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This NORSOK standard is developed with broad petroleum industry participation by interested parties in theNorwegian petroleum industry and is owned by the Norwegian petroleum industry represented by The NorwegianOil Industry Association (OLF) and The Federation of Norwegian Industry. Please note that whilst every effort hasbeen made to ensure the accuracy of this NORSOK standard, neither OLF nor The Federation of NorwegianIndustry or any of their members will assume liability for any use thereof. Standards Norway is responsible for the

administration and publication of this NORSOK standard.Standards Norway Telephone: + 47 67 83 86 00Strandveien 18, P.O. Box 242 Fax: + 47 67 83 86 01N-1326 Lysaker Email: [email protected] Website: www.standard.no/petroleum

Copyrights reserved

NORSOK STANDARD M-101Edition 5, October 2011

Structural steel fabrication

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NORSOK standard M-101 Edition 5, October 2011

NORSOK standard Page 3 of 62

Foreword 5

Introduction 5

1

Scope 6

2 Normative and informative references 6 2.1 Normative references 6

2.2

Informative references 7

3 Terms, definitions and abbreviations 7 3.1

Terms and definitions 7

3.2

Abbreviations 7

4 Selection of steels 8 4.1

Design classes 8

4.2 Selection of steel quality level 8

5

Qualification of welding procedures and welders 8

5.1 Welding procedure specification (WPS) 8 5.2 Qualification of welding procedures 8 5.3

Welding procedure qualification record (WPQR) - Range of approval 9

5.4 Examination of the test weld 10 5.5

Welder and welding operators qualifications 12

6

Fabrication and welding requirements 12

6.1 General 12 6.2 Drawings for fabrication 12 6.3

Welding coordination 12

6.4 Welding inspection and qualification of welding inspectors 13 6.5 Forming 13 6.6

Assembly 13

6.7 Preparation for coatings 15 6.8 Preparation and fit-up of weld bevels 15 6.9

Welding processes 15

6.10 Welding consumables 15

6.11

Preheat and interpass temperature 15 6.12

Production welding 16

6.13 Post weld heat treatment (PWHT) 16 6.14 Grinding 17 6.15

Peening 17

7 Production tests 17

8

Fabrication tolerances 17

9 Non-destructive testing (NDT) 17 9.1

General 17

9.2 Qualification of non-destructive testing (NDT) operators 18 9.3 Extent of visual examination and non-destructive testing (NDT) 19

9.4

Visual examination and finish of welds 20

9.5

Radiographic testing 20

9.6 Ultrasonic testing 20 9.7

Magnetic particle and penetrant testing 21

9.8 Acceptance criteria 21

10 Repair 24 10.1

Definitions 24

10.2 Correction of welds containing defects 25 10.3 Repair by welding 25 10.4

Repair welding procedure 25

10.5 Correction of distortion 25

Annex A (Informative) Details for high fatigue utilisation 26

Annex B (Informative) Correlation between steel quality level, MDS number and steelgrade/designations 28

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Annex C (Normative) Qualification of welding consumables by data sheets 30

Annex D (Normative) Welding consumable documented by batch testing 32

Annex E (Normative) Fabrication tolerances 33

Annex F (Informative) Weld inspection, typical check points 57

Annex G (Normative) Components in stainless steel and Ni-alloys 59

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Foreword

The NORSOK standards are developed by the Norwegian petroleum industry to ensure adequate safety,value adding and cost effectiveness for petroleum industry developments and operations. Furthermore,NORSOK standards are, as far as possible, intended to replace oil company specifications and serve asreferences in the authorities’ regulations.

The NORSOK standards are normally based on recognised international standards, adding the provisionsdeemed necessary to fill the broad needs of the Norwegian petroleum industry. Where relevant, NORSOKstandards will be used to provide the Norwegian industry input to the international standardisation process.Subject to development and publication of international standards, the relevant NORSOK standard will bewithdrawn.

The NORSOK standards are developed according to the consensus principle generally applicable for moststandards work and according to established procedures defined in NORSOK A-001.

The NORSOK standards are prepared and published with support by The Norwegian Oil Industry Association(OLF), The Federation of Norwegian Industry, Norwegian Shipowners’ Association and The Petroleum Safety

Authority Norway.

NORSOK standards are administered and published by Standards Norway.

Annex A, B and F are informative. Annexes C, D, E and G are normative.

Introduction

Edition 5 of this NORSOK standard has been necessary due to an extensive change in referencedinternational standards. In addition new annexes have been included. Some corrections and improvementshave also been implemented

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1 Scope

This NORSOK standard covers the requirements for fabrication and inspection of offshore steel structures

with SMYS < 500 MPa and with a minimum design temperature down to -14 C.

NOTE 1 Lower minimum design temperatures require project specific evaluations. For special application steels with SMYS upto 690 MPa may be used.

NOTE 2 For highly fatigue utilized structures, more severe requirements may apply, and these will be shown on the designdrawings.

2 Normative and informative references

The following standards include provisions and guidelines which, through reference in this text, constituteprovisions and guidelines of this NORSOK standard. Latest issue of the references shall be used unlessotherwise agreed. Other recognized standards may be used provided it can be shown that they meet therequirements of the referenced standards.

2.1 Normative references

BS 7448, Part 1, Fracture mechanics toughness testsBS 7910, Guide on methods for assessing the acceptability of flaws in fusion welded

structuresDNV RP D404, Unstable fractureIIW International Welder, Minimum requirements for education, training and qualification of welding

personnelEN 287-1, Qualification test of welders – Fusion welding – Part 1: SteelsEN 473, Qualification and certification of NDT personnel – General principlesEN 1011- (all parts), Welding – Recommendation for welding of metallic materials - (all parts)EN 1011-3, Welding – Recommendation for welding of metallic materials – Part 3: Arc

welding of stainless steelsEN 1090-1:2009+ EN 1090-1:2009/AC:2010, Execution of steel structures and aluminium structures – Part 1: Requirements

for conformity assessment of structural componentsEN 10204, Metallic products – Types of inspection documentsEN 10225, Weldable structural steels for fixed offshore structures – Technical delivery

conditionsISO 2553, Welded, brazed and soldered joints – Symbolic representation on drawingsISO 3452-1, Non-destructive testing – Penetrant testing – Part 1: General principlesISO 3690, Welding – Determination of hydrogen indeposited weld metal arising from the

use of covered electrodes for welding mild and low alloy steelsISO 3834-2, Quality requirements for welding of metallic materials – Part 2: Comprehensive

quality requirementsISO 6520-1, Welding and allied processes – Classification of geometric imperfections in

metallic materials – Part 1: Fusion weldingISO 6847, Welding consumables – Deposition of a weld metal pad for chemical analysis

ISO 8062:1994, Castings – System of dimensional tolerances and machining allowancesISO 9016, Destructive tests on welds in metallic materials – impact tests – Test specimen

location, notch orientation and examinationISO 9606-4, Approval testing of welders – Fusion welding – Part 4: Nickel and nickel alloysISO 9712, Non-destructive testing – Qualification and certification of personnelISO 14731, Welding coordination – Tasks and responsibilitiesISO 14732, Welding personnel – Approval testing of welding operators for fusion weldingISO 15607, Specification and qualification of welding procedures for metallic materials –

General rulesISO 15609-1, Specification and qualification of welding procedures for metallic materials –

Welding procedure specification – Part 1: Arc weldingISO 15614-1, Specification and qualification of welding procedures for metallic materials –

Welding procedure test – Part 1: Arc and gas welding of steels and arc welding

of nickel and nickel alloysISO/TR 15608, Welding – Guidelines for a metallic materials grouping system

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ISO 15792-1, Welding consumables – Test methods – Part 1: Test methods for all-weld metaltest specimens in steel, nickel and nickel alloys

ISO 17025, General requirements for the competence of testing and calibrationlaboratories

ISO 17636, Non-destructive testing of welds – Radiographic testing of fusion-weldedISO 17637, Non-destructive testing of welds – Visual testing of fusion welded joints.ISO 17638, Non-destructive testing of welds – Magnetic particle testing.ISO 17640, Non-destructive testing of welds – Ultrasonic testing of welded joints.ISO 22825, Non-destructive testing of welds – Ultrasonic testing – Testing of welds in

austenitic steels and nickel-based alloysNORSOK M-120, Material data sheets for structural steelNORSOK N-004, Design of steel structuresNORSOK M-601, Welding and inspection of pipingNS 477, Welding. Rules for approval of welding inspectors

2.2 Informative references

EN 10025-(all parts), Hot rolled products of structural steels – (all parts)EN 10210-(all parts), Hot finished structural hollow sections of non-alloy and fine grain steels – (all

parts)EN 10219-(all parts), Cold formed welded structural hollow sections of non-alloy and fine grain steels

– (all parts)ISO 3834-3, Quality requirements for welding of metallic materials – Part 3: Standard quality

requirements

3 Terms, definitions and abbreviations

For the purposes of this NORSOK standard, the following terms, definitions and abbreviations apply.

3.1 Terms and definitions

3.1.1

shallverbal form used to indicate requirements strictly to be followed in order to conform to this NORSOK standardand from which no deviation is permitted, unless accepted by all involved parties

3.1.2

shouldverbal form used to indicate that among several possibilities one is recommended as particularly suitable,without mentioning or excluding others, or that a certain course of action is preferred but not necessarilyrequired

3.1.3

mayverbal form used to indicate a course of action permissible within the limits of this NORSOK standard

3.1.4

canverbal form used for statements of possibility and capability, whether material, physical or casual

3.2 Abbreviations

AFC approved for constructionBS British StandardCEV carbon equivalent value (IIW, International Institute of Welding Formula

CEV1556

Cu NiV MoCr MnC

CTOD crack tip opening displacementDAC distance amplitude curveDNV Det Norske Veritas

EN (pr EN) European Standard (proposal for EN)EWF European Welding Federation FCAW flux cored arc welding

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FSH full screen heightHAZ heat affected zoneHDM hydrogen content, deposit metalIIW International Institute of WeldingIW International WelderIWT International Welding TechnologistIWE International Welding EngineerIWI International Welding Inspector ISO International Organization for StandardizationMDS material data sheetMSF main support frameMT magnetic particle testingNDT non destructive testingOD outside diameterPcm carbon equivalent (cold cracking susceptibility)

Pcm BV Mo NiCr Cu MnSi

C 51015602030

PT penetrant testingPWHT post weld heat treatment

RT radiographic testingSAW submerged arc weldingSMYS specified minimum yield strengthSQL steel quality levelSS stainless steelUT ultrasonic testingVT visual testingWPS welding procedure specificationWPQR welding procedure qualification record

4 Selection of steels

4.1 Design classes

The design classes will be decided by the designer and shall form the basis for selection of SQL. Referenceis made to NORSOK N-004.

4.2 Selection of steel quality level

The steel quality level will be decided by the designer in compliance with NORSOK N-004.

Annex B gives the correlation between the steel quality levels I, II, III and IV, and designations on equivalentsteels given in NORSOK M-120.

Selection of a better steel quality level in fabrication than the minimum required by the designer shall not leadto more stringent requirements in fabrication.

5 Qualification of welding procedures and welders

5.1 Welding procedure specification (WPS)

Specification and qualification of welding procedures for metallic materials shall be in accordance with ISO15607. WPS shall be established in accordance with ISO 15609-1.

5.2 Qualification of welding procedures

Welding procedures used for structures requiring steel quality level I and II for all strength levels and steel

quality level III for SMYS 355 MPa shall be qualified in accordance with ISO 15614-1 and the additionalrequirements in this NORSOK standard.

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The qualification is primarily valid for the workshop performing the welding tests, and other workshops underthe same technical and quality management. It may also be transferred to and used by a subcontractor,provided the principles of ISO 3834-2 and ISO 14731 are implemented and documented.

Requirements to components in stainless steel and Ni-alloys are given in Annex G.

The WPQR documentation shall include the material certificates for the base material and filler materialsapplied in the weld qualification test. PWHT report and chart shall be included in the WPQR.

5.3 Welding procedure qualification record (WPQR) - Range of approval

5.3.1 For welding of steels in all strength classes

The WPQR is valid within the limitations specified in ISO 15614-1, with the following clarifications andmodifications:

a) control of heat input according to ISO 15614-1, 8.4.8, shall apply. If an approval testing have beenperformed at both a high and a low heat input level (all specified mechanical testing to be performed forboth high and low heat input), then all intermediate heat inputs are also qualified;

b) when the steel to be welded has a Pcm 0,21, or a carbon content C 0,13 %, then an increase of morethan 0,02 Pcm units or 0,03 CEV (IIW formula) units over the value on the approval test shall require a

new qualification test;c) a change from wrought (rolled, forged) steel to cast steel or converse;d) for all strength levels for SQL I and II and for SMYS > 400 MPa for SQL III, a change in delivery condition

(normalised, thermomechanically controlled processed or quenched and tempered);

e) a change in microalloying element or manufacturing technique for steel with SMYS 400 MPa;f) a decrease in groove angle of more than 10° . For groove angles less than 30°, the limitation is +20°/- 0°;g) a qualification of fillet welds carried out on plate thickness equal to or greater than 30 mm, applies for all

plate and throat thicknesses. Single layer fillet welds qualifies multi-layer, but not the converse;h) qualification of WPS with manual welding methods 135 and 136 applies also for partly mechanized and

mechanized welding, but not vice versa;i) CTOD testing shall be included in the qualification of welding procedures for weldments with a plate

thickness above 50 mm for all strength levels for steel quality level I and II and for SMYS > 400 MPa forsteel quality level III. CTOD testing shall be included in the qualification of welding procedures forweldments with a plate thickness below and equal 50 mm if requested by the designer for the specifiedsteel quality level.CTOD testing shall be executed from as welded and PWHT weld assemblies as applicable, covering thefollowing combined conditions:

1) full penetration buttweld with K-, or half V -groove as deemed most representative for the actualfabrication. V and X groove are acceptable for weld metal test;

2) a welding procedure representing the maximum heat input to be used in fabrication;3) maximum joint thickness (within 10 %).

Assemblies shall be made and tested for the actual combination of steel manufacturer, welding processand welding consumable (brand) used, except welding consumables used for root passes only, providedthese are removed completely by gouging and grinding.

NOTE The changes specified in d) and e) above need not require re-qualification if HAZ properties for the material to be welded havebeen documented from the steel manufacturer for relevant thicknesses and heat input ranges. If sufficient documentation from the steelmanufacturer is not available, a change of material shall require re-qualification of a reduced number of procedures. The number ofprocedures to be re-qualified shall be sufficient to verify that the HAZ properties of the new material is comparable with that used for theprevious qualifications.

5.3.2 For welding of steels with SMYS 500 MPa

In addition to the requirements given in 5.3.1 the following additional requirements apply for welding of steelswith SMYS > 500 MPa:

a) a change in steel manufacturer;b) CTOD testing as described in 5.3.1 i) shall be executed for thicknesses above 30 mm;

c) stress relieving if required/specified by designer.

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5.4 Examination of the test weld

5.4.1 General

The type and number of tests shall be in accordance with Table 1. Testing shall be performed in accordancewith ISO 15614-1 and the additional requirements given below.

The test weld shall be 100 % examined for both surface and volumetric defects with the relevant NDT

methods. The soundness of the weld shall comply with Clause 9.

Test laboratories shall have a quality system in compliance with ISO 17025 or equivalent.

Table 1 Type and number of tests

Mechanical testing

Joint

configuration

Joint

thicknessmm

Tensile

test

Bend

tests a

Charpy V-

notch

tests

Hardness

and

macroe

CTOD

Buttwelds

(Tubulars andplates)

t ≤ 50

t 50

2

2

4

4

4 sets

6 sets

1

1

See 5.3.1 i),

5.3.2 b) and5.4.4

T-joints (plates)d

t ≤ 50

t 50c

c 4 sets6 sets

22

Tubular jointsd t ≤ 50

t 50c

c 4 sets

b

6 sets22

Fillet welds All 2

aBend tests shall consist of 2 face and 2 root bend specimen for t < 12 mm and 4 side bend

specimens for t 12 mm.b

If the dimensions of the joint does not allow Charpy V-notch testing, the Charpy V-notchproperties shall be documented on a butt weld joint made with the same consumable and samebase material, and welding parameters and thickness within the range qualified for the joint.

c It shall be documented on a butt weld test that the welding consumable used will have sufficienttensile strength.

dT-joints on plates qualify for tubular joints, and vice versa.

eFor welds on submerged structures with cathodic protection, the hardness limits in NORSOK M-001 shall apply in addition to the requirements of ISO 15614-1.

fFor T-joints with t > 50 mm, CTOD testing shall be documented on a buttweld.

5.4.2 Charpy V-notch testing

Sampling of Charpy V-notch impact tests shall be carried out in accordance with ISO 9016, with the notch inthe positions listed below. All specimens shall be machined with the notch through the thickness, 2 mm belowthe surface of the material. Designation in parenthesis refers to Figure 1 and Table 2 in ISO 9016.

Notch in centre of weld (VWT 0/2).

Notch in fusion line (VHT 0/2).

Notch in HAZ, 2 mm from fusion line (VHT 2/2).

Notch in HAZ, 5 mm from fusion line (VHT 5/2).

For welds with a joint thickness T 50 mm or more, two additional sets of Charpy V-notch tests shall betaken from the root area, with the notch in the following positions:

notch in centre of weld (VWT 0/b);

notch in fusion line (VHT 0/b).

The test temperature and energy requirements shall comply with Table 2.

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Table 2 Charpy impact test temperatures and energy requirements for welding procedure

qualifications.

Material Steel quality level

thickness I II III

(mm) SMYS

400

°C

400<

SMYS 500°C

SMYS

500

°C

SMYS

400

°C

400<

SMYS 500°C

SMYS

500

°C

355

SMYS500°C

SMYS

500

°C

t 12 0 -20 -20 0 -0 -20 -0 0

12 < t 25 -20 -40 -40 0 -20 -40 0 -20

25 < t 50 -40 -40 -40 -20 -40 -40 -20 -40

t > 50 -40 -40 -40 -40 -40 -40 -40 -40

Energyrequirement

a

36 J 42 J 60 J 27 J 42 J 60 J 27 J 42 J

a The minimum average value is given in the table. No individual value shall be less than 70 % of the

minimum average value. Reduction factors of energy requirements for subsize specimens shall be5/6 for 7,5 mm and 2/3 for 5 mm.

5.4.3 Transverse tensile testing

Testing shall be carried out in accordance with ISO 15614-1. The fracture shall be located outside the weldmetal, i.e. maximum 20 % of the fracture surface shall consist of weld metal/HAZ.

5.4.4 Crack tip opening displacement (CTOD) testing

The CTOD-technique with the Bx2B through-thickness notched type specimen according to BS 7448, Part 1,should be used. Three valid test specimens shall be obtained for each test position.

CTOD-testing of welds shall be carried out with the fatigue notch tip positioned in the coarse grained regionof the heat affected zone and in the weld metal. For HAZ, determination of the actual location of the fatiguecrack tip shall be performed after testing, see EN 10225.

NOTE Test assemblies may be given hydrogen diffusion treatment prior to testing, and specimens may be precompressed.

If not specified otherwise, the test temperature for design temperature down to -14 °C shall be

-10 °C for splash zone or above,

0 °C for submerged parts.

Other test temperature may be prescribed by the designer.

The requirement for minimum CTOD value shall be prescribed by the designer. If not specified, therequirement for minimum CTOD value shall be as for the steel purchase order.

CTOD-testing of HAZ can be omitted if relevant CTOD properties in HAZ have been documented previouslyin accordance with requirements in this NORSOK standard, provided the requirements for the essentialvariables are met.

CTOD-testing of weld metal can be omitted if relevant CTOD properties in weld metal have beendocumented previously in accordance with requirements in this NORSOK standard, provided therequirements for the essential variables are met.

The required fracture toughness level shall be decided in design for joints when steel quality level I and II are

required. Testing is normally not requested for structures with plate thickness below 40 mm for SMYS 500MPa or for structures with plate thickness below 25 mm for SMYS > 500 MPa.

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5.5 Welder and welding operators qualifications

The welders shall be certified by an accredited body according to EN 287-1 and/or ISO 9606-4.Welding operators shall be certified according to ISO 14732.

For tack welders, an internal test according with EN 287-1 and/or ISO 9606-4 is accepted without use of 3rd

part.

For welding in inspection category C, D and E, diploma as IW-International Welder (fillet- plate-pipe welder)within actual welding method and material may be accepted, see IIW, Minimum requirements for theeducation, training, examination and qualification of welding personnel.

For welding of single sided acute angled tubular joints with < 70º, welders shall be qualified with a realistic

joint, representing the minimum angle to be used in production.

6 Fabrication and welding requirements

6.1 General

All welding work shall be according to recommendations given in relevant part of the EN 1011-series. The

manufacturer shall have an implemented and documented quality system according with ISO 3834-2.

For fabrication of structural steel in inspection category D and/or E, ISO 3834-3 may be accepted (used).

All types of inspection/examination shall be performed by personnel other than those performing and beingresponsible for the production work.

The fabricator shall apply a weld numbering system for identification on all shop drawings and as reference inall documentation.

6.2 Drawings for fabrication

Symbolic presentation of welds shall be according to ISO 2553.

Welds in inspection category A and B shall have unique weld number. Welds in inspection category C,D andE may be group numbered, but only within the same node/essential member and same drawing sheet.

The shop drawings shall have enough information to enable correct selection of WPS. The followinginformation shall be used as relevant:

material type/grade and grouping number (ISO/TR 15608);

dimension (outside diameter and wall thickness);

PWHT requirements, if relevant;

required toe grinding;

etc.

6.3 Welding coordination

All welding coordination shall be according to ISO 14731. The manufacturer shall appoint a responsibleauthorized welding coordinator. The responsible welding coordinator shall be qualified as an IWE, see ISO14731, Annex A.

The responsible welding coordinator may delegate welding coordination activities at fabrications sites to anIWT, see ISO 14731.

If only fabrication/welding in inspection category D and/or E, an IWT may be accepted.

All other personnel who are carrying out one or more welding activities according to ISO 14731, Annex B, arewelding coordinators. The level of technical knowledge, tasks, responsibility and authority shall be identifiedfor each person/function in a job description.

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6.4 Welding inspection and qualification of welding inspectors

Welding inspector’s tasks and responsibilities is to be familiar with all standards, rules and specifications, andcontinuously verify that all requirements and adequate parts in ISO 3834-2 are implemented and followed.

Welding inspection shall be performed before, during and after welding according to typical check pointslisted in Annex F.

All inspections shall be reported to the responsible welding coordinator.

The inspection frequency shall be sufficient to report weekly quality status during fabrication based onwelding inspection reports.

Prior to fabrication start-up, contractor shall implement a system for recording of quality status.

Causes for non-conformance shall be immediately investigated and corrective action shall be taken toprevent further occurrence. Non-conformance shall require documented investigation/action by theresponsible welding coordinator.

Welding inspectors shall be qualified according to NS 477 or EWF/IIW rules for approval of IWI-InternationalWelding Inspector

6.5 Forming

Cold forming of steel (i.e. forming below 250 C) shall be carried out within the deformation rangerecommended by the steel manufacturer. For steel quality level I and II, the deformation limit withoutdocumentation of mechanical properties is 5 %.

If the deformation is more than the above given limits, either heat treatment shall be performed, or strainageing tests shall be carried out according to the following requirements:

the material shall be permanently strained locally to the actual deformation;

the material shall be artificially aged at 250 C for 1 h;

one set of 3 impact test specimens shall be tested from the base material in the strained plus artificially

aged condition. The notch shall be located within the plastically strained portion of the material, in the partof the cross section which have received the highest strain;

the impact testing temperature shall be as specified for the actual steel grade in question;

the Charpy-V impact value shall comply with the minimum requirements for the steel grade and shall notbe more than 25 % lower than the impact value for the material before deformation and strain ageing.

If forming is performed at temperature above 250 C, it shall be documented that the base materialproperties, weldability, weldmetal and HAZ properties satisfy the actual MDS and this NORSOK standard.

The percentage strain due to forming is defined as follows:

%100xdiameter thicknessmidForming

thicknessWallstrainPercent

6.6 Assembly

6.6.1 General

In tubular joints, circumferential and longitudinal weld joints should not be placed in the shaded areas shownin Figure 1, unless otherwise shown on design drawings.

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W 1

W 1

W 1

W 1

W 2

W 3

D

W 2

W 2

W 2

Longitudinal welds Circumferential welds

W1 = 75 mm or minimum 2 times chord thicknessW2 = 150 mm or minimum D/4W3 = 600 mm or minimum D

Figure 1 Prohibited location of welds in tubular joints

6.6.2 Splices

Splices shall not be located in areas, noted as restricted on design drawings.

6.6.3 Tapering

Tapering shall be in accordance with the requirements given in relevant standards or drawings. If no otherrequirements are specified, a tapering of 1:4 should be used.

6.6.4 Bolting connection

Bolting material shall comply with requirements in NORSOK M-001. Holes shall be made by machine drilling.

6.6.5 Seal/blind-compartments.

Crevices and areas which become inaccessible after fabrication or assembly shall be sealed off from theoutside atmosphere. Seal welds shall have a throat thickness of at least 3 mm. Where steel items shall behot dip galvanised, hollow sections shall be ventilated.

6.6.6 Temporary cut-outs

Temporary cut-outs shall not be located in restricted areas as shown on design drawings. Temporary cut outsshall have a corner radius not less than 100 mm. Temporary cut-outs shall be closed by refitting the same oran equivalent plate and employing the same welding, inspection and documentation procedures andrequirements that govern the structural part in question.

6.6.7 Straightening of structural members

Members distorted by welding shall be straightened according to a detailed work instruction. The basematerial properties shall satisfy the specified requirements after straightening.

Maximum temperature for straightening shall not exceed the temperature limit recommended by the steel

manufacturer, but it shall in no case be higher than 600 C.

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6.6.8 Doubler plates

All temporary attachments which shall be flame cut or welded under water shall be attached to the structureby using doubler plates.

All attachments in the splash zone shall be attached to the structure by using doubler plates.

6.7 Preparation for coatings

Edges of plates and structural shapes which are intended to be coated shall be rounded to approximately 2mm radius, unless otherwise indicated on fabrication drawings.

6.8 Preparation and fit-up of weld bevels

Permanent backing strips are not accepted, unless shown in fabrication drawings.

Buttering shall be welded in accordance with applicable WPS. The WPS shall be supported by a butt weldWPQR. The responsible NDT-coordinator/personnel shall be notified every time buttering is performed in anygroove. Maximum buttering is limited to t/2, maximum 20 mm in the joint.

Tack welds shall normally have a length of minimum 100 mm.For material thickness less or equal to 25 mm, tack length may be minimum 4 x plate thickness.

6.9 Welding processes

The welding processes listed in ISO 15614-1 are acceptable.

6.10 Welding consumables

The manufacturers shall ensure that welding consumables applied for joints where steel quality level I, II andIII are required, meet the requirements for mechanical properties as specified for the welding procedurequalification, in both as welded and (where applicable) PWHT condition.

This may be achieved through (alternatively):

batch testing including chemical analysis and mechanical properties, see Annex D;

an established and reliable system of batch certification against accepted supplier data sheets, see AnnexC;

for steels with SMYS > 500 MPa, Annex D is mandatory.

Except for solid wires such consumables shall be classified by the supplier as extra low hydrogen, i.e. HDM

5 ml/100 g weld metal. For self shielded flux cored wire HDM 8 ml/100 g may be accepted, providedpreheating temperature and post weld holding temperature and time is assessed to avoid hydrogen cracking.Hydrogen testing shall be according to ISO 3690 or equivalent.

For all steels with SMYS > 500 MPa special precautions shall be taken to verify that selected consumablescomply with hydrogen requirements. Stricter requirements than given above may be relevant. Prequalificationwith mock-up structures shall apply if there is a risk for high restraint in welding or erection.

Consumables for joints in steel quality level III (with SMYS < 355 MPa) and IV and for joining stainless tocarbon steel shall be selected with due consideration of base material properties, thickness and weldability, toensure sufficient weld strength, toughness and homogenity. Such consumables shall be delivered withEN 10204, type 2.2, certificate, as a minimum.

All welding consumables shall be individually marked.

When certification according to Annex C is used, welding consumables (except welding fluxes) shall besupplied with an inspection certificate type 3.1 in accordance with EN 10204, including a statement ofcompliance with the welding consumable data sheet and the chemical composition of the weld deposit(elements of the data sheet). Welding fluxes shall be supplied with a test report (EN 10204, type 2.2),declaring conformity with the approved product type.

6.11 Preheat and interpass temperaturePreheating above 50 °C should be achieved by electric heating elements. Cutting torches are not allowed forpreheating.

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The minimum interpass temperature shall not drop below the minimum required preheat temperature. If nototherwise stated in the WPS, and qualified by the WPQR, the maximum interpass temperature shall not

exceed 250 C measured at the edge of the groove. For C- and C/Mn-steels, a maximum interpass

temperature of 250 C may be used, even if a lower temperature was recorded on the WPQR.

The preheat temperatures used during repair welding should be minimum 50 C higher than the preheat usedfor the original weld.

NOTE Production welding of high strength steels with SMYS > 500 MPa is normally more sensitive to hydrogen cracking thanexperienced during welding for qualification. Special precautions, including preheating temperature, minimum holding temperature andextended post weld holding temperature for 24 h or more, shall be taken into consideration.

6.12 Production welding

6.12.1 General

Welding shall be carried out in accordance with the WPS and applicable drawings.

The applicable WPS shall be given directly to the welder and be available at the site of welding at all times A collection of WPS`s on walls or boards are only for general information and not accepted used for welding.

Butt welds in joints where steel quality level I and level II for all strength levels, or steel quality level III forSMYS > 400 MPa are required shall, whenever possible, be welded from both sides.

If any welding is conducted after PWHT, the PWHT shall be repeated.

For joints in inspection category A, the ”straight” edges of K- and half V-butt weld grooves shall have a grooveangle of at least 10

º, unless it is documented that possible defects can be detected by the UT technique used.

For K-grooves, the 10º should be machined from the root to each plate surface.

Any occurrence of cracking during production welding shall be investigated. Welding should be suspendeduntil the cause of cracks and defects has been identified and measures taken to prevent their reoccurrence.Cracks or other persistent weld defects may lead to revision and requalification of the WPS.

6.12.2 AttachmentsTemporary attachments as lifting lugs, lugs for scaffolding and assembly, supports for cables, equipment,ladders or other fabrication and erection aids should be removed. If indicated on design drawings thatremoval (full or partial) is not required, the temporary attachments may be left as is, or removed only partially.

All welding of attachments shall comply with the requirements for the structure to which they are attached.Temporary attachments shall be cut minimum 3 mm from the base metal and ground. The ground area shallbe visually examined and magnetic particle/penetrant tested (as relevant) in accordance with the inspectioncategory in question.

6.12.3 Stainless steel components

Permanent or temporary structural elements, attachments or penetration sleeves in stainless steel materialsmay be selected for various purposes.

Requirements for welding and inspection of stainless outfitting structures shall follow similar classificationprinciples as for other structural steel elements, see annex G. All welding and inspection of welds to carbonsteel structures shall as a minimum comply with the requirements for the structure to which they areattached.

Welding consumables shall be selected in accordance with G.4.

6.13 Post weld heat treatment (PWHT)

PWHT shall be required for structural welds in steel quality level I or level II, or quality level III with yieldstrength Re > 400 MPa, when the nominal thickness as defined in ISO 15614-1, exceeds 50 mm, unlessadequate fracture toughness can be documented in the as welded conditions. For restrained joints of

complicated design, PWHT may be required for smaller thicknesses, independent of steel quality level.

PWHT shall be carried out in accordance with a procedure which shall include

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heating rate,

cooling rate,

soaking temperature and time,

heating facilities,

insulation,

control devices,

recording equipment,

configuration of structure to be PWHT or details if local PWHT shall be carried out, number and location of thermocouples to be used during PWHT.

The holding time and temperature shall be as recommended by the steel manufacturer.

The temperature difference between different parts of the structure during soaking time shall not exceed

30 C within the heated area. Double sided heating shall be used as far as possible.

The temperatures shall be continuously and automatically recorded on a chart.

6.14 Grinding

When grinding is specified on design drawings or is instructed as a corrective action, the grinding shall beperformed according to a detailed procedure. Grinding tools, direction, surface roughness and final profileshall be specified. Reference samples for typical joints and sections may be prepared and used foracceptance of treated welds. Typical examples for requirements for grinding of joints are given in A.1.

6.15 Peening

Weld improvement by peening shall be performed in accordance with detailed procedures.

Normally pregrinding of a groove will be required to assure correct location of peening area. Tools forgrinding and peening, surface roughness and profile of grinding as well as peening shall be specified. Toolsfor check and measurements shall be described and shall be available during operations. Documentation ofcorrect performance shall include macrophotography. Typical examples of requirements for peening of jointsare given in A.2.

7 Production tests

Production tests shall be selected on weldments in critical regions to verify that the specified requirementshave been meet. Minimum one test coupon is required from each applied welding process.

Test coupons shall be welded in a manner which realistically simulates the actual production welding,normally as extension of the production weld, and meet the requirements for welding procedure approvaltests.

CTOD testing is not required for production testing.

If a production test fails, the reason for the failure shall be determined and remedial action implemented.

8 Fabrication tolerances

Fabrication tolerances shall be in accordance with Annex E, unless otherwise specified on drawings.

9 Non-destructive testing (NDT)

9.1 General

The inspection category shall be decided by the designer in accordance with NORSOK N-004, and shall bespecified on the design drawings.

Final inspection and NDT of structural steel welds shall not be carried out before 48 h after completion except

where PWHT is required. The time delay may be reduced to 24 h for steel grades with SMYS of 355 MPa orlower, and for steel grades with SMYS of 420 MPa or lower for plate thicknesses below 40 mm, provideddelayed cracking have not been observed for the materials and/or welding consumables in question.

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When PWHT is performed, the final NDT shall be carried out when all heat treatment have been completed.

Prior to fabrication start-up, contractor shall implement a system for recording of weld defect rates. Thedefect rates shall be recorded on a weekly basis for VT, MT, PT, UT and RT from each production area(geographically split in production areas at the same yard) and shall be reported together with theaccumulated defect rate. The defect rate statistics shall be used as a tool in weld quality control. Causes fordefects shall immediately be investigated and corrective actions shall be taken to prevent further occurrence.Cracks detected with any NDT method shall require documented investigation/action by the responsiblewelding engineer.

The defects shall be reported with reference to the numbering system according with ISO 6520-1.

At a weekly high defect rate or at repeated occurrence of planar defects, two trigger levels apply for extendedNDT for welds in inspection category B, C and D. Two steps of actions apply within trigger level 2.

Trigger level 1If a defect rate for any method exceed 10 % for a single week the extent shall be increased to 100 % for allwelds in question.

Trigger level 2If a defect rate for any method of 5 % to 10 % for a single week is observed the following two steps ofextended NDT shall apply:

Step 1. A defect rate for any NDT method exceeding 5 % (1 % for MT) for a single week require doubling of theextent of NDT according to the inspection category. Spot extent shall be increased to 20 %.

Step 2.If the defect rate for the weld length where the extended NDT is taken in accordance with Step 1 aboveexceed 5 %, the extent shall be increased to 100 % for all welds in question

The increased NDT extent shall cover welds of the same inspection categories, welded in the same period oftime by the specific welder(s) and WPS when the high defect rate was produced, to assure that the weld

quality is maintained also with the lower extent of NDT. Unless the causes for defects found leads toimmediate and documented preventive actions, the higher level of extent of NDT shall be maintained until theweekly defect rate is well below 5 %.

Generally, if the defect rate approaches 10 % during any stage in production welding, further welding shouldbe held until investigations are completed and corrective actions implemented.

A low defect rate may be used as basis for a reduction in the extent of NDT for inspection categories B, Cand D, provided that a correct defect rate identification is prepared for each weld method, each NDT methodand each production area, see Table 3, table footnote

b.

welds)of partstestedof (Length

%)100length x(Defect:asdefinedisratedefectThe

NOTE “Tested part of welds” means the part that is tested with the same NDT method. Defect rate shall be based on at least 5 weldsor 1 m tested weld length.

NDT after repair shall not be included when calculating the defect rate.

9.2 Qualification

of non-destructive testing (NDT) operators

Personnel responsible for all NDT activities shall be qualified according to EN 473, Level 3 (or ISO 9712) orequivalent 3

rd party certification scheme.

NDT personnel performing visual inspection of welded joints shall be qualified in accordance with EN 473, VTlevel 2 or equivalent 3

rd party certification scheme. NS 477 latest revision may be used.

The NDT operator shall be qualified according to EN 473, level 2 or equivalent 3rd

party certification scheme.

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Operators simply producing radiographs and not performing evaluation, do not require level 2, but shall havesufficient training.Ultrasonic operators performing inspection of welds in duplex stainless steel material shall be speciallytrained and qualified for the purpose according to EN 473 or equivalent 3

rd party certification scheme

When testing of castings or forgings, the NDT operator shall document experience with forged and castproducts.

9.3 Extent of visual examination and non-destructive testing (NDT)

The required minimum extent of examination/testing is given in Table 3. Design drawings may show areas ofwelds where testing is mandatory.

Testing performed shall be representative for the weld quality. Partial NDT shall normally be planed for on allshop drawings.

Ultrasonic testing to reveal the presence of possible weld metal transverse cracking shall be included for buttwelds with thickness more than 25 mm. The testing shall be performed on minimum 5 % of welds ininspection category A and B for SAW (12) and FCAW (131 and 136).

Table 3 Minimum extent (in %) of non-destructive testing for structural welds

Inspectioncategory

Type ofconnection

Visualexamination

Extent of testing%

% RT UT MT A Buttweld

T-connectionFillet/partial

100100100

10--

10010020

c

100100100

Ba Buttweld


100100100

Spot--

50b

50b

10b c

100b

100b

100b

Ca Buttweld


100

100100

-

--

20

20

b

spot c

20

20

b

20b

Da All connections 100 - - spot

E All connections 100 - - -

Key

Spot means 2 % to 5 %.

a Increased extent of NDT shall be as defined in relevant Trigger levels in 9.1.

The required level of increased extent shall be maintained until a defect rate below 5 % is re-

established and documented.

bThe extent may be reduced to 50 % of the specified extent, based on experience and documented

records with similar joints, provided the defect rate (see 9.1) for UT/RT is < 2,0 % and for MT is < 0,2% during the last 100 m of weld. The last 100 m shall be continuously updated every week. If the

defect rate exceeds the limits given above, the normal extent of NDT shall apply again.

A possible reduction in the extent of NDT shall be considered separately for each welding method

and each production area.

c Applies only for partial penetration welds with a penetration depth greater than 12 mm.

When partial testing is defined for welds in an area, the testing shall be spread such that the most essentialmembers and nodes are included in the inspection, and such that areas of welds most susceptible to welddefects are covered.

The specified percentage to be tested in Table 3 refers to the total length of welds in each inspectioncategory.

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All WPSs used and welds representing all welding personnel involved in the fabrication shall be subject toNDT.

During the initial fabrication the extent of UT and MT of inspection category B and C welds shall beintensified, normally to twice the level given in Table 3. This extent shall be maintained for a weld and testlength sufficient to conclude that the weld repair percentage is at a reasonable level.

The increased initial testing may be accounted for in the overall extent provided the initial testing confirmsconsistent good workmanship.

In addition to what is listed in Table 3, the following shall apply for inspection category A and B:

a) one film at each end for longitudinal welds of tubulars (including tubulars for nodes and stubs);b) where radiographic testing is required, intersection welds, and those locations where presence of defects

is deemed to be most harmful, shall be tested;c) ultrasonic and radiographic testing shall not overlap, except when 100 % UT is specified. However,

ambiguous imperfections revealed by UT shall in addition be tested by RT;d) ultrasonic testing is normally not applicable for thicknesses less than 10 mm. For such thicknesses, UT

shall be replaced with RT. In general, RT should be considered if UT is not possible. Radiographic testingis normally not applicable for thicknesses above 40 mm.

9.4 Visual examination and finish of welds

The visual examination shall be carried out in accordance with ISO 17637.

9.5 Radiographic testing

Radiographic testing shall be carried out in accordance with ISO 17636, Class A.

The general film density shall be ≥ 2,0. However, if X-ray are used, the minimum film density may be reducedto 1,5.

Suspect planar indications discovered by RT shall be type determined, located and sized by UT.

9.6 Ultrasonic testingUltrasonic testing of welds in plate and tubular butt welds and double side welded tubular joints shall beperformed in accordance with ISO 17640, examination level C.

Reference blocks shall be made with thickness and side-drilled holes in accordance with Table 4. DACreference curves shall be established.

The effective test range of a DAC curve shall be determined by the point at which the curve has fallen to25 % FSH, when it will be necessary to raise the curve using reflectors at increased depth. The referenceblock shall be from a steel type that is representative for the steel to be inspected.

Where ultrasonic testing is to be performed on steel produced by controlled rolling or thermo mechanicaltreatment, reference blocks shall be produced both perpendicular to, and parallel to, the direction of rolling.

The rolling direction shall be clearly identified.

The actual refracted angle for each probe measured from the reference block or as measured on the actualobject being examined, shall be used when plotting indications.

Ultrasonic testing procedures shall be sufficiently detailed to ensure 100 % of the weld body and heataffected zones are examined for longitudinal defects.

All indications exceeding -10dB DAC shall be investigated to the extent that they can be evaluated in terms ofthe acceptance criteria.

For butt welds, (C and D) or (E and F) according to ISO 17640 shall be utilised for the detection of transverseimperfections, providing that the surface finish of the weld cap is sufficiently smooth and in accordance with

clause 8 of ISO 17640.

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Alternatively techniques (X and Y) or (W and Z) according to ISO 17640 can be utilised by placing the probealongside the weld connection, so that the beam forms a small angle with the centreline.If the surface finish adjacent to the weld is such that testing with an angle probe using techniques (C and D)or (E and F) along the centre line of the weld is judged to be the only reliable method of examination, than theweld cap is to be dressed smooth or ground flush with the parent material in accordance with clause 8 of ISO17640.

Scanning is in all cases to be performed from both sides of the weld and in both directions.

The examination record shall include the position, the echo height, length, depth and type of indication.

Table 4 Calibration reference block requirements

Thickness of material

to be examinedmm

Thickness of block

mm

Diameter of hole

mm

Distance of hole from

one surfacemm

10 < t < 50 40 or t 3 +/-0,2

50 < t

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Defects may be accepted by the relevant parties when repair work is considered detrimental to the totalintegrity of the weld. Such acceptance shall be based on a fitness for purpose evaluation in accordance withBS 7910, DNV RP D404 or other recognised methods.

Table 5 Structural steel welds - Visual and MT acceptance criteria for structural steel welds

Welding Acceptance criteriaType of defect Insp. cat. A, B Inspection category C, D, E

Cracks Not acceptable Not acceptable

Incompletepenetration or lack offusion

Not acceptable Single - side weld:Length < t/2, max. 10 mm

Undercutc

Max. depth 0,5 mmContinuous undercutis not permitted

Max. depth 0,75 mmContinuous undercut is not permitted

Surface porosityExposed slag

Not acceptable Not acceptable. However, the following defectsmay be acceptable if it does not conflict withsurface treatment requirements:

Accumulated pore diameters in any area of 10 mm

x 150 mm is not to exceed 15 mm. Max. size of asingle pore is t/4 or 4 mm, whichever is the smaller.

Concave root Max. concavity 0,5 mm if the transition is smoothly formed.

Excessive pen.a Max. 3 mm

Roughness of weld,see Figure 2a and 2b.

“U” shall be less than 2,5 mm. Weld surface shall be smooth, without sharptransitions. The bottom of roughness in butt welds shall not be below thebase material surface.

Misalignment of buttwelds, see Figure 2c.

Max. misalignment (M), 0,15 x t or max. 4 mm,whichever is the smaller.

Reinforcement of buttwelds, see Figure 2d.a

“t” less or equal to 10 mm Max. reinforcement “C” 2 mm “t” greater than 10 mm, up to 25 mm Max. reinforcement “C” 3 mm “t” greater than 25 mm, up to 50 mm Max. reinforcement “C” 4 mm “t” greater than 50 mm Max. reinforcement “C” 5 mm

Reinforcement offillet/partial pen.welds, see Figure 2eand 2f.

a

“a” less or equal to 10 mm Max. reinforcement “C” 2 mm “a” greater than 10 mm, up to 15 mm Max. reinforcement “C” 3 mm “a” greater than 15 mm, up to 25 mm Max. reinforcement “C” 4 mm “a” greater than 25 mm Max. reinforcement “C” 5 mm

Symmetry of filletwelds, see Figure 2g.

“a” less or equal to 6 mm Max. difference, b - h: 3 mm“a” greater than 6 mm, up to 13 mm Max. difference, b - h: 5 mm“a” greater than 13 mm Max. difference, b - h: 8 mm

Grinding arc strikesetc. Removal oftemporaryattachments

b

Grinding of base material shall not exceed 7 % of the wall thickness ormax. 3 mm. Repair welding and inspection shall be performed if removal ofthe base metal exceeds the specified requirements.

Sharp edges Minimum 2 mm radius, see 6.7.

aLocalised reinforcements exceeding the above requirements are acceptable.

b Temporary attachments shall be cut minimum 3 mm from the base metal and ground smooth. Theground area shall be visually inspected and MT shall be performed in accordance with theinspection category in question.

C Defects shall be regarded as a continuous defect if the distance between them is < t.

NOTE When required (see 6.14), grinding of the surface shall be specified. Typical examples ofgrinding requirements are given in A.1.

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1)

U

U

Figure 2a Roughness of weld Figure 2b Roughness of weld

c

t

M t

Figure 2c Misalignment of butt weld Figure 2d Reinforcement of butt weld

c

a

c

a a

b

h

Figure 2e Reinforcement of fillet weld Figure 2f Reinforcement of Figure 2g Symmetri of fillet weld

partial pen. weld

Figure 2 – Weld defects

Table 6 Structural steel welds - RT acceptance criteria

Type of defect Inspection category

A, B C, D, E

Internal porositya

Isolated:Pore diameter Max. t/4, but max.6 mm Max. t/3, but max. 6 mm

Cluster:Pore diameter Max. 3 mm Max. 4 mm

Scattered: Accumulated pore diameters in any 10 mmx150 mm area of weld

Max. 20 mm Max. 25 mm

Slag inclusions, or piping porosityWidth t/4, max. 6 mm t/3, max. 6 mmLength

c 2t, max. 50 mm 4t, max. 100 mm

Incomplete penetration, lack of fusionLength t, max. 25 mm 2t, max. 50 mm

Cracks Not acceptable Not acceptable

aIf more than one pore is located inside a circle of diameter 3 times the pore diameter, the pores are tobe considered as a cluster.

bDefects in a line where the distance between the defect is shorter than the longest defect shall be

regarded as one continuous defect.c No length limitation for width 2 mm for t 20 mm and for width 1 mm for t 20 mm.

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Table 7 Structural steel welds - UT acceptance criteria

Description Inspection category A + B

Inspection categoryC, D, E

NOTE

General If the type of defect can not be ascertained with certainty the defectshall be repaired when the length exceeds 10 mm and the echo heightexceeds the reference curve.

123

4Cracks Unambiguous cracks are unacceptable regardless of size or

amplitude.

Lack of fusionor incompletepenetration

Internal defects :I: The echo height exceeds the reference curve:Max. length t, Max. length 2t,Max. 25 mm Max. 50 mm

II: The echo height is between 50 and 100% of the referencecurve:

Max. length 2t, Max. length 4t,Max. 50 mm Max. 100 mm

Surface defects are not acceptable except:For root defects in single sided welds, the max. length for which theecho height exceeds the reference curve shall be:Max. length t, Max. length 2t,Max. 25 mm Max. 50 mm

12345

Slaginclusions

When echo height exceeds the reference curve:Max. length 2t, Max. length 4t, Max. 50 mm Max. 100 mm

12

Porosity Repair is required if porosity may mask for other defects. 1

NOTE 1 Type of defect shall be decided by:I: Supplementary non-destructive testing.

II: The ultrasonic operator's assessment of the defect, using his knowledge of the weldingprocess, signal geometry, defect position etc.

NOTE 2 If elongated defects are situated on line and the distance between them is less than thelength of the longest indication, the defects shall be evaluated as one continuous defect.

NOTE 3 Defect length is defined as the distance between points where the echo reach or pass 50% DAC (for defects larger than the beam).For defects smaller than the beam, the maximum amplitude technique may be used.

NOTE 4 With UT performed from only one side of the weld with only one surface accessible, theacceptable echo heights are reduced from 100 % to 50 % and from 50 % to 20 %,respectively.

NOTE 5 With “internal defects” it is meant defects which are located more than 6 mm from thenearest surface. A defect is classified as a “surface defect” if any part of the defect islocated less than 6 mm or t/4, whichever is smaller, from the nearest surface.

10 Repair

10.1 Definitions

Weld discontinuities: Irregularities in the body of the weld or on the weld surface classified as either weldimperfection or as weld defect.

Weld imperfection: Discontinuities that are within the acceptance criteria defined in Clause 9 and areconsidered to have no practical limitations on the intended use of the product. Weld imperfections may be leftwithout remedial work. Cosmetic grinding may be performed at the discretion of the fabricator.

Weld defect: Discontinuity with a size and/or density that exceeds the acceptance criteria defined in Clause 9.

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10.2 Correction of welds containing defects

All repairs shall be carried out in accordance with established procedures.

Welds containing cracks shall not be repaired, until the reason for the cracking has been determined. Ifnecessary, the defective part of the weld shall be cut out for further examination. Crater cracks may berepaired by grinding followed by NDT and subsequent repair welding according to an accepted repair weldingprocedure.

Other defects shall be corrected by grinding, repair welding or re-welding.

When weld defects are removed by grinding only, the final weld surface and the transition to the basematerial shall be smooth. Removal of defects shall be verified by local visual inspection, aided by applicableNDT methods. If applicable, the remaining thickness in the ground area shall be measured. Repair welding isrequired if the remaining thickness is less than that specified.

10.3 Repair by welding

10.3.1 Repair and re-repair welding

Before repair welding, the defect shall be completely removed.

The excavated area shall have smooth transitions to the metal surface and allow good access for both NDTafter excavation and subsequent repair welding. After excavation, complete removal of the defect shall beconfirmed by MT or PT. PWHT shall be performed after repair if specified for the original weld.

The excavated groove shall be minimum 50 mm long, measured at defect depth even if the defect itself issmaller. Defects spaced less than 100 mm shall be repaired as one continuous defect.

After repair welding the complete weld (i.e. the repaired area plus at least 100 mm on each side ) shall besubjected at least to the same NDT as specified for the original weld.

Repair welding may only be carried out twice in the same area.

10.3.2 Re-weldingRe-welding shall be performed in accordance with the procedures and WPS utilised for the original weld, andincludes complete removal of the original weld and HAZ.

10.4 Repair welding procedure

Repair and re-re-repair welding may be performed using the same WPS as for the original weld, or aseparately qualified procedure.

For repairs using a different process, and/or consumable, a separate WPS shall be qualified if required by5.2. Mechanical testing may be limited to HAZ Charpy V-notch testing in the original weld, provided theprocess/consumable is backed up by other welding procedure qualification records (WPQRs).

10.5 Correction of distortionImproperly fitted parts should be cut apart and re-welded in accordance with the applicable qualified WPS.

Parts distorted by welding, beyond the tolerances, should be straightened in accordance with the requirementin Clause 6.

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Annex A

(Informative)

Details for high fatigue utilisation

A.1 Typical grinding details

TYP. TUBULAR JOINT GRINDING DETAIL

TYPICAL GRINDING DETAILSFOR HIGH FATIGUE UTILISATION

T4= 2mm or 0,05 x T3 max.

(wichever is less)

Removesharp edges

O U T S

I D E

B R A C E W A L L

T 4

T 3

T2 = 2mm or 0,05 x T1 max.(wichever is le ss)

T 1

Removesharp edges

Weld rad.

Rotary burr grinder

chord wall

Remove overlap flushwith plate surface

Blend out to remove edge on undercut

Maximum depth below platesurface for blend is not to exceed

1,5mm

Grinding direction

TYP. BUTT WELD JOINT GRINDING DETAIL

NOTE 1 For removal of undercuts the toe of the weld should be blended in a smooth transition and extended below the platesurface in order to remove the toe defects.

NOTE 2 Grinding should extend below plate surface to a minimum of 0,5 mm below the bottom of any visible undercut and ensuringthat no exposed defects remain, using a rotary burr grinder. Grinding marks should run at right angels to weld axis andunder no circumstances parallel to it.

NOTE 3 Minimum radii of weld profiles after blending should not be less than 10 mm.

NOTE 4 Upon completion of blending of toe the whole of the ground surface shall be inspected with 100% visual examination and100 % MT.

NOTE 5 Ground surface shall be free of any cracks or crack like indications, and there shall be no evidence of undercut or overlap.

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A.2 Typical peening details

A.2.1 General

Peening of local area as weld toe or weld trasition is an acceptable method to improve fatigue life ofstructures. Peening is applied together with grinding where grinding serves the purposes to remove stressrisers such as surface defects and to define a steering grove for the tool in the area to be peened. Bothgrinding and peening require skills and preparations not normally available in fabrication yards. Due to thedependancy of correct performance specific precautions shall be taken when peening is planned for.

A.2.2 Requirements for application

When peening is planned for the following preparations are required:

nomination of responsible engineer for preparations, performance and documentation;

a complete responsibility and personnel matrix;

statement on expected or required improvements;

detailed work instructions;

documentation on operators experience, skill or training;

selection of peening methods to be applied;

detailed mark up drawings showing all areas of application;

detailed stepwise procedure for the work, including grinding details as tools, radius, depth and direction,

tools to be used for peening,

method, intensity and extent of peening,

quality control measures,

documentation of performance and results.

verification of performance, e.g. experiments, tests or other relevant information;

as built record index for the final design, fabrication and installation resume.

As preparation for peening the surface shall be dressed in a way that makes lack of coverage detectable,preferably by stone grinding. Applicable tool for grinding is normally a rotary burr or stone of 6 mm to 8 mmdiameter when a single tool hammer is used and 10 mm to 12 mm when a needle hammer is used. Thedepth of the groove is approximately 0,5 mm below the original surface.

All surface defects shall be removed by grinding prior to peening.

Applicable tool for peening is normally pneumatic hammers. A needle hammer is normally used when a widerarea shall be covered. For local toe peening a single tool hammer is recommended. Correct tool is essentialto maintain correct peening in compliance with requirements.Special tools with adjusted curvature shall be prepared in accordance with weld geometry.

Needle peening shall be applied with a coverage of minimum 200 %. Single hammer peening shall result in afully covered hammered groove where the surface is smooth with uniform indentation. All traces fromprevious grinding shall be completely removed.

Devices for quality control and documentation shall be thoroughly selected. Groove depth measuring toolsand macro photo is normally applied. Reference specimens shall be prepared for comparison betweenground and final peened surfaces.

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Annex B

(Informative)

Correlation between steel quality level, MDS number and steel

grade/designations

Steelqualitylevel

MDSNo.

Rev.no.

Standard Product type Steel grade(see product

standard)

ISO/TR15608

Y20 5 Plates S355G10+N/G10+M

1.2/2.1/3.1

Y21 5 Rolled sections S355G12+N/G12+M

1.2/2.1

Y22 5 Seamless tubulars S355G15+Q/G15+N

1.2/2.1/3.1

Y30 5 Plates S420G2+Q/G2+M 1.2/2.1/3.1

Y31 5 Rolled sections S420G4+M 2.1

Y32 5 Seamless tubulars S420G6+Q 3.1I Y40 5 EN 10225 Plates S460G2+Q/G2+M 1.2/3.1

Y41 5 Rolled sections S460G4+M 2/2.1/3.1

Y42 5 Seamless tubulars S460G6+Q 2.1./2.2

Y50 5 Plates S500G2+Q/G2+Ma

2.2/3.1

Y51 5 Rolled sections S500G4+M a 2.2/3.1

Y52 5 Seamless tubulars S500G6+Q a 2.2/3.1

Y25 5 Plates S355G9+N/G9+M 1.2/2.1/3.1

Y26 5 Rolled sections S355G11+N/G11+M

1.2/2.1/3.1

Y27 4 Seamless tubulars S355G14+Q/G14

+N

1.2/2.1/3.1

Y28 3 Welded tubulars S355G13+N 1.2

Y35 4 Plates S420G1+Q/G1+M 2.1/3.1

Y36 5 Rolled sections S420G3+M 2.1

Y37 5 Seamless tubulars S420G6+Q 3.1

Y45 5 Plates S460G1+Q/G1+M 2.2/3.1

II Y46 5 EN 10225 Rolled sections S460G3+M 2.2

Y47 5 Seamless tubulars S460G6+Q 3.1

Y55 5 Plates S500G1+Q/G1+Ma

3.1

Y56 5 Rolled sections S500G3+M a 2.2

Y57 5 Seamless tubulars S500G6+Q a 3.1

Y05 3 EN 10025-(all parts) Plates S355J2S355K2

1.2/2.1

EN 10025-(all parts) Plates and sections S355J2S355K2

1.2/2.1

Y06 3 EN 10225 Hot finishedseamless tubulars

S355G1+N 1.2

III Y07 3 EN 10210-(all parts) Hot finished tubulars S355NH/S355K2H

2.1

Y08 3 EN 10219-(all parts) Cold formed tubulars S355MLH 2.1

Y15 3 EN 10025-(all parts) Plates and sections S420ML 2.1

Y16 3 EN 10219-(all parts) Cold formed tubulars S420MLH 2.1

Y01 5EN 10025-(all parts)EN 10210-(all parts)EN 10219-(all parts)

Plates and sectionsHot finished tubularsCold formed tubulars

S235JRS235JRHS235JRH

1.1

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Steelqualitylevel

MDSNo.

Rev.no.

Standard Product type Steel grade(see product

standard)

ISO/TR15608

IV Y02 4EN 10025-(all parts)EN 10210-(all parts)EN 10219-(all parts)

Plates and sectionsHot finished tubularsCold formed tubulars

S275JRS275J0HS275J0H

1.2

Y04 2

EN 10025-(all parts)

EN 10210-(all parts)EN 10219-(all parts)

Plates and sections

Hot finished tubularsCold formed tubulars

S355J0

S355J0HS355J2H

1.3/2.1

a This steel grade designation is not included in EN 10225. (Note from Table 1 of M-120)

NOTE NORSOK material data sheets are published in NORSOK M-120.

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Annex C

(Normative)

Qualification of welding consumables by data sheets

C.1 General

The purpose of certification is to verify that each batch of consumables has a chemical composition withinlimits as specified by the supplier in conformance with a recognised classification standard. By controlled andcertified chemistry the supplier also confirms that mechanical properties of the weld metal fulfil the minimumrequirements specified for the product.

For this specification a batch (or lot) is defined as the volume of product identified by the supplier under oneunique batch/lot number, manufactured in one continuous run from batch controlled raw materials.

Each individual consumable (brand name and dimension) shall be certified per batch, except for solid wire(gas tungsten arc welding, gas metal arc welding, SAW), originating from the same heat, where one diametermay represent all.

C.2 Data sheet

Each welding consumable or combination of consumables shall have a unique data sheet, issued as acontrolled document within the suppliers quality system. The purchaser shall base his selection, ordering andreceiving of consumables upon reviewed and accepted data sheets.

The data sheet shall give guaranteed limits and/or minimum values for composition and mechanicalproperties, determined under defined reference conditions.

If the consumable shall be used for welds in PWHT condition, then the properties shall also be documentedin PWHT condition in addition to the as-welded condition.

Specifically this shall include, as applicable:

chemical analysis limits for solid wires and metal powders. For information also typical weld metalanalysis, using a relevant shielding gas or flux;

chemical analysis limits of weld metal from coated electrodes and cored wires, deposited according to ISO6847. For information also specified limits for S, P and N in the core wire or strip;

The analysis shall include limits for all elements specified in the relevant classification standard and/orintentionally added and for residual elements known to influence weld metal quality.

Minimum:C, Si, Mn, S, P, Cu, Ni, Cr, Mo, V, Nb.

For SAW fluxes the analysis shall be given as ranges for all main ingredient and flux basicity as follows:

mechanical properties (range or/and guaranteed minimum) of the weld, deposited and tested according toISO 15792-1 and including tensile strength, yield strength elongation, notch toughness Charpy-V at -40ºC. For information also typical properties of a relevant butt weld should be added;

diffusible hydrogen content HDM maximum, including any information on drying, restricted weldingparameters etc. required to ensure this value in practice;

when relevant for the product, basic information about CTOD properties, to be supported by separate testreports as required and agreed.

Data sheets shall also contain product classification according to recognised standards, relevant approvalsand information on packing, storage etc. as required for correct application and use of the product.

C.3 Certificate

Every batch of consumables shall be supplied with an inspection certificate 3.1.B, containing as a minimumthe specific tested chemical composition of the wire or weld metal, as applicable. The chemical elements

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shall conform to those of the data sheets, with a statement “below specified maximum” acceptable forresidual elements.

The supplier may optionally add information about mechanical properties, based on specific or non-specifictype of control, see EN 10204. Other tests may also be agreed between supplier and purchaser.

Certificates shall be actively used by the purchaser to control received consumables against the accepteddata sheet. Full conformance of chemical composition shall be required to release each batch for fabricationwelding.

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Annex D

(Normative)

Welding consumable documented by batch testing

D.1 General

The purpose of the batch testing is to verify that the consumables remains nominally equivalent to that usedfor welding procedure qualification, with respect to chemistry and mechanical properties.

For this specification a batch (or lot) is defined as the volume of product identified by the supplier under oneunique batch/lot number, manufactured in one continuous run from batch controlled raw materials.

Each individual product (brand name and dimensions) shall be tested once per batch, except for solid wireoriginating from the same heat, where one diameter may represent all. SAW fluxes do not require individualtesting, while SAW wires shall be tested in combination with a selected nominal batch of flux.

D.2 Chemical analysis

For solid wires and metal powders the analysis shall represent the product itself.

For coated electrodes and cored wires the analysis shall represent the weld metal, deposited according toISO 6847.

The analysis shall include

all elements specified in the relevant classification standard and /or intentionally added,

the main impurities S, P and N.

D.3 Mechanical properties

Unless otherwise specified the properties shall represent all weld metal, deposited and tested according to

ISO 15792-1.

Properties tested shall include

tensile strength, yield strength and elongation,

impact strength Charpy-V at temperatures -40 °C, or as specified by purchaser.

The need for other types of tests shall be evaluated for the application in question, e.g.:

mechanical properties based on a defined butt weld rather than all weld metal test;

mechanical properties in the PWHT condition;

CTOD testing;

testing of hydrogen level.

D.4 Documentation

Batch tests shall be documented by an inspection certificate in accordance with EN 10204, 3.1B, withreference to a recognised product classification standard and containing all specified test results.

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Annex E

(Normative)

Fabrication tolerances

E.1 Scope and objectives

This annex defines the maximum allowable dimensional tolerances for offshore steel items and structures.

The designer may, however, specify stricter tolerances and additional tolerances. These will, in case takepresedence over this annex.

NOTE It should be observed that the requirement to fabrication tolerances in this annex may be more strict than the manufacturingtolerances for steel products according to NORSOK M-120.

The intention of this annex is to give dimensional tolerances which will ascertain that

the calculated strength and fatigue resistance is present in the structures,

items and structures can be assembled without dimensional rework, all parts of the structures are suitable for their intended use,

the structures are trustworthy relative to measurements given on the structural drawings,

the relevant components tolerances are achieved and maintained after the components final incorporationin the completed structure(s).

E.2 Codes, standards and specifications

Reference standards for this annex are ISO 8062:1994 and EN 1090-1:2009.

E.3 Definitions

Terminology used in conjunction with this annex:

AFC drawing engineering drawings formally approved for construction

centrelinereal or imaginary line that is equidistant from the surface or sides of the (measured) object

deflectionload imposed curves, bends, angles or irregularities from an unloaded structure

NOTE Opposed to straightness deviation.

flatnessvertical offset at any point from a plane parallel with the surveyed object

grid systemdesign reference system for all parts, components and elements of a completed structure

NOTE The grid system defines the 3D position of any item within a completed structure.The grid system is normally denoted in one of the following manners:

x, y and z coordinates;

north, east and height coordinates;

longitudinal, transversal and elevation coordinates.

The grid system defines the design origo (location and elevation datum) for a structure.

position deviationaspecified point's actual position relative to it's nominal position

NOTE Measured value minus nominal value equals deviation.

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reference linesmarked lines on construction parts and assemblies which are parallel to, and in determined distances fromgrid lines

straightness deviation curves, bends, angles or irregularities from a straight generator

NOTE Straightness deviation is regarded to be fabrication imposed irregularities and not caused by elastic deformation.

survey reference systemreference system constituting of fixed and coordinate determined points, from where surveys can beperformed, and where the location and elevation of the fixed points are identifiable relative to the grid system

work pointmarked or imaginary point on a member or structure from which dimensions shall be related

E.4 General requirements

E.4.1 Implementation policy of requirements

The tolerances given in this annex shall be applied for completed structures.

For single elements to be parts of complex structures, specification of detailed and more stringent tolerancesfor each fabrication and erection sequence may be necessary in order to meet the requirements of this annexin the completed structure. Such tolerances shall be presented in the plan/scope of work for fabrication.

Specification of detailed and more stringent tolerances for intermediate and final interfaces may also benecessary in order to meet the requirements of this annex in the completed structure.

The allowable tolerances given for individual members shall not cumulate to give unacceptable deviation forthe finished section or complete structure.

If tolerances given for individual sections and components are conflicting, those tolerances representing thestricter values shall be governing.

If no appropriate tolerance is stated in this NORSOK standard, the tolerance requirements shall be agreed.

All tolerance requirements are based on nominal values on unloaded structure.

E.4.2 Procedures and documents

The following procedures and documents shall be prepared:

a) plan for fabrication and erection including methods, techniques and dimensional control to assure that allstructures can be fabricated and assembled to dimensions within the specified tolerances.The plan shall assure that all allowable tolerances for individual elements are not cumulative to theextent of exceeding the allowable tolerance for the complete structure;

b) dimensional inspection procedures relevant for the structures and any additional specifications neededto those included in this NORSOK standard, subject drawings or other regulations/guidelines for thestructural fabrication;

c) the following documents shall be prepared prior to start of fabrication:1) plan for dimensional assurance/inspection;2) dimensional inspection procedures.

d) during fabrication and erection deviations outside the specified tolerances shall be identified andinformed of in advance of the formal handling of deviations.The detailed dimensional deviation reports shall be available at all stages in fabrication, and shall besubmitted on request;

e) final documentation shall be prepared in correspondence with the requirements for as builtdocumentation and fabrication record.

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E.4.3 Qualification of inspectors

Personnel responsible for dimensional control activities shall have a minimum background of at least 5 yearsrelevant experience in industrial surveying.

Personnel monitoring dimensions and tolerances shall have relevant training in use and understanding ofinstruments, and subsequent calculations, enabling them to perform all necessary controls of own workperformance.

E.4.4 Instrument reliability

All instruments used shall be in accurate permanent adjustment, have current valid control certificates and besubject to a programme of periodic checking.

E.4.5 Reference temperature

Reference temperature for survey activities should be +20 ºC.

The field work temperature shall as a minimum be noted on all dimensional reports, when this is necessaryfor future use of the report and the component surveyed. For components to be assembled, built undersignificantly different temperature conditions, dimensions shall be computed to the reference temperatureand this shall be annotated on any subsequently produced document or report.

E.4.6 Control methods

E.4.6.1 Reference system

Prior to fabrication a survey reference system related to the grid system, shall be established. The surveyreference system shall use the same numerical values, and the same orientation directions of the systemaxis as the grid system.

The following apply:

the system's north axis shall be positive toward platform north (or bow,

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