OFFSHORE STANDARDDET NORSKE VERITASDNV-OS-C401FABRICATION AND TESTING OF OFFSHORE STRUCTURESOCTOBER 2008Comments may be sent by e-mail to rules@dnv.comFor subscription orders or information about subscription terms, please use distribution@dnv.comComprehensive information about DNV services, research and publications can be found at http://www.dnv.com, or can be obtained from DNV, Veritasveien 1, NO-1322 Hvik, Norway; Tel +47 67 57 99 00, Fax +47 67 57 99 11. Det Norske Veritas. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, including photocopying and recording, without the prior written consent of Det Norske Veritas.Computer Typesetting (FM+SGML) by Det Norske Veritas.If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall pay compensation to such personfor his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten times the fee charged for the service in question, provided that the maximum compen-sation shall never exceed USD 2 million.In this provision "Det Norske Veritas" shall mean the Foundation Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agents and any other acting on behalf of DetNorske Veritas.FOREWORDDET NORSKE VERITAS (DNV) is an autonomous and independent foundation with the objectives of safeguarding life, prop-erty and the environment, at sea and onshore. DNV undertakes classification, certification, and other verification and consultancyservices relating to quality of ships, offshore units and installations, and onshore industries worldwide, and carries out researchin relation to these functions.DNV Offshore Codes consist of a three level hierarchy of documents: Offshore Service Specifications. Provide principles and procedures of DNV classification, certification, verification and con-sultancy services. Offshore Standards. Provide technical provisions and acceptance criteria for general use by the offshore industry as well asthe technical basis for DNV offshore services. Recommended Practices. Provide proven technology and sound engineering practice as well as guidance for the higher levelOffshore Service Specifications and Offshore Standards.DNV Offshore Codes are offered within the following areas:A) Qualification, Quality and Safety MethodologyB) Materials TechnologyC) StructuresD) SystemsE) Special FacilitiesF) Pipelines and RisersG) Asset OperationH) Marine OperationsJ) Wind TurbinesO) Subsea SystemsAmendments and Corrections Whenever amendments and corrections to the document are necessary, the electronic file will be updated and a new Adobe PDFfile will be generated and made available from the Webshop (http://webshop.dnv.com/global/).DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Changes Page 3CHANGES GeneralBeing class related, this document is published electronicallyonly(asofOctober2008)andaprintedversionisnolongeravailable. The update scheme for this category of documents isdifferent compared to the one relevant for other offshore doc-uments (for which printed versions are available). For an overview of all types of DNV offshore documents andtheirupdatestatus,seetheAmendmentsandCorrectionsdocumentlocatedat:http://webshop.dnv.com/global/,undercategory Offshore Codes. Main changesSincethepreviousedition(April2004),thisdocumenthasbeen amended, latest in October 2007. All changes have beenincorporated.DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 4 ChangesDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008 Contents Page 5CONTENTSCH. 1 INTRODUCTION................................................ 7Sec. 1 Introduction........................................................... 9A. General.................................................................................... 9A 100 Introduction....................................................................... 9A 200 Objective........................................................................... 9A 300 Organisation of contents ................................................... 9B. Normative References ............................................................ 9B 100 General.............................................................................. 9B 200 Offshore service specifications and rules ......................... 9B 300 Offshore Standards ........................................................... 9B 400 Other references................................................................ 9C. Informative References........................................................... 9C 100 General.............................................................................. 9D. Definitions ............................................................................ 10D 100 Verbal forms ................................................................... 10D 200 Terms .............................................................................. 10D 300 Abbreviations.................................................................. 10D 400 Latin symbols.................................................................. 11D 500 Greek symbols ................................................................ 11CH. 2 TECHNICAL PROVISIONS ............................ 13Sec. 1 Welding Procedures and Qualification of Welders................................................................. 15A. General.................................................................................. 15A 100 Scope............................................................................... 15A 200 Welding processes .......................................................... 15B. Welding Procedures.............................................................. 15B 100 General............................................................................ 15B 200 Preliminary welding procedure specification, pWPS..... 15B 300 Welding Procedure qualification test (WPQT)............... 15B 400 Welding procedure qualification record (WPQR) .......... 15B 500 Welding procedure specifications (WPS)....................... 15C. Welding Procedure Tests, C-Mn Steel and Low Alloy Steel.................................................................... 15C 100 Butt welds on plates........................................................ 15C 200 Butt welds in pipes.......................................................... 17C 300 Full penetration T-, Y-, and K- joints ............................. 18C 400 Tubular joints.................................................................. 18C 500 Fillet welds...................................................................... 19C 600 Re-testing........................................................................ 19C 700 Validity of a WPS........................................................... 19C 800 Fracture mechanic (FM) testing ..................................... 22D. Welding Procedure Tests, Aluminium................................. 23D 100 General............................................................................ 23D 200 Butt welds ....................................................................... 23D 300 Fillet welds...................................................................... 24D 400 Re-testing........................................................................ 24E. Welding Procedure Tests, Stainless Steel............................. 25E 100 General............................................................................ 25E 200 Supplementary requirements for austenitic stainless steel .................................................. 25E 300 Supplementary requirements for ferritic-austenitic stainless steel................................................................... 25F. Qualification of Welders ...................................................... 26F 100 General............................................................................ 26F 200 Standards for qualification testing.................................. 26G. Testing .................................................................................. 26G 100 General............................................................................ 26G 200 Tensile testing at ambient temperature ........................... 26G 300 Bend testing .................................................................... 26Sec. 2 Fabrication and Tolerances...............................28A. General.................................................................................. 28A 100 Objective and scope........................................................ 28B. Fabrication Planning............................................................. 28B 100 General............................................................................ 28B 200 Quality system and workmanship................................... 28C. Inspection.............................................................................. 28C 100 General............................................................................ 28D. Material Identification, Cutting and Forming....................... 28D 100 Material identification .................................................... 28D 200 Cutting and forming........................................................ 28E. Tolerances............................................................................. 29E 100 Tolerances for alignment and straightness.................... 29F. Assembly, Welding, Heat Treatment and Repairs................ 32F 100 Assembly and welding.................................................... 32F 200 Post weld heat treatment (PWHT).................................. 33F 300 Repairs ............................................................................ 33Sec. 3 Non-Destructive Testing ....................................35A. General.................................................................................. 35A 100 Scope............................................................................... 35B. Non-Destructive Testing (NDT)........................................... 35B 100 General............................................................................ 35B 200 NDT procedures.............................................................. 35B 300 Personnel qualification ................................................... 35B 400 Extent of NDT ................................................................ 35B 500 Acceptance criteria for NDT .......................................... 37Sec. 4 Other Tests..........................................................39A. General.................................................................................. 39A 100 Scope............................................................................... 39B. Testing of Tightness ............................................................. 39B 100 General............................................................................ 39C. Structural Tests ..................................................................... 39C 100 General............................................................................ 39Sec. 5 Corrosion Protection Systems ...........................40A. General.................................................................................. 40A 100 Scope............................................................................... 40A 200 General............................................................................ 40A 300 Application of coating .................................................... 40A 400 Fabrication and installation of sacrificial anodes ........... 40A 500 Fabrication and installation of impressed current systems .............................................. 40Sec. 6 Miscellaneous......................................................41A. Use General .......................................................................... 41A 100 Scope............................................................................... 41B. Bolts...................................................................................... 41B 100 Bolts and nuts ................................................................. 41C. Mechanical Fastening ........................................................... 41C 100 Contact surfaces in slip resistant connections ................ 41CH. 3 CERTIFICATION AND CLASSIFICATION43Sec. 1 General ................................................................45A. Introduction........................................................................... 45A 100 Scope............................................................................... 45DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 6 ContentsB. Specific Certification and Classification Requirements....... 45B 100 General ............................................................................45B 200 Basic requirements..........................................................45B 300 Welding shops and -contractors......................................45B 400 Welding consumables .....................................................45B 500 Welding procedures and qualification of welders...........45B 600 Corrosion protection systems..........................................45C. Records and Documentation................................................. 45C 100 General ............................................................................45DET NORSKE VERITASVeritasveien 1, NO-1322 Hvik, Norway Tel.:+47 67 57 99 00 Fax:+47 67 57 99 11OFFSHORE STANDARDDNV-OS-C401FABRICATION AND TESTING OFOFFSHORE STRUCTURESCHAPTER 1INTRODUCTIONCONTENTS PAGESec. 1 Introduction................................................................................................................................ 9DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.1 Sec.1 Page 9SECTION 1INTRODUCTIONA. GeneralA 100 Introduction101This standard contains requirements for fabrication andtesting of offshore structures.A 200 Objective201The objectives of this standard are to: provideaninternationallyacceptablestandardtoensurethe quality of all welding operations used in offshore fab-rication,throughidentifyingappropriateweldingproce-dures, welder qualifications and test methods serveasatechnicalreferencedocumentincontractualmatters between purchaser and contractor serve as guideline for designer, purchaser and contractor specifyminimumrequirementsforweldingoperationssubject to DNV certification and classification.A 300 Organisation of contents301Ch.2Sec.1toCh.2Sec.6givecommonrequirementsthat are considered applicable to all types of offshore units andinstallations.B. Normative ReferencesB 100 General101The references given in Table B1, Table B2 and TableB3includeprovisions,whichthroughreferenceinthistextconstitute provisions for this standard.B 200 Offshore service specifications and rules201TheoffshoreservicespecificationsandrulesgiveninTable B1 are referred to in this standard.B 300 Offshore Standards301The offshore standards given in Table B2 are referred toin this standard.B 400 Other references401The other references given in Table B3 are referred to inthis standard.C. Informative ReferencesC 100 General101ThedocumentslistedinTableC1includeacceptablemethods for fulfilling the requirements in the standard and maybe used as a source of supplementary information. Other rec-ognised documents as listed below may be used provided it isshown that they meet or exceed the level of safety of the actualstandards.Table B1 DNV Offshore Service Specifications and rulesReference TitleDNV-OSS-101 Rules for Classification of Offshore Drilling and Support UnitsDNV-OSS-102 Rules for Classification of Floating Production and Storage UnitsRules for Classification of ShipsTable B2 DNV Offshore StandardsReference TitleDNV-OS-B101 Metallic MaterialsDNV-OS-C101 Design of Offshore Steel Structures, General (LRFD method)DNV-OS-C201 Structural Design of Offshore Units (WSD method)Table B3 Other referencesReference TitleANSI/AWS D1.1Structural Welding Code - SteelASME Section IX, Welding and Brazing Qualifications Non-Interfiled (Boiler and Pressure Vessel Codes)ASTM G48 Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solu-tionASTM E562 Standard Test Method for Determining Volume Fraction by Systematic Manual Point CountBS 7448-2 Fracture mechanics toughness tests. Method for determination of KIc, critical CTOD and critical J values of welds in metallic materialsEN 287 Approval testing of welders - Fusion weldingEN 1418 Welding personnel Approval testing of welding operators for fusion welding and resistance weld setters for fully mechanized and automatic weld-ing of metallic materialsIACS Shipbuilding and Repair Quality Standard, Part A - Shipbuilding and repair Quality Standard for New Construction and Part B - Repair Quality Standard for Existing ShipsISO 148 Steel - Charpy impact test (V-notch)ISO 898 Mechanical properties of fasteners made of car-bon and alloy steelISO 6507-1 Metallic materials - Vickers hardness test - Part 1: Test methodISO 8501-1 Preparation of steel substrates before application of paints and related products -- Visual assess-ment of surface cleanliness - Part 1: Rust grades and preparation grades of uncoated steel sub-strates and of steel substrates after overall removal of previous coatingsISO 9001:2000 Quality management systems - Requirements ISO 9606 Approval testing of welders - Fusion weldingISO 10042 Arc-welded joints in aluminium and its weldable alloys - Guidance on quality levels for imperfec-tionsNACE MR0175 Sulphide Stress Cracking Resistant Metallic Materials for Oilfield Equipment - Item No. 21302DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 10 Ch.1 Sec.1D. DefinitionsD 100 Verbal forms101Shall: Indicates a mandatory requirement to be followedfor fulfilment or compliance with the present standard. Devia-tions are not permitted unless formally and rigorously justified,and accepted by all relevant contracting parties.102Should:Indicatesarecommendationthatacertaincourse of action is preferred or particularly suitable. Alterna-tive courses of action are allowable under the standard whereagreedbetweencontractingpartiesbutshallbejustifiedanddocumented.103May: Indicates a permission, or an option, which is per-mitted as part of conformance with the standard.104Can:Can-requirementsareconditionalandindicateapossibility to the user of the standard.105Agreement,orbyagreement:Unlessotherwiseindi-cated, agreed in writing between contractor and purchaser.D 200 Terms201Purchaser:Theowneroranotherpartyactingonhisbehalf, who is responsible for procuring materials, componentsor services intended for the design, construction or modifica-tion of a structure.202Contractor: A party contractually appointed by the pur-chaser to fulfil all, or any of, the activities associated with fab-rication and testing.203Weldingprocedure:Aspecifiedcourseofactiontobefollowedinmakingaweld,includingreferencetomaterials,weldingconsumables,preparation,preheating(ifnecessary),method and control of welding and post-weld heat treatment (ifrelevant), and necessary equipment to be used.204Preliminaryweldingprocedurespecification(pWPS):Atentativeweldingprocedurespecificationprovidingrequiredwelding variables,which is assumed tobe adequateby the contractor, but which has not been qualified by the pur-chaser.205Welding procedure specification (WPS): A welding pro-cedurespecification,whichhasbeenqualifiedbythepur-chaser to conform with an agreed qualification scheme.206Weldingprocedurequalificationtest(WPQT):Theprocess of accomplishing welding and testing of a standardisedtest piece, as indicated in the pWPS.207Weldingprocedurequalificationrecord(WPQR):Arecord comprising a summary of necessary data needed for theissue of a pWPS.208Non-destructive testing (NDT): Visual inspection, radi-ographictesting,ultrasonictesting,magneticparticletesting,penetrant testing and other non-destructive methods for reveal-ing defects and irregularities.209Structuraltestingisahydrostatictest,carriedoutinorder to demonstrate the tightness of the tanks and the struc-tural adequacy of the design. Where hydrostatic testing is notpractically feasible, hydropneumatic testing may be carried outinsteadunderprovisionthatthetestissimulating,asfaraspracticable, the actual loading of the tank. 210Leak testing is an air or other medium test, carried out inorder to demonstrate the tightness of the structure.211Hydropneumatic testing is a combination of hydrostaticand air testing, carried out in order to demonstrate the tightnessof the tanks and the structural adequacy of the design.212Hosetestingisawatertestcarriedouttodemonstratetightness of structural items.213Shop primer is a thin coating applied after surface prep-arationandpriortofabricationasaprotectionagainstcorro-sion during fabrication.214Protective coating is a final coating protecting the struc-ture from corrosion215Watertight means capable of preventing the passage ofwater through the structure under a head of water for which thesurrounding structure is designed.216Weathertight means that in any sea conditions water willnot penetrate into the ship.D 300 Abbreviations301TheabbreviationsgiveninTableD1areusedinthisstandard.Table C1 DNV Recommended Practices and Classification NotesReference TitleDNV-RP-C203 Fatigue Strength Analysis of Offshore Steel StructuresClassification Note 30.1Buckling Strength AnalysisTable D1 AbbreviationsAbbreviation In fullAC Alternating currentANSI American National Standards InstituteASME American Society of Mechanical EngineersASTM American Society for Testing of MaterialsAWS American Welding SocietyBM Base materialBS British Standard (issued by British Standard Institu-tion)CE Carbon equivalentC-Mn Carbon manganeseCTOD Crack tip opening displacementDAC Distance amplitude curveDC Direct currentDNV Det Norske VeritasECA Engineering critical assessmentEN European de NormalisationFM Fracture mechanics HAZ Heat affected zoneIACS International Association of Classification Socie-tiesISO International Organisation for StandardisationMAG Metal active gas (welding)MIG Metal inert gas (welding)NACE National Association of Corrosion EngineersNDT Non-destructive testingPWHT Post weld heat treatmentpWPS Preliminary welding procedure specificationRP Recommended practiceSMAW Shielded metal arc weldingSMYS Specified minimum yield stressTIG Tungsten inert gas (welding)WM Weld metal or DepositWPQR Welding procedure qualification recordWPS Welding procedure specificationWPT Welding production testDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.1 Sec.1 Page 11D 400 Latin symbols401The following Latin symbols are used:D 500 Greek symbols501The following Greek symbols are used:a = size of test specimenb = size of test specimen d = diameter of round tensile test specimendf= distance from the plane of the fatigue pre-crack to the fusion linee = plastic deformationhT= test pressure heighthop1= vertical distance from the load point to the posi-tion of maximum filling height hs3= vertical distance from the load point to the top of the tankhp0= height corresponding to valve opening pressure when exceeding the general valuehop2= vertical distance from the load point to the posi-tion of maximum filling height. For tanks adja-cent to the sea that are situated below the extreme operational draught (TE), hop2 is not normally to be taken as being less than TEhD2= pressure head due to flow through pipesle= equivalent parameter for conical shellslmin= breadth of test assembly plateslr= length of template or rodr = nominal radius of the shellra= actual distance from the centre of the sphere to the shell wallre= equivalent parameter for conical shellsra= actual distance from the cylinder axis to the shell walls = distance between stiffeners or girderst = thicknesst1 = wall thickness of the greater tube (can)t2 = wall thickness of the smaller tube (brace)A = diameter used in wrap around bending testC = diameter of roller in bend testD = outside diameterD1 = outside diameter of the greater tube (can)D2 =outside diameter of the smaller tube (brace)KV = impact energy requirementLo= length of test area in test specimensLmin= length of test assembly platesN = number ofR = radiusRc= forming radiusT = thickness of plate in bend testW = width of weld = tubular joint angle = measure of deformation compared to theoretical geometryi= length of area with acceptable location of the fatigue pre-crack = Poisson's ratio1= largest compressive principal membrane stress2= principal membrane stress normal to 1 = ratio between principal stresses.DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 12 Ch.1 Sec.1DET NORSKE VERITASVeritasveien 1, NO-1322 Hvik, Norway Tel.:+47 67 57 99 00 Fax:+47 67 57 99 11OFFSHORE STANDARDDNV-OS-C401FABRICATION ANDTESTING OFOFFSHORE STRUCTURESCHAPTER 2TECHNICAL PROVISIONSCONTENTS PAGESec. 1 Welding Procedures and Qualification of Welders.................................................................. 15Sec. 2 Fabrication and Tolerances ...................................................................................................... 28Sec. 3 Non-Destructive Testing .......................................................................................................... 35Sec. 4 Other Tests ............................................................................................................................... 39Sec. 5 Corrosion Protection Systems .................................................................................................. 40Sec. 6 Miscellaneous........................................................................................................................... 41DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.2 Sec.1 Page 15SECTION 1WELDING PROCEDURES AND QUALIFICATION OF WELDERSA. GeneralA 100 Scope101Thissectionspecifiesrequirementsforweldingproce-dures and welding procedure tests for C-Mn steel and low alloysteel, aluminium, austenitic stainless steels and ferritic-auste-nitic (duplex) stainless steels as well as qualification of weld-ers.A 200 Welding processes201Welding may be performed with the following processesunless otherwise specified: manual metal arc welding (metal arc welding with coveredelectrode) self-shielded tubular-cored arc welding submerged arc welding with one wire electrode submerged arc welding with strip electrode metal inert gas welding, (MIG) welding metal active gas welding, (MAG) welding tubular-cored metal arc welding with active gas shield tubular-cored metal arc welding with inert gas shield tungsten inert gas arc welding, (TIG) welding plasma arc welding.B. Welding ProceduresB 100 General101A welding procedure specification shall as a minimumcontain the following information as relevant for the weldingoperation: material: standard, grade and modification nominal thickness or diameter range (dimensions) welding process joint or groove design with tolerances welding position(s) and direction of progression welding consumables: trade name, electrode or wire diam-eter, shielding gas, flux and recognised classification welding sequence: number and order of passes or layers electrical parameters: voltage range, current range, polar-ity travel speed- and heat input ranges preheat and interpass temperatures post weld heat treatment parameters details on cleaning processes employed and restrictions ifany.B 200 Preliminary welding procedure specification, pWPS201ApWPSshallbepreparedforacceptancebythepur-chaser prior to starting up the agreed welding procedure qual-ification test (WPQT).B 300 Welding Procedure qualification test (WPQT)301Whenaweldingprocedurespecification(WPS)isrequired to be qualified by a WPQT, the welding process shallbe performed based on the accepted pWPS. (See Sec.2 F112).B 400 Welding procedure qualification record (WPQR)401A WPQR can be basis for the purchasers acceptance ofa WPS. Prior to starting up production the WPQR shall be sub-mitted to the purchaser for review including any corrosion testresults, as applicable.B 500 Welding procedure specifications (WPS)501AWPSshallbeacceptedbythepurchaseruponcon-formitywiththerequirementsofanagreedqualificationscheme.502A WPS shall be valid under the provision that produc-tionweldingiscarriedoutwiththesametypeofweldingequipment on which the WPS has been established.503The conditions on which the WPS has been establishedshallberepresentativeoftheworkingenvironmentfortheworkshoporsitewheretheproductionweldingwillbeper-formed. (See C700).C. Welding Procedure Tests, C-Mn Steel and Low Alloy SteelC 100 Butt welds on plates101Thetestassemblymayconsistoftwoplatesweldedtogether. As far as possible the plates shall have a size that cansimulate the heat transfer during the production welding. Formanual or semiautomaticwelding, atest assembly accordingto Fig.1 shall be carried out with:For automatic welding, the dimensions shall be:Edge preparation and fit-up shall be as detailed in the pWPS.The plates shall be joined and held by tack welds to provide thecorrect gap for the edge preparation used. 50 mm at each endof the test piece shall be discarded.lmin= 300 mmLmin= 350 mmlmin= 400 mmLmin= 1000 mmDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 16 Ch.2 Sec.1Figure 1Test assembly for butt welds on plates102NDT shall be carried out in accordance with the specifi-cation given for the production welding in question. The extentof the testing shall be as follows: 100% visual inspection 100% radiographic or ultrasonic testing 100% surface crack detection (dye penetrant or magneticparticle testing).Thesoundnessoftheweldshallcomplywithrequirementsgiven in Sec.3 B.103The following mechanical tests are required from eachassembly (see Fig.2): 2 tensile tests (flat specimen transverse to the weld) 1rootand1facebendtestswhent 20mmand2sidebend tests when t > 20 mm 4 (6) sets of Charpy V-notch tests with the notch locationas given in 107 1macrosectiontest(metallographicexamination+hard-ness measurements).104Specimensfortransversetensiletestingshallbeinaccordance with G, type B.The tensile strength shall not be below the specified minimumtensile strength for the steel grade in question. Figure 2Sampling of test specimens in plates105Transversesidebend,rootbendandfacebendspeci-mens shall be machined to the dimensions shown in G300.For a mixed or heterogeneous butt joint longitudinal bend testspecimens may replace transverse bend test specimens.The test specimens shall be bent on a mandrel with diameter4 t, where t is the thickness of the specimen, except for extrahigh strength steel grades NV 550, NV 620 and NV 690 wherethe diameter shall be 5 t.The bendingangle shall beatleast 120. Afterbending, thetest specimens shall not reveal any open defects in any direc-tion greater than 3 mm. Defects appearing at the corners of atest specimen during testing may be ignored in the evaluation,if not associated with obvious defects.106Themacrosectionshallincludeabout10mmofunaf-fected base material and shall be prepared and etched on oneside to clearly reveal the fusion line and the HAZ. Cracks andlack of fusion are not accepted.Theweldedjointsshallhavearegularprofilewithsmoothtransitionstothebasematerialsandwithoutsignificantorexcessive reinforcement.107TheCharpyV-notchspecimensshallbemachinedinaccordancewiththerequirementsgiveninDNV-OS-B101.Foursetsofthreespecimenseachshallbesampled2mmbelow the surface of the parent material and transverse to theweld. 12 Charpy V-notch specimens shall be localised in thewelded joint as follows: 3specimenswiththenotchalongtheweldmetalcen-treline 3 specimens with the notch in the fusion lineDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.2 Sec.1 Page 17 3specimenswiththenotchintheHAZ,2mmfromthefusion line 3specimenswiththenotchintheHAZ,5mmfromthefusion line.The V-notch shall be perpendicular to the plate surface.For plate thickness t > 50 mm two additional sets of specimensshall be taken from the root area: one with the notch in centreof weld and one with the notch in the fusion line.For dissimilar metal joints and/or joints between cast or forgedandrolledmaterials,impacttestsshallbecarriedoutontestspecimens with notch in fusion line, 2 mm from fusion line and5 mm from fusion line in each parent material.The Charpy V-notch test temperature and the average value forabsorbedenergy(KV)inweldmetal,fusionlineandHAZshall be the same as required for the base material in transversedirection (see DNV-OS-B101).The requirements given by the DNV Rules for Classificationof Ships Pt.2 Ch.3 Sec.2 B308 can be applied as an alternative.For grades of improved weldability (see DNV-OS-B101), theCharpyV-notchtesttemperatureandtheaveragevalueforabsorbed energy in weld metal, fusion line and HAZ shall bethesame asrequired for the basematerial of the comparablenormal weldability grade in transverse direction.108InthecaseofreducedCharpyV-notchtestspecimens(10 mm x 7.5 mm and 10 mm x 5 mm), the impact energy val-ues to be obtained shall satisfy the requirements in Table C1.109Theaverageimpactrequirementsshallbesatisfiedforeach notch location, but one single value of three values fromspecimensfromthesamenotchlocationmaybebelowtheaveragerequirements,butnot below70%ofminimumaver-age.110Where the results from a set of three impact test speci-mens do not comply with the requirements, an additional set ofthree impact test specimens may be taken.The results obtained shall be combined with the original resultsto form a new average, which, for acceptance, shall be not lessthantherequiredvalue.Additionally,forthesecombinedresults not more than two individual values shall be less thantherequiredaveragevalue,andofthese,notmorethanoneshall be less than 70% of the average required value.When the result of any test, other than impact test, fails to meetthe requirements, two further tests may be made from the samewelded joint. If both these additional tests are satisfactory, thetest is acceptable.111ThehardnesstestingshallbeinaccordancewithISO6507-1orequivalent.TheVickersmethod(HV10)shallbeused.Indentations shall be made along traverses in the weld, HAZand the parent metal approximately 1 mm below the surface.For each traverse a minimum of 3 indentations shall be madeintheweld,HAZ(bothsides)andparentmetal(bothsides).ForHAZthefirstindentationshallbeplacedasclosetothefusion line as possible. For double sided welds, for fillet and T-buttweldsoneadditionalrowofindentationsshallbemadethrough the root area.For material grades up to and including NV 460, a maximumhardnesslimitof350HV10shallbemetforweldsinsub-mergedstructuresexposedtocathodicprotection.Hardnesslimits for higher grades shall be subject to agreement.Guidance note:For NV 500, NV 550, NV 620 and NV 690 grades a maximumhardness limit of 420 HV10 is recommended for welds in sub-merged structures exposed to cathodic protection.---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---112When a butt weld is made between two different mate-rialgrades,thetesttemperatureandachievedimpactenergyshall comply with the minimum specified requirements for thelower steel grade.Inthesameway,thetensilestrengthtobeobtainedonthewelded assembly shall be in agreement with the requirementsrelating to the plate steel having the lower strength.As an example the test temperature, impact energy and tensilestrengthforthebuttweldedjointsgiveninFig.3arethoserequired for the plate of grade D in the left assembly and forthe plate of grade E in the right assembly.Figure 3Butt welded plate joints of different gradesC 200 Butt welds in pipes201The test assembly shall be in accordance with Fig.4.Figure 4Test assembly for butt welds in pipes202NDT shall be carried out in accordance with the specifi-cation given for the production welding in question. The extentof the testing shall be as follows: 100% visual inspectionTable C1 Impact energy requirement for sub-size specimensDimensions of Charpy V-notch test specimen Impact energy10 x 10 mm KV10 x 7.5 mm 5/6 KV10 x 5 mm 2/3 KVa = minimum value 150 mmD = outside diameterDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 18 Ch.2 Sec.1 100% radiographic or ultrasonic testing 100% surface crack detection (dye penetrant or magneticparticle testing).Thesoundnessoftheweldshallcomplywithrequirementsgiven in Sec.3 B.203The following mechanical tests are required from eachassembly (see Fig.5): 2 tensile tests (flat specimen transverse to the weld) 1rootand1facebendtestswhent 20mmand2sidebend tests when t > 20 mm 4 (6) sets of Charpy V-notch tests with the notch locationas given in 107 macrosection test (metallographic examination + hardnessmeasurements).Figure 5Sampling of test specimens in pipes204The results of mechanical testing shall comply with therelevant requirements given in C100.C 300 Full penetration T-, Y-, and K- joints301WPQT'sforfullpenetrationgrooveweldsbetweenplates at right angles or inclined, i.e. T- or Y- and K- configu-rations,shallcoveraweldlengthofminimum350mm(seeFig.6).302NDT shall be carried out in accordance with the specifi-cation given for the production welding in question. The extentof the testing shall be as follows: 100% visual inspection 100% ultrasonic testing 100% surface crack detection (dye penetrant or magneticparticle testing).Thesoundnessoftheweldshallcomplywithrequirementsgiven in Sec.3 B.Figure 6Test assembly for full penetration T-joints303The following mechanical tests are required from eachassembly (see Fig.7): 4 (6) sets of Charpy V-notch tests with the notch locationas given in 107 1macrosectiontest(metallographicexamination+ hard-ness measurements).The results of mechanical testing shallcomplywith the rele-vant requirements given in C100.Figure 7Sampling of test specimens on full penetration T-jointsC 400 Tubular joints401The test assembly shall be in accordance with Fig.8.402NDT shall be carried out in accordance with the specifi-cation given for the production welding in question. The extentof the testing shall be as follows: 100% visual inspection 100% ultrasonic testing 100% surface crack detection (dye penetrant or magneticparticle testing).Thesoundnessoftheweldshallcomplywithrequirementsa = 3 t, minimum value 150 mmb = 6 t, minimum value 350 mmDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.2 Sec.1 Page 19given in Sec.3 B.Figure 8Test assembly for tubular joints403The following mechanical tests are required from eachassembly (see Fig.9): 12 Charpy V-notch tests sampled at 9 o'clock and with thenotch location as given in 107 2 macro section tests (metallographic examination + hard-ness measurements) at 12 and 6 o'clock.404The results of mechanical testing shall comply with therelevant requirements given in C100.405Restrictions and testing for joint configuration involvingacute angles (less than 15) should be specified. AWS D1.1 isa good reference for structural welds.C 500 Fillet welds501The two plates are assembled and positioned edgewiseso as to constitute a tee-assembly with no clearance. As far aspossible the plates shall be of a sufficient size to ensure a rea-sonable heat distribution.For fillet welds the test assembly shall be as defined in Fig.9.Figure 9Test assembly for fillet weldsFor manual and semi-automatic welding the length of the testpiece shall be:For automatic welding the length shall be:Weld and fit-up shall be as detailed in the pWPS.The test assembly shall be welded on one side only. For man-ual and semi-automatic welding, the stop and restart positionshall be included in the test length and shall be clearly markedfor subsequent examination.The ends of the specimen are exempted from examination overa length of 50 mm.502NDT shall be carried out in accordance with the specifi-cation given for the production welding in question. The extentof the testing shall be as follows: 100% visual inspection 100% surface crack detection (dye penetrant or magneticparticle testing).Thesoundnessoftheweldshallcomplywiththespecifiedrequirements given in Sec.3 B.If the stop and restart spot is included in the test length, specialattention shall be paid to this position with respect to profile,proper fusion and absence of crater defects.503The following tests shall be performed: 2 macro section tests (metallographic examination, hard-ness measurements).One of the macrosections shall be taken at the marked positionof the stop and restart (for more details see 106).For hardness testing, see 111.C 600 Re-testing601If the welding procedure test fails to comply with any ofthe requirements for NDT one extra test shall be welded andsubjectedtothesametesting.Ifthisadditionaltestdoesnotmeet the relevant requirements, the actual pWPS shall be con-sideredasnotqualifiedandare-specificationofthepWPSshall be made prior to a new welding procedure test.C 700 Validity of a WPS701ThevalidityofaWPSshallberestrictedtothework-shopperformingthequalification.Workshops,worksiteorworkshop branches under the same technical management andworking in accordance with the same QA-program and pro-cedures are considered as one workshop or site work. 702Qualification of a welding procedure remains valid pro-videdtheparametersarekeptwithinthequalifiedrangesofessentialvariableduringproductionwelding.Theessentialvariables andqualifiedranges are given in703.Whenvaria-tionsoutsidethequalificationrangesofessentialvariablesoccur, the welding procedure qualification shall be consideredinvalid,andtheWPSshallthereforebere-specifiedandre-qualified.703A qualified welding procedure shall be used within theranges of the parameters of essential variables listed below.Base materialThe following changes shall lead to a new qualification:a) In general, significant change of material properties whichwill obviously affect the weldability and mechanical prop-erties.a = minimum value 150 mmD1 = outside diameter of the greater tubular (can)t1 = wall thickness of the canD2 = outside diameter of the smaller tube (brace)t2 = wall thickness of the braceLmin= 350 mmLmin= 1000 mmDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 20 Ch.2 Sec.1Guidance note:When qualifying a welding procedure, it is recommended to usespecified material with highest carbon equivalent (CE) availableintheworkshoporworksite,especiallywhenthethicknessislarge.---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---b) Morespecifically,structuralsteelsofbothnormalandimprovedweldabilityaregroupedinthreestrengthgroups:i) Normal strength steel, grades A, B, D and E or equiv-alent structural steels with tensile strength 400 to 520N/mm2.ii) High strength steel, grades A 27, D 27, E 27, A 32, D32, E 32, F 32, A 36, D 36, E 36, F 36, A 40, D 40, E40, F 40 or equivalent structural steels with minimumspecified yield strength 265 to 390 N/mm2.iii) Extra high strength steels, grades A-F 420, A-F 460,A-F500,A-F550,A-F620,A-F690orequivalentstructuralsteelswithminimumspecifiedyieldstrength 420 to 690 N/mm2.The qualification on steel grades of higher toughness require-ments will qualify the grades of lower toughness but not viceversa.704Thickness, is defined as follows:a) For a butt weld:Thebasemetalthickness,whichforweldsbetweendis-similar thickness is that of the thinner material.b) For a fillet weld:Thebasemetalthickness,whichforweldsbetweendis-similar thickness is that of the thicker material. However,foreachthicknessrangequalified,asgiveninTableC2there is an associated range of qualified throat thickness.c) For a set-on tubular joint:The thickness of the brace.d) For a set-in or set-through tubular joint:The thickness of the can.e) For a T-butt joint in plate:The thickness of the prepared plate (abutting member).The requirements for qualified thickness range for butt weldsshall be as given in Table C2.The requirements for qualified thickness range for single runfillet welds are in addition to the requirements of Table C2, thatthe throat thickness, tw, shall be in the range 0.75 tw to 1.5 tw.However,atestwithathroatthickness10mmshallgivequalification for all throat thicknesses 10 mm.Where a fillet weld is qualified by means of a butt weld test,the throat thickness range qualified shall be based on the thick-ness of the deposited weld metal.Diameter of pipes and tubular jointsThequalificationofaweldingproceduretestondiameterDshallincludequalificationfordiametersinthefollowingranges as given in Table C3.Angle of tubular jointsAweldingproceduretestcarriedoutonatubularjointwithangle shall qualify all tubular joint angles in the range of to 90.Welding consumablesThe following changes shall lead to a new qualification: any change in consumable classification changeofconsumablebrandwhenimpacttestingisrequired at temperatures below 20C anysignificantchangeofmixtureorcomposition(e.g.changefromargonormixedgastoCO2gas),flowrate,fillingtimeandfillingvolumeforshieldingandpurginggases.Welding positionsThe following changes shall lead to a new qualification. Change from one principal welding position (see Fig.10,Fig.11andFig.12)toanother,unlesscomplyingwithTable C4.Figure 10Plate test positionsTable C2 Qualified thickness rangeThickness t in mm of test pieceQualification range 1) 2)for single run or single run from both sidesfor multi-run welding and all fillet weldst 12 0.8 t to 1.1 t 3 mm up to 2 t12 < t 100 0.8 t to 1.1 t 0.5 t to 2 t(maximum 150)t > 100 - 0.5 t to 1.5 t1) The qualification range for vertical downward position is 0.5 t to 1.1 t2) For butt welds in plates of thickness > 50 mm, the Charpy V-notch requirement for the root area, ref. 107, shall be complied with.Table C3 Qualified range for pipes and tubular jointsDiameter of the test piece D (mm) 1) 2)Qualification rangeD < 168.3 0.5 D to 2 DD 168 0.5 D and plates1) D is the outside diameter of the pipe or outside diameter of the brace2) Qualification given for plates also covers pipes when the outside diam-eter is greater than 500 mmDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.2 Sec.1 Page 21Figure 11Pipe test positionsType of jointThe following changes shall lead to a new qualification: change from fillet weld to butt weld change from two sided welding to one side (but not viceversa) deletion of back gouging addition or deletion of ceramic backing deletion of backing in cases where the backing material isequivalent to the base material change from T-, Y- or K-joint to butt joint change from butt joint in plates to butt joints in pipes withoutside diameter less than 500mm anychangeofgroovedimensionsspecifiedintheWPSand agreed with the purchaser, such as change of specifiedtype of groove, root face and gap, which may significantlyaffect penetration, fusion and dilution of the weld. Welding conditionThe following changes shall lead to a new qualification: any change of welding process changefromweavingtostringerbeadtechniqueorviceversa stringer to weave ratio outside the tolerances specified inthe agreed WPS change from multi-pass welding to one-pass welding changeinweldingcurrentfromA.C.toD.C.,orviceversa, or change of polarity. If recommended by the con-sumable manufacturer particular exemption may be givenfor SMAW in change from A.C. to D.C. change in metal powder or wire addition beyond 10%. change from spray arc to short arc pulse, or vice versa any change beyond 25C of the maximum interpass tem-perature change in heat input beyond 25% for steel up to 420 MPainspecifiedyieldstrength.Formaterialwithspecifiedyield strength equal to or above 420 MPa the change shallnot be more than 10%, unless otherwise qualified any decrease in preheating temperature change of post weld heat treatment parameters except forholdingtime,whichmaybeadjustedasafunctionofthickness.Figure 12Positions of test plate for fillet weldsTable C4 Qualified principal positions for butt welds and fillet welds, steelTest weldJoint configuration 1)2)Principal positionsQualified positions 3)Butt welds Fillet weldsPlates or PipesPlates PipesButt welds in plates 2G + 3G1G2G3G4GAll1G1G, 2G, 4G3G1G, 4GAll1F1F, 2F, 4F3F1F, 4FButt welds in pipes 2G + 5G = 6G1G2G5GAll1G1G, 2G, 4GAllAll1G1G, 2G1G, 5GAll1F1F, 2F, 4FAllFillet welds 2F + 3F1F2F3F4F5FAll1F1F, 2F, 4F3F1F, 2F, 4FAll1) Pipes with D > 500 mm are considered equivalent to plates (apply only to the can in tubular joints)2) Tubular joints shall be qualified separately3) The vertical downwards position shall be qualified separatelyDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 22 Ch.2 Sec.1C 800 Fracture mechanic (FM) testing 801Requirements to fracture mechanic testing are given inDNV-OS-C101 or DNV-OS-C201. 802Thetestweldshallbemadeandtestedfortheactualcombination of steel grade, manufacturer, welding process andwelding consumable (brand) used. FM testing is, however, notrequiredforconsumablesusedforrootpassesonlyintwo-sided welds.803TheFMtestsshallbecarriedoutonafullpenetrationbutt-weld with K- or single V-preparation. The back of the Kand one of the legs of the single V (on which the FM test shallbe carried out) shall be perpendicular to the plane of the plate.Tests on either of these weld bevel preparations qualify for alltypes of bevel preparations.804Thetestweldshallbeweldedwithaheatinputrepre-sentingthemaximumheatinputusedinthefabrication.Thetest weld shall be made on a plate with a thickness not smallerthan 90% of the maximum plate or wall thickness for which thewelding procedure shall apply. The test weld also qualifies forplate thicknesses down to 50% of the test weld plate thickness.805On each test weld at least three FM test specimens shallbe tested in each of the weld deposit and the heat affected zone(HAZ).(Detailsregardingtherequirednumberoftestspeci-mens and the location of fatigue pre-cracks aregiven furtherbelow.)806Testing of the HAZ or the weld deposit can be omitted iftests with satisfactory results according to the requirements inthisstandardhavebeencarriedoutpreviouslybyeitherthesteel manufacturer or the welding consumable manufacturer.807The FM tests shall be carried out according to BS 7448Part2(withdetailedrequirementsasgivenbelow)using3-pointbendspecimens.TheCTOD-techniquewithBx2Bspecimens shall be used. For nominal plate thicknesses of thetest weld equal to or exceeding 80 mm, B x B specimens maybe used.All specimens shall be tested with the fatigue pre-crack placedin the through-thickness direction. For tests of the weld depositthefatiguepre-crackshallsamplethecentralpartofthedeposit.FortestsintheHAZtherequiredlocationofthefatigue crack depth is given in 108.Anevaluationoftherelevanttesttemperatureshallbemadefor all joints in question. Unless there is a high probability thatthe extreme loads on the joints will concur with lower temper-atures the test temperature shall be:808Subsequent to the CTOD-test the specimens in the HAZshall be sectioned and examined as described below.A metallographic section according to BS 7448 Part 2 Section11.2 shall be prepared from each HAZ specimen. The metallo-graphic section shall include weld metal and base metal. If nec-essary, in order to determine the exact location of the fatiguepre-crack,sectionsfrombothsidesofthepre-crackshallbeprepared. The faces of the metallographic sections shall not betaken deeper than the deepest point of the fatigue pre-crack andnot more than 3 mm from the deepest point of the fatigue pre-crack.A figure of a cross-section through the weld (of an un-fracturedspecimen) is shown in Fig.13.Figure 13Cross-section through the weldBM = Base materialWM = Weld metal or depositdf= distance from the planeofthefatigue pre-crack tothe fusion line (varies along the fatigue pre-crack)li= length (in mm) of area with acceptable location ofthe fatigue pre-crack (see below)t = Plate thicknessMeasurementsofthedistance,df,betweentheplaneofthefatigue pre-crack and the fusion line shall be taken. Within thecentral 75% of the plate thickness the areas where df 0.5 mmshall be identified. The length, i of each of these areas shallbe determined. The location of the fatigue pre-crack shall sat-isfy the following criteria:Ni= 3 mm for t 20 mm= 0.15 t for 20 < t 80 mm= 12 mm for t > 80 mmN = number of areas with df 0.5 mm809Results from HAZ specimens on which the location ofthefatiguepre-crackdoesnotsatisfytherequirementabove,are not valid. In addition to these requirements given for HAZspecimens,alltherequirementsspecifiedinBS7448Part2apply for both HAZ and weld deposit specimens.ThreevalidtestsforeachofwelddepositandHAZshallbecarried out. The critical CTOD for all of the specimens shall beequal to or larger than 0.15 mm.If (for HAZ or weld deposit) one or more of the three speci-mens has a critical CTOD lower than 0.15 mm additional testsmay be carried out. In such a case the characteristic value, asdefined in Table C5, shall be equal to or larger than 0.15 mm.810IfthecharacteristicvalueasspecifiedinTableC5islarger than 0.15 mm an ECA (Engineering critical assessment)may be carried out with the purpose of demonstrating that extracapacity may be available in the structure.For joints submerged at lowest waterline: 0COther joints: design temperature.Table C5 Characteristic value of CTODNumber of valid tests 1)Characteristic value3 to 5 Lowest result6 to 10 Second lowest result11 to 15 Third lowest result1) All valid tests that have been carried out shall be included in the evaluation. It is not permissible to discard any valid test result.DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.2 Sec.1 Page 23D. Welding Procedure Tests, AluminiumD 100 General101Qualified welding procedures are required for all impor-tant structural joints. The procedure tests shall be representa-tive of the following: each base material or alloy and temper used in production the thickness and diameter range in question (see Table C2and Table C3) each type of consumable and welding process welding position (see Table D1) joint and groove design number of passes preheat (if any) volt-ampere characteristics shielding gas.D 200 Butt welds201Each test assembly consists of 2 plates with dimensions300 x 150 mm. The plates shall be joined with a longitudinalbutt weld. For extruded sections and pipes the assembly shallconsistof2sectionseach150mmlong(seeFig.14andFig.15).202Weld and fit-up shall be as detailed in the pWPS. Weld-ing consumables are those recommended in Table D2.203If back-sealing run is specified, this run shall be laid inthe same position as for the respective weld.204Theweldsshallbesubjectedtovisualinspection,dyepenetrant testing and ultrasonic- or X-ray testing. The require-mentsfor qualitylevelfor imperfections shall beas giveninISO 10042 level B.205Side-bend tests shall be carried out for thickness equal toandabove10mm.Twobendspecimensshallbetakenfromeach of the welded assemblies.Figure 14Location of test specimens for a butt weld on plate206For thickness below 10 mm one face bend and one rootbend test specimens shall be taken. The width shall be 30 mmand the thickness equal to the plate thickness. The diameter ofthe bending mandrel shall be as given in Table D3.207RequirementNocracksoropendefectsexceeding3mmmeasuredontheTable D1 Qualified principal positions for butt welds and fillet welds, aluminium Test weldJoint configurationPrincipal positionsQualified positions1)Butt welds, plates Butt welds, pipes Fillet weldsButt welds on plates1G2G3G4G1G1G, 2G, 3G1G, 2G, 3GAll1G 1F1F, 2F, 3F1F, 2F, 3FAllButt welds in pipes1G2G5G1G1G, 2G, 3GAll1G2G1G, 5G1F1F, 2F, 3FAllFillet welds1F2F3F4F5F1F1F, 2F, 3F1F, 2F, 3FAllAll1) The vertical downward position shall be qualified separately.Table D2 Selection of suitable consumables for combinations of aluminium alloysBase metal alloy NV-5052, NV-5754 NV-5154,NV-5454 NV-5086NV-5083NV-5383 NV-6060, NV-6061 NV-6063, NV-6005A NV-6082NV-5052, NV-5754 NV-5154, NV-5454 NV-50865356, 5556, 5183 5356, 5556, 5183 5356, 5556, 5183NV-5083, NV-5383 5356, 5556, 5183 5183 1)5356, 5556, 5183NV-6060, NV-6061 NV-6063, NV-6005A NV-60825356, 5556, 5183 5356, 5556, 5183 5356, 5556, 5183Note:All consumables are covered by the AWS specification. The prefix ER is omitted.1) Other consumables may be used if allowable stresses are reduced.Table D3 Former diameter for bend testsBase metal alloyCondition0, H111H116, H32, H321, H34T4 T5, T6NV-5052, NV-5754 NV-5154, NV-54544t 4t - -NV-5086, NV-5083, NV-53836t 6t - -NV-6060, NV-6061 NV-6063, NV-6005A NV-6082- - 6t 7tDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 24 Ch.2 Sec.1convexsurfaceafterbendingareaccepted.Smallercracksdeveloping from the edges of the specimens should not be con-sideredassignificant,unlessthereisdefiniteevidencethattheyresultfrominclusionsorotherdefects.Wraparoundbending as shown in Fig.16 is the preferred bending method.Figure 15Location of test specimens for a butt weld in pipeFigure 16Wrap around bending208Onetensilespecimenshallbetakenfromeachofthewelded assemblies. The test specimen, 25 mm wide and withfullplatethicknessandorientatedtransversetotheweld,isshown in Fig.17.Figure 17Tensile test specimen209Thetensilestrengthofthetestspecimensshallnotbeless than specified for the parent alloy in Table D4.210One macrosection shall be prepared from the test assem-bly to reveal the weldment macro structure. The macrosectionshall be visually inspected using a magnification of 5 to 10X.Themacrosectionshallshowaregularweldprofilewithasmoothtransitiontothebasematerialwithoutsignificantundercut or excessive reinforcement and show thorough fusionbetween adjacent layers of weld metal and base metal. Thereshall be no cracks, lack of fusion and incomplete penetration.D 300 Fillet welds301The two plates are assembled and positioned edgewiseso as to constitute a tee-assembly with no clearance. As far aspossible the plates shall be of a sufficient size to ensure a rea-sonable heat distribution.For fillet welds the test assembly shall be as defined in Fig.9. For manual and semi-automatic welding the length of the testpiece shall be:For automatic welding the length shall be:Weld and fit-up shall be as detailed in the pWPS.The test assembly shall be welded on one side only. For man-ual and semi-automatic welding, the stop and restart positionshouldbeincludedinthetestlengthandshallbeclearlymarked for subsequent examination.The ends of the specimen are exempted from examination overa length of 50 mm.302NDT shall be carried out in accordance with the specifi-cation given for the production welding in question. The extentof the testing shall be as follows: 100% visual inspection 100% surface crack detection (dye penetrant).The soundness of the weld shall comply with ISO 10042 levelB.If the stop and restart spot is included in the test length, specialattention shall be paid to this position with respect to profile,proper fusion and absence of crater defects.303The following tests shall be performed: two macrosection tests (metallographic examination).One of the macrosections shall be taken at the marked positionof the stop and restart (for more details see C106).D 400 Re-testing401Ifanyofthetestsdonotsatisfythespecifiedrequire-ments,newproceduretestsinduplicatemaybecarriedout.Theresultsofbothre-testsshallmeetthespecifiedrequire-ments, otherwise the test shall be rejected.Guidance note:HAZ softening adjacent to weldsThe strength of a weldment is a function of the welding process,filler metal and the aluminium alloy in question. For design pur-posesitisassumedthatthestrengthisreducedinHAZ.Theextent of the HAZ is assumed to have the same width as the weld-mentplustheplatethicknessineachdirectionoftheweldasshown in Fig.18.Ifthestrengthshallbemeasuredforinformation,thisshallbecarried out on a gauge length 2 t + W of the weld (approximately3 t).lmin= 300 mmLmin= 350 mmlmin= 400 mmLmin= 1000 mmDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.2 Sec.1 Page 25Figure 18Extent of HAZ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---E. Welding Procedure Tests, Stainless SteelE 100 General101Whenweldingproceduretestsarerequired,thetestsshall be performed in accordance with C and the supplemen-taryrequirementsstatedinD200andD300(ifnototherwisespecified herein).102Theweldingproceduretestsshallcoverallrelevantdimensions,positionsandmaterialcombinations.DetailsregardingessentialvariablesandvalidityoftheprocedureshallbeasdescribedinC.MechanicaltestingshallbeasdescribedinC100,ifnototherwisespecifiedinD200andD300.E 200 Supplementary requirements for austenitic stain-less steel201Impacttestingisnotrequiredfordesigntemperaturesabove 105C. If used at below 105C, the test temperatureshall be at minimum design temperature.202Ifimpacttestingisrequired,theaverageimpactvaluefor the three specimens shall not be less than 34 J.203Whenabuttweldismadebetweendissimilarmaterialgrades, both sides of the weld shall be impact tested.E 300 Supplementary requirements for ferritic-auste-nitic stainless steel301Impact testing shall be carried out at design temperatureor 20C, whichever is the lower. The average impact valuefor the three specimens shall not be less than 27 J.302Whenabuttweldismadebetweendissimilarmaterialgrades, both sides of the weld shall be impact tested.303Buttweldsandfilletweldsshallbecorrosiontestedaccording to ASTM G48, Method A. The test specimen shallbe in the as welded state after normal weld cleaning operation.The test specimens shall be exposed to the solution at a con-stant temperature of 20C for 24 hours.The following test requirements shall be fulfilled: no pitting attack shall be visible on the test face(s) general weight loss shall be less than 4 g/m2.Guidance note:Welds between ferritic-austenitic stainless steels and C- and C-Mn steels need not be subjected to corrosion test.---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---304Amicrostructuralexaminationcomprisingtheweldmetal, heat affected zone and base metal is required for eachwelded assembly. The microstructure shall be suitably etchedt = Plate thicknessW = With of weldTable D4 Mechanical properties in the welded conditionAlloy Temper FillerTensile strengthRm, minimum(N/mm2)Yield stressin HAZ, Rp minimum(N/mm2)NV-50520 F, H111 H32, H345356 170 65NV-5754 0, F, H111, H24 5356-5183 190 80NV-5154A 0, H111 5356-5183 215 85NV-5454 0, F, H111, H34 5356-5183 215 85NV-5086 0, F, H111,H116, H32, H345356-5183 240 100NV-5083 0, F t < 6 mm0, F t > 6 mmH116, H321H116, H32151835356-518353565183270270270270125115115125NV-5383 0, H111, H116,H3215183 290 140NV-6060 T5 5356-5183 95 65NV-6061 T4T5 or T65356-5183 165165115115NV-6063 T5T65356-5183 1001006565NV-6005A T5 or T6 5356-5183 165 115NV-6082 T4T5 or T65356-5183 170170110115DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 26 Ch.2 Sec.1andexaminedat400Xmagnificationandshallbefreefromgrain boundary carbides and precipitates. The ferrite content inthe weld metal root and not re-heated weld cap shall be deter-minedinaccordancewithASTME562andshallbeintherange of 25% to 70%.F. Qualification of WeldersF 100 General101Theweldingprocessesforwhichqualificationsarerequiredincludethosewhicharedesignatedasmanualorpartly mechanised welding. Welders shall pass a qualificationtest in accordance with 200. Contractors are required to keeprecords of the welders' qualifications and, when required, fur-nish copies of valid welders' certificates.F 200 Standards for qualification testing201Welders shall be tested according to a recognised stand-ard, e.g. EN 287, ISO 9606, ASME Section IX or ANSI/AWSD1.1.202Welding operators using fully mechanised or fully auto-maticprocessesneedgenerallynotpassaqualificationtest.However,operatorsshallreceiveadequatetraininginsettingorprogrammingandoperatingtheequipment.Appropriaterecordsoftrainingshallbemaintained.Contractorsmayberequiredtofurnishvalidqualificationtestcertificates.EN1418 may be used as a reference.G. TestingG 100 General101Testing of welds shall be carried out as specified in 200and 300.G 200 Tensile testing at ambient temperature201For tensile testing of all-weld-metal and butt welds twodifferent types of test specimens may be used, round test spec-imens or flat test specimens (see Fig.19) as described below:A - Deposited metal tensile testNormally, round test specimens with the following dimensionsshall be used:B - Butt weld tensile test for testing of the weld as a wholeFlat test specimens with the weld machined flush with the sur-face of the plate, shall be used. The dimensions shall be as fol-lows:C - Butt weld tensile testFlat test specimens with the weld machined flush with the sur-face of the plate, shall be used. The dimensions shall be as fol-lows:Figure 19Tensile test specimenG 300 Bend testing301Flatbendtestspecimens,asgiveninFig.20shallbeused. Edges on tension side shall be rounded to a radius of 1 to2 mm.Figure 20Bend test specimenFigure 21Wrap around bend test302When the wrap around bend test, exemplified Fig.21 isused, e.g. for the side bend test of a weld, the length of the testspecimen shall be greater than the length 11a shown in Fig.20.303Forbuttweldbendtestspecimens,theweldshallbemachined flush with the surface of the plate.304Fortransverseface-bendandroot-bendtestspecimensfor butt weld test the dimensions shall be as follows:d = 10 mmLo= 50 mmLc= 60 mmR 5 mma = thickness of plate, tb = 25 mmL0= LC = 3 t or 2 t + width of weld, (whichever is the greatest)R = 25 mma = thickness of plate, tb = 30 mmLo= 6 mm + width of weld + 6 mmR = 50 mma = as rolled thickness t of the plateb = 30 mmDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.2 Sec.1 Page 27Iftheasrolledthicknesstisgreaterthan25mm,itmaybereduced to 25 mm by machining on the compression side of thetest specimen.305Fortransverseside-bendtestspecimensforbuttweldtest the dimensions shall be as follows:If t 40 mm, the side-bend test specimen may be subdivided,each part being at least 20 mm wide.306When a longitudinal face-bend or root-bend weld test isrequired, a test specimen according to an appropriate standardwill be accepted.a = 10 mmb = as rolled thickness t of the plateDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 28 Ch.2 Sec.2SECTION 2FABRICATION AND TOLERANCESA. GeneralA 100 Objective and scope101This section gives requirements for fabrication and tol-erances of offshore structures.102Inordertodeterminethestructuralcategorisation,thissection shall be read in conjunction with the following applica-ble standards: DNV-OS-C101 Section 4 and relevant Object Standard, Sec-tion2SelectionofMaterialandExtentofInspectionorDNV-OS-C201 Section 4. B. Fabrication PlanningB 100 General101As a prerequisite for fabrication, procedures, inspectionand test plans and work instructions for execution and controlof fabrication activities shall be established. The purpose of theprocedures and work instruction shall be: toprovideinstructionsandinformationregardingtherequirements for and the principles of the work execution to identify and document the responsibilities and plans forthe work execution in accordance with the project require-ments to provide information to the purchaser on how the workis executed and controlled to identify applicable procedures, test plans, work instruc-tions, acceptance criteria, hold points and documents to begenerated to serve as basis for quality audits.102Relevantprocedures,includinginformationofpre-assembled items and the sequence of fabricating the parts intostructure, shall be prepared.B 200 Quality system and workmanship201Contractorsinvolvedinfabricationofstructuralmem-bers shall have a documented and implemented quality systemaccording to ISO 9001 or equivalent. The extent of the qualitymanagement system shall be dependent on the size and type oftheorganisation,complexityandinteractionoftheprocessesand competence of personnel.202Workmanship shall be in accordance with written proce-dures accepted by the purchaser.203All work shall be executed with adequate control by thecontractor. Repair work shall be carried out in accordance withwritten procedures accepted by the purchaser . Faults and defi-cienciesshallbecorrectedbeforepaintingorothermeansofpermanent covers have been applied.204Prior to commencement of the work the contractor shallsubmitaplanforNDT,NDTproceduresanddocumentsforNDT inspectors certification for acceptance by the purchaser.The programme shall contain information and documents forplanning,controlling,reportingetc.AcceptancecriteriaforNDT shall be accepted by the purchaser if they are not speci-fied in relevant documents.C. InspectionC 100 General101Inspectionshallbecarriedoutbythecontractorinaccordance with accepted inspection and test plans to confirmthat all project requirements are fulfilled to the satisfaction ofthe purchaser.The inspection shall cover items such as: correct identification and documentation and use of mate-rials qualification and acceptance of fabrication procedures andpersonnel inspectionofpreparatorywork(assembly,fit-upformwork, reinforcement etc.) welding inspection inspection of fabrication work for compliance with speci-fications and procedures witnessing NDT, control and testing inspection of repairs inspection of corrosion protection systems ensure functionality of examination or testing equipmentand of recording and/or measuring devices vital for correctfunctioning of equipment and machinery used in fabrica-tion.102Dueconsiderationshallbegiventotheaccessandthetime required for adequate inspection during fabrication.103High non-conformance rates in execution of the work orin the product itself shall call for special considerations. Suchspecialconsiderationsmayinclude,butnotbelimitedto,increasedinspection,re-qualificationofpersonnelorotheragreed remedial actions.104Inspectorsshallbequalifiedaccordingtoarecognisedschemeandshallbeabletoprovidedocumentationofprofi-ciency.D. Material Identification, Cutting and FormingD 100 Material identification101Atraceabilitysystemthatensurescorrectinstallationanddocumentationofthematerialgradesorstrengthclassesshall be established by the contractor throughout the prefabri-cation and installation process.Proper care shall be exercised during handling and storage topreserve identification of such material.D 200 Cutting and forming201Theeffectofworkhardeningshallbeconsideredifshearing is used for cutting of material. Special attention shallbe paid to the risk of cracked edges.202Attention shall be paid to excessive local hardening andcarboncontaminationsbythermalcutting.Thismaybereduced by suitable heat treatment or removed by mechanicalmeans.203Formingandstraighteningofmaterialsshallbeper-formedaccordingtoagreedprocedures.Suchworkshallbecontrolled by the contractor.204The degree of cold deformation of special and primarystructuralelementsshallbelessthan5%.Ifthedeformationexceeds 5%, either heat treatment or strain ageing tests shall becarried out according to an agreed procedure.DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.2 Sec.2 Page 29Guidance note:Theplasticdeformationemaybecalculatedbythefollowing,simplified formulae:Single-curvature deformationCold rolling or pressing of plates to cylindrical forms:Cold bending of straight pipes to bends:Double curvature deformationForming of plates to spheres:---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---E. TolerancesE 100 Tolerances for alignment and straightness 101Allowablefabricationtolerancesshallbesubmittedtothe purchaser for acceptance.102Specialconsiderationsshallbegiveninprovidingproper alignment of structural members. Allowable fabricationtolerances shall be established on basis of due consideration tothe criticality of the design.103Themaximumfabrication tolerances maygenerally betaken in compliance with IACS Shipbuilding and Repair Qual-ity Standard Part A Sec.6 and Sec.7.Guidance note:Specialandprimarycategoryareasshallberegardedas"strength"membersandsecondarycategoryareashallberegarded as "other" in the IACS Shipbuilding and Repair Stand-ard.---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---104Straightnessofmembers shallbewithinthetolerancesgiven by the buckling code. 105StraightnessofmemberswhicharebasedonbucklingcalculationsaccordingtoDNV-RP-C201and/orDNV-RP-C202 shall be within the tolerances given in Table E3.106Alignmentsofthenon-continuousplatesincruciformjointsandbuttweldsshallbewithinthetolerancesgiveninFig.1, Table E1 and Table E2.Guidance note:Larger imperfections may be applied provided accounted for inthe design calculations. See e.g. DNV-RP-C203, Sec. 2.5.---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---Figure 1Alignment of cruciform jointt = material thicknessD = outside diameter of pipe or vesselRc= forming radius = Poisson's ratio (0.5 for plastic condition).etD----100% =eD2Rc---------100% =et 1 v + ( )2Rc-------------------100% =Table E1 Cruciform joints Misalignment aStructural category Maximum misalignmentSpecial 0.15 t1Primary 0.30 t1Secondary 0.50 t1t1 is the smaller thickness of t1, t2 and t3Table E2 Butt welds. Misalignment aStructural category Maximum misalignmentSpecial 0.10 t1Primary 0.15 t1Secondary 0.30 t1t1 is the smaller of the two abutting thicknessesMaximum tolerance is 4 mm.DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 30 Ch.2 Sec.2Table E3 Tolerances for straightnessDetail Tolerance Fig. CommentsBars and frames Max. out of straightness = 0.0015 ll = unsupported lengthPillars, vertical col-umnsMax. inclination = 0.001 ll = unsupported lengthStiffened plane plates. Stiffener or girder webs relative to the plate plane.Max. out of straightness = 0.0015 ll = Unsupported length of the stiffener or girderStiffened plane plates. Stiffener or girder flanges relative to the web plateMax. out of straightness = 0.0015 ll = Unsupported length of the flangeStiffened plane plates. Parallel stiffeners or girdersMax. misalignment = 0.02 ss = distance between parallel stiffeners or girdersStiffened plane plates. Plates between stiff-eners or girders.Max. out of plane displace-ment = 0.005 s s = unsupported width of the plate panelDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.2 Sec.2 Page 31Circular cylindrical shells.Max. deviation from the nominal radius measured at ringstiffener or bulkhead = (ra - r) = 0.005 rra = actual distance from the cylinder axis to the shell wall.r = nominal radius of the shellCircular cylindrical shells.Longitudinal stiffen-ers or girders.Max out of straightness = 0.0015 ll = Unsupported length of the stiffener or girder.Circular cylindrical shells.Flanges of longitudi-nal stiffeners or girder webs.Max. out of straightness = 0.0015 ll = Unsupported length of the flangeCircular cylindrical shells.Longitudinal stiffen-ers.Max. misalignment = 0.02 ss = stiffener spacingCircular cylindrical shells.Local out of round-ness.Local out of straight-ness.Max. imperfection A circular template or straight rod held anywhere on the shell.g = length of template or rod.The length of the circular tem-plate shall be the smallest of:s, and s = stiffener spacing (of longi-tudinal stiffeners)l = distance between rings or bulkhead.The length of the straight rod shall be taken equal to the smallest of:l and. Conical shells The tolerance requirements given for cylindrical shells are applicable also for conical shells. Table E3 Tolerances for straightness (Continued)Detail Tolerance Fig. Comments0.01g1gr +------------------- =1.15l rt r2---4 rtDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 32 Ch.2 Sec.2F. Assembly, Welding, Heat Treatment and RepairsF 100 Assembly and welding101Assembly and welding operations shall be carried out byqualified personnel and supervision.102Afabricationsequenceshallbeestablishedtoensurethat the structure can be assembled in a manner which allowsfor effective control at all stages of work. 103Fit-up, preparation for welding and welding operationsshall take place in accordance with procedures accepted by thepurchaser.104The welding sequence shall be such that the amount ofshrinkage, distortions and residual stresses are minimised.105Difference in plate thickness of butt welds exceeding 4mm the thicker plate shall be tapered not steeper than 1 : 3 gen-erally. Butt joints, which are prone to fatigue loading shall betapered not steeper than 1 : 4. See Fig. 2.Figure 2Tapering of butt joints106Tubular members framing into joints shall be carefullycontouredtoobtainaccuratealignment.Thebevelshallbeformedprovidingacontinuoustransitionfrommaximumtominimumbevelanglearoundthecircumference.Generally,thefabricationshallbeplannedinsuchamannerthatbackwelding can be performed to the largest extent possible.107Memberstobeweldedshallbebroughtintocorrectalignmentandheldinpositionbyclamps,othersuitabledevices or by tack welds until welding has been completed orprogressed to a stage where the holding devices or tack weldscanberemovedwithoutdangerofdistortion,shrinkageorcracking. Suitable allowances shall be made for distortion andshrinkage where appropriate.108Theuseofpermanentsteelbackingstripsmaybeper-mitted after thorough corrosion evaluation and when properlyaccounted for in the design analysis.109Corners of cut-outs shall be given appropriate radii min-imising local stress concentrations. Where temporary cut-outsaremade,suchcut-outsshallbemadeofsufficientsizetoallow sound replacement.110Thefit-upshallbecheckedfordimensionalaccuracybefore welding. Surfaces to be welded shall be free from millscale, slag, rust, grease, paint etc. Edges are to have a smoothand uniform surface. No welding shall be performed when thesurfaces are damp. Suitable protection shall be arranged whenweldingisperformedduringinclementweatherconditions.The groove shall be dry at the time of welding.111Preheatingshallpreferablybeperformedwithelectricheatingelements.Gasburnersmaybeusedundercontrolledconditions. Cutting torches should not be used.112Forweldsofstructuralcategoryspecial,primaryandbutt-weldsinsecondarystructuralelementsaWPSshallbeestablished for acceptance by the purchaser. Guidance note:The weld connection between two components shall be assignedthestructuralcategoryareaequaltothehighercategoryofthejoinedcomponents.Forstiffenedplatesnotclassifiedasstruc-tural category special, the weld connection between stiffener andstringer and girder web to plate may normally be assigned struc-tural category secondary. ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---113A WPS can be established by one of the following meth-ods: performing of welding procedure test(WPQT) and subse-quentreviewoftheweldingprocedurequalificationrecords(WPQR) reviewofpreviouslyqualifiedweldingprocedurestests(WPQT) which has been witnessed by a party recognisedby the purchaser review of WPS reviewandverificationofdocumentationshowingsuc-cessfulapplicationofweldingproceduresoverapro-longed period of time.114Tack welding shall, when integrated in production weld-ing,bequalified.Forweldsspecifiedin112aWPSshallbesubmitted to the purchaser for acceptance. 115Allfabricationweldingshallbeperformedwithinthelimits of essential variables of the qualified welding procedure.This also includes tack welding, seal welding, welding of lift-ing lugs and attachment welds as well as repair welding.116When resuming welding on partially filled joints in spe-cial areas, preheating shall be performed and the temperaturewithin the specified tolerances, shall if not otherwise agreed,beequaltotheinterpasstemperaturefortheweldingpassinquestion.117Groovesproducedbygougingshallbefollowedbygrinding removing carbonised material and the groove shall bedressed to a shape consistent with tolerances in agreement withthe purchaser. 118Welding consumables shall be classified with respect tostrength , application area and hydrogen level according to rec-ognised scheme. Electrodes for welding of high strength steels (see DNV-OS-B101) shall satisfy a hydrogen test requirement for at least suf-fix H10, i.e. HDM 10 ml/100gin weld metal. Electrodes for welding of extra high strength steel (see DNV-OS-B101) shall satisfy a hydrogen test requirement for the suf-fix H5, i.e. HDM 5ml/100g in weld metal. Hydrogen testing shall be according to ISO 3690 or equivalent.119Consumables that have been contaminated by moisture,rust, oil, grease, dirt or other deleterious matter, shall be dis-carded unless properly reconditioned.Storageandhandlingofweldingconsumablesshallbeinaccordance with the manufacturer's recommendations, and inaccordancewithproceduresgivingdetailsregardingcondi-tions in storage rooms, temperature in storage ovens and quiv-ers, length of exposure and conditions, as applicable.Recyclingoffluxesforsubmerged-arcweldingshallbeper-formed in a manner that ensures a mixture of new and used fluxwith continually homogenous properties.120Welds shall be terminated in a manner that will ensuresoundweldswithoutend-craters.Extensionbarsandrun-offplatesshallberemoveduponcompletionandcoolingoftheweld. The end of the weld shall be made smooth and flush withthe edges of abutting parts.121GrindingofweldswiththeintentionofincreasingtheDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.2 Sec.2 Page 33fatiguelifeand/orreducingtheprobabilityofbrittlefractureshall be carried out according to agreed specifications.122Welding production tests shall be made during fabrica-tionofweldsinspecialareasandinprimarystructuralele-mentstoverifythattheproducedweldsareofacceptablequality.Minimumonetestcouponisrequiredfromeachapplied welding process.The welding parameters for the WPT shall be as for the actualweld and the environmental conditions shall be kept as realisticaspossible.TherequirementsforaWPTareingeneralthesame as for the relevant welding procedure test.123If one or more production tests fail to give satisfactoryresults,twomoreshallbemade,bothofwhichshallgiveacceptable results.Should one or both of the additional tests fail, the total produc-tionweldingperformedwiththeweldingprocedureinques-tionshallbeevaluatedbasedontestingofweldsandbasematerial cut-out from the actual structure fabricated.124In all cases the failure of a production test shall lead to areview of the welding performed to establish the reason for thefailure, and appropriate corrective action shall be carried out.125Shopprimersappliedoverareas,whichwillsubse-quently be welded, shall be of a suitable quality demonstratedto have acceptably low detrimental effect on the finished weld.F 200 Post weld heat treatment (PWHT)201Postweldheattreatment(PWHT)ofC-MnsteelsifrequiredbyDNV-OS-C101orDNV-OS-C201,shallbeper-formedinaccordancewithaprocedurespecificationinclud-ing: heating and cooling rates temperature gradients soaking temperature range and minimum holding time heating facilities insulation control devices recording equipment configuration of structure to be post-weld heat treated ordetails if local PWHT shall be carried out.Heat treatment records shall be kept throughout the heat treat-ment process.Guidance note:The procedure specification may be worked out on basis of com-bined material thicknesses as shown in Figure 3.---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---202Heat treatment shall be performed at a soaking tempera-ture in the range 580 to 620C, for a time of at least 2 minutespermmthickness.Soakingtemperatureandtimeshallbeselectedconsideringrecommendationsfortheweldingcon-sumables and steel grade in question. Soaking temperature forquenched and tempered steels shall be decided in each case.203The temperature difference between the outside and theinside surface during soaking shall not exceed 30C within theheatedarea.Double-sidedheatingshallbeappliedasfaraspossible.204Heating,soakingandcoolingshallbecarriedoutinacontrolled manner that prevents cracking or distortions outsidethe dimensional tolerances. The temperature difference alonglinesorplanesofsymmetryshallnormallynotexceed30Cwhen the material temperature is above 300C.205The heat-treatment cycle and the actual metal tempera-tureshallberecordedusingthermocouplesequallyspacedexternally,andwheneverpossibleinternally,throughouttheheated region.Figure 3Guidance on material thickness for PWHT206Heattreatment,wherever possible,shallbecarriedoutin an enclosing furnace according to written procedures agreedupon.Thetemperaturedistributionthroughoutheatingfur-naces shall be controlled within 15C.Where it is impractical to heat-treat the whole item in a closedfurnace, local heat treatment may be adopted.207Only welding consumables recommended for PWHT bythe manufacturer shall be used for joints to be post weld heattreated.F 300 Repairs301Repairs shall be carried out in accordance with qualifiedrepair procedures subject to agreement.302GuidancetorepairworkmaybefoundinIACSShip-building and repair Quality Standard, Part A Sec.9 and Part B.303Membersdistortedbyweldingmay bestraightenedbymechanical means or by carefully supervised application of alimitedamountoflocalisedheat.Theapplicationofheatormechanical force shall be in accordance with a written proce-dure.304Defects in welds may be rectified by grinding, machin-ingorwelding.Weldsofinsufficientstrength,ductilityornotch toughness shall be completely removed prior to repair.The mechanical properties of repair weld shall satisfy the min-imum specified properties of the steel in question.305Repairweldinginthesameareamaybecarriedouttwice.Furtherrepairsshallbeevaluatedineachindividualcase.306Whenever a defect is removed, the gouged and groundareashallbeexaminedbymagneticparticletestingorothersuitable methods to verify complete removal.307Repairweldingshallbeperformedusingweldingcon-sumablessatisfyingthehydrogentestrequirementgivenin118.Thepreheatingandworkingtemperatureshallwhenmaking shallow and local repairs in special and primary struc-tural elementsbe raised 50C above the level specified for pro-duction welding and be at least 100C unless otherwise agreed.The working temperature shall be maintained until the repairhas been completed. To ensure sound repair welds, the singlerepair length shall not be shorter than 50 mm.308Repair of welded joints shall be carried out by removingtheunacceptableportionoftheweldwithoutsubstantialremoval of base material. For planar defects the repair lengthon either side of the defect shall be 50 mm longer than the sizeDET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Page 34 Ch.2 Sec.2ofthedefectasconfirmedbyNDT.Longdefectsmayberequiredrepairedinseveralstepstoavoidoverloadingorcracking. Each repair step shall be controlled so as not to causeplastic deformation of the remaining material when removingthe defect.309Repairweldingofpost-weldheat-treatedjointsshallunless otherwise agreed initiate a new heat treatment.310Minordiscontinuitiesmayberemovedbygrindingormachining,makingasmoothtransitionintothesurroundingmaterial. The thickness shall not be reduced to less than 93%ofthenominalthicknessbutinnocasebymorethan3mm.The extent of such repair shall be agreed upon.311Allrepairsshallbere-inspectedwiththesameNDTmethods to the same or increased extent as necessary.DET NORSKE VERITASOffshore Standard DNV-OS-C401,October 2008Ch.2 Sec.3 Page 35SECTION 3NON-DESTRUCTIVE TESTINGA. GeneralA 100 Scope101This section gives requirements for non-destructive test-ing.B. Non-Destructive Testing (NDT)B 100 General101Priortocommencementoffabricationthecontractorshall submit a plan for NDT, NDT procedures and documentsforNDTinspectorscertificationforacceptancebythepur-chaser.Theprogrammeshallcontaininformationanddocu-ments for planning, controlling and reporting. 102The inspection categories shall be defined in accordancewith DNV-OS-C101 Sec.4 or DNV-OS-C201 Sec 4 and shallbe specified in relevant design drawings. 103Welds shall be subject to NDT in progress with fabrica-tion.Theresultsoftheseactivitiesshallbeconsecutivelyreported to the purchaser.104Methods of NDT shall be chosen with due regard to theconditionsincludingthesensitivityofthemethodandthemethodsabilitytodetectdefectslikelytooccurasaconse-quence of the chosen welding process.105Final inspection and NDT of structural steel welds shallnotbecarriedoutbefore48hoursaftercompletion,exceptwhere PWHT is required.ThetimedelaymayuponagreementbereducedforNV36grades or lower and for NV 420 grades or lower for plate thick-nesses less than 40 mm, if consistent low failure rate of delayedcracking has been documented for the materials and weldingconsumables in question.106When heat treatment is performed, the final NDT shallbe carried out when all heat treatments have been completed.107All welds shall be 100% visually inspected prior to car-rying out NDT.108AllNDTshallbeproperlydocumentedinsuchawaythat the performed examination can be duplicated. The reportsshall identify the defects present in the weld area and state ifthe weld satisfies the acceptance criteria or not.B 200 NDT procedures201NDT shall be performed in accordance with agreed writ-ten procedures that, as a minimum, give detailed informationon the following aspects: applicable code or standard materials and dimensions welding process joint configuration and dimensions technique equipment, main and auxiliary sensitivity calibration techniques and calibration references testing parameters and variables assessment of imperfections reporting and documentation of results reference to applicable welding procedure(s) personnel qualification acceptance criteria.B 300 Personnel qualification301Personnel performing NDT and interpretation of exami-nation results shall be certified according to a recognised cer-tificationschemesubjecttoagreementandshallprovideavalidcertificateofproficiency.Thecertificateshallstatethequalificationsastowhichexaminationmethodandwithinwhich category the operator is qualified.B 400 Extent of NDT401The extent of NDT shall be based on type and level ofdesignstressesandontheimportanceoftheconnectioninquestion.Theweldsshallbeassignedinspectioncategoriesequal to the highest structural categ