Piping Systems
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Engineering Encyclopedia Saudi Aramco DeskTop Standards
PIPING SYSTEMS
Note: The source of the technical material in this volume is the Professional Engineering Development Program (PEDP) of Engineering Services. Warning: The material contained in this document was developed for Saudi Aramco and is intended for the exclusive use of Saudi Aramco’s employees. Any material contained in this document which is not already in the public domain may not be copied, reproduced, sold, given, or disclosed to third parties, or otherwise used in whole, or in part, without the written permission of the Vice President, Engineering Services, Saudi Aramco.
Chapter : Civil and Structural File Reference: CSE-110.03
For additional information on this subject, contact PEDD Coordinator on 874-6556
Engineering Encyclopedia
Analysis and Design of Tanks, Vessels and Piping Piping Systems
MODULE COMPONENT
PAGE
INTRODUCTION............................................................................................................. 6 TYPES, COMPONENTS, AND USES OF PIPING SYSTEMS........................................ 7 Background .......................................................................................................... 7 Plant Piping .......................................................................................................... 7 Components .............................................................................................. 7 Uses........................................................................................................... 9 Cross-Country Pipelines ....................................................................................... 9 Components ............................................................................................ 10 Uses......................................................................................................... 10 Underground Pipelines ............................................................................ 10 Aboveground Pipelines ............................................................................ 11 Submarine Pipelines ................................................................................ 12 APPLICABLE CODES AND STANDARDS FOR PIPING SYSTEMS AND THEIR COMPONENTS................................................................................................. 14 Industry Standards for Piping Systems and Their Components ......................... 14 ANSI/ASME B31.3, Chemical Plant and Petroleum Refinery Piping....................................................................................................... 14 ANSI/ASME B31.4, Liquid Transportation Systems for Hydrocarbons, Liquid Petroleum Gas, Anhydrous Ammonia, and Alcohols ................................................................................................... 15 ANSI/ASME B31.8, Gas Transmission and Distribution Piping ............... 16 ANSI and API Standards and Publications .............................................. 16 Saudi Aramco Standards for Piping Systems and Their Components................ 17 SAES-A-004, Pressure Testing ............................................................... 17 SAES-A-005, Safety Instruction Sheet..................................................... 18 SAES-H-002, Internal and External Coatings for Steel Pipelines and Piping................................................................................................ 18 SAES-L-001, Basic Criteria for Pressure Piping Systems........................ 18 SAES-L-002, Design Conditions for Pressure Piping............................... 19 SAES-L-003, Design Stress Criteria for Pressure Piping......................... 19 SAES-L-004, Pressure Design of Piping Components ............................ 19 Saudi Aramco DeskTop Standards
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SAES-L-005, Limitations on Piping Components..................................... 19 SAES-L-006, Metallic Pipe Selection ....................................................... 20 SAES-L-007, Selection of Metallic Pipe Fittings ...................................... 20 SAES-L-008, Selection of Valves ............................................................ 20 SAES-L-009, Metallic Flanges, Gaskets, and Bolts ................................. 20 SAES-L-010, Limitations on Piping Joints................................................ 21 SAES-L-011, Flexibility, Support, and Anchoring of Piping...................... 21 SAES-L-012, Design of Piping Systems Inside Plant Areas .................... 21 SAES-L-032, Materials Selection for Piping Systems .............................. 21 SAES-L-033, Corrosion Protection Requirements for Pipelines/Piping ....................................................................................... 21 SAES-L-041, Utility Piping Connections to Process Equipment............... 22 SAES-L-044, Anchors for Cross-Country Pipelines ................................. 22 SAES-L-045, Scraper Trap Station Piping and Appurtenances ............... 22 SAES-L-046, Pipeline Crossings Under Roads and Railroads ................ 22 SAES-L-050, Construction Requirements for Metallic Plant Piping....................................................................................................... 23 SAES-L-051, Construction Requirements for Cross-Country Pipelines .................................................................................................. 23 SAES-L-052, Hot Tap Connections ......................................................... 23 SAES-L-055, Inspection of Piping Systems ............................................. 23 SAES-L-060, Nonmetallic Piping ............................................................. 23 Saudi Aramco Design Practices ......................................................................... 23 SADP-L-001, Basic Criteria for Pressure Piping Systems ....................... 24 SADP-L-002, Design Conditions for Pressure Piping .............................. 24 SADP-L-003, Design Stress Criteria for Pressure Piping......................... 24 SADP-L-004, Pressure Design of Piping Components ............................ 24 SADP-L-011, Flexibility, Support, and Anchoring of Piping...................... 24 SADP-L-012, Design of Piping Systems Inside Plant Areas .................... 24 SADP-L-014, Design of Pump and Compressor Station Piping ............... 24 SADP-L-020, Transportation Piping Systems .......................................... 24 SADP-L-021, Design of Submarine Pipelines and Risers........................ 25 SADP-L-022, Design of Well Flowlines and Trunklines ........................... 25 SADP-L-044, Anchors for Cross-Country Pipelines ................................. 25 Saudi Aramco DeskTop Standards
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SADP-L-046, Pipeline Crossings Under Roads and Railroads ................ 25 SADP-L-050, Construction Requirements for Metallic Plant Piping....................................................................................................... 25 SADP-L-051, Construction Requirements for Cross-Country Pipelines .................................................................................................. 25 MAJOR CONSIDERATIONS FOR DESIGN OF PIPING SYSTEMS AND THEIR EFFECT ON PIPE SUPPORT LOADING.......................................................... 26 Background ........................................................................................................ 26 Supports .................................................................................................. 26 Restraints................................................................................................. 26 Major Considerations for Layout of Piping Systems ........................................... 27 Operations Requirements ........................................................................ 27 Maintenance Requirements ..................................................................... 29 Safety Requirements ............................................................................... 29 Major Considerations for Detailed Design of Piping Systems............................. 31 Material Selection .................................................................................... 31 Allowable Stress ...................................................................................... 32 Flexibility .................................................................................................. 33 Equipment Tie-In ..................................................................................... 33 Weight Stress .......................................................................................... 34 Deflection Tolerance ................................................................................ 34 Other Support Considerations ................................................................. 35 Effect on Support and Restraint Loading............................................................ 35 Weight...................................................................................................... 36 Effect of Restraints on Movement............................................................ 36 CALCULATING SELECTED CIVIL/MECHANICAL LOADS ON PIPING SYSTEMS ..................................................................................................................... 39 Estimating the Wall Thickness Required for Internal Pressure ........................... 39 Dead and Live Loads.......................................................................................... 42 Hydrostatic Test Weight ..................................................................................... 44 Wind ................................................................................................................... 45 Saudi Aramco Standards ......................................................................... 45 Wind Shielding ......................................................................................... 45 Saudi Aramco DeskTop Standards
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Calculation Procedure.............................................................................. 46 Friction................................................................................................................ 48 TYPES AND FUNCTIONS OF SUPPORTS AND RESTRAINTS FOR VARIOUS PIPING SYSTEMS ....................................................................................... 49 Background ........................................................................................................ 49 Types and Functions of Supports ....................................................................... 50 Rigid Supports ......................................................................................... 50 Flexible or Resilient Supports .................................................................. 56 Stops........................................................................................................ 60 Guides ..................................................................................................... 60 Anchors.................................................................................................... 63 SUMMARY.................................................................................................................... 68 WORK AID 1: PROCEDURES AND INFORMATION FOR CALCULATING CIVIL/MECHANICAL LOADS ON PIPING SYSTEMS .......................... 69 Work Aid 1A: Procedures and Information for Calculating Dead and Live Load on a Support for a Straight Pipe Run........................... 69 Dead Load ............................................................................................... 69 Live Load ................................................................................................. 74 Total Static Load...................................................................................... 75 Work Aid 1B: Procedure for Calculating the Hydrostatic Test Load on a Support for a Straight Pipe Run ................................................ 75 Work Aid 1C: Procedure and Information for Calculating Wind Load on a Piping Support in Open Terrain ................................................ 76 Work Aid 1D: Procedure for Calculating Friction Force on a Piping Support ........................................................................................ 78 GLOSSARY .................................................................................................................. 79
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FIGURE LIST Figure 1. Process Plant Piping System Diagram........................................................... 8 Figure 2. Aboveground and Underground Pipelines.................................................... 11 Figure 3. Submarine Pipeline ...................................................................................... 13 Figure 4. Wind on a Piping System ............................................................................. 45 Figure 5. Wind Shielding ............................................................................................. 45 Figure 6. Pipes in Pipe Support Diagram .................................................................... 46 Figure 7. Shoe Support ............................................................................................... 51 Figure 8. Saddle Support ............................................................................................ 51 Figure 9. Base Adjustable Support.............................................................................. 52 Figure 10. Dummy Support ......................................................................................... 52 Figure 11. Trunnion ..................................................................................................... 53 Figure 12. Sling-Type Pipe Hanger ............................................................................. 54 Figure 13. Pipe Hanger Suspended From Side of Structure ....................................... 55 Figure 14. Pipe Support Beam Suspended By Rods................................................... 56 Figure 15. Variable Load Support................................................................................ 57 Figure 16. Constant Load Support .............................................................................. 58 Figure 17. Stop............................................................................................................ 60 Figure 18. Channel Guide ........................................................................................... 61 Figure 19. Sleeve Guide.............................................................................................. 61 Figure 20. Box-In Guide .............................................................................................. 62 Figure 21. Vertical Box-In Guide on Side of Vessel..................................................... 62 Figure 22. Anchor........................................................................................................ 63 Figure 23. Anchor........................................................................................................ 64 Figure 24. Anchor........................................................................................................ 65 Figure 25. Concrete Block Anchors............................................................................ 66 Figure 31. Commercial Wrought Steel Pipe Data........................................................ 69 Figure 32. Height and Gust Factors ............................................................................ 77 Figure 33. Coefficients of Friction................................................................................ 78
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INTRODUCTION CSE 110.03, Piping Systems, provides civil and mechanical engineers with an overview of the civil/mechanical engineering aspects that govern the analysis and design of piping systems. The module identifies the various types of piping systems, their components, their uses, and the applicable codes and standards that are used in their design, fabrication, inspection, installation, and testing. This module also identifies the major considerations for the design of piping systems and the impact of design on pipe support loading. CSE 110.03 demonstrates how selected loads that are imposed on piping systems are calculated. In addition, the module identifies the types and functions of supports and restraints for piping systems.
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TYPES, COMPONENTS, AND USES OF PIPING SYSTEMS Background Fluids are substances that conform to the outline of their containers. Gases and liquids are fluids. The function of piping systems is to safely contain and convey fluids from one location to another. This section discusses the primary components and uses of the following general types of piping systems: •
Plant piping
•
Cross-country pipelines
Plant Piping Plant piping is used within the boundaries of a process plant, such as a petroleum refinery or chemical plant. Components Figure 1 illustrates a typical process plant piping arrangement. The following components are commonly required in plant piping systems: •
Connections for sampling and monitoring.
•
Fittings to establish pipe layout geometry.
•
Flanged connections to plant equipment to facilitate maintenance.
•
Guides and restraints.
•
Pipe, typically 600 mm (24 in.) and less in diameter.
•
Steam traps to remove condensate from steam piping.
•
Supports.
•
Valves to control process conditions or flow, isolate equipment, and separate process streams.
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Horizontal drum
Vertical drum
H80 . SC n i 10 A
A
R HE-B
H40 . SC n i 8
δ HE-A
S
R
R
Y
S
Z
X
S
where: R
= Rigid support
S
= Spring support = Thermal expansion at equipment nozzles
HE = Heat exchanger A
= 10" x 8" concentric reducer
Figure 1. Process Plant Piping System Diagram
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Uses Plant piping transports liquids or gases from one item of plant equipment to another, or between plots within one plant area. Plant equipment consists of items such as the following: •
Compressors
•
Furnaces
•
Heat exchangers
•
Pressure vessels
•
Pumps
•
Storage tanks
Cross-Country Pipelines Cross-country pipelines are used outside the boundaries of process plants, and convey liquid petroleum, petroleum products, liquid-gas mixtures, or natural gas. Depending on the application, these pipelines connect one or more of the following: •
Wellhead
•
GOSP
•
Pumping or compressing facilities
•
Oil termination and shipping facilities
•
Refineries and chemical plants
•
Temporary storage facilities
•
Gas treating
•
Gas metering and regulation
•
Gas mains
•
Gas service to end users
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Components The types of components that are required for cross-country pipelines are generally the same components required for plant piping. The size of pipe for cross-country pipelines is usually (but not always) larger than the size used in plant piping; that is, diameters 750 mm (30 in.) and greater in most cases. Crosscountry pipelines are also much longer than plant piping and can run for many miles. Cross-country pipelines require the following components that are in addition to the components usually found in plant piping: •
Scraper launcher and receiver equipment at pump or compressor stations.
•
Pressure relief systems at pump or compressor stations.
Uses Cross-country pipelines transport liquids, gases, or liquid-gas mixtures between the facilities previously cited. These pipelines provide a convenient method of transferring material from one facility to another and from the source of crude oil or gas to the final delivery terminals or end users. This section discusses the following general types of crosscountry pipelines: •
Underground
•
Aboveground
•
Submarine
Underground Pipelines The most common type of cross-country pipeline is buried underground. A cross-country pipeline is normally buried because it is: •
Usually the least expensive form of construction.
•
Safer than aboveground construction.
Underground pipelines are buried by digging a trench, leveling the trench bottom, installing appropriate bedding material to provide uniform support, placing the pipe in the trench, and filling the trench back in. Sufficient cover must be used over the Saudi Aramco DeskTop Standards
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pipe to restrain the line and protect it from external loads. Figure 2 illustrates a section of underground and aboveground cross-country pipeline. Note that underground pipelines are often located inside steel casings where they cross under roads or railroads. The casing provides additional protection from the concentrated loads that exist at these crossings. Edge of road pavement or railroad bed Traffic barrier
Edge of road berm Warning sign
Edge of berm
Valve
Mound
Pipe support (typical)
Casing
Vent
Support (typical)
Figure 2. Aboveground and Underground Pipelines Aboveground Pipelines Aboveground pipelines are cross-country pipelines that are constructed above the surface of the ground. Aboveground pipelines are used when a buried pipeline is not practical. The primary reasons for the use of aboveground pipelines include terrain features, such as solid rock, that make underground piping expensive or impossible to construct. It is not unusual to use sections of aboveground pipeline in an otherwise buried system to avoid local terrain features. Aboveground pipelines are supported by support structures and associated foundations, similar to plant piping. An aboveground pipeline with its associated supports and foundations is usually more expensive than digging and filling trenches for an underground pipeline. Differential thermal expansion is a more significant design issue for aboveground pipelines than for underground pipelines because of the former's direct exposure to the sun.
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Aboveground pipelines may either be restrained or unrestrained. A restrained pipeline has anchors or restraints installed to restrict its thermal expansion movements and limit the loads that are imposed on any above-to-belowground transition points. An unrestrained pipeline does not have anchors installed; therefore the pipe is theoretically free to expand or contract due to changes in its metal temperature. Most aboveground pipelines are designed as restrained systems, since the free thermal movements can result in excessive loads being imposed on any above-to-belowground transitions. It is also possible that large friction loads at support points could prevent the free thermal movement of the pipe when the metal temperature decreases. Subsequent temperature increases would then start the pipe thermal movement from this already displaced position. In extreme cases, this could eventually cause the pipe to move off its supports. The anchors that are used in restrained piping systems, and their associated foundations, must be designed for the anticipated loads that are caused by pipe thermal expansion/contraction and friction. Submarine Pipelines Submarine pipelines are cross-country pipelines that deliver oil or gas that is produced offshore. They are submerged in water, rest on the marine bottom, or are trenched and buried in the sea bed. To counteract buoyancy, submarine pipelines may be coated with concrete. Figure 3 illustrates a submarine pipeline.
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Production platform
Anchor
Sea level Grade Riser
Anchor Sea bed
Figure 3. Submarine Pipeline
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APPLICABLE CODES AND STANDARDS FOR PIPING SYSTEMS AND THEIR COMPONENTS Industry Standards for Piping Systems and Their Components This section summarizes the scope of the following codes and standards that apply to Saudi Aramco piping systems and components: • -
ANSI/ASME codes ANSI/ASME B31, Code for Pressure Piping +
ANSI/ASME B31.3, Chemical Plant and Petroleum Refinery Piping
+
ANSI/ASME B31.4, Liquid Transportation Systems for Hydrocarbons, Liquid Petroleum Gas, Anhydrous Ammonia, and Alcohols
+
ANSI/ASME B31.8, Distribution Piping •
Gas
Transmission
and
ANSI and API standards and publications
ANSI/ASME B31.3, Chemical Plant and Petroleum Refinery Piping ANSI/ASME B31.3 establishes requirements for the safe design, construction, inspection, and testing of chemical plant and petroleum refinery piping. This code applies to all piping within the property limits of facilities that process or handle chemical, petroleum, or related products. It applies to piping for all fluids, including the following: •
Gas, steam, air, and water
•
Fluidized solids
•
Petroleum products
•
Raw, intermediate, and finished chemicals
•
Refrigerants
ANSI/ASME Code B31.3 excludes systems that operate above 0 but below 103 kPa (15 psig) (within specified service and temperature restrictions), piping within a fired heater enclosure, process equipment (for example, pressure vessels, heat exchangers, etc.), and other specified items. Piping components that are included in this code are pipe, fittings, valves, flanges, gaskets, and bolting.
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ANSI/ASME B31.4, Liquid Transportation Systems for Hydrocarbons, Liquid Petroleum Gas, Anhydrous Ammonia, and Alcohols ANSI/ASME B31.4 establishes requirements for the safe design, construction, inspection, testing, operation, and maintenance of piping that transports the following liquids: •
Condensate
•
Crude oil
•
Liquid alcohol
•
Liquid anhydrous ammonia
•
Liquefied petroleum gas
•
Liquid petroleum products
•
Natural gas liquids
•
Natural gasoline
Piping components that are covered in this code include the following: •
Pipe
•
Flanges
•
Bolting
•
Gaskets
•
Valves
•
Relief devices
•
Fittings
•
Pressure-containing components
parts
of
other
piping
This code excludes systems that operate at or below 103 kPa (15 psig), below -29°C (-20°F), or above 121°C (250°F); auxiliary piping systems for specified services; equipment items; and other specified components and systems.
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ANSI/ASME B31.8, Gas Transmission and Distribution Piping ANSI/ASME B31.8 establishes requirements for the safe design, construction, inspection, testing, operation, and maintenance of gas transmission and distribution piping. This code applies to: •
Gas transmission and distribution systems, including gas pipelines, gas compressor stations, gas metering and regulation stations, gas mains, and service lines up to the outlet of the customer’s meter set assembly.
•
Gas storage equipment of the closed-pipe type, fabricated or forged from the pipe or fabricated from the pipe fittings, and gas storage lines.
•
Pipe, valves, fittings, flanges, bolting, gaskets, regulators, pressure vessels, pulsation dampers, and relief valves.
ANSI/ASME B31.8 excludes systems operating at or below 29°C (-20°F) or above 232°C (450°F), equipment items, piping beyond the customer’s meter set, and other specified components and systems. ANSI and API Standards and Publications The industry codes that are noted above, and the Saudi Aramco standards and specifications that will be discussed later, include references to ANSI, API, and other industry standards and publications. By reference, these publications become integral parts of the industry and Saudi Aramco design standards. These publications provide additional detailed requirements for specific piping system components, such as valves and flanges, and for particular piping system applications, such as offshore production platform piping or liquefied petroleum gas (LPG) installations. These ANSI and API standards are not discussed since they provide detailed information that is beyond the scope of this course. Participants are referred to the ANSI/ASME B31 Codes and relevant Saudi Aramco standards and specifications as necessary for additional information.
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Saudi Aramco Standards for Piping Systems and Their Components The “L series” of the Saudi Aramco Engineering Standards (SAES's) is the primary group of standards that specify additional Saudi Aramco engineering requirements for piping systems that are within the scope of the ANSI/ASME B31 Codes. These SAES's also include other pressure piping services that are excluded from the Code. SAES-L-000, Piping Standard Forward and Index, provides an index that identifies the content of each standard in the series. The Saudi Aramco engineer should refer to SAES-L-000 to identify the applicable standards as required during his work. Saudi Aramco engineering standards from other groups (for example, the A, B, H, J, and N series) are referred to from within these standards, as required for particular piping systems and/or applications. Saudi Aramco Material Systems Specifications (SAMSS's) provide detailed design, fabrication, inspection and testing requirements for particular piping system components, such as valves, fabricated carbon steel pipe, or pipe in wet, sour service. The SAMSS's are primarily “purchase type” documents that are included in the purchase order for an item to further specify its technical requirements. They are not discussed in this course, and the Participants are referred to the Saudi Aramco Material System Specifications Manual as required for information. The following material highlights several of the SAES's that are relevant to piping system design. SAES-A-004, Pressure Testing SAES-A-004 provides the general principles that apply to pressure testing of plant equipment and plant piping. This standard applies to newly installed and existing equipment and piping. The standard specifies that a pressure test be performed as follows: •
Before the equipment or piping is placed into service.
•
After repairs or alterations that affect the strength of the equipment.
•
At scheduled intervals.
•
Whenever considered necessary or advisable by the responsible manager.
This standard provides conditions, limits, and exceptions for pressure testing. Saudi Aramco DeskTop Standards
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SAES-A-005, Safety Instruction Sheet SAES-A-005 outlines the procedure for preparing Safety Instruction Sheets (SIS's) for new plants, for additions to existing plants, and for re-rating existing equipment. SIS's provide information in a consistent format on safe operating limits, protection devices, and special safety precautions. This information is primarily used by operations, maintenance, and inspection personnel. Critical plant piping and cross-country pipelines must have SIS's. SAES-H-002, Internal and External Coatings for Steel Pipelines and Piping SAES-H-002 provides the mandatory internal and external coating selection and installation requirements for steel pipelines and piping, including the associated fittings and appurtenances. SAES-L-001, Basic Criteria for Pressure Piping Systems SAES-L-001 provides the scope and definitions of terms that apply to the SAES's that concern piping. This standard specifies the minimum basic requirements for pressure piping systems. The SAES's on piping, in general, adopt the latest edition of the relevant ANSI/ASME B31 Code as the primary minimum requirement for all pressure piping systems and then supplement this code as required. SAES-L-001 (and therefore ANSI/ASME B31) applies to pressure piping in plants, Saudi Aramco camps, and cross-country and offshore pipelines, with the following exceptions: •
Piping systems built before the date of approval.
•
Sanitary and other gravity sewers in which the static head does not exceed 103 kPa (15 psig).
•
Plumbing, as defined in the Saudi Aramco Plumbing Code.
•
Stacks, flues, vents, and ducts.
•
Tubes, tube fittings, and headers for boilers, heat exchangers, and furnaces.
•
Piping that is inside fluid handling or processing equipment.
•
Casing, tubing, and wellhead valve assemblies in gas, oil, or water wells.
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SAES-L-002, Design Conditions for Pressure Piping SAES-L-002 defines the design conditions for plant piping and pipeline services. Among its requirements and exclusions are the following: •
Exposed piping systems are to be designed for a 35 m/s (78 mph) fastest wind speed. Where applicable, the effects of wind-induced vibration are to be included.
•
Above-grade piping and pipelines that are in vapor services and their supporting structures are to be designed to withstand slug forces that act at changes in pipe direction.
•
Seismic loads are not applicable to piping in Saudi Aramco operating areas.
•
Adequate damping and/or restraint is to be provided for piping that is subject to induced vibration (caused by pressure-reducing valves, rotating or reciprocating equipment, two-phase flow, wind, and wave currents).
SAES-L-003, Design Stress Criteria for Pressure Piping SAES-L-003 defines the design criteria for plant piping and pipeline services. SAES-L-004, Pressure Design of Piping Components SAES-L-004 provides additional requirements and limitations for the pressure design of components and branch connections in metallic piping in plants and pipelines. SAES-L-005, Limitations on Piping Components SAES-L-005 covers the selection of compatible piping material items which are used together in a specific system or service. This standard establishes general requirements for listing in a piping specification and related identification on Piping and Instrument Diagrams (P&IDs) and other drawings.
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SAES-L-006, Metallic Pipe Selection SAES-L-006 provides limitations on the selection of metallic pipe and tubing for pressure services in plant piping and transportation piping. This standard limits selection of pipe and tubing to materials, types, and sizes that are in the Saudi Aramco Materials System (SAMS) Catalog, unless no suitable material is listed. This standard also places other restrictions on pipe sizes and materials based on pipe service and for standardization purposes. SAES-L-007, Selection of Metallic Pipe Fittings SAES-L-007 provides limitations on the selection of metallic pipe fittings, bends, miters, laps, and branch connections for pressure services in plant piping and transportation piping. This standard limits selection of pipe fittings to items in the SAMS Catalog unless no suitable material is listed. It also places other restrictions on fittings based on the type of pipe and the usage. SAES-L-008, Selection of Valves SAES-L-008 provides limitations on the selection of all valves normally classified under SAMS Class 04. This class normally includes angle, ball, check, diaphragm, needle, butterfly, gate, globe, choke, and plug valves used for on-off, for manual control service, or for prevention of reverse flow. The standard places other restrictions on valve type selection based on use. This standard excludes: •
Control, safety-relief, relief, surge relief, solenoid, pilot, and other valves that are classified under SAMS Class 34.
•
Applications that involve flues and chimneys, as well as air conditioning and ventilating ducts.
•
Drilling and wellhead valves and chokes that are classified under SAMS Class 45.
SAES-L-009, Metallic Flanges, Gaskets, and Bolts SAES-L-009 provides limitations on the selection of metallic pipe flanges, gaskets, and bolting for pressure services in plant piping and transportation piping.
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SAES-L-010, Limitations on Piping Joints SAES-L-010 provides limitations on the type of joints that are used in metallic piping for pressure services in plants and pipelines. The joint types that are included are welded, flanged, expanded, threaded, and tubing joints. SAES-L-011, Flexibility, Support, and Anchoring of Piping SAES-L-011 provides the design requirements that are related to the flexibility and the full or partial restraint, supporting, and anchoring of plant piping and transportation piping, when the piping is metal or lined metal. SAES-L-012, Design of Piping Systems Inside Plant Areas SAES-L-012 provides the general design requirements for pressure piping that is located within plant areas. Further requirements related to specific plant piping systems are covered by separate SAES's in the series SAES-L-013 through SAES-L-029. These SAES's include the following: •
SAES-L-014, Design of Pump and Compressor Station Piping
•
SAES-L-015, Design of Piping on Offshore Structures
•
SAES-L-020, Design of Transportation Piping Systems
•
SAES-L-021, Design of Submarine Pipelines and Risers
•
SAES-L-022, Design of Well Flowlines and Trunklines
SAES-L-032, Materials Selection for Piping Systems SAES-L-032 provides guidelines for selection of the basic construction materials used for piping systems. These guidelines depend on the fluid to be transported and the fluid's temperature. SAES-L-033, Corrosion Protection Requirements for Pipelines/Piping SAES-L-033 provides the minimum corrosion control measures for carbon steel pipelines and piping in the following applications:
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•
Cross-country and hydrocarbon service.
offshore
pipelines
in
•
Critical water service lines in all locations, including plants, industrial areas and communities, and crosscountry and offshore pipelines.
•
Piping in plant areas.
SAES-L-041, Utility Piping Connections to Process Equipment SAES-L-041 provides limitations applicable to the piping that connects a supply of steam, water, air, nitrogen, or other inert gas to process equipment in hazardous services. This standard covers connections for purging or cleaning when the process equipment is not in operation. This standard excludes connections to open furnaces or fire boxes and to process equipment where the process flow and utility flow remain physically separated. SAES-L-044, Anchors for Cross-Country Pipelines SAES-L-044 provides the design requirements for anchors that are used on cross-country pipelines. The standard includes the design bases for calculating the resisting force of concrete anchors (on the basis of bearing and soil friction loads) and attachment requirements between the anchor and pipe. SAES-L-045, Scraper Trap Station Piping and Appurtenances SAES-L-045 provides minimum requirements for the design of piping and appurtenances for permanent pipeline scraper launching and receiving stations. SAES-L-046, Pipeline Crossings Under Roads and Railroads SAES-L-046 provides the requirements that govern pipeline crossings under roads, parking lots, railroads, and airport runways within Saudi Aramco jurisdiction. It also applies to pipelines in any service within plant and residential areas as well as sewers and culverts of flexible materials. The standard defines traffic load classifications used to establish applicable external loads and specifies when the pipeline must be enclosed in a steel casing for protection from external loads.
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SAES-L-050, Construction Requirements for Metallic Plant Piping SAES-L-050 specifies fabrication and installation requirements for plant piping systems within the scope of ANSI/ASME B31.3. This standard applies to metallic plant piping, piping assemblies such as jumpovers for cross-country pipelines, and piping on offshore platforms. SAES-L-051, Construction Requirements for Cross-Country Pipelines SAES-L-051 provides the construction requirements for steel cross-country pipelines, aboveground or buried, restrained or unrestrained, in all services. The standard does not apply to offshore pipelines and nonmetallic pipelines. SAES-L-052, Hot Tap Connections SAES-L-052 provides the requirements for piping connections that are made to existing pipelines, tanks, and pressure vessels by hot tapping, (i.e., by installation while the pipe or equipment is in service). SAES-L-055, Inspection of Piping Systems SAES-L-055 provides the basic, code-related requirements for examination, inspection, and testing of all pressure piping systems and related work before or during the commissioning for initial operation. SAES-L-060, Nonmetallic Piping SAES-L-060 provides the requirements and limitations for the design, installation, and testing of nonmetallic piping in all areas except plumbing. Saudi Aramco Design Practices Saudi Aramco Design Practices (SADP's) supplement the corresponding Saudi Aramco Engineering Standard (SAES's) by providing additional information on the background and use of specific SAES's. The following paragraphs overview specific SADP's that are of most interest to civil and mechanical engineers.
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SADP-L-001, Basic Criteria for Pressure Piping Systems SADP-L-001 provides background information on the basic requirements for pressure piping systems. The design practice also defines terms that are applicable to the SAES-L series of standards. SADP-L-002, Design Conditions for Pressure Piping SADP-L-002 provides background information on design conditions for pressure piping. SADP-L-003, Design Stress Criteria for Pressure Piping SADP-L-003 provides background information on design stress criteria for plant piping and transportation piping. SADP-L-004, Pressure Design of Piping Components SADP-L-004 provides background information on the pressure design of piping components. SADP-L-011, Flexibility, Support, and Anchoring of Piping SADP-L-011 provides background information that is related to the flexibility and the full or partial restraint of piping and the requirements for supporting and anchoring. SADP-L-012, Design of Piping Systems Inside Plant Areas SADP-L-012 provides general design considerations that relate to pressure piping inside plant areas. The design practice addresses items such as general layout, aboveground versus underground installation, and general system requirements. SADP-L-014, Design of Pump and Compressor Station Piping SADP-L-014 provides guidelines for the design of piping in pump and compressor stations. SADP-L-020, Transportation Piping Systems SADP-L-020 provides background information on the design requirements that generally apply to cross-country and offshore transportation piping systems. The design practice also provides specific requirements such as material selection, fabrication, testing, and limitations on components for certain services. Saudi Aramco DeskTop Standards
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SADP-L-021, Design of Submarine Pipelines and Risers SADP-L-021 is a reference to the latest revision of SAER-1337, Submarine Pipeline Project Guidelines. This design practice and SAER-1337 provide background information for SAES-L021. SADP-L-022, Design of Well Flowlines and Trunklines SADP-L-022 provides background information on the design requirements for oil pipelines that are in flowline service. SADP-L-044, Anchors for Cross-Country Pipelines SADP-L-044 provides background information on the design of concrete and steel anchors for buried or aboveground restrained cross-country pipelines. SADP-L-046, Pipeline Crossings Under Roads and Railroads SADP-L-046 provides background information on pipeline crossings under roads, parking lots, railroads, and airport runways within Saudi Aramco jurisdiction. SADP-L-050, Construction Requirements for Metallic Plant Piping SADP-L-050 provides background information on the fabrication and installation requirements for metallic plant piping. SADP-L-051, Construction Requirements for Cross-Country Pipelines SADP-L-051 provides background information on the construction requirements for steel cross-country pipelines. These requirements are in addition to the requirements of ANSI/ASME B31.4, Chapter V, Sections 434 and 435. For services containing free gas, these requirements are also in addition to the requirements of ANSI/ASME B31.8, Sections 841.13 through 841.27.
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MAJOR CONSIDERATIONS FOR DESIGN OF PIPING SYSTEMS AND THEIR EFFECT ON PIPE SUPPORT LOADING This section provides information on the factors that affect the design of piping systems and their effect on support and restraint loading. The factors that affect piping system design are covered in two parts as follows: • •
Layout considerations Detailed design considerations
Background The following material is a general introduction to supports and restraints. A later section of this module provides more information on supports and restraints. Supports Pipe supports are used to support the weight of the piping system and the contents of the system. The supports keep the pipe elevated at a desired height above the ground. The specific number and locations for pipe supports are determined to ensure the following: • • •
The pipe stress that is caused by the weight load must be kept within allowable limits. The pipe must not sag excessively. Reaction loads at equipment connections must not be excessive.
Restraints Restraints control or limit movement of the pipe in one or more directions. Such restraint may be required to reduce thermal expansion reaction loads at equipment connections, or to limit pipe vibration. Some restraints keep the pipe from moving vertically or laterally but allow the pipe to move longitudinally. Other restraints do not allow the pipe to move in any direction. A support is a specialized type of restraint that prevents pipe movement under vertical weight loading.
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Major Considerations for Layout of Piping Systems The primary considerations that influence the layout of a piping system are related to requirements in the following areas: •
Operations
•
Maintenance
•
Safety
These considerations influence both the overall and detailed design of the structural steel and associated foundations needed for piping systems. Operations Requirements Operating and control equipment, such as valves, flanges, instruments, sample points, drains, and vents, must be located for easy and safe access. For example, valves must be located so that they can be reached. This may require locating the valve near an existing platform or adding a new platform with appropriate ladder or stairway access. Clearances Below Piping - There must be sufficient clearance
below the pipe to perform operations on valves and flanges, such as removing a valve or unbolting a flange. In addition, suspending pipe above the ground helps prevent corrosion that may be caused by water accumulation or contact with corrosive substances. SAES-L-011 requires aboveground piping to have the following minimum clearances between the bottom of the pipe and finished grade: •
0.3m (1 ft.), in plant areas and where the grade under the pipe is a hard surface.
•
0.45 m (1-1/2 ft.), outside of plant areas without nearby unstabilized sand dunes.
•
0.9 m (3 ft.), in areas with moving sand dunes.
Clearances Above Piping - There must be sufficient clearance above the pipe to perform operations on valves and flanges. These operations include the opening and closing of valves as well as the operation and replacement of equipment. Clearance Around Piping - The minimum clearances between buried pipelines at crossings and pipe, flanges, or valves and any structure that is not used to support the piping are as follows:
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•
If the length is three pipe diameters or less, 0.3 m (1 ft.).
•
If the length is greater than three pipe diameters, 0.6 m (2 ft.).
•
For aboveground piping and structures, sufficient to provide reasonable access for inspection and to avoid interference with pipe movement.
Scraper Traps - A scraper is a device that is used for internal cleaning, gauging, inspection, or batching of a piping system. Scraper traps are the locations for inserting and removing scrapers. Operation personnel need enough space around the scraper trap to remove and reinsert scrapers. SAES-L-045 specifies that the clearance between grade and the bottom of the trap in onshore plants must be approximately 1 m (40 in.), and that a surface drainage system must be provided. Scrapers are primarily used in pipeline rather than plant systems. Existing Pipeways and Supports - When practical, new piping
should use existing supports to minimize costs. As much as possible, new piping should be located in existing pipeways. Intersecting pipeways are located at different elevations to facilitate access and future piping installation. Standard Drawing AC-036207 specifies the minimum spacing of lines that are supported on sleepers or pipe racks.
Thermal Expansion - Sufficient clearance must be provided between adjacent lines, and between lines and structures, to allow for thermal expansion of the piping. The clearances provided must also consider the thickness of fireproofing that may be installed on nearby structures, pipe insulation, and any projections from the pipe (for example, small-diameter connections and flanges). Facilitating Support and Restraint - Piping systems should be
routed to facilitate their support and restraint, to minimize cost, and to limit additional structural and foundation requirements. The following guidelines should be considered: •
The piping system should support itself to the extent possible to minimize the amount of additional structural steel that is required to provide support.
•
Piping with excessive flexibility may require the addition of restraints to minimize excessive movement and/or vibration that may be caused by
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fluid flow, wind, or earthquake. Therefore, piping systems should be designed with only the flexibility needed to accommodate the expected thermal movement without causing excessive pipe stresses or end point reaction loads. Systems should not be overly flexible. •
Piping that is prone to vibration, such as reciprocating compressor suction and discharge systems, should be supported independently from other piping systems. This independent support keeps the effects of the vibration-prone system confined to that system and directly associated structures. The effects are not transmitted to other systems.
•
Piping that is located in structures should be routed beneath platforms and near major structural members, at points that permit added loading. Routing beneath platforms avoids access interference problems. Routing near major structural members minimizes the need to increase the size of structural members or to provide additional local reinforcement, due to increased bending moment.
•
When possible, piping should be routed near existing structural members to minimize the need for additional structure and foundations.
Maintenance Requirements The layout of the piping system must allow for inspection, repair, or replacement of components with minimum difficulty. The layout must provide adequate clearance for maintenance equipment, such as cranes and trucks, and provide access to the supports. The system also must not interfere with maintenance and possible removal of large pieces of equipment. For example: •
Heat exchanger tube bundles must be pulled out for cleaning.
•
Rotating equipment requires frequent monitoring and maintenance, and sometimes must be removed.
Safety Requirements
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The layout of the piping system must consider the safety of personnel who may be near the pipe. Major pieces of equipment, particularly heat exchangers, vessels, and tanks, must be accessible for fire-fighting equipment. Pipeways must be routed to provide this access.
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There must be adequate space under pipeways for people to walk and work. Typically, 2 m (7 ft.) of clearance under a pipeway is sufficient. Firewater piping must be routed so that it is not damaged if piping that contains hazardous fluids ruptures. Major Considerations for Detailed Design of Piping Systems Major considerations for the detailed design of piping systems include the following: • • • • •
Material selection Allowable stress Flexibility Equipment tie-in Deflection tolerance
Material Selection Pipe and piping components such as flanges, fittings, and valves are available in a wide variety of materials. These materials include plastics, cast iron, copper, nickel, carbon steel and high alloy materials. The first consideration in the selection of a piping material is to determine the material's resistance to corrosion or to other forms of chemical attack that may occur in service. Since there are many different types of corrosion or chemical attack mechanisms, some guidance to material selection is required. In many cases, the basic material selection may be based on criteria that are contained in SAES-L-032. These criteria consider the fluid service, temperature, and flow velocity. Table 1 in this standard lists materials for many common services that are found in Saudi Aramco facilities. If the particular service is not covered by SAES L-032, a corrosion/metallurgical engineer in CSD should be consulted. Note that if the service contains even small quantities of some chemicals such as H2S, then additional requirements on pipe fabrication or manufacture may be required by the SAES's or SAMSS's. For many services, carbon steel has adequate corrosion resistance or a nominal corrosion allowance may be used to account for corrosion. Corrosion allowance is additional thickness that is added to a pipe for corrosion that takes place during service. Carbon steel pipe and piping components are manufactured to various ASTM and API specifications, and they are available in various grades or strength levels.
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Steel pipe is also available in two basic varieties: seamless or welded. In the case of piping that is less than 600 mm (24 in.) in size, seamless pipe is often used. For larger diameter pipe, electric resistance welded or electric fusion welded pipe may be used. However, it should be noted that there may be restrictions on the use of various types of welded pipe in refinery service. In addition to corrosion resistance, other pipe material selection considerations include strength at elevated temperatures, fracture toughness at low temperatures, cost, and availability. Allowable Stress The loads that are imposed on a piping system due to pressure, weight, differential thermal expansion, and other external factors, cause stresses in the pipe and piping components. The term "allowable stress" refers to the maximum limit that these stresses are permitted to reach within the system design parameters. There must also be a safety margin between the allowable stress and the stress level that would cause a pipe failure. Before an allowable stress can be determined, the Code that governs the piping system must be determined. If the piping is in a refinery, then the piping would typically be covered by the ANSI/ASME B31.3 piping code. In this case, the allowable stress for ferritic materials is usually determined based on 1/3 of the ultimate tensile strength of the material or 2/3 of the material yield strength, whichever is greater. If the piping is crosscountry piping, then the allowable stress may be as high as 72% of the yield strength or as low as 40% of the yield strength, depending on how close the piping system is to a populated area. The different piping codes also permit different allowable stresses for longitudinal stress in the pipe, such as stress that is due to weight effects. In the B31.3 code, the stress in the pipe due to sustained weight loads is also limited to the above allowables. Since the longitudinal stress in the pipe due to pressure is equal to about 1/2 of the circumferential stress due to pressure, approximately one half of the allowable stress may be considered available for the support of the pipe.
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Flexibility When a pipe or piece of equipment heats up (or cools down) from its installation temperature, thermal expansion (or contraction) occurs. Sufficient flexibility must exist in the piping system to accommodate the thermal expansion or contraction of both the piping and any attached equipment. If the piping system does not have sufficient flexibility, thermal expansion and contraction may cause excessive pipe stresses and/or equipment reaction loads. In extreme cases, this can lead to the following: •
Damaged equipment
•
Excessive maintenance
•
Leaky flanges
•
Pipe failure
•
Operating problems
The flexibility of the piping system may be increased by the use of the following: •
Offsets
•
Bends
•
Expansion loops
•
Expansion joints (SAES-L-011 limits the use of expansion joints.)
•
Spring supports instead of rigid supports
Restraints are sometimes installed to minimize thermal and friction loads at equipment and/or to direct thermal movement toward a more flexible portion of the system that is better able to absorb the movement. Equipment Tie-In Wherever equipment connects to the pipe, the pipe must align properly with the equipment connection, within relatively tight tolerances. If the pipe does not align properly with the equipment, excessive loads may be imposed on the equipment nozzle during the process of connecting the pipe to the nozzle. Excessive loads could cause the following problems:
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•
Equipment may not function correctly. For example, high loads can cause excessive vibration of rotating equipment.
•
Excessive stress may cause component failure.
•
Equipment maintenance needs, such as bearing and seal problems with rotating equipment, can be increased.
•
Nozzles may be damaged or flanges may leak.
Weight Stress Pipe weight stress is not a consideration for properly installed underground pipelines because the pipe is continuously supported by the bedding. Supports for aboveground sections of pipeline and plant piping systems must be spaced closely enough to ensure that the pipe stress due to weight loads is within acceptable limits (based on the relevant ANSI/ASME B31 Code requirements). Support spacing for horizontal pipes in open areas is generally governed by the strength of the pipe, and only enough structural steel is added to provide the needed support. Support spacing for pipes that are inside process plants is determined more by the spacing of conveniently located columns, since a large quantity of structural steel is already present for other piping systems and equipment support structures. Spacing of pipe racks usually provides for the weakest pipe. In some cases, small-diameter lines can be supported off larger lines, bundled with other small lines, or increased in diameter to be selfsupporting. Deflection Tolerance To avoid excessive sag, pipes need to be adequately supported. It is possible for an excessive sag in a pipe to cause flow problems in liquid systems due to pocketing. Excessive sag also makes a poor visual impression even if it does not cause any technical problems. Maximum deflection is generally limited to about 19 mm (3/4 in.) for process plant piping and to 25 mm (1 in.) for offsite piping and pipelines.
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Other Support Considerations Other practical considerations also influence the location and spacing of supports, especially within process plants. For example: •
Pipe and structural steel come in standard lengths. For example, pipe and structural steel are commonly available in 6 m (20 ft.) lengths. The use of standard lengths of pipe and steel is maximized to reduce the required number of cuts and splices. This is one of the main reasons why the column spacing and level elevations of pipe rack structures look very similar worldwide.
•
Erection efficiency can be a consideration in locating structural steel. For example, conveniently located structural steel can facilitate and expedite pipe erection by reducing personnel and heavy equipment requirements. The addition of permanent structural steel solely for the purpose of pipe erection is generally not done. However, if the erection needs are anticipated, detailed dimensioning and spacing of structural steel that is required can help pipe erection with little, if any, cost penalty.
•
Saudi Aramco Standard Drawing AC-036697 defines the maximum allowed spacing between supports on unrestrained pipelines.
Effect on Support and Restraint Loading The design requirements of the piping system determine the location and requirements for supports and restraints. Factors in the design that affect the support and restraint requirements are as follows: •
Pipe layout.
•
Pipe design conditions, especially temperature.
•
Location of end points and any thermal movements to be considered.
•
Location of support and restraint points.
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•
Amount and direction of pipe movements that are allowed at the support or restraint (if any).
•
Weight of the pipe to be supported, including its contents, insulation, and lining.
•
Pipe vibration dampening required (if any).
•
Weight of other pipe components (valves, flanges, etc.) to be supported.
Of these design factors, pipe component weight and the amount of restraint required have the strongest effect on support and restraint design. Weight Support structures and associated foundations for a piping system must be able to support the weight of the pipe, its contents, and all other components in the system. Such support is particularly required during hydrostatic testing. However, if the support structures are adequate for normal operation but are marginal or inadequate for hydrostatic testing, temporary support structures can be added during hydrostatic testing. In this case, because re-hydrotesting may be required in the future as a part of maintenance, repairs, or alterations, the design records must indicate that hydrostatic testing requires additional support for the pipe. Special attention should be paid to systems that operate in vapor service, since the hydrostatic test weight can be much higher than the operating weight. This weight difference becomes greater as the pipe diameter increases. Effect of Restraints on Movement If a pipe were allowed to move without restraint under weight, thermal, or other imposed loads, there would be no stress in the pipe or loads to absorb. Not allowing the pipe to move freely results in added stresses in the pipe and loads (that is, forces and moments) that must be absorbed by the restraint, with its associated structure and foundation. A restraint may be designed to prevent pipe translation and/or rotation in one or more directions at a given location, depending on the pipe design requirements. When the pipe is not allowed to move in a particular direction, the support or restraint and its associated foundation must be designed to withstand the forces that attempt to move the pipe. These forces include those that result from the following: Saudi Aramco DeskTop Standards
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•
Thermal expansion and contraction
•
Wind
•
Slug, surge, or other vibrational loads
Thermal Expansion and Contraction - Whenever a pipe is heated or
cooled, the pipe material attempts to expand or contract from its as-installed position. When the pipe movement is prevented by a restraint, stresses result in the pipe, and loads are imposed on the restraint. The detailed design of the restraint attachment to the pipe, and the steel structure and foundation that are associated with the restraint, must be able to absorb these loads without being overstressed themselves or experiencing excessive deformation or movement. Since the purpose of the restraint is to limit pipe movement, the restraint will not perform its intended function if the structure to which it is attached deflects excessively under the applied loads. Wind - Exerts a force on exposed pipe and tends to deflect it,
resulting in additional pipe stresses and end-point reaction loads. It is sometimes necessary to add additional lateral restraints to a piping system to resist wind-induced forces and to prevent excessive deflection. Addition of lateral restraints is commonly done for pipe that is attached to tall, vertical towers that are exposed to the wind. These restraints must be designed to withstand the forces imposed by the wind without excessive deflection. Slug, Surge, or Other Vibrational Loads - In two-phase flow,
interaction between the liquid and vapor phases can lead to flow-induced vibration in certain flow regimes. In slug flow, slugs of liquid can form intermittently and travel down the pipe at relatively high velocity. This liquid slug can cause large reaction forces at changes in pipe direction, such as at bends and branch intersections. In extreme cases, these forces have been large enough to lift pipe off its supports and cause considerable damage. It is sometimes necessary to add supplemental restraints to a piping system in order to absorb these slug forces and to prevent excessive pipe movements. These restraints must be attached to structures and associated foundations that are designed to be strong enough to absorb the slug forces without excessive deflection.
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Hydraulic surge develops in a piping system when the steadystate fluid velocity is suddenly altered. The most common causes of surges are rapid valve closure or opening, vapor pocket collapse, safety valve blowdown into a liquid-filled line, and starting or stopping a centrifugal pump. When the flow is altered suddenly, a pressure wave moves down the pipe at the speed of sound. Such surge pressures and resulting forces have caused pipe to jump off its supports, damage to anchors and restraints, and damage due to system overpressure or vacuum. Surge is of concern only in liquid-filled systems due to the much higher fluid density when compared to gaseous systems. In extreme situations, as with slug flow, it may be necessary to add restraints to the piping system to absorb these surge loads. Vibration loads may also be imposed by other flow-related problems or connected machinery. For example, steady pressure pulsations are normal in reciprocating compressor piping systems. The piping system must be designed so that its mechanical natural frequency does not coincide with the forcing pressure pulsation frequency to prevent resonant vibration. Avoiding coincidence between the mechanical natural frequency and the forcing frequency may require addition of supports and/or restraints or alteration of their spacing. Again, the design of the structural steel and foundations must be strong enough to resist the pulsation-induced loads. Since the loads in this case are applied at a regular frequency, the structural steel and foundation designs must also consider the potential for fatigue failure. As highlighted above, addition of restraints is a common method for control of excessive piping vibration. However, these additional restraints also directly affect pipe thermal expansion. Therefore, care must be taken to ensure that the addition of restraints to solve a vibration problem does not introduce a thermal expansion stress and/or load problem.
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CALCULATING SELECTED CIVIL/MECHANICAL LOADS ON PIPING SYSTEMS This section calculations:
discusses
and
demonstrates
the
following
•
Wall thickness required for internal pressure
•
Dead and live loads
•
Hydrostatic test weight
•
Wind
•
Friction
Estimating the Wall Thickness Required for Internal Pressure The first step in determining the dead weight loads on a piping system is to determine the required pipe wall thickness. In many cases the required pipe wall thickness is determined based on the thickness required for internal pressure, plus allowances for corrosion and mill tolerance. In some cases various minimum thicknesses that are indicated in SAES-L-006 must be used. The following equation can be used to estimate the minimum wall thickness that is required for internal pressure. For definitive work, the applicable code equation should be used, since this equation contains slight simplifications. t=
PD + A (2SE )
(1 − M.T.) where: t
P D S
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= Minimum thickness that is required for pressure plus allowances for corrosion, erosion, thread, and groove depth, as required by the applicable code, in inches. = Internal design pressure of the pipe at the point under consideration, in psig. = Outside diameter of the pipe, in inches. = Allowable stress for the pipe material at the design temperature considering the piping code used for the design, in psi. Note that in ANSI/ASME B31.1 and B31.3, "S" denotes the material allowable stress. B31.1 and B31.3 contain tables that specify allowable stress as a function of material specification and design 39
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temperature. In ANSI/ASME B31.4 and B31.8, the material specified minimum yield strength must be multiplied by factors to account for pipeline location and temperature to arrive at an allowable stress. E=
Longitudinal joint efficiency of the pipe which is based on the piping code that is used for design and on whether the pipe is seamless or has a welded seam. E = 1 for seamless pipe. For welded pipe, the different codes have different joint efficiencies that depend on the type of welding details and inspection requirements that are used when manufacturing the pipe. The joint efficiency accounts for the quality of the welded seam and will typically range from 0.8 to 1.0 for the details that are commonly used.
A=
Sum of the mechanical allowances, in inches. A nominal corrosion allowance of 1.5 to 3 mm (0.0625 to 0.125 in.) is typically used for B31.3 piping to account for corrosion that occurs during operation. However, the corrosion allowance may also include a thread depth allowance for small pipes or a groove depth if special fittings are used.
M.T. = Mill Tolerance factor to account for the variations in pipe wall thickness that is due to the manufacturing process that was used to make the pipe. Note that consideration of mill tolerance varies with the piping code that is used for design. In the case of B31.3 piping, a 12.5% tolerance is used for seamless pipe that is made to the ANSI/ASME B36.10 Standard. Thus, pipe may be supplied up to 12.5 % thinner than the specified nominal thickness, and M.T. = .125 in this case. In the case of piping that is designed to the B31.4 and B31.8 Codes, mill tolerance is not normally used and M.T. = 0. Pipe is manufactured to standard diameters and wall thicknesses. ANSI/ASME B36.10 and API 5L are two industry Saudi Aramco DeskTop Standards
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specifications that define standard diameters and wall thicknesses that are manufactured worldwide. Figure 31 in Work Aid 1 summarizes design information for standard pipe sizes and includes standard nominal wall thicknesses (or schedules). After the minimum required pipe wall thickness for internal pressure is determined using the previous equation, then the next higher standard nominal thickness is used for the pipe. In this manner, the as-supplied pipe thickness will, after the maximum possible mill tolerance is subtracted, will still be sufficient for the internal pressure. Note that API 5L lists many more nominal pipe thicknesses than ANSI/ASME B36.10 but that all these thicknesses may not be readily available.
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Sample Problem 1 - Determine the nominal pipe wall thickness or pipe schedule for a 12 inch NPS pipe. Given: •
The B31.3 refinery piping code is applicable
•
The internal design pressure is 300 psig
•
The actual outside diameter of a 12 inch NPS pipe is 12.75 inches
•
The pipe is A106 Grade B seamless pipe
•
A106 Grade B has an allowable stress of 14500 psi
•
The corrosion allowance is 0.125 inch
Solution: t = ((300 x 12.75)/(2 x 14500 x 1.0) + 0.125)/(1 - 0.125) t = 0.2936 inch A review of a standard pipe wall thickness table (Figure 31 in Work Aid 1) indicates that the next larger nominal pipe thickness would be 0.33 inch. This corresponds to a Schedule 30 pipe. Therefore, at least a Schedule 30 pipe should be used. Dead and Live Loads The design engineer must design the piping system and its associated supports for the weight of the pipe, its contents, and other piping components. Work Aid 1A provides the procedure for calculating the dead and live weight of the piping system. Sample Problem 2: Dead and Live Loads Calculate the dead and live loads on a piping system. Given: The piping system: •
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Is made of NPS 24, Schedule 80 pipe
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•
Has supports every 20 ft.
•
Transports material with a specific gravity of 0.75
•
Pipe uninsulated, components
unlined,
no
other
pipe
The pipe is uninsulated and unlined, and there are no additional pipe components to be supported. Solution: The following step numbers correspond to the step numbers in Work Aid 1A: Dead Weight 1.
The weight of pipe is 296.36 lb./ft.
2.
LDW
=
[(WPPF + WILPF)DS] + WC
LDW
=
296.36
LDW
20
5,927 lb.
Live Load 1.
The weight of water is 158.26 lb./ft.
2.
LLL =
Wwpf GDS
LLL =
158.26
LDW
0.75
20
2,374 lb.
Total Static Load LS =
LDW + LLL
LS =
5,927 + 2,374
LS =
8,301 lb
Answer: The dead weight on each support is approximately 5,927 lb. The live load on each support is approximately 2,374 lb. The total static load on each support is approximately 8,301 lb.
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Hydrostatic Test Weight When designing the support system for the piping, the design engineer must consider the weight of the empty pipe and the maximum weight of its contents. Since petroleum products are all lighter than water, and since almost all piping systems are hydrostatically tested, the heaviest content load occurs during hydrostatic testing. However, if a support holds more than one pipe, such as in a pipe rack structure, typically only one pipe at a time undergoes hydrostatic testing. Therefore, the design engineer designs the support and associated foundation for the worst-case combination of one pipe undergoing hydrostatic testing while the other pipes are under normal operating load. Work Aid 1B provides the procedure for calculating the hydrostatic test weight. Sample Problem 3: Hydrostatic Test Weight Calculate the hydrostatic test weight load on a support for the pipe given in the Sample Problem 2: Dead and Live Loads. Solution: The following step numbers correspond to the step numbers in Work Aid 1B: 1.
The dead weight is approximately 5,927 lb. as previously calculated.
2.
LW =
Wwpf DS
Lw =
158.26
Lw
3,165 lb.
LH =
LDW + LW
LH =
5,927 + 3,165
LH =
9,092 lb.
3.
20
Answer: The hydrostatic test weight load on a support is approximately 9,092 lb.
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Wind If the design engineer does not properly design an aboveground piping system with its supports and restraints, a strong wind can cause serious damage to the piping system, supports, restraints, and associated structure. Therefore, it is critical that the designers of piping systems provide for possible wind forces. Figure 4 is a diagram of wind on a piping system.
Wind
Figure 4. Wind on a Piping System Saudi Aramco Standards
SAES-L-002 requires that the design of exposed piping systems allow for the wind loading that corresponds to a 35 m/s (78 mph) wind speed. When applicable, it also requires that design engineers consider wind-induced vibration. Wind Shielding
When multiple pipes are installed on a pipe rack, one pipe may shield or partially shield another pipe from the wind. The placement of a small pipe near to and on the lee side of a large pipe may even eliminate the wind load from being imposed on the small pipe. Figure 5 illustrates wind shielding. Shielded area Wind A D
B X = 5D
NOTE: When X is more than 5D, no appreciable shielding effect on pipe B occurs.
Figure 5. Wind Shielding
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Calculation Procedure
Work Aid 1C provides the procedure and information that are needed to calculate wind forces on a pipe rack due to the pipes. Sample Problem 4: Wind
Calculate the design wind load on the pipe in a pipe rack and the resulting overturning moment on the pipe rack. Given:
Figure 6 represents the pipes in the pipe rack. The pipe supports are located 20 ft. apart. The pipes are supported 10 ft. above the ground.
For the purpose of simplifying the calculation, this pipe layout is assumed to be as shown below: 1.05 in.
8.625 in.
2.375 in.
16 in.
4.5 in.
Wind
12 in. Pipe
1
20 in. 2
12.5 in. 3
6 in. 4
5
Figure 6. Pipes in Pipe Support Diagram
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Solution:
In this sample problem, the wind direction is given. In a practical application, the calculation is made with the wind from each side; and the worst case is used for the design load. The following step numbers correspond to the step numbers in Work Aid 1C: 1.
D
e−
j
i
5.5D i – d ji = Dj – 5.5
De − 1 = 1.05 0
De − 2 = 8.625 in . since 5.5 x 1.05 - 12 ≤ 0 i
(5.5 × 8.625) − 20 De − 3 = 16 − = 11.01 in. 2 5.5 (5.5 × 16) − 12.5 =0 D e − 4 = 2.375 − 3 5.5 (5.5 × 16) − 18.5 =0 De − 5 = 4.5 − 3 5.5
2.
DE = ∑De D E = 1.05 + 8.625 + 11.01 + 0 + 0 D E ≅ 20.685 in. = 1.72 ft
3.
Lwp = CsKhDsDEGqr Lwp = 1.2 x 0.8 x 20 x 1.72 x 1.32 x 15.6 Lwp
4.
680 lb
Mwind-p = hLwp Mwind-p = 680 x 10 Mwind-p
6,800 ft-lb
Solution:
The design wind load on the pipes in the pipe rack is approximately 680 lb. The base shear force is approximately 680 lb. The base overturning moment from this wind load is approximately 6,800 ft.-lb.
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Friction
As pipe expands and contracts due to heating and cooling, the pipe applies forces to anything to which it connects to or rests against. If design engineers do not design the pipe support structure properly, the forces from the pipes supported by the structure could damage the structure. For pipe racks that support rather than actively restrain the pipe, these forces result from friction between the structural steel supports and the pipe. The frictional forces act opposite to the direction of pipe movement. Unless a pipe is restrained at a support point, the friction forces act both longitudinally and laterally. When designing the pipe support structure for friction loads, engineers generally assume that all the pipes expand (or contract) in the same direction at the same time, which is the worst possible case. Engineers sometimes must reduce the magnitude of friction loads in order to reduce the size of the structural steel and foundations that are required. These reductions are accomplished through use of special materials with lower coefficients of friction. A common method of reducing friction loads between pipe and pipe rack structures is to install Teflon bearing pads on both the pipe supports and the structural steel. Work Aid 1D provides the procedure for calculating frictional force. Sample Problem 5: Friction
Calculate the friction force on a support rack from the pipe in Sample Problem 2: Dead and Live Loads. Given:
The pipe and pipe rack do not have any special friction-reducing mechanisms (steel-on-steel). Solution:
The following step numbers correspond to the step numbers in Work Aid 1D: LS = 8,301 lb. Ff = CfLS Ff = 0.4 x 8,301 Ff 3,320 lb Answer: 1. 2.
The force due to friction on the pipe rack is approximately 3,320 lb. from this pipe.
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TYPES AND FUNCTIONS OF SUPPORTS AND RESTRAINTS FOR VARIOUS PIPING SYSTEMS
This section discusses and illustrates various types of supports and restraints for piping systems. Background
A piping system needs supports and restraints to do the following: •
Permit the piping system to function under normal operating conditions without failure of the pipe or associated equipment.
•
Support piping system weight loads to: -
Keep sustained longitudinal pipe stress within allowable limits.
-
Limit pipe sag to avoid process flow problems.
-
Limit loads on connected equipment.
•
Control or direct thermal movement of the pipe to: -
Keep pipe thermal expansion stresses within allowable limits.
-
Limit loads on connected equipment.
•
Absorb other loads imposed on piping system to: -
Limit loads on connected equipment.
-
Limit pipe deflection.
-
Limit resultant pipe stresses.
Selection of a particular type of support or restraint depends on such factors as the following: •
Weight load
•
Restraint load
•
Clearance available for attachment to pipe
•
Availability of nearby existing structural steel
•
Direction of loads to be absorbed or movement to be restrained
•
Design temperature
•
Allowance required for thermal movement of pipe
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Types and Functions of Supports
The two general classes of supports are as follows: •
Rigid
•
Flexible or resilient
Rigid Supports
Rigid supports are the more common of the two support types. Engineers use rigid supports when weight support is needed and no provision to permit vertical thermal expansion is required. A rigid support does the following: •
Allows lateral movement and rotation.
•
May or may not prevent movement up.
•
Prevents movement down.
Figures 7 through 11 illustrate some of the rigid support types that are available. The rigid support that is selected for a particular application depends primarily on the following: •
Amount of load to be carried
•
Distance to solid attachment (structure, grade, etc.)
•
Point of attachment to pipe (horizontal or vertical run, elbow, etc.)
Saudi Aramco drawing AB-036100 shows the construction details for a large diameter pipe saddle that is bolted to a support structure.
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Figure 7. Shoe Support
Figure 8. Saddle Support
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Figure 9. Base Adjustable Support
Figure 10. Dummy Support
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Figure 11. Trunnion
Pipe hangers are also a form of rigid support. Pipe hangers support the pipe from structural steel or other facilities that are located above the pipe and carry the pipe weight load in tension. A pipe hanger rod moves freely parallel and perpendicular to the pipe axis; therefore, thermal expansion is not restricted longitudinally or laterally. The rod does restrict vertical thermal expansion. The rod also must be long enough so that it does not restrict pipe lateral or longitudinal movement. Figures 12 through 14 show some examples of pipe hangers.
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Figure 12. Sling-Type Pipe Hanger
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Figure 13. Pipe Hanger Suspended From Side of Structure
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Figure 14. Pipe Support Beam Suspended By Rods Flexible or Resilient Supports
Flexible or resilient type supports carry the weight load and allow the piping system to move in all three directions. A coil spring that has the correct stiffness and precompression to carry the weight load supports the weight. Because the spring is resilient, it permits vertical movement while still carrying the weight. The ability to move vertically allows the support to carry the weight while permitting the pipe to expand and contract as needed for thermal expansion. The thermal expansion may be due to the heating of the pipe or of a vessel to which the pipe attaches, or both. Two basic types of flexible supports are as follows: •
Variable load
•
Constant load
The type of flexible support selected from standard available models is based on the following factors: •
Design load
•
Required movement
•
Installation geometry
•
Standard models available
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Analysis and Design of Tanks, Vessels and Piping Piping Systems Variable Load Flexible Support - The variable load flexible support is the more common of the two types of flexible support. With variable load supports, pipe movement stretches or compresses the spring, changing the load that the spring exerts on the pipe. The spring is selected to provide the correct amount of support load to the pipe throughout the movement range. Figure 15 shows an example of a variable load support.
Load and deflection scale
Figure 15. Variable Load Support
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Analysis and Design of Tanks, Vessels and Piping Piping Systems Constant Load Flexible Support - With constant load flexible supports, the load that is exerted by the support on the pipe remains constant throughout the movement range. The use of a variable-length internal-moment arm mechanism accomplishes this constant load. This type of support is required when the load variation caused by the vertical thermal movement in a variable-load-type spring is too large to be accommodated by the piping system, or when the thermal movement is greater than approximately 3 in. (75 mm). Figure 16 shows an example of a constant load support.
Large change in effective lever arm
Small change in effective lever arm
Relatively constant load
Figure 16. Constant Load Support
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Restraints have the following two primary purposes in a piping system: •
They control the unrestricted thermal movement of the pipe by directing or limiting it.
-
Generally, a piping system is totally restrained at its end connections to equipment.
-
Restraints control, limit, or redirect the thermal movement either to reduce the thermal stress in the pipe or to reduce the loads exerted due to thermal movement on equipment connections.
•
They absorb loads imposed on the pipe by other conditions. Examples of these other conditions are as follows:
-
Wind
-
Earthquake
-
Slug flow
-
Water hammer
-
Flow-induced vibration
Several different types of restraints may be used. The selection of the type of restraint and its specific design details depends primarily on the following: •
Direction of pipe movement to be restrained.
•
Location of the restraint point.
•
Magnitude of the load to be absorbed.
One or more types of restraint or support may be combined at one location, depending on the piping system design needs. Three types of restraints are as follows: •
Stops
•
Guides
•
Anchors
Note: Multiple types may be used.
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Stops
Stops are restraints that limit the movement of the pipe in the longitudinal direction. Stops are designed to keep the pipe from moving axially beyond a point or from moving axially at all. Figure 17 shows an example of a stop.
Figure 17. Stop Guides
Guides are types of supports that limit the movement of the pipe perpendicular to the pipe axis in one or more directions while allowing movement along the pipe axis. Pipe rotation may or may not be restricted. Typical applications for guides are as follows: •
Long pipe runs on a pipe rack to: -
Control thermal movement.
-
Prevent buckling.
•
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Straight runs down the side of towers to: -
Prevent wind-induced movement.
-
Control thermal expansion.
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Figures 18 through 21 show examples of guides.
Figure 18. Channel Guide
Figure 19. Sleeve Guide
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Figure 20. Box-In Guide
Vessel
Figure 21. Vertical Box-In Guide on Side of Vessel
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Anchors
Anchors stop pipe movement in all three translational directions. Engineers use anchors to totally isolate one section of a piping system from another section in terms of loading and deflection. A total anchor that eliminates all translation and rotation at one location is not as common as one or more restraints that act at a single location. It is difficult to design effective rotational anchors or restraints. Plant piping more commonly uses directional anchors that restrain the pipes only in their translational directions. Figures 22 through 24 show examples of anchor types that are typically used in aboveground plant piping systems.
Figure 22. Anchor
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Figure 23. Anchor
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Figure 24. Anchor
Aboveground and buried cross-country pipelines require anchors to control pipeline movement and resulting pipe stresses. Anchors are needed to limit movement at the ends of the pipeline, at changes in direction or size, and at above- to below-ground transition points. Excessive movement of a buried pipeline can cause shifting of the soil that supports the pipe, subsidence of the cover, or damage to the pipe's external coating (if one is installed). In extreme cases, excessive movement could cause pipe overstress, inadequate cover depth, or external pipe corrosion.
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Since cross-country pipelines are typically large diameter and much longer than plant piping systems, their anchors are designed for much larger loads and thus use stronger design details to be effective. Aboveground pipe anchors typically employ local reinforcement at their attachment to the pipe, such as sleeves and ring girders, to avoid local overstress in the pipe. Also, the aboveground anchor structures are designed with sufficient strength to prevent excessive deflection under the applied loads, which would render the anchor ineffective. Anchors for buried pipelines use local pipe reinforcement as well. Buried pipelines are restrained by attachment to buried concrete blocks. The concrete block anchors must be sized to resist the applied loads considering the local terrain (for example, soil or rock characteristics) and friction. Figure 25 illustrates typical concrete block anchors for buried pipelines.
Bearing surface
Bearing surface Typical thrust block for 90° bend or elbow
Typical thrust block for 45° bend or elbow
Typical thrust block for TEE connection
Bearing surface
Bearing surface Typical thrust block for end cap
Typical thrust block for reducer
Source: Cited from Saudi Aramco Standard Drawing AB-036415
Figure 25. Concrete Block Anchors
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Aboveground restrained pipelines must have thrust anchors on the ends that are designed to resist the full axial forces due to differential thermal expansion and contraction, and internal fluid pressure. The anchor structure must be designed to limit the maximum pipe deflection under the applied loading to 6 mm (0.25 in.). Differential thrust anchors are also provided on aboveground restrained pipelines where there is a change in thrust due to a change in pipe diameter or wall thickness, unless the axial pipe movement is calculated to be less than 6 mm (0.25 in.). The potential end movements of buried pipelines must be conservatively estimated. If these movements exceed 50 mm (2 in.), a full thrust or drag anchor must be provided. A thrust anchor is designed for the full axial forces that are expected at the location. A drag anchor is not designed for the complete thrust load that is expected and permits some movement of the pipe. In this case, the drag anchor installation must limit the end movement of the pipeline to a maximum of 6 mm (0.25 in.).
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SUMMARY
This module has provided an overview of piping systems. The Participant should be able to identify the general types of piping systems and the codes and standards that apply to them. In addition, the Participant should understand the effect of additions or modifications to piping systems. Also, the Participant should be able to calculate some of the common civil/mechanical loadings that are imposed on piping systems.
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WORK AID 1:
PROCEDURES AND INFORMATION FOR CALCULATING CIVIL/MECHANICAL LOADS ON PIPING SYSTEMS
Work Aid 1A:
Procedures and Information for Calculating Dead and Live Load on a Support for a Straight Pipe Run
Dead Load
1.
Look up the specified pipe in Figure 31 and determine the weight per foot, wppf.
NPS (in.)
1/8
1/4
3/8
1/2
3/4
1
1-1/4
1-1/2
2
OUTSIDE DIAMETER (in.)
SCHEDULE NUMBERS (see note)
0.405
0.540
0.675
0.840
1.050
1.315
1.660
1.900
2.375
WALL THICKNESS (in.)
INSIDE DIAMETER (in.)
AREA OF METAL (in. 2 )
WEIGHT OF PIPE (lb/ft)
WEIGHT OF WATER (lb/ft)
40s
0.068
0.269
0.0720
0.244
0.025
80x
0.095
0.215
0.0925
0.314
0.016
40s
0.088
0.364
0.1250
0.424
0.045
80x
0.119
0.302
0.1574
0.535
0.031
40s
0.091
0.493
0.1670
0.567
0.083
80x
0.126
0.423
0.2173
0.738
0.061
40s
0.109
0.622
0.2503
0.850
0.132
80x
0.147
0.546
0.3200
1.087
0.102
160
0.187
0.466
0.3836
1.300
0.074
xx
0.294
0.252
0.5043
1.714
0.022
40s
0.113
0.824
0.3326
1.130
0.231
80x
0.154
0.742
0.4335
1.473
0.188
160
0.218
0.614
0.5698
1.940
0.128
xx
0.308
0.434
0.7180
2.440
0.064
40s
0.133
1.049
0.4939
1.678
0.375
80x
0.179
0.957
0.6388
2.171
0.312
160
0.250
0.815
0.8365
2.840
0.230
xx
0.358
0.599
1.0760
3.659
0.122
40s
0.140
1.380
0.6685
2.272
0.649
80x
0.191
1.278
0.8815
2.996
0.555
160
0.250
1.160
1.1070
3.764
0.458
xx
0.382
0.896
1.534
5.214
0.273
40s
0.145
1.610
0.7995
2.717
0.882
80x
0.200
1.500
1.068
3.631
0.765
160
0.281
1.338
1.429
4.862
0.608
xx
0.400
1.100
1.885
6.408
0.42
40s
0.154
2.067
1.075
3.652
1.45
80x
0.218
1.939
1.477
5.022
1.28
160
0.343
1.689
2.190
7.440
0.97
xx
0.436
1.503
2.656
9.029
0.77
Note:
The letters s, x, and xx in the SCHEDULE NUMBERS column indicate standard, extra strong, and double extra strong pipe, respectively. Source: “Crane Technical Paper No. 410 - Flow of Fluids.” Reprinted with permission of Crane Valves.
SI Conversion Factors: in. = 25.4 mm, lb./ft. = 14.6 N/m
Figure 31. Commercial Wrought Steel Pipe Data
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NPS (in.)
OUTSIDE DIAMETER (in.)
2-1/2
2.875
3
5
6
8
WALL THICKNESS (in.)
INSIDE DIAMETER (in.)
AREA OF METAL (in. 2)
WEIGHT OF PIPE (lb/ft)
WEIGHT OF WATER (lb/ft)
40s
0.203
2.469
1.704
5.79
2.07
80x
0.276
2.323
2.254
7.66
1.87
160
0.375
2.125
2.945
10.01
1.54
xx
0.552
1.771
4.028
13.70
1.07
40s
0.216
3.068
2.228
7.58
3.20
80x
0.300
2.900
3.016
10.25
2.86
160
0.438
2.624
4.205
14.32
2.35
xx
0.600
2.300
5.466
18.58
1.80
40s
0.226
3.548
2.680
9.11
4.29
80x
0.318
3.364
3.678
12.51
3.84
40s
0.237
4.026
3.174
10.79
5.50
80x
0.337
3.826
4.407
14.98
4.98
120
0.438
3.624
5.595
19.00
4.47
160
0.531
3.438
6.621
22.51
4.02
xx
0.674
3.152
8.101
27.54
3.38
40s
0.258
5.047
4.300
14.62
8.67
80x
0.375
4.813
6.112
20.78
7.88
120
0.500
4.563
7.953
27.10
7.09
160
0.625
4.313
9.696
32.96
6.33
xx
0.750
4.063
11.340
38.55
5.61
40s
0.280
6.065
5.581
18.97
12.51
80x
0.432
5.761
8.405
28.57
11.29
120
0.562
5.501
10.70
36.40
10.30
160
0.718
5.189
13.32
45.30
9.16
xx
0.864
4.897
15.64
53.16
8.16
20
0.250
8.125
6.57
22.36
22.47
30
0.277
8.071
7.26
24.70
22.17
40s
0.322
7.981
8.40
28.55
21.70
60
0.406
7.813
10.48
35.64
20.77
80x
0.500
7.625
12.76
43.39
19.78
100
0.593
7.439
14.96
50.87
18.83
120
0.718
7.189
17.84
60.63
17.59
140
0.812
7.001
19.93
67.76
16.68
xx
0.875
6.875
21.30
72.42
16.10
160
0.906
6.813
21.97
74.69
15.80
3.500
3-1/2
4
SCHEDULE NUMBERS (see note)
4.000
4.500
5.563
6.625
8.625
Source: “Crane Technical Paper No. 410 - Flow of Fluids.” Reprinted with permission of Crane Valves.
Figure 31. Commercial Wrought Steel Pipe Data, Cont'd
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NPS (in.)
10
12
14
OUTSIDE DIAMETER (in.)
10.750
12.75
14.00
SCHEDULE NUMBERS (see note)
WALL THICKNESS (in.)
INSIDE DIAMETER (in.)
AREA OF METAL (in. 2)
WEIGHT OF PIPE (lb/ft)
WEIGHT OF WATER (lb/ft)
20
0.250
30
0.307
10.250
8.24
28.04
35.76
10.136
10.07
34.24
34.96
40s 60x
0.365
10.020
11.90
40.48
34.20
0.500
9.750
16.10
54.74
32.35
80
0.593
9.564
18.92
64.33
31.13
100
0.718
9.314
22.63
76.93
29.53
120
0.843
9.064
26.24
89.20
27.96
140
1.000
8.750
30.63
104.13
26.06
160
1.125
8.500
34.02
115.65
24.59
20
0.250
12.250
9.82
33.38
51.07
30
0.330
12.090
12.87
43.77
49.74
s
0.375
12.000
14.58
49.56
49.00
40
0.406
11.938
15.77
53.53
48.50
x
0.500
11.750
19.24
65.42
46.92
60
0.562
11.626
21.52
73.16
46.00
80
0.687
11.376
26.03
88.51
44.04
100
0.843
11.064
31.53
107.20
41.66
120
1.000
10.750
36.91
125.49
39.33
140
1.125
10.500
41.08
133.68
37.52
160
1.312
10.126
47.14
160.27
34.89
10
0.250
13.500
10.80
36.71
62.03
20
0.312
13.376
13.42
45.68
60.89
30s
0.375
13.250
16.05
54.57
59.75
40
0.438
13.124
18.66
63.37
58.64
x
0.500
13.000
21.21
72.09
57.46
60
0.593
12.814
24.98
84.91
55.86
80
0.750
12.500
31.22
106.13
53.18
100
0.937
12.126
38.45
130.73
50.04
120
1.093
11.814
44.32
150.67
47.45
140
1.250
11.500
50.07
170.22
45.01
160
1.406
11.188
55.63
189.12
42.60
Source: “Crane Technical Paper No. 410 - Flow of Fluids.” Reprinted with permission of Crane Valves.
Figure 31. Commercial Wrought Steel Pipe Data, Cont'd
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NPS (in.)
16
18
OUTSIDE DIAMETER (in.)
16.00
18.00
SCHEDULE NUMBERS (see note)
WALL THICKNESS (in.)
INSIDE DIAMETER (in.)
AREA OF METAL (in. 2 )
WEIGHT OF PIPE (lb/ft)
WEIGHT OF WATER (lb/ft)
10
0.250
15.500
12.37
42.05
81.74
20
0.312
15.376
15.38
52.36
80.50
30s
0.375
15.250
18.41
62.58
79.12
40x
0.500
15.000
24.35
82.77
76.58
60
0.656
14.688
31.62
107.50
73.42
80
0.843
14.314
40.14
136.46
69.73
100
1.031
13.938
48.48
164.83
66.12
120
1.218
13.564
56.56
192.29
62.62
140
1.438
13.124
65.78
223.64
58.64
160
1.593
12.814
72.10
245.11
55.83
10
0.250
17.500
13.94
47.39
104.21
20
0.312
17.376
17.34
59.03
102.77
s
0.375
17.250
20.76
70.59
101.18
30
0.438
17.124
24.17
82.06
99.84
x
0.500
17.000
27.49
92.45
98.27
40
0.562
16.876
30.79
104.75
96.93
60
0.750
16.500
40.64
138.17
92.57
80
0.937
16.126
50.23
170.75
88.50
100
1.156
15.688
61.17
207.96
83.76
120
1.375
15.250
71.81
244.14
79.07
140
1.562
14.876
80.66
274.23
75.32
160
1.781
14.438
90.75
308.51
70.88
Source: “Crane Technical Paper No. 410 - Flow of Fluids.” Reprinted with permission of Crane Valves.
Figure 31. Commercial Wrought Steel Pipe Data, Cont'd
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NPS (in.)
20
24
OUTSIDE DIAMETER (in.)
20.00
24.00
SCHEDULE NUMBERS (see note)
WALL THICKNESS (in.)
INSIDE DIAMETER (in.)
AREA OF METAL (in. 2 )
WEIGHT OF PIPE (lb/ft)
WEIGHT OF WATER (lb/ft)
10
0.250
19.500
15.51
52.73
129.42
20s
0.375
19.250
23.12
78.60
125.67
30x
0.500
19.000
30.63
104.13
122.87
40
0.593
18.814
36.15
122.91
120.46
60
0.812
18.376
48.95
166.40
114.92
80
1.031
17.938
61.44
208.87
109.51
100
1.281
17.438
75.33
256.10
103.39
120
1.500
17.000
87.18
296.37
98.35
140
1.750
16.500
100.33
341.10
92.66
160
1.968
16.064
111.49
379.01
87.74
10
0.250
23.500
18.65
63.41
187.95
20s
0.375
23.250
27.83
94.62
183.95
x
0.500
23.000
36.91
125.49
179.87
30
0.562
22.876
41.39
140.80
178.09
40
0.687
22.626
50.31
171.17
174.23
60
0.968
22.064
70.04
238.11
165.52
80
1.218
21.564
87.17
296.36
158.26
100
1.531
20.938
108.07
367.40
149.06
120
1.812
20.376
126.31
429.39
141.17
140
2.062
19.876
142.11
483.13
134.45
160
2.343
19.314
159.41
541.94
126.84
Source: “Crane Technical Paper No. 410 - Flow of Fluids.” Reprinted with permission of Crane Valves.
Figure 31. Commercial Wrought Steel Pipe Data, Cont'd
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2.
Using the following formula, determine the approximate dead weight from the pipe on each support: LDW = (( Wppf +Wilpf ) Ds )+ Wc
(Eqn. 1)
where:
LDW
= Dead weight load of the pipe on a support, N (lb.)
Wppf
= Weight of the pipe from Figure 31, N/m (lb./ft.)
Wilpf
= Weight of any installed insulation or lining, N/m (lb./ft.)
Ds
= Distance centerline-to-centerline between supports, m (ft.)
Wc
= Weight of additional pipe components, such as valves, flanges, etc., to be carried by the support, N (lb.)
Live Load
1.
Look up the specified pipe in Figure 31 and determine the weight of water that the pipe can hold per foot of pipe, Wwpf.
2.
Using the following formula, determine the live load from the pipe on each support: LLL = WwpfGDs
(Eqn. 2)
where:
LLL
= Live load on a support, N (lb.)
Wwpf
= Weight of water the pipe can hold from Figure 30, N/m (lb./ft.)
G
= Specific gravity of the pipe contents
Ds
= Distance centerline-to-centerline between supports, m (ft.)
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Total Static Load
Using the following formula, calculate the total static load on a support: LS = LDW + LLL
(Eqn. 3)
where:
LS
= Static load on a support, N (lb.)
LDW
= Dead weight load of the pipe on a support, N (lb.)
LLL
= Live load on a support, N (lb.)
Work Aid 1B:
Procedure for Calculating the Hydrostatic Test Load on a Support for a Straight Pipe Run
1.
Using the Dead Weight portion of Work Aid 1, calculate the dead weight from the specified pipe on a support.
2.
Using the following formula, calculate the hydrostatic weight from the specified pipe on a support: LW = WwpfDs
(Eqn. 4)
where:
3.
LW
=
Load from the water that a pipe can hold, N (lb.)
Wwpf
=
Weight of water the pipe can hold (from Figure 31), N/m (lb./ft.)
Ds
=
Distance centerline-to-centerline between supports, m (ft.)
Using the following formula, calculate the hydrostatic test load on a support: LH
= LDW + LW
(Eqn. 5)
LH
=
Hydrostatic test load on a support, N (lb.)
LDW
=
Dead weight load from the weight of the pipe on a support, N (lb.)
LW
=
where:
Load from the water that a pipe can hold, N (lb.)
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Work Aid 1C:
1.
Procedure and Information for Calculating Wind Load on a Piping Support in Open Terrain
Determine the amount, if any, of the shielding from one pipe to another. The pipes must have their centerlines aligned perpendicular to the prevailing wind direction. Use the following formula: 5.5D i – d ji D e− j = D j – i 5.5
(Eqn. 6)
where: =
Effective diameter of the pipe j being shielded by pipe i, m (in.)
Dj
=
Actual outer diameter of the pipe j being shielded including any insulation, m (in.)
Di
=
Actual outer diameter of the pipe i doing the shielding including any insulation, m (in.)
dji
=
Distance between the pipes, centerline-to-centerline, m (in.)
D e− j
i
Note: If the quantity of 5.5 Di-dji is ≤ 0, then Dej/i = Dj. If Dej/i ≤ 0, then use zero for the effective diameter of the pipe in subsequent calculations. 2.
Using the following formula, calculate the effective total cross section exposed to the wind from all of the pipes: DE = ∑De-j/i
where: DE
(Eqn. 7)
= Effective diameter of all of the pipes in the pipe rack combined, m (ft.)
De-j/i = Effective diameter after shielding of each of the pipes in the pipe rack, m ( ft.) 3.
Using the following formula, calculate the wind force on the pipes in the pipe rack: Lwp = CsKhDsDEGqr (Eqn. 8)
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where:
Lwp = Wind force on the pipes, N (lb.) Cs
= Shape factor, 1.2 is typical for pipes
Kh
= Height factor from Figure 32
Ds
= Distance centerline-to-centerline between pipe supports, m (ft.)
DE = Effective diameter of all of the pipes in the rack combined, m (ft.) G
= Gust factor for the height of the pipes from Figure 32
qr
= Reference wind pressure at 10 m (33 ft.) above grade. qr equals 747 N/m2 in SI units and is equal to 15.6 lb./ft.2 in U.S. units.
HEIGHT ABOVE GRADE (ft)
Kh
G
0 to 15
0.80
1.32
20
0.87
1.29
25
0.93
1.27
30
0.98
1.20
40
1.06
1.23
50
1.13
1.21
60
1.19
1.20
70
1.24
1.19
80
1.29
1.18
90
1.34
1.17
100
1.38
1.16
120
1.45
1.15
140
1.52
1.14
160
1.58
1.13
180
1.63
1.12
200
1.68
1.11
250
1.79
1.10
Source: Based on Tables 6 and 8 in "Minimum Design Loads for Buildings and Other Structures," ASCE 7-88 (formerly ANSI A58.1), copyright 1990.
Figure 32. Height and Gust Factors
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4.
Using the following formula, calculate the overturning moment on the support structure resulting from the wind load on the pipe: Mwind-p = hLwp
(Eqn. 9)
where: Mwind-p
Work Aid 1D:
= Overturning moment on the structure due to the pipe being exposed to the design wind, N-m (ft.-lb.)
h
= Height above the ground of the center of the pipes, m (ft.)
Lwp
= Wind force on the pipes calculated in Step 3, N (lb.)
Procedure for Calculating Friction Force on a Piping Support
1.
Use Work Aid 1A to calculate the total static load on the support.
2.
Using the following formula, calculate the friction force on the support: Ff = CfLS
(Eqn. 10)
where: Ff = Force due to friction on the pipe rack, N (lb.). Note that for structural design purposes, this load may be applied both parallel and perpendicular to the pipe axis. Cf = Coefficient of friction from Figure 33 LS = Total static load on the pipe support from the pipe, N (lb.) PHYSICAL CONDITION
FRICTION COEFFICIENT (Cf )
Steel-on-steel
0.4
Teflon-on-Teflon
0.1
Figure 33. Coefficients of Friction
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GLOSSARY anchor
A rigid restraint providing substantially full fixation, ideally not allowing translational or rotational displacement of the pipe along any of the three reference axes. It is used for restraint but usually serves equally well for support or as a brace.
brace
A device primarily intended to resist piping displacement due to the action of any forces other than those due to thermal expansion or gravity.
constant-effort support
A support that is capable of applying a relatively constant force at any displacement within its useful operating range (that is, counterweight or compensating spring device).
corrosion
Material degradation due to chemical or electro-chemical attack that involves metal loss.
damping device
A dashpot or other frictional device that offers high resistance against rapid displacements caused by dynamic loads, while permitting essentially free movement under gradually applied displacement, such as from thermal expansion.
expansion joint
A flexible pressure-containing component of a piping system that is designed to absorb thermal movement.
guide
A device preventing movement in one or more directions. In common usage, a guide normally permits translation along the pipe axis but prevents it perpendicular to the pipe axis.
hanger
A support by which piping is suspended from a structure or other fixed point located above it and which functions by carrying the piping load in tension.
limit stop
A device that restricts translational movement to a limited amount in one direction along any single axis. Paralleling the various stops, there may also be double-acting limit stops, two-axis limit stops, etc.
pipe rack
An aboveground support structure designed to carry a relatively large number of pipes within a process plant.
resilient or flexible support
A support that includes one or more largely elastic members (that is, a spring).
resting or sliding support
A device for providing support from beneath the piping but offering no resistance other than friction to horizontal motion.
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restraint
An attachment to a pipe that prevents the pipe from moving in one or more directions.
rigid (solid) support
A support providing stiffness in at least one direction that is comparable to the stiffness of the pipe.
scraper
A cylindrical, plug-like device equipped with blades, wire brushes, and toothed rollers to remove accumulations from pipelines.
single support
A support structure designed to carry only one pipe.
sleeper
A rigid type pipe support located at grade. concrete block or structural steel.
stop
A device that permits rotation but prevents translational movement in at least one direction along any desired axis. If translation is prevented in both directions along the same axis, the term "double-acting stop" is applied. In common usage, a stop normally acts along the direction of the pipe axis.
support
An attachment to a pipe that primarily supports the weight of the pipe.
two-axis limit stop
A device that prevents transitional movement in one direction along each of the two axes. A "two-axis double-acting limit stop" prevents transitional movement in the plane of the axes while allowing such movement normal to the plane.
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