0003-MI20-00S1-0260-0
Short Description
Welding & Weld Inspection of Offshore Structures...
Description
MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
TABLE OF CONTENTS 1.0
EXECUTIVE SUMMARY...................................................................................... 4
2.0
BACKGROUND ................................................................................................... 4
3.0
BASIS .................................................................................................................. 4 3.1 3.2
4.0
GENERAL ............................................................................................................ 5 4.1 4.2 4.3 4.4 4.5 4.6
5.0
GENERAL ........................................................................................................... 10 WELDER IDENTIFICATION................................................................................ 10 METHOD OF TESTS .......................................................................................... 10 TEST AND INSPECTION RESULTS .................................................................. 11 RETESTS ............................................................................................................ 11 REQUALIFICATION ............................................................................................ 11
PRODUCTION WELDING ................................................................................. 11 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12 8.13
9.0
PROCEDURES ..................................................................................................... 8 INSPECTION AND TESTING ............................................................................... 8
WELDER QUALIFICATION ............................................................................... 10 7.1 7.2 7.3 7.4 7.5 7.6
8.0
EQUIPMENT ......................................................................................................... 6 GASES .................................................................................................................. 7 FLUX ..................................................................................................................... 7 ELECTRODES ...................................................................................................... 7
WELDING PROCEDURE QUALIFICATION........................................................ 8 6.1 6.2
7.0
SAFETY ................................................................................................................ 5 WELD QUALITY.................................................................................................... 5 WELD SIZE AND SPECIFICATION ...................................................................... 5 COMPATIBILITY OF WELDS AND PARENT METAL .......................................... 6 PROTECTION OF WORK..................................................................................... 6 ALLOWABLE PROCESSES ................................................................................. 6
EQUIPMENT AND CONSUMABLES .................................................................. 6 5.1 5.2 5.3 5.4
6.0
REFERENCES ...................................................................................................... 4 DEFINITIONS AND ACRONYMS ......................................................................... 4
GENERAL ........................................................................................................... 11 CLEANING .......................................................................................................... 11 PRE-ERECTION PAINTING ............................................................................... 12 SEQUENCE ........................................................................................................ 12 WINDOW CUT-OUTS ......................................................................................... 12 CONNECTIONS AND JOINTS............................................................................ 12 REPAIR OF ROOT OPENINGS.......................................................................... 15 PREHEAT ........................................................................................................... 15 PROFILE CONTROL OF FATIGUE JOINTS ...................................................... 16 SEAL WELDS ..................................................................................................... 16 TEMPORARY WELDS ........................................................................................ 16 STRESS RELIEF ................................................................................................ 16 CLEANING AFTER WELDING............................................................................ 17
REPAIR OF DEFECTS ...................................................................................... 18
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MODEC International, Inc. FPSO 9.1 9.2 9.3 9.4 9.5
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
GENERAL ........................................................................................................... 18 PROCEDURES ................................................................................................... 18 CRACKS ............................................................................................................. 18 DOCTORED WELDS .......................................................................................... 18 RANDOM ARC STRIKES.................................................................................... 19
APPENDIX A – NDE REQUIREMENTS FOR STRUCTURAL MEMBERS.................. 20
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MODEC International, Inc. FPSO
1.0
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
EXECUTIVE SUMMARY This document defines the minimum requirements for welding and weld inspection of offshore topsides structures / modules for FPSOs.
2.0
BACKGROUND Company facilities must meet minimum Industry standards to ensure that Quality, Health, Safety, Environmental, and Operations goals are attained. Standard specifications are used to communicate the minimum standards within the Company as well as to Suppliers and Contractors.
3.0
BASIS Industry codes, standards, and practices, as well as Company experience and preferences are the basis for this document. The following references apply only as specified in the body of this document. If the reference is not mentioned within, it is not applicable. Latest reference editions, including addendums, in force at contract award apply. Reference requirement conflicts shall be brought to Company attention for resolution. The most stringent requirement of the following references applies unless otherwise specified in writing by the Company.
3.1
REFERENCES
3.1.1
Company
Number / Identification
Title
None
3.1.2
Client
Number / Identification
Title
None
3.1.3
Industry Codes, Standards, Rules, and Regulations
Number / Identification
Title
API Spec 2H
Specification for Carbon Manganese Steel Plate for Offshore Structures
API RP 2A-WSD
Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms – Working Stress Design
ASTM A 370
Standard test Methods and definitions for Mechanical Testing of Steel Products
ASTM E 23
Standard Test Methods for Notched Bar Impact Testing of Metallic Materials
ASTM E 1290
Standard Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement
AWS D1.1
Structural Welding Code
3.2
DEFINITIONS AND ACRONYMS The following definitions apply within the body of this specification:
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MODEC International, Inc. FPSO Term
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0 Definitions
ABS
American Bureau of Shipping
API
American Petroleum Institute
ASTM
American Society for Testing and Materials
CA
Classification Authority
Client
MODEC International, Inc. Client and / or its assigns
Company
MODEC International, Inc. and / or its assigns
Contractor
Any entity contracted for the performance of Work
Facility
Supplier or Subcontractor shop and/or any property owned by a Supplier or Subcontractor where any portion of the work shall be performed
HAZ
Heat Affected Zone
ITRs
Integrated Test Ranges
Services
Any service or work performed by a Supplier that must be performed to comply with the requisition requirements or the contract to procure, design, manufacture, and deliver the work
Standards
Industry Codes, Standards, Guides, and Recommended Practices referenced herein, meaning the latest issue or edition in force at the end of the Supplier bid validity date or the contract date
Supplier
At quote stage: any entity invited to provide a quotation for the equipment and/or any Subcontractors thereto At Purchase stage: any entity contracted for the supply of the equipment and/or any Subcontractors thereto In all cases, the Supplier shall be responsible for performance of all Work and shall be the single point of contact for all Work related issues. The Company shall not receive information from nor respond directly to Subsuppliers.
Welder
Any person performing welding or tacking on the Work
Work
Any material or item or service listed in the requisition or contract as being in the Supplier’s Scope of Supply
4.0
GENERAL
4.1
SAFETY During welding operations, inspection, and testing, the Contractor shall observe and follow the current applicable regulations for personnel safety as well as for the prevention of fire, explosions, and accidents.
4.2
WELD QUALITY The Company requires a weld with notch toughness, fusion, and penetration throughout its entire length, including the points at which tacks occur, to ensure that the strength, ductility, and toughness of the joint shall not be less than the parent metal properties of the members being welded.
4.3
WELD SIZE AND SPECIFICATION Welds shall be of size, length, and type as shown on the Drawings or specified herein.
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
If no designation is given, butt joint structural welds shall be continuous, full penetration groove welds unless alternatives have been submitted to and approved by the Company. Welds shall be sized to develop the full strength of the smaller of the two members being joined.
4.4
COMPATIBILITY OF WELDS AND PARENT METAL Welds shall develop the strength, ductility, and notch toughness specified for the steel being welded. Welds forming connections between steel of different grades shall develop the unit strength specified for the higher strength steel and shall develop the ductility and notch toughness of the higher value of those specified for the grades of steel being joined.
4.5
PROTECTION OF WORK Procedures shall be established to provide the Welder and weld area with protection during periods of inclement weather and/or excessive wind conditions as determined by the Company. Procedures shall include means for the protection of electrodes, wire, flux, etc. Welding operations shall be prohibited if the ambient air temperature in the immediate vicinity of the weld site is below –18°C (0°F). Welding operations shall be prohibited if surfaces to be welded, welding consumables, or welding personnel are wet or exposed to rain, snow, or wind velocities exceeding 2.2350 meters per second (5 miles per hour), except for FCAW-G welding process where the limit is 6.7 meters per second (15 miles per hour).
4.6
ALLOWABLE PROCESSES Only automatic submerged arc (SAW), manual, or semiautomatic shielded metal arc (SMAW), and gas-shielded flux core arc (GFCAW) welding processes shall be used. Self-shielding flux core arc welding (SFCAW) may be accepted upon written Company approval. All procedures and Welders proposed for this process shall be tested under Company witness. Gas metal arc welding (GMAW) using spray or pulsed metal transfer modes may be accepted upon written Company approval. Shortarc welding shall not be permitted except as backing to an SAW weld which shall subsequently be subjected to backgouging. Other welding processes shall be evaluated by the Company based on documentation submitted by the Contractor. The judgement of the Company shall be final. Structural welding and all other welding, including tack welding, shall be accomplished with low hydrogen processes. The use of E-6010 5P welding electrode may be permitted for seal welds with preheat using an approved welding procedure.
5.0
EQUIPMENT AND CONSUMABLES
5.1
EQUIPMENT
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
Welding equipment shall be in good condition and subject to Company inspection. Voltage, amperage, and/or wire feed speed gauges on SAW, GFCAW, and GMAW machines shall be fully operable and properly calibrated. The controls of SFCAW equipment shall be fully operable, properly calibrated, and capable of being locked behind an access panel after being set to the approved WPS parameters. Equipment found in need of repairs shall not be used for production welding until repairs have been made and the equipment has been approved for use by the Company.
5.2
GASES Gases may be mixed on site only upon Company receipt and approval of a detailed procedure defining the mixing equipment and method of operation.
5.3
FLUX A flux conditioning procedure shall be prepared and shall define the following: • Methods of ensuring dryness before use •
Recovery of flux after use
•
Screening of foreign material and fused flux
•
Storage of flux to prevent contamination
Flux that has been wet shall not be used. Recycled flux shall be mixed with a minimum of 50% new flux.
5.4
ELECTRODES Prior to beginning work, the Contractor shall establish detailed procedures for electrode handling and storage. The procedure shall comply with Section 5.3 of AWS D1.1 and this specification. Electrodes showing signs of deterioration or damage shall be rejected. The maximum size of electrodes shall be 4 mm (5/32 inch) for stringer or starting beads and 5 mm (3/16 inch) for passes following starting beads in multipass welds. Jet rods shall not be used. Low hydrogen electrodes shall be stored in a heated oven. Upon removal from the oven to the fabrication site, electrodes shall be placed in heated quivers. Only one package of electrodes of each size shall be removed from the store at a time by each Welder. Shielded metal arc electrodes shall be stored in accordance with the electrode Manufacturer's recommendation. Electrodes left exposed to the atmosphere for a period longer than six hours shall not be used without reheating and drying. Electrodes shall be predried at 82°C (180°F) for one to two hours before redrying at 371°C (700°F).
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
A positive means of identification of wire and electrodes shall be established and maintained. Unidentified wire or electrodes shall not be used. Electrodes that come into direct contact with water shall not be used.
6.0
WELDING PROCEDURE QUALIFICATION
6.1
PROCEDURES
6.1.1
General Procedures shall be established prior to the start of production welding. Procedures shall conform to AWS D1.1 and this specification. A change of welding consumable Manufacturer shall require requalification of the welding procedure.
6.1.2
Procedure Specification Each procedure to be used shall be compiled into a Procedure Specification Manual.
6.1.3
Previously Certified Procedures If procedures exist for similar materials and thicknesses that have been previously certified, retesting may be waived only at the discretion of the Company.
6.2
INSPECTION AND TESTING
6.2.1
General The Contractor shall establish detailed procedures for control of welding quality. The following procedures shall be submitted for review and approved by the Company prior to starting fabrication: • Welding and weld repair •
Storage, control, and identification of welding consumables
•
Welder qualification records
•
Inspection/NDE
•
Post-weld heat treatment, if required
•
Monitoring the progress and quality of welding
•
Material and NDE traceability
Procedure qualifications shall conform to Section 4, Parts A and B, of AWS D1.1 and this specification. Qualification tests shall not be performed until approved by the Company. Procedure qualification tests shall be at the sole expense of the Contractor.
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
Procedure qualification tests shall be performed with the base materials listed in Company document Inspection and Quality Control Specification1. Procedures shall be tested and certified by a Company approved testing laboratory, agency, or equivalent. The Company shall witness all welding and all testing. Procedure testing shall be valid in the range 0.75T to 2T, where T is the plate thickness of the test specimen. Procedures shall be subject to the mechanical tests described below in Section 6.2.2 prior to use on production welds.
6.2.2
Method of Tests Visual Inspection shall be performed in accordance with the applicable paragraph of Section 4.8.1 of AWS D1.1. Reduced Section Tension Tests and Root, Face, and Side Bend Tests shall be performed in accordance with Section 4.8.3 of AWS D1.1. Macroetch Tests shall be performed in accordance with Section 4.8.4 of AWS D1.1. Charpy V-notch Tests shall be performed in accordance with ASTM A 370 and ASTM E 23. Radiographic or Ultrasonic Inspection (chosen by the Company when required) shall be performed in accordance with Section 4.8.2 of AWS D1.1. The requirements of structural nondestructive examination (NDE) for structural members are tabulated in Appendix A.
6.2.3
Test and Inspection Results Visual Inspection, Reduced Section Tension Test, and Root, Face, and Side Bend Test results shall conform to Section 4.8.1 and 4.8.2 of AWS D1.1. Charpy V-notch Tests of the weld metal in the weld test procedure for Type 1 and Type 2 steels shall show minimum average impact test values meeting the base metal requirements of API Specification 2H. Macroetch Test results shall conform to Section 4.8.4 of AWS D1.1. In addition, fillet leg welds legs shall be equal to 3 mm (1/8 inch). Radiographic or Ultrasonic Inspection (chosen by the Company) test results for plate shall conform to Section 6.12.1 and 6.13.1 respectively of AWS D1.1. Test results for tubulars shall conform to Section 6.13.3 of AWS D1.1.
6.2.4
Retests Retests of Welding Procedures shall be in accordance with Section 4.8.5 of AWS D1.1.
1
Refer to Section 3.1.1.
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MODEC International, Inc. FPSO
7.0
WELDER QUALIFICATION
7.1
GENERAL
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
Only Welders and welding Operators qualified in accordance with AWS D1.1, Section 4, Part C shall be acceptable. Each Welder and welding Operator, who has not been engaged in a given process of welding for which they are qualified for a period exceeding 6 months, and who has not been qualified by the Company within the past 1 year, shall be tested. Qualification tests for Welders and welding Operators shall be performed prior to employment on the work. The Contractor shall bear the expense of each Welder Qualification Test. Welding Operators shall be qualified in the appropriate position for the work to be performed. Qualification shall be established with the base materials to be used in fabrication or with materials of similar weldability. Qualification tests shall be witnessed and approved by the Company's Welding Inspector before the Welder or welding Operator shall be permitted to work on the structure. The decision of the Company Welding Inspector regarding the qualifications of any Welder or welding Operator shall be final. The Contractor shall provide all equipment and material for the qualification tests, including cutting, machining, and testing of specimens. Welders and welding Operators who do not pass the tests are disqualified from working on the job. Qualification of Welders for shielded metal arc, gas metal arc, or flux cored arc welding shall be based on destructive testing in accordance with AWS D1.1.
7.2
WELDER IDENTIFICATION Each Welder and welding Operator shall be assigned an identifying number or symbol that shall be used to identify all welding performed by a particular Welder. Welder identification numbering systems and/or symbols shall not be duplicated among the Material Supplier, Contractor, and Subcontractors. The symbol with which a Welder or welding Operator is qualified shall not change after qualification. The symbol of Welders who leave the job shall not be used by other Welders.
7.3
METHOD OF TESTS Visual Inspection shall conform to Section 4.19.1 of AWS D1.1. Bend Tests and Macroetch Tests shall be performed in accordance with Section 4.19.1 of AWS D1.1. Ultrasonic Inspection shall be performed in accordance with Section 4.8.2 of AWS D1.1.
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
Radiographic Tests shall be performed in accordance with Section 4.30.3 of AWS D1.1.
7.4
TEST AND INSPECTION RESULTS Visual Inspection, Bend Test results, and Macroetch Test results shall conform to Sections 4.8.1, 4.8.3 and 4.30.2 respectively of AWS D1.1. Ultrasonic and Radiographic Test results shall conform to acceptance criteria shown in the ITR (Integrated Test Ranges).
7.5
RETESTS Retests shall conform to Section 4.32 of AWS D1.1. The Contractor shall be responsible for all retesting costs.
7.6
REQUALIFICATION Welders and welding Operators shall be subject to requalification during fabrication at the discretion of Company when their work appears to be below the requirements of this specification. If a Welder fails the requalification test, the Contractor shall be responsible for all costs for the test. If the Welder passes the requalification test, the Company shall be responsible for Welder time (according to the Contractor Rate Schedule contained in the Agreement) and radiographic, ultrasonic, and laboratory testing costs for the test. Welders and welding Operators who have been disqualified by the Company for defective work may be retested at the Contractor's request if they have received additional training. Expenses for qualification test for disqualified Operators shall be borne solely by the Contractor whether the welder passes or fails.
8.0
PRODUCTION WELDING
8.1
GENERAL Procedures shall be posted in a conspicuous location in each fabrication area. Adequate supervision shall be provided to ensure strict adherence to the Company approved procedures. SFCAW equipment shall be locked after setting to WPS parameters and the key kept in possession of the foreman. Welders shall not have access to the key.
8.2
CLEANING Surfaces to be welded shall be free from loose scale, slag, rust, hydrocarbons (oil, grease, etc.), paint, and any other foreign material; however, mill scale that withstands vigorous wire brushing may remain.
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MODEC International, Inc. FPSO
8.3
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
PRE-ERECTION PAINTING Surfaces that shall be welded after erection may receive pre-erection painting. Unless a Company approved welding procedure is used for welding over pre-erection paint, the paint on surfaces adjacent to joints to be welded shall be thoroughly removed to expose clean steel for a distance of at least 152 mm (6 inches) on either side of the joint.
8.4
SEQUENCE The sequence in assembling, joining, and welding various parts of the structure shall be carefully designed and scheduled to minimize distortion, warpage, and accumulations of residual joint stresses in each part of the structure. Distortion and shrinkage shall be controlled in accordance with Section 5.21 of AWS D1.1. Special care shall be taken to minimize through thickness residual stresses. Welding shall not commence until the members have been properly aligned. Members shall be aligned and held in position during welding by bolts, clamps, wedges, tack welds, or other suitable means. The Contractor shall provide and exert all necessary supervision to ensure that the planned sequences are observed. When distortion, warpage, or residual joint stresses cannot be avoided, the Contractor, at no additional cost to the Company, shall take remedial action, such as heat treatment, corrections, repairs, or modifications, to relieve their effects. Remedial action shall be performed successively after each weld.
8.5
WINDOW CUT-OUTS The assembly sequence shall be planned to minimize window cut-outs. A written Window Cut-Out Procedure shall be approved by the Company prior to making a window cut-out. The Window Cut-Out Procedure shall include details such as the size of window and corner radius.
8.6
CONNECTIONS AND JOINTS
8.6.1
Joint Details Joint details shall be in accordance with Section 2 of AWS D1.1 and shall be subject to Company approval.
8.6.2
Edge and Bevel Preparation Edge preparation, including the limits of acceptability and the repair of edge defects, shall conform to Section 5.15 of AWS D1.1. Edge preparation by gas cutting shall be performed with a mechanically guided torch whenever practical.
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
Edges shall be ground smooth and uniform and shall be free from fins, tears, cracks, and other defects, as well as from loose scale, slag, rust, grease, moisture, or anything that prevents proper welding. Where practical, pipe bevels shall be made using a bevelling machine. Excessive roughness of gas cut surfaces and notches or gouges not more than 4.75mm (3/16inch) deep shall be removed by machining or grinding.
8.6.3
Joint Alignment and Gaps Parts to be joined by fillet welds shall be brought into as close contact as practical. The gap between parts shall not exceed 5 mm (3/16 inch). If the gap is larger than 1 ½ mm (1/16 inch), the leg of the weld shall be increased by the amount of the gap. The separation between faying surfaces of lap joints shall not exceed 1 ½ mm (1/16 inch). The use of fillers shall not be allowed. Parts to be joined by butt welds shall be carefully aligned. Dimensions of the cross section of groove welded joints shown on the Drawings shall be within the tolerances specified in Section 5.22 of AWS D1.1.
8.6.4
Splices Splices shall be prepared for full penetration welds with single or double V-butt joints, depending on the size of the member. Splices shall be continuous, full penetration welds. Welded joints of axially aligned structural members of different material size, thicknesses, diameters, or widths shall be made in such a manner that the slope through the transition zone does not exceed 1:3. The transition shall be accomplished by chamfering the thicker part, tapering the wider part, sloping the weld metal, or combining both. The mismatch of mating surfaces of the joint preparation root face on tapered member splices shall not exceed 3/32 inch. Splices may be introduced into the fabrication of members according to API RP 2AWSD. This requirement applies equally to open and closed sections. The location of all splices shall be clearly indicated on the Shop Drawings and shall be subject to Company approval. Shapes and Plates For cantilever beams, no splices may be located closer to the point of support than one-half of the cantilevered length. For span beams, there should be no splice within one-eighth of the span from beam center, nor within the eighth of the span nearest a support, nor directly over a support. Web-to-web and flange butt weld locations shall be offset a minimum of 150mm (6 inches). If single side splice welds are necessary, approval shall be obtained from the Company before welding. All edges of plate and/or structural shapes to be broken with a power disk to a 2mm chamfer and dressed to remove burrs.
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
Tubular T-, Y-, and K-Joints Adjacent structural braces that are not specifically shown as overlapping shall be provided with a separation between adjacent weld toes. The minimum gap shall be: • 100mm (4 inches) when measured prior to welding - measured as an extension of brace surface, and •
50mm (2 inches) after completion of welding measured between adjacent weld toes.
All appurtenances, temporary, or other welds shall be at least 64mm (2 1/2 inches) measured toe-to-toe from any structural joint weld. Overlapped member joints shall not be permitted unless specifically detailed on the drawings. When overlapped joints are detailed, the assembly order shall be strictly in accordance with the detail. Tubular members shall not intersect a larger through member within 50mm (2 inches) of an existing weld on the through member. This is applicable to both girth and longitudinal welds on the through member.
8.6.5
Butt Joints Butt joints in tubular members, rolled shapes, plates, and built-up sections shall be full penetration welds unless specifically indicated otherwise in the Drawings.
8.6.6
Tubular Joints Tubular joints shall be prepared for full penetration welds. Tubular members shall be carefully contoured to obtain accurate alignment, and the bevel shall provide a continuous transition from maximum to minimum bevel angle around the circumference. Root openings prior to fit-up repair shall be not less than 1 ½mm (1/16 inch) and not more than 5 mm (3/16 inch). If fit-up results in a root opening greater than 4 ¾mm (3/16 inch), the brace shall be reworked. Tubular joints shall be welded with full penetration welds. Cap welds to T-, K- and Y-type tubular joints shall be developed with a minimum of 2-1/2 weld bead passes, with a maximum allowable bead width of 2-1/2 electrode diameters or 10 mm (⅜ inch), whichever is smaller. Electrode diameter shall be defined as the rod diameter minus the thickness of the flux coating. Maximum allowable bead width for the FCAW process shall be 13 mm (½ inch). If the weld cap cannot be developed with two maximum width passes, then multiple passes shall be necessary within the limits permitted by the Company approved weld procedure and AWS D1.1.
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MODEC International, Inc. FPSO
8.6.7
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
ROLLED SHAPES TO TUBULARS If one or more structural rolled shape sections are connected to a tubular member that is the continuous member, the rolled shapes shall be appropriately coped and positioned to allow welding completely around the edges. Preparation of the ends of shapes shall be made in such a manner that the flanges and webs shall be full penetration butt welded to the tubular unless otherwise shown on the Drawings.
8.6.8
Backing Rings Backing rings or strips shall not be used on pipe greater than 610mm (24 inches) in diameter and shall be approved by the Company. Ceramic backup tapes shall be permitted provided a Company approved welding procedure using the specific tape type is used.
8.7
REPAIR OF ROOT OPENINGS
8.7.1
Excessive Root Openings The repair of excessive root openings shall require prior Company approval. Excess root openings shall be corrected by applying build-up passes to the bevel face using a method approved by the Company. In tubular intersection joints, the build-up shall be applied to the branch member side of the joint. The maximum allowable build-up shall not exceed 10mm (3/8 inch) unless approved by the Company. The Company reserves the right to require the brace, beam, etc. to be removed and replaced at no additional cost in lieu of build-up. Corrected root openings shall conform to project documentation and shall be capable of closure with a single downhill pass of an electrode approved by the Company. Weaving technique shall not be permitted for closure of excessively wide root openings.
8.7.2
Insufficient Root Openings Air arc gouging of tight grooves shall be permitted only when followed by grinding or grit blasting where approved by the Company to brighten metal.
8.8
PREHEAT Welding shall not be performed when metal temperatures are below 0°C (32°F). If surface moisture has gathered on the steel, the weld joint shall be dried by preheating the surface to remove the moisture. Procedures shall be established for operations involving preheat and temperature control. Preheat temperatures and procedures shall be sufficient to prevent crack formation and shall conform to AWS D1.1, Section 5.6. Preheat shall be maintained during multipass welding.
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
Temperature recording devices or temperature indicating crayons shall be supplied, calibrated, and tested by the Contractor prior to performing welds that require preheat. The brand and melting temperature of crayons shall be made available to the Company. Crayon marks shall be adjacent to the weld joint.
8.9
PROFILE CONTROL OF FATIGUE JOINTS Joints designated as “Fatigue Joints” on the Drawings shall have welds with a profile such that the weld metal merges smoothly with the base metal. To achieve the required profile, it may be necessary to make extra weld passes or profile grind the joint for a weld contour other than what would normally be required. This shall be done at the sole discretion of the Company. The finished profile shall comply with AWS D1.1 or API RP 2A-WSD requirements. Welds that require profile control shall be subject to magnetic particle inspection for surface and near-surface discontinuities. Defects that cannot be corrected by light grinding shall be repaired in accordance with Paragraph 5.26.1.4 of AWS D1.1. In order to gain the maximum possible fatigue properties in welded joints, the maximum permissible weld bead width shall be 2-1/2 times (2.5x) the electrode diameter or 10mm (3/8 inch) whichever is less. For the FCAW process, the maximum bead width shall be 13mm (½ inch), and the maximum bead depth shall not exceed the actual bead width.
8.10
SEAL WELDS Surfaces inaccessible to coating that require coating shall be sealed by seal welds or by “boxing in” with steel plate. “Boxing in” by the Contractor shall require prior Company approval. Faying surfaces shall be sealed against corrosion by continuous fillet welds. Seal welds need not exceed 3 mm (1/8 inch) regardless of base metal thickness.
8.11
TEMPORARY WELDS The use of tack welds and temporary welds shall be minimized. If temporary attachments are made, they shall adhere to a qualified welding procedure and be performed by qualified Welders. Temporary attachments shall be removed by thermal cutting no closer than 1/8 inch from the member, and the area shall be ground flush and smooth and inspected using magnetic particle inspection.
8.12
STRESS RELIEF Full penetration welds in materials greater than 51 mm (2 ½ inches) wall thickness shall be stress relieved in accordance with Section 5.8 of AWS D1.1.
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
Stress relief requirements may be waived at the Company's discretion, and in cases where excessive distortion may result, provided that CTOD tests are in accordance with ASTM E1290 are performed as follows: • The rectangular geometry specimen (B x 2B) shall be used.
8.13
•
The specimen shall be oriented transverse to the weld seam, so that the crack-tip line is in the through-thickness direction.
•
Three weld metal and three heat-affected zone (HAZ) specimens shall be required.
•
The specimen thickness shall be the full thickness of the test weldment less the minimum amount of machining necessary to comply with the specified rectangular cross section.
•
The specimen shall be etched to delineate the weld and HAZ.
•
For weld metal specimens, the notch and fatigue crack tip shall be located entirely within the weld metal and shall preferably be at the center of the weld where joint geometry permits.
•
For HAZ specimens, a microhardness traverse shall be carried out to locate the area of maximum hardness. The notch and fatigue crack tip line shall cross the area of maximum hardness.
•
The minimum required CTOD value shall be provided by the Company based on an ECA level 2 analysis of the weld joint concerned or 0.25mm (0.01 inch), whichever is greater.
•
Testing shall be carried out at minimum service temperature.
•
If one of three specimens fails to meet the minimum requirements, then a second set of three specimens shall be tested. Five of the six total specimens must meet the minimum requirements in order for the test to be considered satisfactory. Retests shall be performed only on the type of specimen that failed, either weld metal or HAZ; both need not be retested. Both the weld metal and HAZ tests must meet the minimum CTOD value in order for the entire test to be considered satisfactory.
•
Notwithstanding the calculated value of critical defect size, NDT acceptance criteria shall remain as required by this specification.
•
Specimen locations in tubular weldments shall be at 12, 3, and 6 o’clock positions. For plate weldments, specimens shall be taken 204 mm (8 inches) from either end and at the center. Specimens shall be permanently marked to clearly identify the original location.
•
The test report shall comply with Section 10 of ASTM E1290 and shall include an approved copy of the load displacement record and photographs of fracture surfaces.
CLEANING AFTER WELDING Upon completion of welding, the surfaces shall be cleaned of spatter, rust, loose scale, oil, and dirt. Slag and flux deposits shall be cleaned from all welds.
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MODEC International, Inc. FPSO
9.0
REPAIR OF DEFECTS
9.1
GENERAL
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
The Contractor shall monitor and report performance of weld quality. It shall be reported on a weekly basis through out the fabrication. The Company considers that acceptance level of weld defect based on linear length is 2% max. The Fabricator shall ensure that this performance level is achieved and maintained through out the fabrication phase; otherwise, repair shall be required. Costs connected with repairs and retests shall be at the Contractor’s sole expense. Defects in weld deposits, except cracks, may be repaired without prior authorization by the Company. Removal of defects for repair must be carried out in accordance with the approved repair welding procedure and must produce a clean, uncontaminated surface for installation of the repair weld. Oxygen-acetylene gouging shall not be acceptable. Air arc gouges shall be power disc ground or grit blasted to remove residual carbon.
9.2
PROCEDURES Repair procedures that deviate from the qualified welding procedures shall be submitted in writing for approval before the repair can be made. Removal of defects and deposition of repair welds shall be in accordance with the approved repair welding procedure and requirements of Section 5.26 of AWS D1.1. The Company shall determine the number of repairs that may be allowed. A third repair of the same area in normalized material with specified impact properties shall not be allowed.
9.3
CRACKS The removal and repair of cracks in weld deposits or base metal shall be witnessed and approved by the Company. Cracks shall be removed to sound metal plus 51 mm (2 inches) of sound metal on each end of the crack as determined by magnetic particle, ultrasonic, or dye penetrant inspection. The surface of the chord member in tubular intersection joints containing root cracks or transverse cracks shall be inspected by nondestructive method to detect propagation into the base metal. The intersecting member shall be completely removed if in the opinion of the Company Representative the surface of the chord member cannot be properly inspected or repaired.
9.4
DOCTORED WELDS Welds shall not be doctored with a torch or any other means to change their appearance. Peening of welds shall not be permitted.
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MODEC International, Inc. FPSO
9.5
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
RANDOM ARC STRIKES Random arc strikes outside of the weld groove shall be repaired in accordance with a Company approved procedure. The procedure shall define methods to determine the extent of and methods to repair arc strikes.
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
APPENDIX A – NDE REQUIREMENTS FOR STRUCTURAL MEMBERS
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
STRUCTURAL NON-DESTRUCTIVE EXAMINATION REQUIREMENT %Total Weld Length Weld Type
Visual
Ultrasonic
Magnetic Particle(f)
(a) (d) Plate Girders -Full Penetration welds
100
Plate Girders – Fillet Welds
100
Splices in primary structure and primary column/tubular members
100
100
Radiography (b)(e)
100 100 100
Splices in secondary structure 100 / tubular/ chords
10
Longitudinal Welds in Primary Tubular columns
100
10
100
Longitudinal Welds in Secondary Tubular Chords
100
100
10
Primary structural connections / TKY welds in diagonals - full penetration welds
100
Primary structural connections- fillet welds
100
Secondary structural connections/ misc. full penetration welds
100
100
100 10
Secondary structural 100 connections-misc. fillet welds TKY Welds in diagonals / braces
100
Deck Plate Splices
100
Handrails
100
Padeye attachment and 100 associated welds (including those temporary lifting padeyes used in construction phase) Seafastening structural attachment welds Full penetration welds Fillet welds
0003-MI20-00S1-0260-0.doc
100
10
10 100
100 10
100 ©
100
100%
100%
5
100
100%
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MODEC International, Inc. FPSO
Welding and Weld Inspection of Offshore Structures Specification 0003-MI20-00S1-0260, Rev. 0
Notes: •
Ultrasonic testing shall be applicable for thickness greater than 8 mm only.
•
Radiography can be substituted with Ultrasonic Inspection only with Company approval. In this case, 100% MT and 10% RT shall be applied.
•
100 % laminations scan of the padeye plate and attachment location and 100 % ultrasonic testing of the weld with acceptance criteria API 2X Level A.
•
Ultrasonic testing acceptance criteria shall be API 2X Level C.
•
Radiographic Inspection shall be in accordance with AWS D1.1 and acceptance criteria shall be in accordance with AWS D1.1: Cyclically Loaded Nontubular Connections and Tubular Connections, whichever is applicable.
•
Magnetic-Particle Testing shall be in accordance with AWS D1.1.
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