DNV Structure Steel Fabrication.pdf

7/22/2019 DNV Structure Steel Fabrication.pdf

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NORSOK STANDARD

STRUCTURAL STEEL FABRICATION

M-101Rev. 3, September 1997


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Please note that whilst every effort has been made to ensure the accuracy of the NORSOK standards

neither OLF nor TBL or any of their members will assume liability for any use thereof.


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Structural steel fabrication M-101Rev. 3, September 1997

NORSOK standard Page 1 of 60

CONTENTS

FOREWORD 3

INTRODUCTION 31 SCOPE 4

2 NORMATIVE REFERENCES 4

3 DEFINITIONS AND ABBREVIATIONS 5

3.1 Definitions 53.2 Abbreviations 5

4 SELECTION OF STEELS 6

4.1 Design classes 64.2 Selection of steel quality level 6

5 QUALIFICATION OF WELDING PROCEDURES AND WELDERS 6

5.1 Welding procedure specification (WPS) 65.2 Qualification of welding procedures 65.3 Welding procedure approval record (WPAR) - Range of approval 65.4 Examination of the test weld 75.5 Welder and welding operators qualifications 10

6 FABRICATION AND WELDING REQUIREMENTS 10

6.1 General 106.2 Forming 106.3 Assembly 11

6.4 Preparation for coatings 126.5 Preparation and fit-up of weld bevels 126.6 Welding processes 126.7 Welding consumables 126.8 Preheat and interpass temperature 136.9 Production welding 136.10 Post weld heat treatment (PWHT) 146.11 Grinding 14

7 PRODUCTION TESTS 15

8 FABRICATION TOLERANCES 159 NON-DESTRUCTIVE TESTING (NDT) 15

9.1 General 159.2 Qualificationof inspectors and NDT-operators 169.3 Extent of visual examination and NDT 169.4 Visual examination and finish of welds 189.5 Radiographic testing 189.6 Ultrasonic testing 189.7 Magnetic particle testing 199.8 Acceptance criteria 19

10 REPAIR 2510.1 Definitions 25


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Structural steel fabrication M-101 Rev. 3, September 1997


10.2 Correction of welds containing defects 2510.3 Repair by welding 2510.4 Repair welding procedure 2610.5 Correction of distortion 26

ANNEX A TYPICAL GRINDING DETAILS FOR HIGH FATIGUE UTILISATION

(INFORMATIVE) 27

ANNEX B CORRELATION BETWEEN STEEL QUALITY LEVEL, MDS NUMBER AND

STEEL GRADE/DESIGNATIONS (NORMATIVE) 28

ANNEX C QUALIFICATION OF WELDING CONSUMABLES BY DATA SHEETS

(NORMATIVE) 29

ANNEX D WELDING CONSUMABLE DOCUMENTED BY BATCH TESTING

(NORMATIVE) 31

ANNEX E FABRICATION TOLERANCES (NORMATIVE) 32


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FOREWORD

NORSOK (The competitive standing of the Norwegian offshore sector) is the industry initiative toadd value, reduce cost and lead time and remove unnecessary activities in offshore field

developments and operations.

The NORSOK standards are developed by the Norwegian petroleum industry as a part of theNORSOK initiative and are jointly issued by OLF (The Norwegian Oil Industry Association) andTBL (Federation of Norwegian Engineering Industries). NORSOK standards are administered by

NTS (Norwegian Technology Standards Institution).

The purpose of this industry standard is to replace the individual oil company specifications for usein existing and future petroleum industry developments, subject to the individual company's reviewand application.

The NORSOK standards make extensive references to international standards. Where relevant, thecontents of this standard will be used to provide input to the international standardization process.Subject to implementation into international standards, this NORSOK standard will be withdrawn.

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

INTRODUCTION

Revision 3 of this standard mainly adds of Annex E Fabrication tolerances.


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1 SCOPEThis standard covers the requirements for fabrication and inspection of offshore steel structures withSMYS < 500 MPa and with a minimum design temperature down to -14C.

Note: For highly fatigue utilized structures, more severe requirements may apply, and these will beshown on the design drawings.

2 NORMATIVE REFERENCESThe following standards include provisions which, through reference in this text, constitute

provisions of this NORSOK standard. Latest issue of the references shall be used unless otherwiseagreed. Other recognized standards may be used provided it can be shown that they meet or exceedthe requirements of the standards referenced below.

API 2B Specification for fabricated structural steel pipe.API RP 2X Ultrasonic examination of offshore structural fabrications.ASME, Section V Non-destructive testing.

BS 7448, Part 1 Fracture mechanics toughness tests.BSI PD6493 Guidance on some methods for the derivation of acceptance levels for

defects in fusion welded joints.

DNV RP D404 Unstable fracture.

EN 287 Approval testing of welders - Fusion welding.EN 288 Specification and qualification of welding procedures for metallic

materials.EN 444 NDT - General principles for radiographic examination of metallic

materials by X-rays and gamma rays.EN 462 NDT - Image quality of radiographs.EN 473 Qualification and certification of NDT personnel - General principles.

EN 719 Welding coordination - Tasks and responsibilities.EN 729 Quality requirements for welding - Fusion welding of metallic materials.EN 875 Welding - Welded joints in metallic materials - Specimen location and

notch orientation for impact tests.EN 970 Welding - Visual examination of fusion welded joints.

prEN 1011 Welding - Recommendation for welding of metallic materials, relevantparts.

prEN 1290 NDE of welds - Magnetic particle testing of welds - Method.prEN 1291 NDE of welds - Magnetic particle testing of welds - Acceptance levels

and criteria.prEN 1418 Welding personnel - Approval testing for fully mechanised and automatic

welding.


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prEN 1597-1 Welding consumables - testing for classification.EN 10025 Hot rolled products of non-alloy structural steels: Technical delivery

conditions.EN 10204 Metallic products - Types of inspection documents.

prEN 10225 Weldable structural steels for fixed offshore structures.

EN 26847 Covered electrodes for manual metal arc welding.Deposition of a weld pad for chemical analysis.

ISO 3690 Welding - Determination of hydrogen indeposited weld metal arisingfrom the use of covered electrodes for welding mild and low alloy steels.

ISO 5817 (=EN 25817) Arc welded joints in steel - Guidance on quality levels for imperfections.

NORSOK M-001 Material selection (previously M-DP-001).NORSOK M-120 Material data sheets for structural steel (previously M-CR-120)NORSOK N-001 Structural design (previously N-CR-001)

NS 477 Welding. Rules for approval of welding inspectors.

3 DEFINITIONS AND ABBREVIATIONS3.1 Definitions

Normative references Shall mean normative in the application of NORSOK standards.Informative references Shall mean informative in the application of NORSOK standards.Shall Shall is an absolute requirement which shall be followed strictly in order

to conform with the standard.Should Should is a recommendation. Alternative solutions having the samefunctionality and quality are acceptable.

May May indicates a course of action that is permissible within the limits of the standard (a permission).

Can Can is conditional and indicates a possibility open to the user of thestandard.

3.2 AbbreviationsAWS American Welding SocietyBS British Standard CE Carbon Equivalent equationCTOD Crack Tip Opening DisplacementDAC Distance Amplitude CurveDC Design ClassDIN Deutsche Institut fr NormungDNV Det Norske VeritasEN (pr EN) European Standard (proposal for EN)FCAW Flux Cored Arc WeldingFSH Full Screen Height

HAZ Heat Affected ZoneHDM Hydrogen content, deposit metal


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IIW International Institute of WeldingISO International Organization for Standardization

NDT Non Destructive TestingMDS Material Data SheetMSF Module Support Frame

Pcm Carbon equivalent (Parameter for crack, modified)PWHT Post Weld Heat TreatmentSAW Submerged Arc WeldingSMYS Specified Minimum Yield StrengthSQL Steel Quality LevelWPS Welding Procedure SpecificationWPAR Welding Procedure Approval Record

4 SELECTION OF STEELS4.1 Design classesThe design classes will be decided by the designer and shall form the basis for selection of steelquality level (SQL). Reference is made to NORSOK standard N-001.

4.2 Selection of steel quality levelThe steel quality level will be decided by the designer in compliance with N-001.

Annex B gives the correlation between the steel quality levels I, II, III and IV, and designations onequivalent steels given in NORSOK standard M-120, Material data sheets.

Selection of a better steel quality level in fabrication than the minimum required by the designershall not lead to more stringent requirements in fabrication.

5 QUALIFICATION OF WELDING PROCEDURES AND WELDERS5.1 Welding procedure specification (WPS)WPS shall be established in accordance with EN 288 part 2.

5.2 Qualification of welding proceduresWelding procedures used for structures requiring steel quality level I and II, shall be qualified inaccordance with EN 288 part 3 and the additional requirements in this standard.

The qualification is primarily valid for the workshop performing the welding tests, and otherworkshops under the same technical and quality management. It may also be transferred to and used

by a subcontractor, provided the principles of EN 729 part 2 are implemented and documented.

5.3 Welding procedure approval record (WPAR) - Range of approvalThe WPAR is valid within the limitations specified in EN 288 part 3, with the following

clarifications and modifications:


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a) Control of heat input according to EN 288 part 3, section 8.4.7, shall apply. If an approval testinghave been performed at both a high and a low heat input level (with all specified mechanicaltesting), then all intermediate heat inputs are also qualified.

b)When the steel to be welded has a Pcm0.21, or a carbon content C 0.13%, then an increase ofmore than 0.02 Pcmunits or 0.03 carbon equivalent units (IIW formula) 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)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 change in steel supplier for steels with SMYS 500.g)A change in groove angle more than +20 deg./-10 deg.h)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 notthe converse.

i) CTOD testing shall be included in qualification of welding procedures for joints requiring steelquality level I and II, with a plate thickness above 50 mm for all steels.

Testing shall be executed from weld assemblies covering the following combined conditions(PWHT/as-welded):

Full penetration buttweld with K-, or half V -groove as deemed most representative for theactual fabrication. V -and X -groove are acceptable for weld metal test.

A welding procedure representing the maximum heat input to be used in fabrication.

Maximum joint thickness (within 10%).

Assemblies shall be made and tested for the actual combination of steel grade, welding processand welding consumable (brand) used, except welding consumables used for root passes only.

Note: The changes specified in d) and e) need not require re-qualification if HAZ properties for thematerial to be welded have been documented from the steel supplier for relevant thicknesses andheat input ranges. If sufficient documentation from the steel supplier is not available, a change ofmaterial shall require re-qualification of a reduced number of procedures. The number of proceduresto be re-qualified shall be sufficient to verify that the HAZ properties of the new material iscomparable with that used for the previous qualifications.

5.4 Examination of the test weld5.4.1 GeneralThe type and number of tests shall be in accordance with table 5.1. Testing shall be performed inaccordance with EN 288 and the additional requirements given below.

The test weld shall be 100% examined for both surface and volumetric defects with the relevantNDT-methods. The soundness of the weld shall comply with clause 9.


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Table 5.1 Type and number of tests

Mechanical testing

Joint

configuration

Joint

thickness(mm)

Tensile

test

Bend

tests1)Charpy

V-notchtests

Hardness

andmacro 5)

CTOD

Buttwelds(Tubulars and

plates)

t


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Table 5.2 Charpy impact test temperatures and energy requirements for welding

procedure qualifications.

Material Steel quality levelthickness I II

mm SMYS400MPa SMYS>400MPa SMYS400MPa SMYS>400MPa

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

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

25 < t 50 -40C -40C -20C -40Ct > 50 -40C -40C -40C -40CEnergyRequirement 1)

36J 42J 27J 42J

Note:1. 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 specimensshall be: 7,5 mm - 5/6 and 5 mm - 2/3.

5.4.3 Transverse tensile testingTesting shall be carried out in accordance with EN 288. The fracture shall be located outside theweld metal (i.e. max. 20% of the fracture surface shall consist of weld metal).

5.4.4 CTOD testingThe CTOD-technique with the Bx2B, through-thickness notched type specimen according to BS7448 Part 1 should be used. Three (3) valid test specimens shall be obtained for each test position.

Note: Test assemblies may be given hydrogen diffusion treatment prior to testing, and specimensmay be precompressed.

CTOD-testing of welds shall be carried out with the fatigue notch tip positioned in the coarsegrained region of the heat affected zone and in the weld metal. For HAZ, determination of theactual location of the fatigue crack tip shall be performed after testing. Ref. is made to prEN 10225.

CTOD-testing of HAZ can be omitted if relevant CTOD properties in HAZ have been documentedpreviously for the base material in accordance with requirements in this standard, provided therequirements for the essential variables are met.

CTOD-testing of weld metal can be omitted if CTOD properties in accordance with requirements inthis standard have been documented previously, provided the requirements for the essentialvariables are met.


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Test temperature for all qualification testing for design temperature down to -14 C shall be:

-10C for splash zone and above.

0C for submerged parts.

The required fracture toughness level shall be decided in design for joints with plate thickness above50 mm when steel quality level I and II are required.

5.5 Welder and welding operators qualificationsThe welders, welding operators and tack welders shall be qualified in accordance with EN 287,

prEN 1418 or equivalent. For tack welders, an internal test may be used.

For welding of single sided acute angled tubular joints with < 70, welders shall be qualified witha realistic joint, representing the minimum angle to be used in production.

For welding of joints where steel quality level IV is selected, a certificate for welding of plates inposition PE is sufficient for welding all product forms.

6 FABRICATION AND WELDING REQUIREMENTS6.1 GeneralAll welding work shall be according to recommendations given in prEN 1011. The manufacturershall have a quality system, which fulfil the relevant part of EN 729 and the applicable level of EN719.

The fabricator shall apply a weld numbering system for identification on all shop drawings and asreference in all documentation.

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

If the deformation is more than the above given limits, either heat treatment shall be performed, or

strain ageing tests shall be carried out according to the following procedure: The material shall be permanently strained locally to the actual deformation. The material shall be artificially aged at 250C for 1 hour.

One set of 3 impact test specimens shall be tested from the base material in the strained plusartificially aged condition. The notch shall be located within the plastically strained portion of thematerial, in the part of 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 not be more than 25% lower than the impact value for the material before deformation andstrain ageing.


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

The percentage strain due to forming is defined as follows:

Wall thicknessPercent strain = _______________________________________ x 100%

Forming mid thickness diameter

6.3 Assembly6.3.1 GeneralIn tubular joints, circumferential and longitudinal weld joints should not be placed in the shadedareas shown in fig. 6.1, unless otherwise shown on design drawings.

W 1

W 1

W 1

W 1

W 2

W3

D

W 2

W 2

W 2

Longitudinal welds Circumferential welds

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

Fig. 6.1 Prohibited location of welds in tubular joints. Longitudinal respectively circumferentialwelds shall not be located in shaded area.

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


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6.3.3 TaperingTapering shall be in accordance with the requirements given in relevant standards or drawings. If noother requirements are specified, a tapering of 1:4 should be used.

6.3.4 Bolting connectionBolting material shall comply with requirements in NORSOK standard M-001, Material selection.Holes shall be made by machine drilling.

6.3.5 Seal/blind-compartments.Crevices and areas which become inaccessible after fabrication or assembly shall be sealed off fromthe outside atmosphere. Seal welds shall have a throat thickness of at least 3 mm. Where steel itemsshall be hot dip galvanised, hollow sections shall be ventilated.

6.3.6 Temporary cut-outsTemporary cut-outs shall not be located in restricted areas as shown on design drawings. Temporary

cut outs shall have a corner radius not less than 100 mm. Temporary cut-outs shall be closed byrefitting the same or an equivalent plate and employing the same welding, inspection anddocumentation procedures and requirements that govern the structural part in question.

6.3.7 Straightening of structural membersMembers distorted by welding shall be straightened according to a detailed work instruction. The

base material properties shall satisfy the specified requirements after straightening.

Maximum temperature for straightening shall not exceed the temperature limit recommended by thesteel manufacturer, but it shall in no case be higher than 600C.

6.3.8 Doubler platesAll temporary attachments which shall be flame cut or welded under water shall be attached to thestructure by using doubler plates.

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

6.4 Preparation for coatingsEdges of plates and structural shapes which are intended to be coated shall be rounded toapproximately 2 mm radius, unless otherwise indicated on design drawings.

6.5 Preparation and fit-up of weld bevelsPermanent backing strips are not accepted, unless shown in design drawings.

Buttering shall be carried out in accordance with a relevant WPAR.

6.6 Welding processesThe welding processes listed in EN 288 are acceptable.

6.7 Welding consumablesThe manufacturers shall ensure that welding consumables applied for joints where steel quality level

I or II are required, meet the requirements for mechanical properties as specified for the weldingprocedure qualification, in both as welded and (where applicable) PWHT condition.


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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 annex C.

Except for solid wires such consumables shall be classified by the supplier as extra low hydrogen,i.e. HDM 5ml/100g weld metal. For self shielded flux cored wire HDM 8ml/100g may beaccepted, provided preheating temperature and post weld holding temperature and time is assessedto avoid hydrogen cracking. Hydrogen testing shall be according to ISO 3690 or equivalent.

Consumables for joints in steelquality level III and IV and for joining stainless to carbon steel shallbe selected with due consideration of base material properties, thickness and weldability, to ensuresufficient weld strength, toughness and homogenity.

Such consumables shall be delivered with EN 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 be supplied with an inspection certificate (type 3.1B) in accordance with EN 10204, includinga statement of compliance with the Welding Consumable Data Sheet and the chemical compositionof 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.

6.8 Preheat and interpass temperaturePreheating above 50C should be achieved by electric heating elements. Cutting torches are notallowed for preheating.

The minimum interpass temperature shall not drop below the minimum required preheattemperature. If not otherwise stated in the WPS, and qualified by the WPAR, the maximuminterpass temperature shall not exceed 250C measured at the edge of the groove. For C- and C/Mn-steels, a maximum interpass temperature of 250C may be used, even if a lower temperature wasrecorded on the WPAR.

The preheat temperatures used during repair welding should be minimum 50C higher than the

preheat used for the original weld.

6.9 Production welding6.9.1 GeneralWelding shall be carried out in accordance with the WPS and applicable drawings.

Butt welds in joints where steel quality level I or II are requiredshall, whenever possible, be weldedfrom both sides.

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


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For joints in inspection category A, the straight edges of K- and 1/2V-butt weld grooves shall havea groove angle of at least 10O, unless it is documented that possible defects can be detected by theUT technique used. (For K-grooves, the 10Oshould be machined from the root to each platesurface.)

6.9.2 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 designdrawings that removal (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 areattached. Temporary attachments shall be cut minimum 3 mm from the base metal and ground. Theground area shall be visually examined and magnetic particle inspected.

6.10 Post weld heat treatment (PWHT)PWHT shall be required for structural welds where steel quality level I or II are required, when thenominal thickness (as defined in EN 288-3, section 8.3.2.1) exceeds 50 mm, unless adequatefracture toughness can be documented in the as welded conditions. For restrained joints ofcomplicated design, PWHT may be required for smaller thicknesses, independent of steel qualitylevel.

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

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 temperature shall be as recommended by the steel manufacturer. The holding time shallbe at least 2.5 min per mm thickness (of the thickest member).

The temperature difference between different parts of the structure during soaking time shall notexceed 30C 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.

6.11 GrindingWhen grinding is specified on design drawings or is instructed as a corrective action, the grindingshall be performed according to a detailed procedure. Grinding tools, direction, surface roughnessand final profile shall be specified. Reference samples for typical joints and sections may be

prepared and used for acceptance of treated welds. Typical examples for requirements for grinding

of joints are given in annex A.


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7 PRODUCTION TESTSProduction tests shall be selected on weldments in critical regions to verify that the specifiedrequirements have 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 productionwelding, normally as extension of the production weld, and meet the requirements for welding

procedure approval tests.

CTOD testing is not required for production testing.

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

8 FABRICATION TOLERANCESFabrication tolerances shall be in accordance with Annex E, unless otherwise specified on drawings.

9 NON-DESTRUCTIVE TESTING (NDT)9.1 GeneralThe inspection category shall be decided by the designer in accordance with NORSOK N-001, andshall be specified on the design drawings.

Final inspection and NDT of structural steel welds shall not be carried out before 48 hours aftercompletion except where PWHT is required. The time delay may be reduced to 24 hours for steelgrades with SMYS of 355MPa or lower, and for steel grades with SMYS of 420MPa or lower for

plate thicknesses below 40 mm, provided delayed cracking have not been observed for the materialsand welding consumables in question. When PWHT is performed, the final NDT shall be carriedout when all heat treatment have been completed.

Prior to fabrication start-up, contractor shall implement a system for recording of weld defect rates.

If this system shall be used as basis for a reduction of NDT extent according to table 10.1, thesystem must ensure that a correct rate identification is prepared for each weld method, each NDTmethod and each production area.

The defect rate is defined as: (Defect length x 100%) _ (Length of tested parts of welds) 1)

Note 1: Tested part of welds means the part that is tested with the same NDT method.

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


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9.2 Qualificationof inspectors and NDT-operatorsPersonnel responsible for welding inspection - welding inspectors - shall be qualified in accordancewith NS 477 or equivalent scheme.

Personnel performing visual inspections of welded joints shall be qualified in accordance with

EN 970.

Personnel responsible for all NDT activities shall be qualified according to EN 473/NORDTESTLevel 3 or equivalent.

The NDT operators shall be qualified according to EN 473/NORDTEST Level 2 or equivalent.

Operators simply producing radiographs and not performing evaluation, do not require level 2,but shall have sufficient training.

Ultrasonic operators used in testing of tubular joints shall satisfy the requirements in API RP2X, para 5.3.

(Note: UT operators with EN 473/NORDTEST Level 2 or equivalent qualifications who aretesting tubular joints according to the requirements of API RP 2X, equires no furtherqualification tests, but shall be conversant with the content of the API RP 2X standard).

In undertaking testing of castings or forgings the NDT operator should also document experiencewith forged and cast products.

9.3 Extent of visual examination and NDTThe required minimum extent of examination/testing is given in table 9.1. Design drawings mayshow areas of welds where testing is mandatory.

Ultrasonic testing to reveal the presence of possible weld metal transverse cracking shall beincluded for butt welds with thickness more than 25 mm. The testing shall be performed onminimum 5% ofweldsin inspection category A and B for SAW (12) and FCAW (131 and 136)


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Table 9.1 Minimum extent (in %) of non-destructive testing for structural welds.

Inspectioncategory

Type ofconnection

Visualexamination

Extent oftesting

RT UT MTA Buttw.

T-conn.Fillet/partial

100100100

10--

100100

-

100100100

B Buttw.T-conn.Fillet/partial

100100100

Spot--

50 1)

50 1)

-

100 1)

100 1)

100 1)

C Buttw.T-conn.Fillet/partial

100100100

---

20 1)

20 1)

-

20 1)

20 1)

20 1)

D All conn. 100 - - spotE All conn. 100 - - -

Legend -RT = Radiographic testingUT = Ultrasonic testingMT = Magnetic particle testingSpot means 2 - 5%.

Note:

1. The extent may be reduced to 50% of the specified extent, based on experience anddocumented records with similar joints, provided the defect rate (see clause 10.1and 11.1) for UT/RT is


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

The extent of NDT shall be increased if repeated occurrence of cracks or other significant welddefects are revealed. Corrective actions shall be taken to ensure that all similar defects will be

detected.

In addition to what is listed in table 9.1, 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 ofdefects 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 suchthicknesses, UT may be replaced with RT. In general, RT should be considered if UT is not

possible. Radiographic testing is normally not applicable for thicknesses above 40 mm.e) MT shall be performed on both external and internal surface as accessible.

9.4 Visual examination and finish of weldsThe visual examination shall be carried out in accordance with EN 970.

9.5 Radiographic testingRadiographic testing shall be carried out in accordance with ASME Section V, article 2; orEN444.

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

Penetrameters of wire type (according to EN 462-1 or equivalent) shall be utilised. Sensitivity levelshall be in accordance with EN 462 part 3, Class A. However, if gamma ray sources are used, thesensitivity shall be 2% or better.

9.6 Ultrasonic testingUltrasonic testing of welds in plate and tubular butt welds and double side welded tubular jointsshall be performed in accordance with ASME V Article 5, T-542.7. Ultrasonic testing of weldsmade from the outside only in tubular T, K and Y connections shall be performed in accordancewith API RP 2X, if designed according to API RP 2A.

Reference blocks shall be made with thickness and side-drilled holes in accordance with table 9.2.DAC reference curves shall be established in accordance with ASME V Article 4, Appendix B-20and C-20.

The effective test range of a DAC curve shall be determined by the point at which the curve hasfallen to 25% FSH, when it will be necessary to raise the curve using reflectors at increased depth.The reference block 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 orthermomechanical treatment, reference blocks shall be produced both perpendicular to, and parallelto, the direction of rolling. The rolling direction shall be clearly identified.


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

A transfer correction between the reference block and the test surface shall be performed.

Ultrasonic examination procedures shall be sufficiently detailed to ensure 100% of the weld bodyand heat affected zones are examined for longitudinal defects in accordance with ASME V, Article5, T-542.7.2.3.

All indications exceeding 20% DAC shall be investigated to the extent that they can be evaluated interms of the acceptance criteria.

All indications exceeding acceptance criteria shall be reported, unless more stringent requirementsare given in table 9.5.

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

9.7 Magnetic particle testingMagnetic particle testing shall be carried out in accordance with prEN 1290. Magnetic yokes usingalternating current shall be used. Prods are acceptable where the geometry of the welded joint

prevents the use of yokes. Permanent magnets are not acceptable.

9.8 Acceptance criteria9.8.1 GeneralAll welds shall comply with the requirements given below, in 9.8.2 - 9.8.5.

9.8.2 Visual examinationAll welds shall show evidence of good workmanship. The quality shall comply with therequirements of table 9.3.

9.8.3 RadiographsThe soundness of the welded joint shall comply with the requirements of table9.4.

9.8.4 Ultrasonic testing acceptance criteriaThe acceptance criteria for welds shall comply with table 9.5, except that the acceptance criteria forwelds made from the outside only in tubular T, K and Y connections shall comply with API RP 2Xlevel C, unless more stringent requirements are specified by the designer on the design drawing.

9.8.5 Magnetic particle testingLinear indications (i.e. indications with a length/width ratio above 3 and length above 1.5 mm ) arenot acceptable. Any linear indications shall be ground and re-examined. Rounded indications shall

be evaluated in accordance with the requirements of table 9.3.


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9.8.6 All methodsAll defects shall be repaired according to clause 10.

Defects may be accepted by the relevant parties when repair work is considered detrimental to thetotal integrity of the weld. Such acceptance shall be based on a fitness for purpose evaluation inaccordance with BSI PD6493, DNV RP D404 or other recognised methods.

Table 9.2 Calibration reference block requirements

Thickness ofmaterial to be

examined (mm)

Thickness of block Diameter of hole Distance of holefrom one surface

10 < t < 50 40 or t 3 mm +/-0.2 mm

50 < t < 100 75 or t t/2 and t/4.100 < t < 150 125 or t 6 mm +/-0.2 mm Additional holes are150 < t < 200 175 or t allowed and 200 < t < 250 225 or t recommended

t > 250 275 or t


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Table 9.3 Structural steel welds. Visual and MT-acceptance criteria for structural steel

welds

Welding Acceptance criteria

Type of defect Insp. cat. A, B Inspection category C, D, ECracks Not acceptable Not acceptableIncomplete

penetration or lackof fusion

Not acceptable Single - side weld:Length < t/2, max 10 mmDefects shall be regarded as a continuousdefect if the distance between them is < t.

Undercut Max depth 0.5 mmContinuousundercut is not

permitted

Maximum depth 0.75 mmContinuous undercut is not permitted

Surface porosityExposed slag

Not acceptable Not acceptable. However, the followingdefects may be acceptable if it does notconflict with surface treatment requirements:Accumulated pore diameters in any area of 10x 150 mm is not to exceed 15 mm. Max. sizeof a single pore is t/4 or 4 mm, whichever isthe smaller.

Concave root Max. concavity 0.5 mm if the transition is smoothly formed.Excessive pen. 1) Max. 3 mmRoughness of weld

(fig. 1)

U shall be less than 2.5 mm. Weld surface shall be smooth,

without sharp transitions. The bottom of roughness in butt weldsshall not be below the base material surface.Misalignment of

butt welds (fig. 2)Max. misalignment (M), 0.15 x t or max. 4 mm,whichever is the smaller.

Reinforcement ofbutt welds (fig. 3) 1)

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

Reinforcement offillet/partial pen.welds (fig.4) 1)

a less or equal to 10 Max reinforcement C 2 mma greater than 10, up to 15 Max reinforcement C 3 mma greater than 15, up to 25 Max reinforcement C 4 mm

a greater than 25 Max reinforcement C 5 mm

Symmetry of filletwelds (fig. 5)

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

Grinding arc strikesetc. Removal oftemporaryattachments 2)

Grinding of base material shall not exceed 7% of the wall thicknessor max. 3 mm. Repair welding and inspection shall be performed ifremoval of the base metal exceeds the specified requirements.

Sharp edges Minimum 2 mm radius (Ref. 6.4)


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Notes:1) Localised reinforcements exceeding the above requirements are acceptable.2) Temporary attachments shall be cut min. 3 mm from the base metal and ground smooth.

The ground area shall be visually inspected and MT shall be performed in accordancewith the inspection category in question.

3) When required (ref. 6.11), grinding of the surface shall be specified. Typical examples ofgrinding requirements are given in annex A.

U

U

Fig. 1 Roughness of weldc

t

Mt

Fig. 2 Misalignment of butt weld Fig.3 Reinforcement of butt weld

c

a

c

a a

b

h

Fig. 4a Fig. 4b Fig. 5Reinforcement of fillet weld Reinforcement of partial pen. weld Symmetry of fillet weld


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Table 9.4 Structural steel welds, RT acceptance criteria

Type of defect Inspection categoryA, B C, D, E

Internal porosity (Note 1)

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

mmmax t/3, but max. 6 mm

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

Scattered:Accumulated pore diameters in any

10x150 mm area of weld

max. 20 mm max. 25 mm

Slag inclusions, or piping porosity (Note 2)Width t/4, max .6 mm t/3, max. 6 mmLength (Note 3) 2t, max 50 mm 4t, max. 100 mmIncomplete penetration, lack of fusionLength (Note 2) t, max. 25 mm 2t, max 50 mmCracks Not acceptable Not acceptable

Notes:1)If more than one pore is located inside a circle of diameter 3 times the pore diameter, the

pores are to be considered as a cluster.2)Defects in a line where the distance between the defect is shorter than the longest defect

shall be regarded as one continuous defect.3) No length limitation for width 2 mm for t 20 mm and for width 1 mm for t


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Table 9.5 Structural steel welds. UT acceptance criteria.

Description Inspection categoryA + B

Inspection categoryC, D, E

Notes

General If the type of defect can not be ascertained with certainty the

defect shall be repaired when the length exceeds 10 mm and theecho height exceeds the reference curve.

1

234

Cracks Unambiguous cracks are unacceptable regardless of size oramplitude.

Lack offusion orincomplete

penetration

Internal defects :I: The echo height exceeds the reference curve:Max length t, Max length 2t,max 25 mm max 50 mmII: The echo height is between 50 and 100% of the reference

curve:Max length 2t, Max length 4t,max 50 mm max 100 mmSurface defects are not acceptable except:For root defects in single sided welds , the max length for whichthe echo 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,max50 mm max 100 mm

12

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

Notes: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 thewelding process, signal geometry, defect position etc.

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.

3. Defect length shall be determined by the 6dB drop method from the end of the defect(for defects larger than the beam) or by the maximum amplitude technique (for defectssmaller than the beam).

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.

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.


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10 REPAIR10.1 DefinitionsWeld discontinuities: Irregularities in the body of the weld or on the weld surface classified as eitherweld imperfection or as weld defect.

Weld imperfection: Discontinuities that are within the acceptance criteria defined in clause 9 andare considered to have no practical limitations on the intended use of the product. Weldimperfections may be left without remedial work. Cosmetic grinding may be performed at thediscretion of the fabricator.

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

10.2 Correction of welds containing defectsAll 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.If necessary, the defective part of the weld shall be cut out for further examination. Crater cracksmay be repaired by grinding followed by NDT and subsequent repair welding according to anaccepted repair welding procedure.

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 thebase material shall be smooth. Removal of defects shall be verified by local visual inspection, aidedby applicable NDT methods. If applicable, the remaining thickness in the ground area shall bemeasured. Repair welding is required if the remaining thickness is less than that specified.

10.3 Repair by welding10.3.1 Repair and re-repair weldingBefore repair welding, the defect shall be completely removed.

The excavated area shall have smooth transitions to the metal surface and allow good access forboth NDT after excavation and subsequent repair welding. After excavation, complete removal ofthe defect shall be confirmed by MT or PT. PWHT shall be performed after repair if specified forthe original weld.

The excavated groove shall be minimum 50 mm long, measured at defect depth even if the defectitself is smaller. 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 be subjected at least to the same NDT as specified for the original weld.

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


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

10.4 Repair welding procedureRepair 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 ifrequired by 5.2. Mechanical testing may be limited to HAZ Charpy V-notch testing in the originalweld, provided the process/consumable is backed up by other WPARs.

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

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


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ANNEX A TYPICAL GRINDING DETAILS FOR HIGH FATIGUE

UTILISATION (INFORMATIVE)

TYP. TUBULAR JOINT GRINDING DETAIL

TYPICAL GRINDING DETAILSFOR HIGH FATIGUE UTILISATION

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

(wichever is less)

Removesharp edges

OUT

SIDE

BRACEWALL

T4

T3

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

T1

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

Notes to figures:1. For removal of undercuts the toe of the weld should be blended in a smooth transition and

extended below the plate surface in order to remove the toe defects.2. Grinding should extend below plate surface to a minimum of 0.5 mm below the bottom of any

visible undercut and ensuring that no exposed defects remain, using a rotary burr grinder.Grinding marks should run at right angels to weld axis and under no circumstances parallel to it.

3. Minimum radii of weld profiles after blending should not be less than 10 mm.4. Upon completion of blending of toe the whole of the ground surface shall be inspected with

100% visual examination and 100% MT.5. Ground surface shall be free of any cracks or cracklike indications, and there shall be no

evidence of undercut or overlap.


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ANNEX B CORRELATION BETWEEN STEEL QUALITY LEVEL, MDS

NUMBER AND STEEL GRADE/DESIGNATIONS

(NORMATIVE)

Steelqualitylevel

NORSOKMDS No.

Note 1

Rev.No.

Referencestandard

Product type Steel grade Former Steelgrade

Y20 2 Plates S355N4z/M4z S355NLO5Y21 2 Rolled sections S355N3z/M3z S355NLO5Y22 2 Seamless tubulars S355Q3z/N3z S355NLO5Y30 2 Plates S420Q3z/M3z S420QLO4Y31 2 Rolled sections S420M3z S420QLO4Y32 2 prEN 10225 Seamless tubulars S420Q3

(z mod)

S420QLO2

(mod.)I Y40 2 Plates S460Q3zM3z S460QLO4

Y41 2 Rolled sections S460M3z S460QLO4Y42 2 Seamless tubulars S460Q3

(z-mod)S460QLO2(mod)

Y50 2 Plates S500Q3z/M3z S500QLO4Y51 2 Rolled sections S500M3z S500QLO4Y52 2 Seamless tubulars S500Q3(z-mod) S500QLO4Y25 2 Plates S355N4/M4 S355NLO3Y26 2 Rolled sections S355N3/M3 S355NLO3

Y27 2 Seamless tubulars S355Q3/N3 S355NLO3Y35 2 Plates S420Q3/M3 S420QLO2Y36 2 Rolled sections S420M3 S420QLO2Y37 2 Seamless tubulars S420Q3 S420QLO2Y45 2 Plates S460Q3/M3 S460QLO2

II Y46 2 prEN 10225 Rolled sections S460M3 S460QLO2Y47 2 Seamless tubulars S460Q3 S460QLO2Y55 2 Plates S500Q3/M3 S500QLO2Y56 2 Rolled sections S500M3 S500QLO2Y57 2 Seamless tubulars S500Q3 S500QLO2

III Y03 2 EN 10025 Plates and sections S355J2G3

prEN 10225 Tubulars S355N1Y01 2 EN 10025 Plates and sections S235JRG2

EN 10210-1 Tubulars S235JRHEN 10219-1 Tubulars S235JRH

IV Y02 2 EN 10025 Plates and sections S275JR EN 10210-1 Tubulars S275JOHEN 10219-1 Tubulars S275JOH

Note 1 NORSOK Material data sheets are published in NORSOK standard M-120.


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ANNEX C QUALIFICATION OF WELDING CONSUMABLES BY DATA

SHEETS (NORMATIVE)

C.1 SCOPEThe purpose of certification is to verify that each batch of consumables has a chemical compositionwithin limits as specified by the supplier in conformance with a recognised classification standard.By controlled and certified chemistry the supplier also confirms that mechanical properties of theweld metal fulfil the minimum requirements specified for the product.

For this specification a batch (or lot) is defined as the volume of product identified by the supplierunder one unique batch/lot number, manufactured in one continuous run from batch controlled rawmaterials.

Each individual consumable (brand name and dimension) shall be certified per batch, except forsolid wire (GTAW, GMAW, SAW), originating from the same heat, where one diameter mayrepresent all.

C.2 DATA SHEET

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

The data sheet shall give guaranteed limits and/or minimum values for composition and mechanical

properties, determined under defined reference conditions.

If the consumable shall be used for welds in PWHT condition, then the properties shall also bedocumented in 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 weldmetal analysis, using a relevant shielding gas or flux.

Chemical analysis limits of weld metal from coated electrodes and cored wires, depositedaccording to EN 26847. For information also specified limits for S, P and N in the core wire orstrip.

The analysis shall include limits for all elements specified in the relevant classification standardand/or intentionally 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.


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Mechanical properties (range or/and guaranteed minimum) of the weld, deposited and testedaccording to prEN 1597 part 1 and including tensile strength, yield strength elongation, notchtoughness Charpy-V at -40C. For information also typical properties of a relevant butt weldshould be added.

Diffusible hydrogen content HDMmax., 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 byseparate test reports as required and agreed.

Data sheets shall also contain product classification according to recognised standards, relevantapprovals and 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 aminimum the specific tested chemical composition of the wire or weld metal, as applicable. Thechemical elements shall conform to those of the data sheets, with a statement below specifiedmaximum acceptable for residual elements.

The supplier may optionally add information about mechanical properties, based on specific or non-specific type of control. (Ref. 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 theaccepted data sheet. Full conformance of chemical composition shall be required to release each

batch for fabrication welding.


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ANNEX D WELDING CONSUMABLE DOCUMENTED BY BATCH

TESTING (NORMATIVE)

D.1 SCOPEThe purpose of the batch testing is to verify that the consumables remains nominally equivalent tothat used for 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 supplierunder one unique batch/lot number, manufactured in one continuous run from batch controlled rawmaterials.

Each individual product (brand name and dimensions) shall be tested once per batch, except forsolid wire originating from the same heat, where one diameter may represent all. SAW fluxes do not

require individual testing, while SAW wires shall be tested in combination with a selected, nominalbatch of flux.

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, depositedaccording to EN 26847.

The analysis shall include: All elements specified in the relevant classification standard and /or intentionally added.

The main impurities S, P and N.

D.2 MECHANICAL PROPERTIES

Unless otherwise specified the properties shall represent all weld metal, deposited and testedaccording to prEN 1597 part1.

Properties tested shall include: Tensile strength, yield strength and elongation.

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

The need for other types of tests shall be evaluated for the application in question, such as: 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.3 DOCUMENTATION

Batch tests shall be documented by an inspection certificate 3.1B to EN 10204, with reference to a

recognised product classification standard and containing all specified test results.


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ANNEX E FABRICATION TOLERANCES (NORMATIVE)

CONTENTS

E.1 SCOPE AND OBJECTIVES 33

E.2 CODES, STANDARDS AND SPECIFICATIONS 33

E.3 DEFINITIONS 33

E.4 GENERAL REQUIREMENTS 34

E.4.1 Implementation policy of requirements 34E.4.2 Procedures and documents 35

E.4.3 Qualification of inspectors 35E.4.4 Instrument reliability 35E.4.5 Reference temperature 35E.4.6 Control methods 36E.4.7 Interface criterias 38E.4.8 Alignment Requirement 38

E.5 FABRICATION TOLERANCES FOR STRUCTURAL COMPONENTS 39

E.5.1 I / H- Girders 39E.5.2 Box Girders 40E.5.3 Tubulars 41E.5.4 Panels 44E.5.5 Girder Nodes 45E.5.6 Box Nodes 47E.5.7 Tubular Nodes 48E.5.8 Cast and Forged Elements 50E.5.9 Curved and cylindrical shell 51E.5.10 Conical transitions 51

E.6 ASSEMBLY TOLERANCES 52

E.6.1 Topsides and modules 52E.6.2 Jacket and other tubular frame structures 53E.6.3 Floating production units 58E.6.4 Subsea structures 59

E.7 FABRICATION TOLERANCES FOR SPECIAL ITEMS 60

E.7.1 Crane Pedestal 60E.7.2 Skid Beams 60E.7.3 Outfitting Structure 60E.7.4 Installation Aids 60E.7.5 Grillages 60E.7.6 Cranes 60


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Grid System:

The grid system is defined as the design reference system for all parts, components and elements ofa completed structure.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 Deviation:

The specified point's actual position relative to it's nominal position.(Measured value minus nominal value equals deviation).

Reference Lines:Reference lines are marked lines on construction parts and assemblies. The reference lines shall be

parallel to, and in determined distances from grid 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 byelastic deformation.

Survey Reference System

A reference system constituting of fixed and coordinate determined points, from where surveys canbe performed, and where the location and elevation of the fixed points are identifiable relative to thegrid system.

Work Point:

A marked 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 singleelements to be parts of complex structures, specification of detailed and more stringenttolerances for each fabrication and erection sequence may be necessary in order to meet therequirements of this annex in 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 alsobe necessary 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 unacceptabledeviation for the finished section or complete structure.


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If tolerances given for individual sections and components are conflicting, those tolerancesrepresenting the stricter values shall be governing.

If no appropriate tolerance is stated in this document, 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:

Plan for fabrication and erection including methods, techniques and dimensional control to assurethat all structures 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.

Dimensional inspection procedures relevant for the structures and any additional specificationsneeded to those included in this document, subject drawings or other regulations/guidelines for thestructural fabrication.

The following documents shall be prepared prior to start of fabrication:

Plan for dimensional assurance/inspection Dimensional inspection procedures

During fabrication and erection deviations outside the specified tolerances shall be identified and

informed of in advance of the formal handling of deviations.The detailed deviation reports shall be available at all stages in fabrication, and shall be submittedon request.

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

E.4.3 Qualification of inspectors

Personnel responsible for dimensional control activities shall have a minimum background of atleast 5 years relevant experience in industrial surveying.

Personnel monitoring dimensions and tolerances shall have relevant training in use andunderstanding of instruments, and subsequent calculations, enabling them to perform all necessarycontrols of own work performance.

E.4.4 Instrument reliability

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

E.4.5 Reference temperature

Reference temperature for survey activities should be +20 deg. C.


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The field work temperature shall as a minimum be noted on all dimensional reports, when this isnecessary for future use of the report and the component surveyed. For components to be assembled,

built under significantly different temperature conditions, dimensions shall be computed to thereference temperature and 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. Thesurvey reference system shall use the same numerical values, and the same orientation directions ofthe system axis as the grid system.

The system's north axis shall be positive toward platform north (or bow, if ship).The system's east axis shall be positive toward east (or starboard, if ship).The system's elevation shall be positive upward.The numerical value should be the same for all disciplines and packages.For special structures such as jackets being built laying down, the reference system must be adjustedto this fabrication situation, but the final as built survey shall be related to the platform grid system.

The survey reference system should be established within the following tolerances:

Sections/complete structures: 3 mm

Stricter survey reference system tolerances shall be used on components where the requirements ofthe final product are more stringent than the above tolerance. For components where the tolerance of

the product are less than 2 mm, the proposed survey methods shall be described.

At all stages during fabrication and erection, the Contractor shall ensure that the survey referencesystem and the fabricated item shall be in correct position relative to each other.

Permanent survey stations shall be properly constructed and be protected from disturbance.The permanent survey stations shall be rechecked periodically, or whenever additional permanentsurvey stations are established. All additional or rechecked surveys shall be properly documented.


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Fig. E.4.6-1 Principal reference system

Figure E.4.6.1, indicates sample of applicable and practical reference systems.

The layout of the reference system may be specially designed to suit the task at hand and themethods chosen for controls.

E.4.6.2 Marking criterias

During layout and assembly of each structural item all work points and centrelines, which arerelevant for the remaining steps of the construction, shall be marked and identified.

Location of hidden stiffeners, bulkheads etc. shall be marked on the outside of the structure toensure a correct assembly, if relevant for the remaining steps of the construction.

All primary datum work points on the structure shall be set out using accepted engineeringsurveying techniques consistent with the tolerances required by this annex. All girders, boxes, nodesand other structures shall be properly and clearly marked relative to the grid system at all interfaces,if relevant for the remaining steps of the construction.

E.4.6.3 Accuracy

Surveys shall be performed using survey techniques and technology which enables the achievementof a survey accuracy better than the specified tolerances.The methods and equipment used must enable verification of the survey accuracy.


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All activities related to measurement and inspection of dimensions and tolerances shall take intoaccount the effects of self weight while the structure is under fabrication.

E.4.7 Interface criterias

All non-adjustable interfaces and interfaces deemed critical prior to erection shall be surveyed anddocumented. A comparison of the interface results prior to erection shall be performed andnecessary actions in order to meet the global requirements shall be carried out.

E.4.8 Alignment Requirement

Requirements to alignments with regard to eccentricity of butt joints and cruciform joints are asfollows:

a) Butt-jointsReference is made to table 9.3.

b) Cruciform JointsEccentricity of non-continuous plating in cruciform joints shall not exceed the followingrequirements, (ref. figure 4.8-1)

e t1/2 (mm), maximum 5 mm, for t220 mme t1/2 (mm), maximum 8 mm, for t2> 20 mmt1 = smaller thickness in mm of non-continuous platet2 = thickness in mm of continuous platet3 = larger thickness in mm of non-continuous plate

e = 2m + t3- t12

m = misalignmente = eccentricity

Fig. E.4.8-1 Cruciform joints


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E.5 FABRICATION TOLERANCES FOR STRUCTURAL COMPONENTS

E.5.1 I / H- Girders

Type of deviation Figure Nota-

tion

Ref.

Length

Allow % of

ref. length

Max.

Deviation mmLateral or verticaldeflection

5.1-1A f L 0.15 10

Length 5.1-1A L L 0.25 3

Height 5.1-1B H H 0.3 3Width 5.1-1B B B 3Inclination of web 5.1-1B V H 0.8 10

Eccentricity of web

on flange

5.1-1B V1 H 1.0 3

Buckling of web 5.1-1B V3 H 0.75 10

Curvature/rotationflange

5.1-1B V2 B/2 2.5 3

Twisting of section 5.1-1C d 5 L 0.10 10

Fig. E.5.1-1 I-/H-Girders tolerance references


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E.5.2 Box Girders

Type of deviation Figure Notation Ref. Length Allow % of ref. Length

Max Dev.mm

Position deviation at

end/interface section

5.2-1A d1 Ref. Centre

Lines

- 3

Length 5.1-1A L L 0.25 3Height 5.1-1B H H 0.3 3Width 5.1-1B B B 3Out of straightness 5.2-1B d2 L 0.15 10

Buckling of plates 5.2-1C d3 H, W 0.5 10

Pos. deviation of loadbearing stiffeners

inclusive inclination

5.2-1D d4 Ref. CentreLines

- 5

Twisting 5.2-1E d5 H 0,5 6

Fig. E.5.2-1 Box Girders tolerance references


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E.5.3 Tubulars

The allowable tolerance given for individual tubular segments shall not be cumulative for thefinished tubular.

a) Circumference:

The external circumference shall not depart from the nominal external circumference by more thanthe following (Ref. Figure 5.3-1):

Measured at joints or within 610 mm from the joint (Zone A in Figure 5.3-1):of the nominal wall thickness or 10 mm whichever is the smallest.

The tolerances in (i) may be increased by 50% for the remaining length of the tubular (Zone B in

Figure 5.3-1).

b) Out-of Roundness (Ovality):

Ovality is defined as the difference between the measured maximum and minimum internal (or

external) diameters and shall not be more than 1% of the nominal OD (ODn) or 8 mm, whichever isthe least. (Ref. Figure 5.3-2)

c) Out of circularity:

Circularity is defined as the difference between the actual and the average radius, both beeing

determined from the optimum centre of the tubular. Maximum difference is not to be more than0.25% of ODn.

d) Straightness:

The maximum allowable deviation from straightness in any 3 m increment of length shall be 3 mm.The straightness deviation over tube length (L), shall not exceed 0.001 x L, with maximum 10 mmdeviation for lengths up to 12 m. Above 12 m length max. allowable deviation is 12 mm. Out ofstraightness shall be checked on two longitudinal planes separated by 90.

e) Length:

Unless otherwise noted, the tubular shall be delivered within following tolerances:

Unbevelled ends: La Ln+25 mm

Bevelled ends: La = Ln 5 mm

f) Tube ends:

The tube ends shall be perpendicular to the longitudinal axis within the following tolerances:

Unbevelled ends: 5 mm

Bevelled ends: 3 mm


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g) Local out-of roundness:

The local out-of roundness shall not deviate from the theoretical curvature by more than e=0.002 x

ODn(ref. fig. 5.3-3). The local out-of roundness shall be measured inside or outside over 20of the

circumference.

h) Local Out-Of Straightness:

Local straightness is defined as the deviation of the shell plate from a straight generator of length(L) parallel to the true centre line of the tubular. This tolerance shall not exceed 20% of the wallthickness. Local straightness shall be checked on the inside or outside of tubulars with a nominalexternal diameter greater than 2000 mm or with a nominal external diameter to nominal wallthickness ratio greater than 65. These checks shall be carried out at 45intervals of arc with L= 3 m.

Above tubular tolerances apply to welded and not seamless tubulars.

Fig. E.5.3-1 Tubulars - Circumfential tolerance

Fig. E.5.3-2 Tubulars - Ovality tolerance


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Fig. E.5.3-3 Tubulars - Local out-of roundness references


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E.5.4 Panels

Type of deviation Figure Notation Ref. Allow. % Max. dev. mm

PANEL SHEET:

Out of plane straightness,sagging/hogging, betweengirders

5.4-1 p1 W 0.15 15

Local buckles betweenstiffeners 5.4-1 p2 W1 0,5 5

GIRDERS/ STIFFENERS:

Out of straightnessin X and Y direction 5.4-1 g1 W 0.15% 10

Position deviation 5.4-1 g2 Gridsystem 10

Inclination 5.4-1 g3 Hg 0.8 10Out of straightness of webnormal to web(web buckles) 5.4-1 g4 Hg , W1 0.75 10

Fig. E.5.4-1 Deck panels tolerance references


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E.5.5 Girder Nodes

Type of deviation Figure Notation Ref. length Allow % of ref. length

Max. deviationmm

Position deviation ofinterfaces

5.5-1B,5.5-1C

d1 Ref. CentreLine

- 5

Lateral and verticalstraightness of node

5.5-1A f L 0.15 5

Lateral and verticalstraightness of stiffeners

5.5-1A f1 L,H 0.1 5

Height of node 5.5-1B s - - 5

Pos. deviation stiffenersinclusive inclination

5.5-1B,5.5-1C

d2 Ref. CentreLine

- 5

Position deviationcolumn interfaces

5.5-1C d3 Ref.CentreLine

- 5

Baseplate flatness/rotation rel.to Z axis

5.5-1A,5.5-1B

b1 Ref. CentreLine

- 2

Pos.deviation baseplaterelative to Z axis

5.5-1B d4 Ref.CentreLine

- 3

Fig. E.5.5-1 Girder nodes tolerance references


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Fig. E.5.5-1 Girder nodes tolerances


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E.5.6 Box Nodes

Type of deviation Figure Notation Ref. Length Allow of

ref. length

Max. deviation

mmPosition deviation of main boxinterface

5.6-1A d1 Ref. CentreLine

- 3

Out of straightness 5.6-1B d2 L 0,10% 10

Buckling of plates 5.6-1C d3 H, W 0,5% 10

Radial and tangential stub enddeviation

5.6-1C,5.6-1E

d4 Ref. CentreLine

- 5

Pos. deviation of load bearing

stiffeners incl. inclination

5.6-1D d5 Ref. Centre

line

- 5

Offset of centrelines at centreof node

5.6-1E,5.6-1F

d6 Ref. CentreLine

- 5

Fig. E.5.6.1 Box nodes tolerance references


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E.5.7 Tubular Nodes

Type of deviation Figure Notation Ref. length Allow of

ref. length

Max.

deviationmm

Overlength of stub 5.7-1A l2 L2 +25-0

Overlength of node can barrel 5.7-1A l1 L1 +10-0

Stub ends perpendicularity 5.7-1A p - 3

Radial and tangential stub end/node cans position

5.7-2 V Gridsystem

0.2of arc 6

Position of intersection pointnode can / stub

5.7-2 E Grid system

6

Internal stiffeners-Position-Inclination of web-Flange width-Bow of web-Rotation of flange-Eccentricity of flange

on web-Height of stiffeners

5.7-1A5.7-1B5.7-1B5.7-1C5.7-1B

5.7-1B5.7-1B

PMB

N

Lx

hb

1,0%1,5%

1,0%

5

5

3

6

6

6+10/-3Local straightness ofstubs/barrel

5.7-1A Wallthickness

25% 8

Straightness of barrel 5.7-1A L 1/1200 10

The centre line of stub shall be within 0.2from the stub angle specified on the design drawings.Maximum position deviation measured at the intersection of stub end / node can shall be 6 mm.For stubs longer than 1 stub diameter, the position deviation between can and stub may be taken at

the 1 diameter location.

Tolerance for:

Circumference

Out-of Roundness (Ovality)

Local out-of roundness

Out-of circularity

are defined in Section E.5.3


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Fig. A

Fig. B (tolerance references)

Fig. C (tolerance references - internal stiffeners)

Fig. E.5.7-1 Tubular nodes


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Fig. E.5.7-2 Node stub location

E.5.8 Cast and Forged Elements

All relevant tolerances regarding these elements geometry i.e. hole positions, flatness, web and ribpositions shall be specified on the design drawings.

The nominal axes, work points, rib centrelines etc. shall be properly marked on each element

interface(s) to adjacent main steel.


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During installation of cast and forged items, special care shall be taken that the parent plate edgesare located within prepared face of casting / forging.

See also ISO-8062 standard for tolerances.

E.5.9 Curved and cylindrical shell

For elements including curved shells (such as semi submersibles pontoons) special dimensionalprocedures shall be implemented for measurement and computing.

Sylindrical shells.The maximum deviation from the nominal radius, measured at ringstiffeners or at bulkheads shallnot exceed the value:

= | ra- r|


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E.6 ASSEMBLY TOLERANCES

E.6.1 Topsides and modules

Type of deviation Figure Notation Ref. Allowable% of ref.length

Max.deviationmm

Position of any point of mainsteel

6.1-1 X1,Y1 Grid system 10

Position of support node 2) 6.1-1 X2, Y2,Z2

Grid system 6

Position of lifting node 6.1-1 X2, Y2,Z2

Grid system 10

Elevation of decks and mezz.

decks sag./hog.

6.1-1 H1, H2,

H3

Grid system 10

Footings deviation fromelevation reference 1)

6.1-1 H Grid system 5

For truss frames without any defined support points the elevation reference should be based on amean of all levelled points on main steel.

NOTES:1) Maximum allowable deviation shall also apply to mating surface level at stab-in onto

jacket legs.

2) Includes Main Support Frame (MSF) stab-in nodes and module footing nodes.

Fig. E.6.1-1 Topside and module tolerance references


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E.6.2 Jacket and other tubular frame structures

E.6.2.1 Assembly tolerances

Type of deviation Figure Notation Ref. Max. dev. mmPosition deviationof centre of nodes 6.2.1-A

x, y Grid system 12

Rotation of node 6.2.1-A S 6Distance deviation

between two nodes6.2.1-A 20

Diagonal distancebetween coloumnin each hor. plane

12

Position of leg

ring stiffeners anddiaphragms 6Inclination ofringstiffeners 6Straightness oflegs / chords 6.2.1-B/C f L X10

Straightness ofbraces 6.2.1-C f L XL/1000

Position ofintersecting braces Grid system 15

NOTE: Local tolerances for sliding and pivoting ends shall be specified on the structural drawings.


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Fig. E.6.2-1 Jacket and tubular frame structures - assembly tolerances


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E.6.2.2 Final Tolerances for Jacket, Interface Jacket/MSF

Type of deviation Figure Notation Reference Max. dev.mm

Horizontal positiondeviation of centre ofstab-in cans

6.2.2 Vx, VyV =

(Vx+Vy)

Grid system1)

6

8

Jacket:Distance between centreof column to centre ofany column at stab-incans

6.2.2 F L 12

Jacket:Mating surface level atstab-in

Grid system2)

3

MSF:Distance between centreof column to centre ofany column at stab-incans

6.2.2 F L 6

Ovality of stab-in can As in sectionE.5.3b

Horizontal positiondeviation of caissons,risers, J-tube

Grid system 6

NOTES:

1) The position of the stab-in cans shall, if the situation allowes, be related to the top-side stab-in cones with the tolerances stated above.

2) The jacket legs shall by preference be cut within above tolerances after grout is cured.

If survey of the deck footings show out-of acceptable elevation/flatness tolerances, ref. SectionE.6.1, the measured deviations shall be considered incorporated when cutting the legs in order tominimise loads due to differential settlements in footings.


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Fig. E.6.2-2 Final tolerance jacket interface jacket/MSF

E.6.2.3 Guides, Sleeves, Piles and clamps

The position deviation of the centre of pile guides/sleeves shall be 25 mm related to thecoordinate system.Local alignment of sleeves 20 mm.Radius of spacer plates 5 mm.


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E.6.2.4 Piles

Type of deviation Figure Notation Ref. Max. dev.

mm.

Length 100

Diameter betweenspacerplates

6.2.4 d1 As specified ondrawing

Diameter in drivinghead

6.2.4 d2 As specified ondrawing

End perpendicularityin driving head

6.2.4 P As specified ondrawing

Pile markings 50

For general tolerances, see E.5.3 Tubulars.

Fig. E.6.2-4 Piles tolerance references

E.6.2.5 Conductor GuidesThe position deviation of the centre of the conductor guides shall be 10 mm related to thecoordinate system for top el. and 15 mm for the other elevations related to the same coordinatesystem.

The maximum deviation of any conductor guide from the optimised centreline through all conductorguides, shall not vary more than 15 mm.


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E.6.2.6 Appurtenances

Caissons, J-tubes and risers.

Type of deviation Figure Notation Ref. Max.dev. mm

Length - - - 25

E.6.3 Floating production units

E.6.3.1 Semi submersibles and tension leg platforms

Overall hull / substructure tolerances:

Type of deviation Figure Ref. Max. dev. mmGlobal position of column top /

bottom6.3.1-16.3.1-2

Globalgrid system 15

Distance between top / bottomof two columns

6.3.1-16.3.1-2

30

Local position of column top /bottom 6.3.1-3

Localgrid system 5

Fig. E.6.3.1-1 Semi submerisibles / tension leg platforms. Global tolerance


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