller stops prior to reversal. 6) Time shaft starts astern or the propeller pitch is positioned for astern way. 7) Time to stop ship "Dead-in-Water". 8) Time to reach required maximum ahead shaft RPM. 9) Ship's position at suitable intervals from GNSS equipment, so that a diagram of the reversal maneuver showing track and heading may be plotted. 10) Depth of water and sea condition. 11) Wind direction and velocity. 12) Ship's drafts. For the purpose of obtaining operating data, additional stopping tests may be conducted from other initial speeds and using other stopping aids such as rudder cycling, as agreed. NOTE: Attempts to determine stern reach from Dutch Log Data is not advised due to the erratic track of the ship when going astern and the effects of the propeller wash.
3.16 LOW SPEED CONTROLLABILITY MANEUVERS NOTE: When scheduling this maneuver for a steam plant, avoid placing it immediately after the astern endurance run, to reduce the severity of thermal shock. With the ship in the trial condition and proceeding into the wind on a steady course at 6 knots ahead, conduct the following maneuvers: 1. 2. 3. 4. 5. 6. 7. 8.
Turn the rudder to 10 degrees Right and hold for 30 seconds. Move the rudder to 10 degrees Left and hold for 30 seconds. Move the rudder to 0 degrees and hold for 30 seconds. Return to the base course and adjust speed to 6 knots with rudder at 0. Turn the rudder to 35 degrees R and hold for 30 seconds. Move the rudder to 35 degrees L and hold for 30 seconds. Move the rudder to 0 degrees and hold for 30 seconds. Return to base course and adjust to next speed.
Repeat the maneuver with speed decreased at 1 knot intervals until the speed at which the ship does not respond to the helm is determined. The following data should be recorded on Table 14: (a) Before starting the test: 1) Time of test and base course. 2) Ship speed and corresponding RPM. 3) Wind velocity and direction. 51
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4) Depth of water and sea condition. 5) Trial draft, fore and aft. (b)
During test: 1) Time to shift rudder, i.e., start and stop of actual rudder motion. 2) Time rudder is held at each position. 3) Maximum heading change from base course. Table 14 Low Speed Controllability Maneuvering Test Data Rudder Angle
Ship Name
Elapsed Time (Sec)
Trial Date
6K
Time of Test Shaft RPM
5K
4K
3K
Start 10R (6k)
Attain 10R
(5k)
Start 10L
(4K)
Attain 10L
(3k)
Start 0
a
a
b
Depth of Water
Attain 0
Sea Conditions
Start 35R
Wind Direction
Attain 35R
Wind Velocity
Start 35L
Trial Draft (Fwd)
Attain 35L
Trial Draft )Aft)
Start 0
a
a
Attain 0
Max. Departure from Base Course Rudder Angle
6K
5K
4K
3k
10R 35R 10L 35L a. Rudder angle is to be held for 30 seconds before starting next rudder movement b
b. Ship Speed is to be restored prior to starting the 35 rudder movement c. Test is to be continued in decreasing 1-knot intervals until the rudder is no longer effective.
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3.17 SLOW STEAMING ABILITY The ability to proceed at steady slow speed can be determined from the ship's speed associated with the lowest possible engine revolutions per minute in calm weather conditions. This is only intended to address engine conditions and not steering control. See Table 15 for a data sheet. Table 15 Slow Steaming Ability Ship Name
Trial Date
Time of Test Sea Condition Wind Direction Trial Draft (FWD) Trial Draft (AFT) Minimum Steady Shaft RPM
3.18 EMERGENCY PROPULSION SYSTEMS Demonstration of emergency modes of main plant operation and of separate "take home" propulsion systems should take place at the dock. Demonstration at sea is not required unless dockside operation is impossible or it is desired to check speed or maneuverability under emergency propulsion.
3.19 NAVIGATION EQUIPMENT Ship's equipment will normally be required for navigation during sea trials. Operability of this equipment should be proven dockside prior to departure and any additional calibration or adjustments necessary, performed during the initial phases of the sea trials. Where calibration or adjustments at sea are necessary, it is generally advantageous to have the services of the manufacturer's representative.
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4.0 STANDARDIZATION TRIALS 4.1 PURPOSE Standardization trials comprise a systematic series of runs over a measured distance to establish the relationship between speed, shaft power, and shaft RPM of a ship at designated drafts. These relationships are required for one or more of the following purposes: a) To fulfill contractual obligations. b) To obtain performance data to be used in the design of subsequent vessels. c) To determine the relationship between ship's speed and shaft RPM to be used by the owner as an aid to navigation after applying the corrections for service conditions.
4.2 GENERAL PLAN The general plan for conducting standardization trials provides for several consecutive runs at each selected speed point alternating in direction over a measured distance at substantially constant shaft power. The observed speeds, powers, and RPM are averaged for each speed point.
4.3 TRIAL AREA Considerations in selecting the trial area for speed runs are method of distance measurement, depth of water, and accessibility to builder's shipyard.
4.3.1 GNSS Deployment of Global Navigation Satellite Systems permits trial area selection solely on the basis of depth and accessibility.
4.3.2 Depth of Water The point at which depth of water affects a ship's speed is dependent on its speed, draft, and length. Minimum recommended depth for standardization runs is given in Section 1.6.2.
4.4 WIND AND SEA The effect of wind on standardization can be very serious and should be considered carefully in conducting a trial. The effect of wind varies widely with the wind direction and duration, the type of ship, its speed, and other conditions. It is greatest for comparatively slow vessels having high bulky superstructures relative to the underwater body. For example, a high-sided, shallow-draft ship will be more affected by wind than a deeply laden seagoing tanker. The direction of the wind relative to the course is also an important factor. The hightest resistance occurs when the relative wind is about 25 degrees off the bow but remains relatively high from 0 to 45 degrees. The wind resistance becomes zero when the relative wind is slightly abaft the beam. Although the effects of wind described above may be largely eliminated by analysis, the calculation is only approximate and, therefore, the correction should not be allowed to become too great, if accurate trial results are required. Furthermore, many ships require helm to counteract the aerodynamic effect of the wind. This causes increased drag which cannot be eliminated by any of the customary methods of analysis.
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4.5 NUMBER OF SPEED POINTS If complete curves of SKW and RPM versus speed are to be obtained, measurements should be made at not less than four speeds covering the range from one-half power to maximum power. Below half power calculated values are sufficiently accurate. If a wide speed range is to be covered, as for highspeed ships, more than four power setting points should be used. Likewise, if the SKW versus speed curves may be expected to have definite discontinuities, sufficient additional points should be taken to develop this region. When the ship is fitted with a controllable pitch propeller, it may be desired to define the speed/RPM/SKW relationship for more than one pitch. In any case, tie points to be measured should be stipulated in ship's specifications to permit optimum scheduling.
4.6 COURSE SELECTION The course selected should be normal (perpendicular) to any swell to minimize vessel roll motion. For GNSS ranges, if the first run at a speed point is aborted, another run may be immediately initiated on the same heading. Alternate runs should be over the same water.
4.6.1 Length of Runs A length of the run of about one nautical mile after the plant is stabilized at the power is sufficient to collect good data. Longer runs may be made if safety and environmental conditions permit.
4.6.2 Number of Runs No less than two consecutive runs in opposite directions should be used to determine a speed point. Three runs should be conducted when currents are known to be variable or when fixed ranges are used. If possible, current should be measured.
4.7 OPERATION OF THE SHIP The operating procedure, both on the bridge and in the engine room, should be directed toward maintaining essentially constant shaft power while on the measured course. The measured course must be approached on a straight run having the same heading as the course and should be long enough to permit accelerating the vessel to the speed corresponding to the shaft power applied, prior to reaching the measured course. This acceleration is required to regain the speed lost in turning and to increase the speed between points. The length of the approach run to accomplish this is a function of the ship's displacement, resistance characteristics, the speed range over which the ship must be accelerated, and the manner in which the machinery is operated. Three and one-half nautical miles is a nominal value which will be found acceptable for most ships. Turns at ends of the runs should be made with not more than 10 degrees rudder, if practicable, to avoid excessive deceleration. During the approach run, the ship should be kept on course with minimum rudder to retard the ship as little as possible. If practicable, the run over the measured course should be made with the rudder held stationary at the minimum angle necessary to maintain a straight course. Careful steering during the approach run should make this possible, however the use of an autopilot is recommended. It is better to allow the ship to swing slightly off the exact compass course rather than to steer constantly. Figure 10 shows a typical standardization course.
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Figure 10 Typical Standardization Course
It is essential that the shaft RPM be steadied prior to entering the measured course. Throttle and machinery operating conditions should not be adjusted during the run. However, to shorten the approach run at low speeds it is permissible to increase the power on the turns provided the power is decreased promptly when the ship has straightened away. When increasing to a higher speed point, power should be increased when the turn is begun. When reducing to a lower speed point, power should be held until the turn is complete.
4.8 DATA REQUIREMENTS See Table 16 for a Data Sheet for speed and power data recording. The following data should be recorded during standardization trials: a) Elapsed time for each run over the measured distance to determine speed and RPM. b) Total shaft revolutions for each run over the measured distance. c) Average propeller torque if torsionmeter is installed; if not, see Section 2.5.5 for means for determining shaft power from internal combustion engines or 2.6.3 for gas turbines. d) Sufficient data to determine the displacement and trim of the ship. e) Clock time at start of each run over the measured distance to identify run and for use in the trial analysis. f) Ship's heading for each run over the measured distance. g) A record of any unusually large rudder angles used on the measured distance or on the straight approach to it. h) The approximate size and direction of waves on each run. i) Apparent Wind speed and direction for each run. j) Current conditions from current tables or from other observations such as buoy positions, for each run. k) Depth of water for each run. l) Temperature and density of water in the Standardization Area. m) Air temperature
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Table 16 Standardization Trials Data Ship Name
Displacement
Trial Date
Water Temperature
Trial Draft (Fwd)
Water Depth
Trial Draft (Aft)
Air Temperature
Speed Point
Run
I
1 2 Avg
II
1
Shaft Power
STANDARDIZATION RESULTS Total Distance Elapsed Revolutions Traveled Time
RPM
Knots
2 Avg 1 2 Avg 1 2
III
IV
Avg Etc. Speed Point
Run
I
1 2
II
1 2
III
1 2
IV
1 2
Time of Trial
Heading
TRIAL CONDITIONS Wind Waves (Estimated) (Estimated) Vel. Dir. Height Dir.
Current (Estimated) Vel. Dir.
Water Depth
Etc.
NOTES:
1. Record data for additional speed points or additional runs at a given speed point when applicable 2. Speed/Power and Speed/RPM curves should be appended to this figure. 3. Type of range used _____________.
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4.9 ORGANIZATION OF OBSERVERS The organization of the personnel involved in standardization trials should provide for clearly defined responsibilities with a single person in charge of run selection and acceptance.
4.10 INSTRUMENTATION FOR STANDARDIZATION DATA The following paragraphs recommend the methods for obtaining the data required in paragraph 4.8. Details of instrumentation installation, calibration and operation are covered in ISO 15016.2
4.11 COORDINATION PROCEDURE The following procedures may be used as a guide to give satisfactory coordination of a standardization run. For this sequence it is assumed that the ship is in the standardization area and on the approach leg for a standardization run: a) b) c) d) e) f) g) h) i) j) k) l)
Check that RPM is correct and propulsion plant is steady. Check that course is correct and area is free of traffic. Check that torque is steady. Check for zero acceleration if GNSS device is being used. Give "standby signals." Give "mark" signal to start the run. Monitor data for evidence of deviation. Give "standby signals." Give "mark" signal to end the run. Evaluate results of the run and announce the next run. Alter heading for leg toward turn. Make turn to reciprocal course.
4.12 TOLERANCES AND LIMITS The acceptable tolerances and limits for standardization trials are provided by Table 17. Table 17 Standardization Trial Tolerances and Limits Item
Tolerance or Limit
Difference in time by separate timing devices for a run
0.25%
Difference in total revolutions from separate revolution counters for a run
0.20%
Difference in RPM for each run from mean for each speed point
0.20%
Difference in RPM of any shaft of a multi-screw ship from the mean for a run provided the rated RPM for all shafts is the same
0.20%
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4.13 DATA REDUCTION During the trial, running plots of RPM, SKW, and speed should be made to check the accuracy and completeness of the data and proper functioning of the instruments. If plots are not smooth, pertinent logs and records should be examined critically. Data from separate observations should be plotted separately. If variance exceeds limits prescribed above, the values which plot smoothly with prediction may be retained and the misfit values discarded. After the trials are completed, the data should be averaged, instrumentation corrections applied, and the results tabulated and plotted. The RPM, SKW and speed for each speed point should be obtained by averaging the data from the two runs in opposite directions. If three runs are used, the run in one direction should be double weighted when averaged with the two runs in the other direction. For Trial Data and Report, see Section 6.0.
4.14 CORRECTIONS When standardization trial conditions are within the limits recommended in this section, corrections to trial data using standard correction factors such as for wind, waves and draft can be utilized. If recommended trial conditions cannot be met due to limited depth of water or wind conditions in the trial area, then additional corrections should be applied to the trial results and included in the trial report. Corrections for water temperature and density are normally of a minor magnitude and normally need not be included in the trial report. Corrections are also made if the draft (displacement) varies from the specified trial draft conditions based on model test data.
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5.0 INSTRUMENTS AND APPARATUS FOR SHIP'S TRIALS 5.1 GENERAL 5.1.1 Introduction The type and condition of the instruments and apparatus which provide data for evaluating the performance of a ship system are essential in determining instrument acceptability. The instrument type, precision, and the sea trial instrument plan beyond the ship's instrumentation should be specified in the contract. Instruments should be selected on the basis of ship system performance requirements and on the basis of the consequential cost for departures from ship systems target performance. If the contract and specifications are silent, it is essential that the shipbuilder prepare a suitable sea trial instrumentation proposal and calibration procedure. It is important to obtain the owner's concurrence at an early date so that the necessary provisions can be incorporated in the original design and other long lead time actions can be initiated as required. This section states the types of instruments available for measurement of each physical quantity pertinent to ship's machinery and systems. Characteristics of each type of instrument, which affects its applicability to ship use, is discussed briefly, leaving the general characteristics and installation methods to be discussed by reference to existing publications. Where such material is not available or where instruments or techniques are peculiar to sea trials, a more extensive coverage is provided.
5.2 TEMPERATURE MEASUREMENTS 5.2.1 Types of Instruments Five types of instruments are commonly used for temperature measurement. These are: a) b) c) d) e) f)
Thermocouples Liquid-in-glass thermometers Distant-reading vapor pressure thermometers Resistance thermometers Bimetallic thermometers Infrared (IR) temperature sensor
All types are readily available from reliable makers. For descriptions, characteristics, and application, refer to reference (c).
5.2.2 Thermowells and Temporary Installations Most permanent installations have the temperature measuring devices installed in a thermowell which is immersed in the fluid whose temperature is to be measured. Due to cost, temporary installations such as for sea trials, do not always warrant the installation of a temporary thermowell during the vessel's design stage. Liquid or bimetallic thermometers strapped on, or distant reading the numbers with sensing elements secured to the surface to be measured have been used with some success when rapid fluctuations are not involved and precision is not required. Securing the thermocouple shorted ends to the fluid container at the point to be measured by drilling a shallow small hole in the surface and peening-in the thermocouple wire has been successful where rapid fluid temperature changes are not involved. The recommended procedure for the installation of temporary thermocouples or liquid thermometers is to remove an existing ship's thermometer and insert the sea trial measuring device in the same thermowell. The thermocouple should be in solid contact with the bottom of the thermowell and for high temperatures should be packed with a suitable material. A thermocouple installed in this manner will sense changes in temperature rapidly enough for sea trial requirements. To insure 60
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precision of fluid temperature measurement, consideration must be given in locating the sensing element to sense an average sample of the fluid. Where high pressures are involved, a thermowell is the safest installation.
5.2.3 Adapters for Sensing Elements If pressure, velocity, and temperature are moderate, the temperature sensing element of the measuring device can be introduced through a pressure gage test connection and held in place by an adapter. The adapter must be designed as a pressure boundary
5.2.4 Instrument compatibility Temperature measuring instrumentation should be compatible with the fluid, pressure and temperature in the system in which it is to be used.
5.2.5 Calibration and Sea Trials It is recommended that the ship's temperature instrumentation intended for use in obtaining sea trial data and all sea trial temperature instrumentation be calibrated in the shop or on the ship where practical within a two week period prior to sea trials. It is further recommended that the means for verifying the accuracy of important thermometers be available during sea trials.
5.2.6 Special Thermocouples Special thermocouples may be made to suit requirements. Instructions and material for the fabrication of thermocouples are outlined in the Instruments standards publication referenced in reference (d). A pressure test of these thermocouples is essential for safety.
5.3 PRESSURE MEASUREMENTS 5.3.1 Types of Instruments Pressure measuring instruments generally are constructed to measure the difference between the ambient atmospheric pressure and the pressure in a pipe or a pressure vessel. Indicating gages for pressure measurement are visually of the elastic type, i.e., Bourdon tube, bellows or diaphragm. For these, pressure is transmitted to an elastic member and the resultant motion displayed using a suitable scale. The following types are readily available from reliable makers: a) Bourdon type gages – The most common pressure measuring devices for vacuum, low, medium, and high pressure. b) Transducers - Convert pressure into pneumatic or electrical signals. They are utilized for remote sensing, particularly on automated ships. c) Bellows gages - Utilized for measuring low pressure differentials up to 50 PSI. d) Diaphragm gages Utilized for pressure 0-1 inch HG to 200 PS1G range and are adaptable for use with corrosive fluids of high temperature and high viscosity. e) Deadweight gages Installed for trials where great accuracy is required. They can be used only for systems without major pressure fluctuations. f) Liquid column gages (Manometers) - Utilize a variety of liquids in various hollow tube configurations and are used to measure gage, differential, atmospheric, vacuum, or absolute pressure.
5.3.2 Proper Connections and Protection Careful consideration should be given to the location and installation of the gages, pressure sensing connections to the ship system and pressure gage sensing lines configuration to maintain the gage 61
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sensing lines empty or full of liquid. Vacuum lines should be self-draining or be provided with loop seals to establish a known water leg. Means of venting gage lines should be provided adjacent to the gage or other suitable place. Gages should be connected to steam lines with a loop seal in the sensing line near the gage to protect the Bourdon tube from high temperature. Bourdon type gages should be protected from shock, violent pressure pulsation, and high temperature. The gage should be located in a zone of normal room temperature, protected from direct radiation and hot surfaces, and carefully mounted to avoid distortion or warping of the gage case.
5.3.3 Zero Adjust for Elevation Pressure gages installed in liquid and steam systems for test data should be zero adjusted for differences in elevation between the gages and their sensing points, where the adjustment exceeds the precision tolerance specified for the gage. The gage tolerance should not be greater than plus or minus one smallest scale division of the gage. Liquid gage sensing lines should be vented of gases to ensure that they are full of liquid. Steam gage sensing lines should be full of water when zeroing the gages, either from prefilling or from service condensation. Steps should be taken to ensure that vacuum gage sensing lines are empty. When ship's instrumentation is used for trial purposes, the correction for elevation differences between the gage and the sensing line connection to the ship system should be noted on the data sheet. This information should be so noted at the gage also. For installation and procedural steps to avoid water-leg error see reference (e).
5.3.4 Calibration and Sea Trials It is recommended that the ship's pressure instrumentation intended for use in obtaining sea trial data and all sea trial pressure instrumentation be calibrated in place within a two week period prior to sea trials. It is further recommended that the means for calibration of important gages be available during sea trials.
5.3.5 Barometers Barometers measure atmospheric pressure, and this information is required for determining absolute pressures from readings on Bourdon gages, deadweight gages, and open-end oil, mercury or water columns. Barometers are of two kinds, aneroid, i.e., bellows type, and mercury column. Either type, if properly designed, manufactured, and calibrated, and carefully handled, will be satisfactory. The barometer should be located in the same compartment as the instruments requiring correction to absolute values. Barometers can be calibrated and certified if necessary. When an absolute pressure gage is used, no barometer correction is necessary. See paragraph 5.3.9.
5.3.6 Manometers Manometers, also known as U-tube type gages, are liquid column gages that are widely used for measuring relatively small differences in gas pressure, viz., differences between a gas pressure and the atmosphere, or other pressure differential. They have an indication scale stated in inches, generally, which is attached beside the liquid column. Columns should be mounted vertically. The use of inclined gages at sea is not advised as they are affected too much by the motion of the ship. Mercury filled gages should not be used on systems containing copper or its alloys. If the mercury escapes into the system, these materials are degraded by amalgamation. Manometers installed on a high-pressure line should be provided with cutoff valves and a valved cross-connection to make it possible to avoid blowing out the liquid when putting the gage on the line. They must be carefully designed and constructed to withstand their rated operating pressures, which should not be exceeded for safety reasons. 62
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5.3.7 Manometers for Flow Measurement Manometers, for measuring differentials across flow nozzles or orifices at high pressure, may be purchased from makers of such equipment.
5.3.8 Liquid Columns Liquid columns for use at or near atmospheric pressure are simple to design and install, and the use of rubber or synthetic hose of a good grade is satisfactory for making connections to ordinary glass or plastic tubing. Generally, no indicating scale is provided with a liquid column. It is important to provide enough column height to avoid a blowout of the sensing fluid in either direction or add float check valves for that purpose.
5.3.9 Zimmerli Gage The Zimmerli gauge is a dependable manometer which has all the desirable features of a manometer but none of its disadvantages. It is easily and rapidly filled, and boiling of the mercury to remove air is totally unnecessary. The Zimmerli gauge is always in working condition, since any air which may have entered the reference limb can quickly be removed without disconnecting the gage. The glass will not be broken by a sudden release of the vacuum.
5.3.10 Absolute Pressure Gages These gages are special mercury columns with one end evacuated and sealed, so that the gage may be used directly to measure absolute pressure. See reference (f). They are very useful for measuring condenser pressures and may replace an open-end mercury column and barometer.
5.3.11 Gage Protection from Pressure Pulsation When measuring a hydraulic system pressure subject to severe pulsation, dampening should be provided either by installation of snubbers or judicious throttling of the gage cutout valve.
5.3.12 Further Information Reference (f) provides a complete description of the types of pressure measuring instrumentation, the installation, and calibration procedures for each.
5.4 FLOW MEASUREMENTS 5.4.1 Types of Instruments During sea trials, fluid flow needs to be measured. Coriolis type flow meters that calculate mass flow directly are currently popular. Flow can also be measured by positive displacement meters, turbine meters, variable area meters, metering flow nozzles, orifices or venturi tubes.
5.4.2 Positive Displacement Flow Meters A positive displacement flow meter may be of either the nutating disk or piston type. Prior to installation for sea trials, meters involved in determining propulsion plant performance should be calibrated over the expected flow range using a fluid at the same viscosity and temperature as expected to be measured during sea trials. Unless specified, post sea trial calibrations of meters should not be required if trial results are as predicted. The following instructions should be followed during the installation and use of positive displacement trial meters: a) Meters should be mounted in the horizontal position. b) Dirt or other foreign matter should be kept out of the meter during installation and use. A strainer installed upstream of a sea trial water meter is desirable.
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c) Meters should be installed and back pressure maintained so that they will be kept filled with liquid at all times. This is particularly important when measuring hot fluids where pressure changes close to the meter can cause the fluid to flash into vapor. Air or vapor passing through a meter will produce an error in the reading and may damage the meter. d) Meters should be located on the discharge side of the pump and preferably on the inlet side of heaters. Pressure drop across the meter at maximum expected flow should be determined and included in the system design. e) If a control valve is used, it is preferable to locate it on the discharge side of the meter. f) Meter should be used to measure only the liquids for which it was designed. g) The meter size should be chosen so that it will operate as near its rated capacity as possible. When precision is required readings below 10 percent of the rated meter capacity should be avoided. h) Since these meters are essentially volume-flow measurement devices, the density of the fluid is necessary to determine the mass flow. This requires precise temperature measurement of the fluid in the line connected to the meter. Upstream fluid temperature is preferred. i) Meters of this type are usually designed for and made of material having specific temperature limits, which should not be exceeded. The operating temperature range for any meter will be provided by the manufacturer. j) The precision of these meters is degraded by fluid densities errors, wear, corrosion, dirt deposits, and friction. Care should be exercised to eliminate these causes of errors insofar as possible. k) Systems should be thoroughly flushed before the installation of meters. Pre-Sea Trial operation of the system should be performed without meters unless checking meter operability. This will help prevent meter malfunction during trials due to dirt accumulation.
5.4.3 Meter Installation for Precise Measurements For precise liquid measurements, e.g., fuel rates for guarantee purposes, two identical positive displacement flow meters installed in series are recommended to insure no loss of data due to failure of a meter, and to provide a check measurement. If meter bypasses are installed, each should be fitted with two block valves and a vent between them so that absolute closure can be verified. A preferred arrangement is to provide individual bypass lines for each meter with the meter isolating valve and differential pressure gage connected to the meter inlet and outlet to indicate when the meter is sticking. A sampling connection should be provided in the active line upstream of the meter.
5.4.4 Orifice Plate, Flow Nozzle, and Venturi Tube Fluid flow measurement may also be accomplished by differential pressure measurement across an accurately designed orifice plate, flow nozzle or venturi tube. Reference (g) provides a complete description of orifice, flow nozzle, and venturi flow measurement design and installation procedures including differential pressure indication secondary element identification. See the meter manufacturer's information for specifics about the accuracy and installation requirements.
5.4.5 Indicating and Recording Mechanism for Orifice Plate, Flow Nozzle, and Venturi Tube Commercial flow meters of the orifice or nozzle type usually include an indicating and recording mechanism. The errors in this mechanism, due to friction and paper displacement, may be determined by connecting a suitable liquid column differential pressure gage in parallel with the indicator or recorder to obtain a direct reading of the differential. To convert this reading to a mass flow value, it is necessary to know the absolute pressure upstream of the device, the fluid temperature, the size and type of orifice or nozzle, the inside diameter of the pipe, and the flow coefficient of the orifice or nozzle. References (h), (i) and (j) will be helpful for this determination. 64
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5.5 TORQUE AND POWER MEASUREMENTS 5.5.1 Power Determined Indirectly Shaft power is the primary performance parameter for ship propulsion plants. Brake power may be determined by measuring the engine RPM and mean indicated pressure of a piston engine. The electrical input to a propulsion motor together with the motor’s efficiency versus power data can be used for an electric motor. These methods, however lack precision and are dependent on dimensional and/or efficiency data or estimates furnished by the manufacturer of the machinery being tested. For methods of determining power which do not involve direct measurement of torque, consult references (k), (1), (m), (n), (o), and (p).
5.5.2 Power Determined From Torque Measurements Propulsion power derived from propeller shaft torque and revolutions over a measured time interval is more exact and provides the desired independence. Some ship installed systems have power measurement and indicator systems which electronically integrate torque and RPM signals. Such systems are valuable for trend studies of ship operation but can lack precision, convenient calibration and zero setting features. However, commercial torsionmeters are available with sufficient precision and reliability for use during sea trials. The calibration of ship installed systems may need to be accomplished using a sea trial torsionmeter. Torsionmeter installation, calibration, and checkout for use on sea trials, should be supervised by competent personnel, preferably by those who have had actual installation, calibration, and operating experience with the type of meter selected or have been specially trained for these tasks. Installation, calibration, and operating instructions are provided by the equipment manufacturer, and they should be followed explicitly.
5.5.3 Shaft Torsionmeters A shaft torsionmeter is an instrument for measuring the torsional deflection of a shaft, over a known portion of its length, while the shaft transmits power from the engine to the propeller. Since torsional deflection is proportional to the transmitted torque, it can be combined with measured shaft revolutions per minute and suitable calibration and physical constants to calculate shaft power. Torsionmeters differ chiefly in the method of gaging torsional deflection. The following types are available:
Variable mutual-inductance gages Resistance-wire strain gages Acoustic-wire strain gages Phase-shift gages Permeability-magnetic
Technical endorsement of any type or make of torsionmeter is contrary to Society policy; however, the following guidelines should be observed in making a selection of trial meters to provide data for demonstration of power or fuel rate contractual requirements: a) b) c) d)
Inherent accuracy should be better than design margins. Zero torque meter readings should be determinable during shaft calibration and at sea. Meter should be suitable for taking shaft calibration readings. All components should be sufficiently rugged and provided with sufficient protection to operate indefinitely in the adverse environment usual for ship installations. e) Meter should be capable of operating on the quality of electrical power available on ships. 65
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5.6 SHAFT-POWER METERS The output of torque measuring devices have been integrated with shaft RPM and designed to read power directly as a permanently installed system on ships. Secondary instrument errors may contribute to overall inaccuracy of these systems and make their use for sea trials unsuitable except as a check instrument. There are benefits to having these meters as a backup to the sea trial torsionmeters. The shipboard meter may be used as the sea trial meter when the owner and contractor agree during their sea trial planning. See reference (p).
5.7 SHAFT THRUSTMETERS 5.7.1 Purpose of Thrustmeter A thrustmeter is an instrument for accurately measuring the thrust developed by the propeller in the axial direction of the shafting. By combining the thrust with the measured speed of the ship, the thrust power can be calculated and compared with model test data.
5.7.2 Useful Installations Although the thrustmeter is not a required instrument for acceptance trials, it may be desired to install such an instrument on "first of a class" ships having an innovative propeller design or a stern configuration where an evaluation of the design propulsion factors is desired. Thrustmeter data in conjunction with other standardization sea trial data afford the only practicable means of breaking down the propulsive efficiency into its various components; it is the only means of evaluating the performance of a full-sized propeller and of determining the resistance of the ship as a check against model scale factors.
5.7.3 Types of Instruments All thrust-measuring devices which have been employed in recent years for shipboard testing belong to one of three general types. They may be described as those in which the thrust is measured by: a) Deformation of an elastic member. b) Hydraulic pressure in cells. c) Strain gage load cells. Any of these types can be designed to suit the range of thrust expected and the configuration of the ship's propulsion and provide satisfactory data. If a thrust meter is specified, the type and design must be established in the early design stages of the power train. Measurement of axial motion of the shat aft of the thrust bearing using proximity probes can be used to provide measurements of thrust vibrations. Instrument manufacturers must be consulted at the early design stages regarding measurements and all details of configuration and operation of instruments obtained from them. Accordingly, no attempt will be made here to provide such information.
5.8 SHAFT SPEED MEASUREMENTS 5.8.1 Propeller Revolution Counters Preferably, propeller shaft speed should be obtained from dual propeller revolution counters which can be shifted electrically on a signal. Counters may be actuated by electrical impulses initiated by interrupter slip rings located on the main shaft, or by microswitches, or by selsyn units driven by any element in the main propulsion train. Care must be taken to have slip rings clean, smooth, and round to avoid false counts. Electric counters located in the space aboard the ship that is designated for trials as the computing room, may be shifted either locally or from range observation station, where the start and end of the 66
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run is determined, to obtain total revolutions for a run. When standardizing a ship, an observer at a range station operates the shift-switch at the beginning and end of a run. The counter in use is read and reset to zero by the computer room observer before the next run. When not standardizing, the electric counter may be shifted by the trial signal system. The ship's counter should also be read on the same interval as the electric counter to obtain accurate backup data. For trials that do not include standardization or accurate fuel rate and water rate measurement, the installation of special counters is not essential. Sufficient accuracy is available from the permanently installed revolution counters read on the same established time interval as the sea trial signal system. Ship's shaft speed indicators in the engine room and on the bridge should be adjusted for minimum error over the operating range prior to sea trials. This requires detachment from the sensing point and driving the transmitter through the operating speed range at known RPM. All receivers which will be simultaneously operative should be actuated when calibrating. During sea trials, accuracy of shaft speed indicators should be checked by comparison with counters. The accuracy of the shaft revolution signal is particularly important when it is used as a control element.
5.8.2 Portable Tachometers and Speed Indicators Portable tachometers and speed indicators can be used to obtain rotating speeds of auxiliary machinery during sea trials and are not subject to the precision and reliability required of propeller revolution measuring equipment. When instantaneous speeds are necessary to evaluate transient conditions, speed recorders should be used. Recorders may be actuated by calibrated tachometer generators or electromagnetic pickups driven by the unit to be observed. Sometimes the signal for the installed tachometer can be utilized to drive the recorder. When totally enclosed machinery is used it may be difficult or sometimes impossible to reach the shaft with the ordinary type of tachometer, and in such cases the vibrating-reed frequency indicator may be used. Care must be taken to avoid reading harmonics of the fundamental speed. The stroboscopic speed-measuring instrument may be useful for measuring frequency of motion of any moving part which is visible but where a mechanical tachometer is not suitable. These instruments operate on the principles of interrupting vision at the same frequency as the motion, whereby the moving part appears to stand still. The instrument has a frequency indicator to determine the frequency at which motion stops. Stroboscopes will also stop motion when they are set at any multiple of the speed of the machine. The operator should preset the stroboscope at the expected fundamental speed to avoid errors.
5.8.3 Additional 'Information For further details about types of instruments and precautions for their use to measure shaft speed see reference (q).
5.9 FLUE AND EXHAUST-GAS ANALYSES 5.9.1 Orsat Analyzer For trial purposes, historically a frequently used instrument for flue-gas analysis is the Orsat. Basically, all Orsats are identical in principle; that is, they all have a number of pipettes containing chemical reagents which absorb the respective gas constituent from the sample. The major difference
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in the various commercially available Orsats is in the design of the pipettes. Some Orsats have the contact type of pipette while others use the bubbling type of pipette. A contact type of pipette usually is filled with many small diameter glass tubes, rods, or in some instances, with a fibrous type of material. The purpose of the tubes, or rods, is to supply a maximum of exposed surface to which the required chemical reagent can adhere. As the gas sample enters the top portion of the pipette, the reagent is driven from the pipette into a reservoir. The gas, as it proceeds to occupy the entire volume of the pipette, passes over the wetted surface provided by the filler material. In the bubbling type of pipette, the gas sample enters the bottom of the pipette and the sample bubbles up through the chemical reagent. Filler material for providing exposed absorption surface is not required and, consequently, a volume of the reagent equal to the unabsorbed volume of the sample is displaced by the gas. The displaced reagent flows into a reservoir and remains there until the gas sample is returned to the collecting burette. A common type of Orsat is provided with a measuring burette and, usually, three pipettes. These are interconnected by a capillary manifold and appropriate stopcocks for routing the gas sample through the apparatus. The pipettes, when filled with the proper chemical reagent, will absorb volumes of carbon dioxide (CO2), oxygen (02), and carbon monozide (CO). The following absorbing reagents are used in the pipettes:
CO2 pipette - Potassium hydroxide solution O2 pipette - Alkaline solution of pyrogallic acid CO pipette - Acid solution of Cuprous chloride
The best results are obtained when these solutions are prepared immediately prior to testing. Full descriptions of the methods for preparing the solutions are stated in reference (ad). To process a gas sample to obtain an analysis, a known volume of flue gas is drawn into the graduated burette. In successive operations the gas sample is forced into the CO 2, O2, and CO absorbing pipettes. Before the sample is allowed to pass from one pipette to the next it is returned to the graduated burette. The measured difference in volume, after each individual gas has been fully absorbed, is considered as the amount of that particular gas present in the flue gas. The difficulty in obtaining a representative sample from a stratified gas stream is the greatest cause of error in gas analysis. There is no single correct method of sampling which is applicable in all cases. One method, which results in obtaining an approximately true sample, requires the taking of a number of simultaneous individual samples at different points in a given plane of a gas cavity or duct. Where high-temperature gas samples must be taken it is customary to use a water-cooled sampler. This sampler is generally constructed from materials similar to the ordinary open-end tube, usually of brass or stainless steel, used for sampling cool gases, but it is fitted with a water-cooled jacket. Water-cooled sampler tubes are superior to refractory tubes since there is less gas composition change due to chemical reactions. Further, refractory tubes are often brittle and subject to breakage if improperly handled. Thus, refractory tubes are usually inferior for service and functional reasons. A continuous gas sample is most desirable as it eliminates the need for purging the sampling lines of the residue from a sample taken previously. For this purpose, an air aspirator generally is used. For sea trials, continuous temporary lines should be run from each uptake through a valved manifold to an air aspirator powered by the ship's compressed air system. The arrangement of valves should allow a new sample to be pulled from either uptake to the Orsat equipment for each sample reading. Two sampling lines are necessary when regenerative type air heaters are installed; one is connected
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upstream and one downstream of the air heater. Both are needed to determine air leakage across the air heater. The comparative readings can be used to compute the corrected stack temperature. Lead, glass, or gum-rubber piping should be used to connect the sampling tube to the gas analyzer. Copper or brass piping also is satisfactory, but in no case should ferrous materials be used.
5.9.2 Manual and Automatic Types of Flue Gas Analyzers There are a variety of manual and automatic types of gas analyzers available as portable or ship installed equipment. These kinds of instrumentation are valuable for determining equipment performance and the content of exhaust gases which enter the environment. See reference (ac) for further information about measuring particulate matter in a gas stream. Some automatic types of gas analyzers will indicate percent oxygen, percent carbon dioxide, net stack temperature, percent excess air, carbon monoxide concentration, particulate matter in the flue gas, and the percent combustion efficiency. Instrument manufacturers need to be consulted for details regarding gas sampling requirements and measurement data available on various instruments for the specific flue gases exhausting from the ship. The shipbuilder and owner may agree to use ship installed flue and exhaust gas analyzers to collect equipment performance data during the conduct of sea trials. The sea trial plan should specify the analyzers to be used, when they are to be used, and the approved methods for analyzer calibration.
5.9.3 Additional Information For more information see reference (ad) and contact manufacturers of equipment.
5.10 VISCOSITY MEASUREMENTS The measurement of viscosity is sometimes required during sea trials. The viscosity of fuels for the propulsion plant or auxiliaries, or for cargo may be necessary to resolve problems during sea trials. For measurement information see reference (af).
5.11 ELECTRICAL MEASUREMENTS 5.11.1 Measuring Devices For ships with alternating current, a portable analyzer equipped with an ammeter, voltmeter, powerfactor indicator meter, and kilowatt meter will be useful. Isolated usage of the meters is also possible. For most A.C. motor installations the input current is sufficiently reliable for indicating the motor load. A portable tong-type ammeter will be found satisfactory for measuring the motor current. Since this meter clamps around the cable one phase at a time and does not have to be inserted in the circuit, it is more convenient to use than the analyzer for this application. A portable poly-phase wattmeter may be installed to assure accurate measurement of generator loads. Additional electrical measuring equipment is available for evaluation of diesel electric plants including harmonics, and hot spots in switchboards, load centers, and power panels.
5.11.2 Calibration Recently calibrated shipboard electrical instruments should be sufficiently accurate for all uses except special performance tests. Before sea trials they should be carefully inspected for signs of damage, and the due dates for the next calibration should be following the completion of sea trials.
5.11.3 Additional Information Electrical measuring Instruments and testing apparatus are covered in detail by reference (k).
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5.12 WIND SPEED AND DIRECTION MEASUREMENTS Wind speed and direction can be measured by a number of different mechanisms.
5.12.1 Cup Anemometer Wind speed is often measured by a cup anemometer which gives apparent or relative wind speed. Apparent wind speed occurs by combining ship's velocity and true wind velocity. Any instrument which measures wind speed may be used to measure apparent wind speed.
5.12.2 Indicators One type of indicator flashes a light every time one-sixtieth of a nautical mile of wind passes the transmitter. The number of flashes per minute is the apparent wind speed in knots. An electric counter can be connected in the flasher circuit and controlled by an observer on the bridge to state the distance traveled during standardization runs. The average apparent wind speed is obtained by dividing the counter reading by the elapsed time across the course. Another type of instrument indicates apparent wind speed instantaneously and continuously and requires no timing. This type of indicator is recommended because of the convenience in obtaining readings from it.
5.12.3 Biram Anemometer The Biram type of anemometer has a register which records linear feet when a gear train is engaged. The register can be zeroed after reading it. Velocity in feet per minute is obtained by dividing the register reading by the elapsed time in minutes. Each instrument requires individual calibration. It is important that the anemometer face squarely into the air stream and that average readings are obtained. For best results, the diameter of the air stream should be several times the diameter of the anemometer. Care should be taken to ensure that the motor bearings are kept clean and free from lint, dirt, or grease, because a lack of cleanliness will cause friction or drag and seriously affect the accuracy of the readings.
5.12.4 Direct-Reading Anemometer The direct-reading anemometer has a vaned rotor and a dial which reads in feet per minute. The same precautions stated above for the Biram type, apply to the direct-reading anemometer.
5.12.5 Deflecting-Vane Anemometer The deflecting-vane type of anemometer indicates air velocity directly in feet per minute. This type of instrument is very useful in studying air currents in staterooms and measuring peak velocities. Other types of instruments, such as the heated thermocouple, the velometer, and the hot-wire anemometer may be used where the accuracy of such instruments is sufficient. They require frequent calibration and are of little use as a wind speed measuring instrument for standardization trials.
5.12.6 Wind Direction Indicator A wind-direction indicating system, which continuously indicates the apparent wind direction relative to the ship, is recommended for sea trials. This system will consist of a remote transmitter and an indicating unit.
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5.12.7 Combination Indicators Combination wind indicators are available. They combine readings of direction and speed, and they are more convenient for sea trial purposes than the separate indicators. They utilize a contact type synchro transmitter to transmit wind speed and direction to a dial readout.
5.12.8 Locating Sensors The sensors for all wind direction and velocity measuring equipment should be located high enough above the ship's structure so it will receive an unobstructed wind flow and not be subject to wind currents and eddies from any nearby object.
5.12.9 Ultrasonic Wind Sensors The ultrasonic wind sensor is a modern method of accurately measuring both wind speed and direction.
5.13 TRACKING SYSTEMS GNSS is the Global Navigation Satellite System. It refers generically to the GPS (United States), GLONASS (Russia), GALILEO (European Union), and BEIDOU (China) satellite constellations. Of these the GPS and GLONASS systems are fully operational. The GALILEO and BEIDOU systems are partially in operation and scheduled for full operation by 2020. For purposes of sea trials, it is best to use DDGNSS – Dual Differential GNSS equipment that can provide sub-meter position accuracy and heading information.
5.14 TIME MEASUREMENTS 5.14.1 Types of Instruments The following types of timing instruments may be used for trial data: a) b) c) d)
Ship's Clocks Stop Watches Electric Timers and Clocks Chronographs
A detailed description of each of the above instruments is stated in reference (ag).
5.14.2 Synchronizing Clocks Ship's clocks may be used to time events. Prior to departure, the master clock should be set to the correct time and secondary units synchronized with the master. Time pieces furnished for trials should be synchronized with the ship's system to avoid disagreement in reporting events.
5.14.3 Stop Watches Stop watches most suitable for sea trial data are electronic watches and timers. These watches and timers are battery powered. All stop watches should be checked against a time piece of known accuracy before the trials begin. The combined stop watch and time piece should be adjusted and regulated so that it does not gain or lose more than thirty seconds over a twenty-four hours period.
5.14.4 Electric Timers and Clocks Electric timers may have a synchronous motor drive and depend upon the ship's power frequency for accuracy. Electric stop clocks with accuracy controlled by quartz crystals are available with dials readable to one one-hundredth of a second. Special timers may be designed and used where desirable. They may have a master clock with accuracy controlled by a quartz crystal design. When 71
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electric time measuring devices dependent on ship’s power are used for sea trials, caution should be exercised to maintain ship’s generator frequency at 60 cps. Electronic timers may replace electric times to maintain standard item, if shipboard power frequency is not constant or is uncertain.
5.14.5 Recorders Recording instruments should be inspected regularly to see that the paper-driving mechanism and paper marking device operate properly to provide correct time indications.
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6.0 TRIAL DATA AND REPORT 6.1 GENERAL A trial report should be prepared by the shipbuilder and delivered to the owner and others as specified or within sixty days after the completion of trials. The report should present the trial results, relate them to requirements, and should contain all data and information needed to evaluate the results reported. This section provides organization and sample formats for identifying the ship and its major characteristics and reporting data for the tests and trials covered in Sections 2, 3, and 4 where sample formats are also found for reporting. In some cases the data are reported directly as taken, in others one or more reductions are required to reach the value to be reported in either tabular or graphic forms. Copies of raw data sheets, if legible and interpretable, may be used for directly reported data. Raw data need not be supplied for values reported in reduced form, but supporting data for such values should be retained and held available for the owners or other acceptance authorities for the life of the contract. Data forms are included for all trials and tests for which procedures are provided by the guide regardless of contract requirement for such a trial or test. Inclusion of the data sheet should not be construed to require that a test or trial be performed. Similarly, data sheets list all data pertinent to the test or trial of a typical plant or system or equipment. A particular ship may not have an instrument or gage to provide a data item, or might not be designed to include the component or apparatus to which the data pertains. Guide data sheets, thus, should be taken as a recommendation rather than an absolute requirement, and data not included on the data sheets but available and pertinent should be included in the report. Also, the presence of a data item does not constitute a requirement to install special instrumentation to provide it. Such requirements are imposed by the section of the guide requiring the test or trial. Critical data as defined by Table 2 and Table 3 should be instrumented to the extent required to provide confidence in the results.
6.2 DATA PLAN Since the Guide is for general application it cannot cover with precision the particular contractual or technical circumstances of a particular ship or class of ship. It is important therefore, as set forth in Section 1, for the shipbuilder to study the guide, the contract, and the ship’s specifications, and prepare a data plan. This plan should include data forms suited to the location and function of the instruments to be read, a system for transmitting raw performance data to a central computing station for processing and process for making data available to authorized parties aboard ship. Data forms should distinguish between data from special sea trial instruments and data from ship’s instruments.
6.3 DATA CREW TRAINING As Section 1 states in general terms, the data crew should be trained in advance of trials in the use and location of the instruments to be read, the corrections to be applied, and the calculations to be made. Training should include familiarization with the data forms so that entries will be made in the correct column, and the instrumentation for data items which should be read on the mark of the data interval. The mark is provided by the sea trial signal system.
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6.4 MANEUVERING TRIALS AND SPECIAL TESTS The figures and tables in this bulletin have been developed to assist the shipbuilder in preparing data tabulation sheets and in reporting results pertinent to maneuvering trials and special tests. All of the data requirements of the various trial events are provided by the tables with the exception of Table 1 through Table 3 which provide guidance. Plots of the data associated with these tables of data should be provided to indicate smoothness of data. Results of the "Z" Maneuver and spiral maneuver tests should be plotted. If GNSS equipment is used during the trials, the resultant plots of the ship's track during turning circle tests and quick engine reversals should be included in the trial report. Plots of turning circles should be corrected for drift by the method explained in Appendix A to Chapter 6.0. When precise tracking is not available, plots of the radar wake return may be made and included in the report. Such plots are indicative rather than definitive of the ship's turning characteristics and need not be corrected for drift.
6.5 STANDARDIZATION TRIALS Table 16 has been developed to assist the shipbuilder in reporting results pertinent to standardization trials. All of the data requirements of the trial event are included therein.
6.6 FUEL ECONOMY AND ENDURANCE TESTS Table 18 and Table 19 have been developed to assist the shipbuilder in reporting results pertinent to main propulsion fuel economy tests. The figures presented are representative of a typical diesel and gas turbine powered ships. Other types of main propulsion plants and variations of plant equipment and systems will require appropriate modifications.
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Table 18 Internal Combustion engine Propulsion Plant Economy Test Ship Name Time of Test
Trial Date Ambient Air Temp.
Duration of Test
Relative Humidity
Power (Average Shaft power [SKW]) Fuel Consumption Measured Flow o Specific Gravity o 60o F b Fuel Oil Temperature at Meter Specific Gravity at Meter Fuel Oil Density (WT. UNIT/VOL.) at Meter Fuel Consumption (WT. UNIT/HR.) Fuel Rate (WT. UNIT/SHP-Hr.) Fuel Rate Correction for Fuels Used c Higher or Lower Heating Value HHV b Correction Factor for Heat Available Corrected Fuel Rate (WT. UNIT/SKW-Hr.)
Test
Design
Diff.
Corr. Factor
Fuel Rate Corrections for Departures from Design Conditions c Ambient Air Temperature ( oF/C) Ambient Air Pressure Shaft Speed (RPM) Engine Speed (RPM) Generator Load (KW) Distilling Plant Load (GPD) Ship Service Steam Total Correction Corrected Fuel Rate a. Average Flow of two meters if two are installed. Flows to be corrected from meter calibration curves. b. From fuel Analysis report for sample collected during trials. c. Correction factors as agreed upon prior to test. Note in each case whether correction is plus or minus. NOTE: Make separate evaluation sheet for test at each specified power.
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Table 19 Gas Turbine Plant Economy Test Data Ship Name Time of Test
Trial Date Ambient Air Temp.
Duration of Test
Relative Humidity
Power (Average Shaft power [SKW) Fuel Consumption Measured Flow o.) Specific Gravity o 60o F b Fuel Oil Temperature of water Specific Gravity at Meter Fuel Oil Density (WT. UNIT/VOL.) of water Fuel Consumption (WT. UNIT/HR.) Fuel Rate (WT. UNIT/SKW-Hr.) Fuel Rate Correction for Fuels Used c Higher or Lower Heating Value HHV b
Test
Design
Diff.
Corr. Factor
Correction Factor for Heat Available Corrected Fuel Rate (WT. UNIT/SHP-Hr.) Fuel Rate Corrections for Departures from Design Conditions c Ambient Air Temperature ( oF/C) Ambient Air Pressure Shaft Speed (RPM) Turbine (RPM) Compressor (RPM) Generator Load (KW) Distilling Plant Load Ship Service Steam Total Correction Corrected Fuel Rate a. Average Flow of two meters if two are installed. Flows to be corrected from meter calibration curves. b. From fuel Analysis report for sample collected during trials. c. Correction factors as agreed upon prior to test. Note in each case whether correction is plus or minus. NOTE: Make separate evaluation sheet for test at each specified power. 76
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6.7 PROPULSION PLANT TRIALS Performance data is reported to support the results of the propulsion plant trials, to assist in interpreting these results, and to provide baseline reference data for operating personnel once the ship enters service. If specific data is pertinent but not available, a note to this effect should be included on the applicable data sheets. Recorded data for the test runs should be averaged, with obviously erroneous readings rejected. If recalibration of ship's instrumentation is accomplished prior to ship delivery, note of such recalibration should be included on the applicable data sheets.
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Table 20 and it data sheets reflects the recommended content for reporting operating data for a typical ship with main propulsion diesel or gas turbine installation.
6.8 TRIAL REPORT The contractor should prepare a trial report with recommended content as follows:
6.8.1 Introduction The introduction should include the contract number, hull number, owner designation, ship's name, principal dates, contractual parties, and construction contract references, preceded by a photograph of the ship or a sister ship underway, if required by the contract.
6.8.2 Ship's Characteristics a) Type of ship Example:
Single-screw Low speed diesel driven Combination bulk and general cargo ship.
(b) Principal Characteristics (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)
Length overall Length between perpendiculars Beam, maximum molded Depth to main deck at side, minimum molded Draft, full load, molded Displacement at full load draft Gross tonnage (approximate) Net tonnage (approximate) Draft, maximum ballast provided by ship system MCR Engine rating Sustained sea speed at full load draft and registered horsepower Estimated fuel consumption at sea Estimated fuel consumption in port Endurance in nautical miles at sustained sea speed with a record of fuel consumed.
(e) Capacities* (1) (2) (3) (4) (5) (6) (7)
Container (TEU) Cargo cubic Refrigerated cargo net cubic Convertible liquid cargo net cubic Non-convertible liquid cargo net cubic Fuel oil Total deadweight at full load draft *May require additional breakdown dependent on type of cargo carried.
(f) Hull characteristics (1) (2) (3)
Block coefficient Midship coefficient Bulk as percent of underwater profile area at full load draft 78
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(4) (5)
(g)
Rudder characteristics (6) (7)
(h)
Type of bow Type of stern
Number and type Rudder as percent of underwater lateral profile area at full load draft
Propeller characteristics* (1) (2) (3) (4) (5) (6)
Type including direction of ahead rotation and number of blades Diameter Pitch Expanded area ratio RPM at full load draft and registered power Design submergence * Include data for each propeller
(i)
Equipment identification data (1) (2) (3)
Main propulsion machinery Important auxiliaries Other equipment as specified. It is recommended that, as a general rule, special and/or unique equipment be listed with identification data.
6.8.3 Trial Data Principal personnel present on trials, including representatives of the owner, acceptance authorities, regulatory bodies, and shipbuilder. (a) (b) (c) (d)
Log of events. Principal personnel present at trials, including representatives of the owner, acceptance authorities, regulatory bodies, and shipbuilder. Trial ballast schedule. Trial results: 1. Maneuvering trials and special tests. See Figures and Tables in Section 3. 2. Standardization trials. See Tables in Section 4. 3. Fuel economy tests. See Tables 17 and 18. 4. Propulsion plant data. See Table 21 and its data sheets.
6.8.4 Other Data (a) (b) (c)
Number of days between sea trials and most recent drydocking. Wind direction and velocity. Sea state.
6.8.5 Appendices - As Elected (a)
Design information and other available information pertinent to the trials.
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Table 20 Propulsion Plant Data Sheet 1 PROPULSION PLANT DATA Data which typically pertain to propulsion systems are set forth below. These data should be recorded as pertinent and available subject to the classification described below for economy trials, ahead endurance trials, and astern endurance trials, in addition to that called for elsewhere. Average values for the trial period should be reported. In cases where more than one instrument is installed to read the same datum, the instrument of greatest inherent precision should be reported. If precision and quality of calibration are equal, their average should be used. As noted in 6.1 and 6.2 hereof, the presence of an instrument to read it must be provided. Yet, data for basic design parameters are necessary to evaluate performance and should be provided in suitable Precision regardless of presence or quality of ship's instrumentation. To a lesser degree ancillary parameters which are applied as correction factors to the basic determination should also be provided commensurate with the effect on the basic performance determination. It is helpful in providing an appropriate data plan to categorize data items as follows: Class A:
Data items for which a trial instrument is required to provide precision or redundancy regardless of the presence of a ship's instrument, or its quality.
Class B:
Data items for which a ship's instrument of suitable precision can be used if specifically calibrated. (A trial instrument should be supplied if there is no ship's instrument.)
Class C:
Data items for which ship's instruments with standard calibration can be used. (If there is no shin's instrument, a trial instrument need not be installed.)
When formulating a data plan, data items should be listed and categorized as illustrated by the listings below. Data obtained from test instruments should be suitably indicated both in the data plan and the report. Ship Name Trial Date Trial: Economy, Ahead Endurance, Astern Endurance, Boiler Overload Shaft Horsepower Shaft Speed Time and Duration of Run Users should develop their own format for reporting the results of this test depending upon the equipment available. However, the following information should be recorded. Note that the information is divided into the following categories: Electric Drive, Diesel Propulsion Plant, and Gas Turbine Plant. Note: This introductory Table is followed by Tables containing Data Sheets which are provided on pages 81 through 86 (Table 21 through Table 25).
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Table 21 Propulsion Plant Data - Diesel Main Engines Class B (As pertinent to power
Barometer Engine Room Temperature
determination
Air to Engine Pressure h Air to Engine Temperature h Air Pressure at Blower Discharge Air Temperature Leaving Intercooler (If any) Air Pressure in Air Box or Manifold Exhaust Temperature Each Cylinder Exhaust Temperature Entering Turbocharger Exhaust Pressure Leaving Turbocharger Exhaust Temperature Entering Silencer Exhaust Pressure Leaving Silencer Exhaust Temperature Leaving Silencer Exhaust Temperature Entering Waste Heat Boiler Exhaust Pressure Leaving Waste Heat Boiler Exhaust Temperature Leaving Waste heat Boiler Crankcase Pressure Fuel Oil
Class B
Main Engine(s) Fuel Meter Type Main Engine Fuel Meter Reading Properties of Fuel Used Main Engine Rack Position F. O. Settler Temperature F. O. Service Tank Temperature F. O. Booster Pump Discharge Pressure F. O. Heater In and Out Temperatures F. O. Heater In and Out Pressures Other Pertinent Temperatures as Applicable (Purifiers, Filters, etc.) Other Pertinent Pressures as Applicable (Purifiers, Filters, etc.) Lube Oil L. O. Pump Discharge Pressures Maine Engine (s) L. O. In and Out Temperatures Main Engine (s) L. O. In and Out Pressures
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DIESEL PROPULSION PLANT (continued) Lube Oil (continued) Gears and Couplings L. O. IN and Out Temperatures Gears and Couplings L. O. In and Out Pressures L. O. Cooler In and Out Temperatures L. O. Cooler In and Out Pressures Other Pertinent Temperatures as Applicable (Purifiers, Filters, etc.) Other Pertinent Pressure as Applicable (Purifiers, Filters, etc.) Cooling Water Sea Temperatures Salt Water Pump Discharge Pressures C. W. Pump Discharge Pressures Heat Exchanger In and Out Pressures (Salt Water) Heat Exchanger In and Out Temperatures (Salt Water) Heat Exchanger In and Out Pressures (C. W.) Heat Exchanger In and Out Temperatures (C. W.) C. W. Temperature to Engine C. W. Temperature from Engine Air Starting Air Pressure Control Air Pressure Diesel Auxiliary Electric Plant d Generator Generator in Operation Type (AC or DC) Voltage Current Power Factor Class B Power Output Load g Diesel Engine F. O. Consumption and Type and Properties of Fuel Used Other Pertinent Data as Applicable Boiler Systems Waste-Heat Boilers Number in Operation Feed Pressure
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Table 22 Propulsion Plant Data - Diesel (Cont2) DIESEL PROPULSION PLANT (cont'd) Boiler Systems (continued) Water Based Boilers (continued) Feed Temperature Steam Pressure Steam Temperatures Feed Flow c Auxiliary Oil-Fired Boilers Number in Operation Uptake Gas Temperature Feed Pressure Feed Temperature Steam Pressure Steam Temperature Feed Flow c Fuel Flow, Type, and Properties Other Data The data for the following other systems as mutually agreed upon, Should be included in the trial report: Distilling Plant Auxiliary Steam Systems Other Salt Water Systems Other Fresh Water Systems Other Air Systems Sewage Systems Refrigeration and Air Conditioning Systems Slip Coupling Data Where geared diesel drive with slip couplings between engines and gears is installed, additional data should be recorded during the trial runs as follows: Engine Speed Pinion Shaft Speed Slip Speed Shaft Speed Shaft Horsepower Coupling Excitation Current (Electromagnetic) Coupling Oil Temperatures In and Out (Hydraulic) Electric Drive (see sheet 5)
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Table 23 Propulsion Plant Data - Electric Drive ELECTRIC DRIVE Where electric main propulsion drive is installed, additional data should be recorded during the trial runs. The following relates specifically to alternating-current, synchronous motor installations. Other types of electric drive will require data adjustments Prime Mover Class B
Class B
Power Output Voltgae, Terminal Voltage, Field Excitatioin Current Field Excitation RPM Current Output Voltage, Filed Excitation Current, Field Excitation Table 24 Propulsion Plant Data - Gas Turbine
GAS TURBINE PLANT Main Propulsion (Each Engine) Main Engines Class B Turbine and Compressor Speeds Instrumented Points of Pressure and Temperature in the Gas Stream Class B Water Temperature, Barometer, and Humidity Class B Engine Air Inlet Pressure and Temperature Class B Exhaust Flange Gas Pressure and Temperature Critical Ambient Temperatures Around Mounted Auxiliaries and Instruments Lubricating Oil Supply Pressure and Temperature Lubricating Oil Return Temperature Vibration Monitor Readings 84
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Gas Temperature and Pressure In and Out of Intercoolers and Regenerators Reduction Gear and Clutch Clutch Fluid Pressures, Air or Hydraulic Lubricating Oil Supply Pressure and Temperature Lubricating Oil Temperatures from Bearings Controllable Pitch Propellers Hydraulic Operating Pressures and Temperatures Blade Position Fuel Oil F. O. Consumption F. O. Pump Discharge Pressure F. O. Pressure to Engine F. O. Pressure from Engine F. O. Temperature at Meter F. O. Settler Temperature F. O. Temperature to Engine F. O. Type and Properties Lube Oil L. O. Strainer IN and Out Pressures L. O. Type and Properties Cooling Water Heat Exchanger In and Out Temperatures
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Table 25 Propulsion Plant Data - Gas Turbine (Cont) GAS TURBINE PLANT (continued) Auxiliary Electric Plant d
Class B
Generator Generator in Operation Frequency Voltage Current Power Factor Power Output Load g Driver F. O. Consumption and Type of Properties of Fuel Used
Other Data The data for the following systems, as mutually agreed upon, should be included in the trial report: Distilling Plant Auxiliary Boiler Data (Including F.O. Consumption) Auxiliary Steam Systems Engine Starting Systems Ship's Service Air Systems Control Air Systems Salt Water Systems Fresh Water Systems Sewage Systems Refrigeration and Air Conditioning Systems Electric Drive (See Table 23)
Footnotes for Tables a. Include remote and thermocouple temperature when applicable. b. Include reheated data when available. If Gas reheated is installed, so indicate. c. When available. d. Include data for each unit or system in operation. e. When applicable f. Include data for each extraction. g. Include auxiliary machinery and hotel loads when separable. h. To engine Intake, scavenging or supercharging blowers, as applicable.
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REFERENCES The American Society of Mechanical Engineers has published Performance Test Codes (PTC) for testing of land plants, and has published Supplements on Instruments and Apparatus which describe each type of instrument and the capabilities and limitations of each. See references (a) and (b) for additional information. In most publications the inherent precision, calibration procedures, and installation instructions are included. The Naval Ship Engineering Center has published "Standards" which provide details on the installation of sensing connections and other information pertinent to shipboard measurements. These documents are listed below and are referenced in the pertinent portions of the text. a. General Instructions, Performance Test Code, Engineers, PTC 1 - 2011
The American Society of Mechanical
b. Definitions and Values Code, Performance Test Code, The American Society of Mechanical Engineers, PTC 2 - 2001) c. Temperature Measurement Performance Test Code, The American Society of Mechanical Engineers, PTC 19.3 - 1974 (R2004) d. Lempa, M.S., editor, Instrument Standards, Naval Ship Engineering Center, Philadelphia Division e. Pressure Measurement Performance Test Code, The American Society of Mechanical Engineers, PTC 19.2 – 2010 f. Application, Part II of Fluid Meters: Interim Supplement on Instrument and Apparatus, Fairfield, N.J., The American Society of Mechanical Engineers, PTC 19.5 - 1972 g. Bean, Howard S., Fluid Meters - Their Theory and Application, 6th edition, New York, The American Society of Mechanical Engineers, 1971 h. Miller, R. W., Flow Measurement Engineering Handbook, New York, McGraw-Hill Book Co., 1983 i. Stein, Peter K., Measurement Engineering, Phoenix, AZ, Stein Engineering Service Inc., 1964 j. Electrical Measurements in Power Circuits, Part 6, Performance Test Code, Fairfield, N.J., The American Society of Mechanical Engineers, PTC 19.6 - 1955 k. Measurement of Indicated Power, Performance Test Code, Fairfield, Society of Mechanical Engineers, PTC 19.8 - 1970(R1985)
N.J.,
The
American
l. Gas Turbine Power Plants, Performance Test Code, The American Society of Mechanical Engineers, PTC 22 - 12014 m. Steam Turbines, Performance Test Code, The American Society of Mechanical Engineers, PTC-6 2004 n. Appendix A to Test Code for Steam Turbines, Performance Test Code, The American Society of Mechanical Engineers, PTC 6A - 2000 o. Measurement of Shaft Power, Performance Test Code, Engineers, PTC 19.7 – 1980 (R1988)
The American Society of Mechanical
p. (R1988)Measurement of Rotary Speed, Performance Test Code, The American Society of Mechanical Engineers, PTC 19.13 - 1951
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q. Code for Shipboard Vibration Measurements, SNAME, 99 Canal Center Plaza, Alexandria, Virginia 22314, 1975, Book No. C-1 r. Machinery Vibration Measurements, SNAME, 99 Canal Center Plaza, Alexandria, Virginia 22314, 1976, Book No. C-4 s. Acceptable Vibration of Marine Steam and Gas Turbine Main and Auxiliary Machinery Plants, SNAME, 99 Canal Center Plaza, Alexandria, Virginia 22314, 1976, Book No. C-5 t. Ship Vibration and Noise Guidelines, SNAME, 99 Canal Center Plaza, Alexandria, Virginia 22314, 1980, Book No. 2-25 u. Guidelines for the Use of Vibration Monitoring for Preventive Maintenance, SNAME, 99 Canal Center Plaza, Alexandria, Virginia 22314, 1987, Book No. 3-42 v. Measurement of Industrial Sound, Performance Test Code, Fairfield, N.J., The American Society of Mechanical Engineers, PTC 36 - 1998 w. Boilerwater/Feedwater Test and Treatment, Naval Ships Technical Manual S9086-GX-STM-02, Chapter 220V2, 15 December 1987 x. Design of Dissolved-Oxygen Testing Cabinet, U.S. Naval Engineering Experiment Station, February 29, 1940, Report No. B-1158 y. Density Determination of Solids and Liquids, Performance Test Code, Fairfield, N.J., The American Society of Mechanical Engineers, PTC 19.16 - 1965 z. Determining the Concentration of Particulate Matter in a Gas Stream, Performance Test Code, Fairfield, N.J., The American Society of Mechanical Engineers, PTC 38 - 1980 (R1985) aa. Flue and Exhaust Gas Analysis, Performance Test Code, Fairfield, N.J., The American Society of Mechanical Engineers, PTC 19.10 1981 bb. Water and Steam in the Power Cycle (Purity and Quality, Leak Detection and Measurement), Performance Test Code, Fairfield, N.J., The American Society of Mechanical Engineers, PTC 19.11 1997 cc. Determination of the Viscosity of Liquids, Performance Test Code, Fairfield, N.J., The American Society of Mechanical Engineers, PTC 19.17 - 1965 dd. Measurement of Time, Performance Test Code, Fairfield, N.J., The American Society of Mechanical Engineers, PTC 19.12 - 1958 NOTE: ASME Publications are available from The American Society of Mechanical Engineers, Marketing Department, at ASME.org SNAME Publications are available from the Publications Department, SNAME, 99 Canal Center Plaza, Alexandria, Virginia 22314. Various Naval publications are available from the Commanding Officer, Naval Publications and Forms Center, Attn: Code 106, 5801 Tabor Avenue, Philadelphia, PA 19120-5009. ASTM publications are available from The American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103.
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APPENDIX A DEFINITIONS The terms defined below were selected to contribute to the clarity of the foregoing sections. No attempt has been made to cover all the shipbuilding terms which may be of interest and no claim is made that the definitions provided represent an industry consensus. The definitions do, however, tell what is meant whenever the term is used in this guide. They are not identical with definitions used in other SNAME publications, but they do not conflict. Definitions are set forth as they apply to sections of the guide.
A.1 GENERAL TERMS. First-of-a-class - the first ship built to a specific design by a particular shipyard. Forensic Data - data relative to maneuverability and other ship characteristics which might have a bearing on legal action involving the ship or its owners. Acceptance Authority - the organizations designated by the owner or contract to rule on the acceptability of trial performance. Regulatory Bodies - the organizations designated by the owner or by law to enforce regulations relative to the safety of the ship, its crew or cargo, for example: U.S. Coast Guard, International Commission for Safety of Life at Sea, U.S. Public Health Service, Canadian Ministry of Transport. Classification Society - an organization which publishes standards of construction for various classes of ships, monitors their observance and maintains a register listing each vessel classified and giving its class and principal characteristics. For example: American Bureau of Shipping, Lloyds Register of Shipping, Det Norske Veritas. "If Elected" - a term used in this guide to designate a trial or test which will be accomplished only if explicitly required by the contract or specifications. Uncertainty - the probability that measurement of a ship's performance parameter will not be within a prescribed range. Sea Trials - at-sea operation of a ship's propulsion plant and other ships' machinery and systems which cannot be properly tested at the dock, to determine performance capability or to demonstrate satisfaction of requirements. Builder's Sea Trials - preliminary sea trials conducted by the builder to verify readiness for official sea trials. Upon agreement between the builder and acceptance authority, specific trial events may be officially conducted during builder's trials. Official Sea Trials - sea trials conducted to demonstrate acceptability of the ship to the owner or his designated representative. Full Load Draft - the maximum draft permitted by the cognizant classification society for the season and waters in which the trials will be conducted. Ballast Draft - the maximum drafts obtainable without use of dry cargo spaces, using the ship's ballast system as installed. Trial Drafts - the drafts during the trial under consideration. See 4.10(d) for method of determination. Free Route - operation of the ship on an elected course with minimum use of the helm without restriction from shallow water effects, channel constraints, or traffic.
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A.2 PROPULSION PLANT TRIALS Endurance Trial - a period of operation of the main propulsion plant at maximum design power or a designated fraction thereof, intended to demonstrate the ability to perform indefinitely at that level. Economy Trial - a period of operation of the main propulsion plant to demonstrate the ability to meet a specified rate of fuel consumption at a prescribed power rate under stated conditions. Prime Mover - the propulsion plant element that converts the thermal energy of the steam or the chemical energy of fuel into rotary mechanical energy. Power Train - all elements between the prime mover and the propeller, inclusive. Shaft Power - the net power supplied by the propelling unit to the propulsion shafting after passing through all speed reducing and other transmission devices and thrust bearings, and after power for all attached auxiliaries has been taken off. Losses between the output flange of the prime mover and the propeller are usually negligible. Normal Shaft Power - the shaft power used to specify design cruising radius and service life. Recent practice is to use maximum design shaft power for all design considerations. Maximum Power - power developed by the ship's propulsion plant expressed in English units is 1 power = 33,000 ft.-lb. per minute, and expressed in metric-units is 1 power = 75 kg-meters per second. Maritime usage distinguishes between powers depending on the point in the power train at which the measurement is taken or to which it is referred. Indicated Power - power derived from the cylinders which is determined by dimensions, pressure, and reciprocation data before correction for internal losses and power supplied to attached auxiliaries. Brake-Power - power delivered by the prime mover output flange after supplying engine attached auxiliaries, but before takeoff of power absorbed Design Shaft Power the maximum shaft power for which the ship is designed to operate continuously. Classification Shaft Power the shaft power appearing in the register of the cognizant Classification Society. In the case of ambiguity in the manufacturers' designation, the classification shaft power should be considered the maximum design shaft power. Trial Shaft Powers - these are distinguished by the method by which they are obtained as follows:
Torsionmeter Installed power being transmitted by the shaft at the paint of torque measurement. No Torsionmeter - Power Derived from Comparison with Shop Data - power delivered by the shaft at the point corresponding to the location of the shop power measuring device, with adjustments for any power-absorbing equipment not present at the shop test. No Torsionmeter - Power Derived from Prime Mover Data - net power after subtracting from the prime mover data estimates of the power absorbed by speed reducing or other transmission devices, and attached auxiliaries.
Fuel Rate - hourly consumption of fuel by weight at a specified power level with specified systems in operation. Corrected Fuel Rate - the fuel rate, all purposes, as derived from test data, corrected for deviations from design conditions. The conditions for which corrections are to be made and the factors to be applied are as specified or agreed. Specific Fuel Rate - fuel rate as defined above divided by the shaft power at which said fuel rate is obtained. Expressed in pounds per shaft power hour. 90
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A.3 MANEUVERING AND SPECIAL TESTS Turning Circle Terms Base Course - ship heading at the start of a maneuver. Advance - the distance the ship moves in the direction of the base course. Advance-to-Clear Base Course - the distance the ship moves in the direction of the base course from the initiation of the held order to the point at which every part of the ship is clear of the projected base course. Advance-to-Change Heading 90° - the distance the ship moves in the direction of the base course from the initiation of the helm order to the point at which the ship's heading has changed 900. NOTE: This dimension is understood if "advance" is used alone. Maximum Advance of Any Part of the Ship - the maximum distance the ship moves in the direction of the base course after the helm order is given. Transfer - the perpendicular distance from projected base course to the mid length of the ship when the ship's heading has changed 90°. Tactical Diameter - the perpendicular distance from the projected base course to the mid length of the ship when the ship's heading has changed 180°. Maximum Departure from Base Track the maximum perpendicular distance from the projected base course of any part of the ship during the turning circle. Final Diameter - the diameter of the track made by the ship after the rate-of-change of heading becomes constant. Z-Maneuver Terms Overshoot - difference in degrees between the departure from base course when the opposite helm order is given and the maximum departure from base course in a given direction. React - time from initiation of "Z" maneuver until the ship's heading returns to base course. The "Z" maneuver is discussed in paragraph 3.8. Period - time required for ship's heading to change from 10°R of base course back to 10°R of base course in response to rudder movements of 10°R to 10°L to 10°R. Quick Reversals Dutch Log - method of determining movement of the ship by throwing a buoyant object (log) overboard from a forward station and throwing succeeding logs on a signal determined from when the proceeding log passes a ship station at known distance aft. The total movement of the ship is the product of the number of logs passing the aft station and the distance between stations, plus the estimated distance between the forward station and the last log when the ship is dead-in-the-water. Ahead Reach - the distance the ship moves ahead after an astern signal is given, commonly determined during trials for a full ahead initial condition and a full astern signal.
A.4 STANDARDIZATION TRIALS GNSS Tracking Systems electronic systems by which ship's position is determined from two carefully surveyed points ashore by the radio signals which indicate the range between the ship and each surveyed point. The ship's position at a particular time is the intersection of the two ranges thus
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determined, and a series of such positions traces the ship's track. The ship's position iscalculated using the two ranges, the distance between the surveyed points, and the position of the surveyed points. Standardization - operation of the ship over a measured distance on reciprocal courses at specified draft and propulsion powers to determine the speeds obtainable at such propulsion powers. Ship's Track - the line describing the positions of a point on the ship from which range measurements are taken during the period of interest.
A.5 INSTRUMENTATION Trial Instrument - a calibrated instrument provided by the builder to measure a particular aspect of ship performance during sea trials. The trial instrument is normally removed by the builder after trials. Jacking Zero - the no-torque torsionmeter reading determined by rotating the shaft in each direction with the turning gear and taking the mean of the average readings from both ahead and astern. Torsionmeter Constant - the constant used in reducing torsionmeter signals to shaft torque. It is obtained by calculation using the known shaft dimensions, the characteristics of the torsionmeter, and a standard modulus of rigidity of the shaft material; or by calibration of the torsionmeter while mounted on the shaft. Water Leg – the correction to pressure gage readings necessary to determine pressure at the sensing point when it is not at the same elevation as the pressure gage and the sensing line is known to contain liquid. Red Hand Setting – position of an adjustable fixed marker on an instrument dial face, which prescribes the high and/or low limits of safe operation.
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APPENDIX B CORRECTING TURNING CIRCLE PLOTS FOR DRIFT B.1 PRINCIPLE A.1.1 The plot derived from shore based reference station data indicates the ship's overground track, i.e., over the sea floor. What is wanted is the track through the water, as this is what is characteristic of the ship, not the track reflecting the particular condition present during the trial. Comparisons of ship with ship or ship with a standard are valid only if both are drift corrected. The tracking precision available from modern positioning systems makes drift correction meaningful. Drift correction is not recommended for imprecise tracking methods. A.1.2 After the ship's turn reaches equilibrium, and there is no drift, the ship's track will be a perfect circle, and repeated turns will coincide. If there is drift, tracks will be distorted circles, and no two will coincide. The degree and location of distortion can be used to measure drift. The procedure is outlined below. The term "Execute" as used in the procedure means the time at which the helm order is given.
B.2 PLOTTING OVERGROUND TRACK A.2.I Plot the change of ship's heading versus time (SHVT). A.2.2 Plot the ship's position versus time (SPVT). A.2.3 Using the SPVT, determine ship's position at suitable time intervals (say 30 seconds). A.2.4 Plot ship's position at the selected intervals, on rectangular coordinates, as shown in Figure 11, using base course for the horizontal axis and orienting the plot to show the ship approaching from top left for a right turn or bottom left for a left turn. Use a scale sufficient to resolve the drift distance encountered. A.2.5 Fair a dashed line through the plotted points. This will represent the overground track of the ship during the maneuver.
B.3 DETERMINATION OF DRIFT A.3.1 The test procedure stated in paragraph 3.7 calls for holding full rudder until ship's heading has changed 540 degrees; thus, the second time around will lap the first by 10 degrees, some part of which will be a factor where the drift displacement of the second circle was maximum, and there was a steady rate of turn both times around. The point at which a steady rate of turn is reached can be verified from the SHVT. The point will be where the slope of the change heading curve is approximately constant. A.3.2 Determine from SHVT the time for heading changes at 10 degree intervals for the portion of the lapped sector of the first circle for which turning rate is steady and the displacement of the second circle is maximum. Similarly determine the time to reach selected heading change points plus 360 degrees. Determine from the SPVT the ship's position at these times. Plot these positions as indicated on Figure 11. A.3.3 Connect the plotted position points at which ship's heading is 360 degrees apart and which fall within that portion of the lapped sector for which turning rate is steady. If there are insufficient points to describe the tracks properly, plot more points using the SHVT and SPVT. The mean length of these connections will be proportional to the distance the ship drifted during a full 93
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turn. The proportionality factor will be the scale of the plot. The mean direction of the connections taken from first toward the second time the same heading is reached will be the direction of drift relative to base course. Indicate drift direction by an arrow as shown on Figure 11. Drift direction in compass terms can be obtained by adding or subtracting base course as appropriate. Report results on Figure 1 or 2.
B.4 DETERMINATION OF DRIFT RATE A.4.1 Determine the time from "execute" for each of the connected points, using the SHVT. A.4.2 Subtract the time to reach the heading the first round from the time to reach it the second round. A.4.3 Take the mean of these values as the mean time to turn 360 degrees. A.4.4 Divide the mean drift distance as plotted by the mean time for a 360 degrees turn to obtain the mean rate of drift expressed in inches of plot per second from "Execute".
B.5 PLOTTING THE DRIFT CORRECTED TURNING CIRCLE A.5.1 Using the time plots, determine the time to or from "Execute" for each plotted point of the overground plot. A.5.2 Multiply the times from "Execute" for each plotted point by the drift rate. This will be the drift distance in inches of plot. A.5.3 Taking the "Execute" point as the origin representing zero time and zero drift, lay off a line extending from each plotted point in a direction opposite the direction of drift after "Execute" and in direction of the drift before "Execute". A.5.4 Mark off on these lines a distance representing drift as prepared for paragraph A.5.2. These points will define the drift corrected track. A.5.5 Pick up a best-fit center using a compass for the drift corrected points which are in the portion of the track in which the turning rate is steady. A.5.6 Draw a best-fit circle around this enter. A.5.7 Fair a line through the remaining points, including a few prior to "Execute", to redefine the base course.
B.6 DETERMINATION OF TURNING CIRCLE DIMENSIONS A.6.1 Scale off the corrected plot and multiply by the scale factor, the dimensions defined in paragraph A.3 in Appendix A. A.6.2 Determine the change of heading for each plot point for corrected circle using the SHVT. When plotting a circle for paragraph A.6.3, indicate the ship's heading by orientation of a scaled representation of the ship's outline as shown on Figure 1 or 2. A.6.3 Replot the corrected circle; appropriately label and indicate the turning dimensions as illustrated in Figure 1 or 2 and include this in the trial report.
B.7 CALCULATION OF DRIFT RATE IN KNOTS A.7.1 Multiply the drift rate in inches of plot per second from paragraph A.4.4 by the scale factor and apply a dimensional constant to convert to knots. Report on Figure 1 or 2.
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Example: Drift Rate (knots) = Drift rate (inches/sec) x scale factor (feet or yards/inch) Dimensional constant (feet or yards/nautical mile)(hour/secs)
Figure 11 Sample Plot Illustrating Correction of Turning Circle for Drift 95
