M-CR-101r2

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M-CR-101, Rev. 2, January 1996 page 1

NORSOK STANDARD

COMMON REQUIREMENT

STRUCTURAL STEEL FABRICATION

M-CR-101

Rev. 2, January 1996

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.

1 FOREWORD

NORSOK (The competitive standing of the Norwegian offshore sector) is the industry initiative to

add 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 the

NORSOK initiative and are jointly issued by OLF (The Norwegian Oil Industry Association) and

TBL (The 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 use

in existing and future petroleum industry developments, subject to the individual company's review

and application.

The NORSOK standards make extensive references to international standards. Where relevant, the

contents 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Subject to implementation into international standards, this NORSOK standard will be withdrawn.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 and D are normative.

2 SCOPE

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

with SMYS < 500MPa and with a minimum design temperature down to -10C.

Note: For highly fatigue utilized structures, more severe requirements may apply, and these shall be

shown on the design drawings.

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3 NORMATIVE REFERENCES

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 Rules for classification of fixed installations, structures. Part 3, chapter 2,

Fabrication and construction.

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.

prEN 970 Welding - Visual examination of fusion welded joints.prEN 1011 Recommendation for arc welding of ferritic steels.

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.

prEN 1597-1 Welding consumables - testing for classification.

prEN 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 weld metal arising from 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.

NS 477 Welding. Rules for approval of welding inspectors.

M-DP-001 Material selection.

M-CR-120 Material data sheets for structural steel.

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N-CR-001 tructural design.

4 DEFINITIONS AND ABBREVIATIONS

4.1 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 same

functionality and quality are acceptable.

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

Can Can-requirements are conditional and indicates a possibility open to the user of

the standard.

Pcm Carbon equivalent equation

4.2 Abbreviations

AWS American Welding Society

CE Carbon Equivalent

CTOD Crack Tip Opening Displacement

DAC Distance Amplitude Curve

DC Design Class

DIN Deutsche Industrie Normen

DnV Det norske Veritas

EN Euronorm

FSH Full Screen Height

HDM Hydrogen content, deposit metalIIW International Institute of Welding

NDT Non Destructive Testing

MDS Material Data Sheet

PWHT Post Weld Heat Treatment

SMYS Specified Minimum Yield Strength

WPS Welding Procedure Specification

WPAR Welding Procedure Approval Record

5 SELECTION OF STEELS

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5.1 Design classes

The design classes will be decided by the designer and shall form the basis for selection of steel

quality level (SQL). Reference is made to NORSOK standard N-CR-001.Selection of steel quality

level

The steel quality level will be decided by the designer in compliance with N-CR-001. Table 5.1

below is shown for information only.

Annex B gives the correlation between the steel quality levels I, II, III and IV, and designations on

equivalent steels given in NORSOK standard M-CR-120, Material data sheets.

Selection of a better steel quality level in fabrication than the minimum required by the designer

shall not lead to more stringent requirements in fabrication.

Table 5.1: Correlation between design classes and steel quality level (informative)

Steel quality levelDesign class

I II III IV

1 X

2 X

3 (X) X

4 X

5 X

(X) = Selection when there is tensile stress in the direction of thickness.

6 QUALIFICATION OF WELDING PROCEDURES AND WELDERS

6.1 Welding procedure specification (WPS)

WPS shall be established in accordance with EN 288 part 2.

6.2 Qualification of welding procedures

Welding procedures used for structures requiring steel quality level I and II, shall be qualified in

accordance 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 other

workshops 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.

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6.3 Welding procedure approval record (WPAR) - Range of approval

The WPAR is valid within the limitations specified in EN 288 part 3, with the following

clarifications and modifications:

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 mechanical

testing), 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 more than 0.02 Pcm units or 0.03% carbon equivalent (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 shall require a new

qualification test.

d) A change in delivery condition (normalised, thermomechanically controlled processed or

quenched and tempered) shall require a new qualification test.

e) A change in steel supplier, microalloying element or manufacturing technique for steel with

minimum specified yield strength >= 400Mpa.

f) A change in groove angle more than +20deg./-10deg.

g) A qualification of fillet welds carried out on plate thickness equal to or greater than 30mm,

applies for all plate and throat thicknesses. Single layer fillet welds qualifies multi-layer, but not the

converse.

Note: The changes specified in d) and e) need not require re-qualification if HAZ properties for the

material to be welded have been documented from the steel supplier for relevant thicknesses and

heat input ranges. If sufficient documentation from the steel supplier is not available, a change of

material shall require re-qualification of a reduced number of procedures. The number of

procedures to be re-qualified shall be sufficient to verify that the HAZ properties of the new

material is comparable with that used for the previous qualifications.

6.4 Examination of the test weld

6.4.1 General

The type and number of tests shall be in accordance with table 6.1. Testing shall be performed in

accordance with EN 288 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 10.

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Table 6.1 Type and number of tests

Mechanical testingJoint

configuration

Joint

thickness

(mm)Tensile

test

Bend

tests1)

Charpy V-

notch tests2)

Hardness and

macro6)

CTOD

Buttwelds

(Tubulars and

plates)

t < 50

t => 50

2

2

2

2

4 sets

6 sets

1

1

Ref.

6.4.4

T-joints (plates) 5)t < 50

t => 50

4)

4)

4 sets 3)

6 sets

2

2

Tubular joints 5)t < 50

t => 50

4)

4)

4 sets 3)

6 sets

2

2

Fillet welds All 2

Notes:

1. Bend tests shall consist of 1 face and 1 root bend specimen for t < 20mm and 2 side bendspecimens for t >= 20mm

2. One set consists of three test specimens.3. If the dimensions of the joint does not allow Charpy V-notch testing, the Charpy V-notch

properties shall be documented on a butt weld joint made with the same consumable and

same base material, and welding parameters and thickness within the range qualified for the

joint.

4. It shall be documented on a butt weld test that the welding consumable used will havesufficient tensile strength.

5. T-joints on plates qualify for tubular joints, and vice versa.6. For welds on submerged structures with cathodic protection, the hardness limits in

NORSOK M-DP-001 (i.e. max 350 HV10) shall apply in addition to the requirements of EN

288.

6.4.2 Charpy V-notch testing

Sampling of Charpy V-notch impact tests shall be carried out in accordance with prEN 875, withthe notch in the positions listed below. (All specimens shall be machined with the notch through the

thickness, 2 mm below the surface of the material.) (Designation in parenthesis refers to prEN 875).

Notch in centre of weld (VWT 0/2) Notch in fusion line (VHT 0/2) Notch in HAZ, 2mm from fusion line (VHT 2/2) Notch in HAZ, 5mm from fusion line (VHT 5/2)

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For welds with a joint thickness of 50mm or more, two additional sets of Charpy V-notch tests shall

be taken from the root area, with the notch in the following positions:

Notch in centre of weld (VWT 0/b1)) Notch in fusion line (VHT 0/b1))

Note: For single sided welds, the face of the Charpy specimen shall be 2mm from the root face to

the weld. For double-sided welds, the centre of the Charpy specimen shall be positioned in the

centre of the root area.

The test temperature and energy requirements shall comply with table 6.2.

Table 6.2 Charpy impact test temperatures and energy requirements for welding procedure

qualifications.

Steel quality levelI IIMaterial thickness

mmSMYS 400

MPa

SMYS 400

MPa

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

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

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

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

Energy Requirement1)

36J 42J 27J 42JNote:

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

6.4.3 Transverse tensile testing

Testing shall be carried out in accordance with EN 288. The fracture shall be located outside the

weld metal (i.e. max. 20% of the fracture surface shall consist of weld metal).

6.4.4 CTOD testing

CTOD testing shall be included in qualification of welding procedures for joints requiring steel

quality level I and II, with a thickness above 50mm for steels with SMYS < 460MPa, and with a

thickness above 30mm for steels with SMYS > 460MPa.

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It shall be executed on weld assemblies in the actual heat treating condition (PWHT/as-welded)

covering the following combined conditions:

Full penetration buttweld with K-, single V- or X-groove as deemed most representative forthe actual fabrication.

A welding procedure representing the maximum heat input to be used in fabrication. Maximum joint thickness (within 10%).

One (1) such assembly shall be made and tested for each combination of steel grade, each welding

process and each welding consumable (brand) used, except welding consumables used for root

passes only.

The CTOD-technique with the Bx2B, through-thickness notched type specimen according to BS

7448 should be used. Three (3) valid test specimens shall be obtained for each test position.

Note: Test assemblies may be given a precompression and/or hydrogen diffusion treatment prior to

testing.

CTOD-testing of welds shall be carried out with the fatigue notch tip positioned in the coarse

grained region of the heat affected zone and in the weld metal. For HAZ, positioning and

determination of the actual location of the fatigue crack tip shall be performed after testing.

HAZ testing can be omitted if relevant CTOD properties in HAZ have been documented previously

for the base material (i.e. on the same grade of material from the same manufacturer).

CTOD-testing of weld metal can be omitted if relevant CTOD properties in accordance with

requirements above have been documented previously.

Test temperature shall be:

-10C for splash zone and above. 0C for submerged parts.

The required CTOD value has to be decided in each case, based on a fracture mechanics evaluation

for the particular structure. When the minimum single CTOD-value at the required temperature

exceeds 0.25 mm (0.20 mm for welds with PWHT), the test series is normally acceptable without a

detailed fracture mechanics evaluation.

CTOD testing should also be performed when required for fitness for purpose evaluations according

to 10.8.6.

6.5 Welder and welding operators qualifications

The 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 with

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

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For welding of joints where steel quality level IV is required, a certificate for welding of plates in

position PE is sufficient for welding all product forms.

7 FABRICATION AND WELDING REQUIREMENTS

7.1 General

All welding work shall be according to recommendations given in prEN 1011. The manufacturer

shall have a quality system, which fulfil the relevant part of EN 729 and the applicable level of EN

719.

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

reference in all documentation.

7.2 Forming

Cold forming of steel (i.e. forming below 250C) shall be carried out within the deformation range

recommended by the steel manufacturer. For steel quality level I and II, the deformation limit

without 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 plus

artificially aged condition. The notch shall be located within the plastically strained portionof the material, 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 and strain ageing.

If forming is performed at temperature above 250C, it shall be documented that the base material

properties, weldability, weldmetal and HAZ properties satisfy the actual MDS and this standard.

The percentage strain due to forming is defined as follows:

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7.3 Manufacturing of welded tubulars

Manufacturing of welded tubulars shall be carried out to a qualified procedure which satisfies the

requirements in API 2B and this standard. The procedure shall contain the following information:

Sequence of operation. Equipment to be used. Cold rolling method. Methods for avoiding "flats" along the longitudinal seam. Method for avoiding local thinning, steps or wavy edges. Welding procedure. Visual inspection and NDT. Mechanical testing. Splices. Dimensional inspection and acceptance criteria, both at tubular ends and intermediate

sections.

7.4 Assembly

7.4.1 General

In tubular joints, circumferential and longitudinal weld joints should not be placed in the shaded

areas shown in fig. 7.1.

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W1 = 150mm or min. 2 times chord thickness

W2 = 300mm or min. D/4

W3 = 600mm or min. D

Fig. 7.1 Prohibited location of welds in tubular joints. Longitudinal or circumferential welds shall

not be located in shaded area.

7.4.2 Splices

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

7.4.3 Tapering

Tapering shall be in accordance with the requirements given in relevant standards or drawings. If no

other requirements are specified, a tapering of 1:4 should be used.

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7.4.4 Bolting connection

Bolting material shall comply with requirements in NORSOK standard M-DP-001, Material

selection. Holes shall be made by machine drilling.

7.4.5 Seal/blind-compartments.

Crevices and areas which become inaccessible after fabrication or assembly shall be sealed off from

the outside atmosphere. Seal welds shall have a throat thickness of at least 3mm. Where steel items

shall be hot dip galvanised, hollow sections shall be ventilated.

7.4.6 Temporary cut-outs

Temporary 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 100mm. Temporary cut-outs shall be closed by

refitting the same or an equivalent plate and employing the same welding, inspection and

documentation procedures and requirements that govern the structural part in question.

7.4.7 Straightening of structural members

Members 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 the

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

7.4.8 Doubler plates

All temporary attachments which shall be flame cut or welded under water shall be attached to the

structure by using doubler plates.

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

7.5 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 design drawings.

7.6 Preparation and fit-up of weld bevels

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

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

7.7 Welding processes

The welding processes listed in EN 288 are acceptable.

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7.8 Welding consumables

The 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

welding procedure qualification, 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 annex C.

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

i.e. HDM

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7.10 Production welding

7.10.1 General

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

Butt welds in joints where steel quality level I or II 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 1 /2 V-butt weld grooves shall

have a groove angle of at least 10O , 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.)

7.10.2 Attachments

Temporary 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 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 are

attached. Temporary attachments shall be flame cut minimum 3mm from the base metal and

ground. The ground area shall be visually examined and magnetic particle inspected.

7.11 Post weld heat treatment (PWHT)

PWHT shall be required for structural welds where steel quality level I or II are required, when the

nominal thickness (as defined in EN 288-3, section 8.3.2.1) exceeds 50mm, unless adequate 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 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 shall

be at least 2.5 min per mm thickness (of the thickest member).

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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.

7.12 Grinding

When grinding is specified on design drawings or is instructed as a corrective action, the grinding

shall be performed according to a detailed procedure. Grinding tools, direction, surface roughness

and 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.

8 PRODUCTION TESTS

Production testing should be conducted on weldments performed in critical regions to verify that the

specified requirements have been meet.

For welds where steel quality level I or II are required, 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 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 action

implemented.

9 FABRICATION TOLERANCES

Fabrication tolerances shall be in accordance with relevant standards and/or drawings issued for

fabrication.

10 NON-DESTRUCTIVE TESTING (NDT)

10.1 General

The inspection category shall be decided by the designer in accordance with NORSOK N-CR-001

,and shall be specified on the design drawings.

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

completion except where PWHT is required. The time delay may be reduced to 24 hours for steel

grades 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 materials

and welding consumables in question. When PWHT is performed, the final NDT shall be carried

out when all heat treatment have been completed.

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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, the

system must ensure that a correct rate identification is prepared for each weld method, each NDT

method and each production area.

The defect rate is defined as:

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.

10.2 Qualification of inspectors and NDT-operators

The NDT operators shall be qualified according to EN 473 level 2. Level 2 operators may whenrelevant be assisted by level 1 operators.

Ultrasonic operators used in testing of tubular joints shall satisfy the requirements in API RP 2X,

para 2.3. (NOTE: UT operators with EN 473 Level 2 qualifications who are testing tubular joints

according to the requirements of API RP 2X, requires no further qualification tests, but shall be

conversent with the content of the API RP 2X standard.)

Personnel qualified according to EN 473 Level 3 shall be responsible for all NDT activities.

Personnel responsible for visual inspection shall be qualified in accordance with NS 477 or an

equivalent scheme.

10.3 Extent of visual examination and NDT

The required minimum extent of examination is given in table 10.1.

Ultrasonic testing to reveal the presence of possible weld metal transverse cracking shall be

included for butt welds with thickness more than 25 mm. The examination shall be performed on

minimum 5% of welds in inspection category A and B for SAW and FCAW.

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Table 10.1 Minimum extent (in %) of non-destructive examination for structural welds.

Extent oftestingInspection category Type of connection Visual examination

RT UT MT

AButtw.T-conn.

Fillet/partial

100100

100

10-

-

100100

-

100100

100

BButtw.

T-conn.

Fillet/partial

100

100

100

Spot

-

-

50 1)

50 1)

-

100 1)

100 1)

100 1)

CButtw.

T-conn.

Fillet/partial

100

100

100

-

-

-

20 1)

20 1)

-

20 1)

20 1)

20 1)

DAll conn. 100 - - spot

E All conn. 100 - - -

Legend -

RT = Radiographic testing

UT = Ultrasonic testing

MT = Magnetic particle testing

Spot means approximately 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 10.1 and 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 testing

confirms consistent good workmanship.

The extent of NDT shall be increased if repeated occurrence of cracks or other significant weld

defects are revealed. Corrective actions shall be taken to ensure that all similar defects will be

detected.

In addition to what is listed in table 10.1, 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 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 10mm. For such

thicknesses, 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 40mm.

e) MT shall be performed on both external and internal surface as accessible.

10.4 Visual examination and finish of welds

The visual examination shall be carried out in accordance with prEN 970.

10.5 Radiographic testing

Radiographic testing shall be carried out in accordance with ASME Section V, article 2; or EN 444.

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

Penetrameters of wire type (according to EN 462-1) shall be utilised. Sensitivity level shall be in

accordance with EN 462 part 3, Class A. However, if gamma ray sources are used, the sensitivity

shall be 2% or better.

10.6 Ultrasonic testing

Ultrasonic testing of welds in plate and tubular butt welds shall be performed in accordance with

ASME V Article 5, T-542.7. Ultrasonic testing of tubular joints (nodes) shall be performed in

accordance with API RP 2X.

DAC reference curves shall be produced from reference block of thicknesses, and containing side-

drilled holes with diameters, in accordance with table 10.2. DAC curves shall be produced in

accordance with ASME V Article 4, Appendix B-20 and C-20.

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The effective test range of a DAC curve shall be determined by the point at which the curve has

fallen 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 or

thermomechanical treatment, blocks shall be produced both perpendicular to, and parallel to, thedirection 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

actual 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 body

and heat affected zones are examined for longitudinal defects in accordance with ASME V, Article

5,

T-542.7.2.3.

All indications exceeding 20% DAC shall be investigated to the extent that they can be evaluated in

terms of the acceptance criteria.

All indications exceeding 50% DAC and having any dimension exceeding 5mm shall be reported,

unless more stringent requirements are given in table 10.5.

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

indication.

10.7 Magnetic particle testing

Magnetic particle testing shall be carried out in accordance with prEN 1290. Magnetic yokes using

alternating current shall be used. Prods are acceptable where the geometry of the welded joint

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

10.8 Acceptance criteria

10.8.1 General

All welds shall comply with the requirements given below, in 10.8.2 - 10.8.5.

10.8.2 Visual examination

All welds shall show evidence of good workmanship. The quality shall comply with the

requirements of table 10.3.

10.8.3 Radiographs

The soundness of the welded joint shall comply with the requirements of table 10. 4.

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10.8.4 Ultrasonic testing acceptance criteria

The acceptance criteria for welds shall comply with table 10.5, except that the acceptance criteria

for tubular joints shall comply with API RP 2X level C, unless more stringent requirements are

specified by the designer.

Table 10.2Calibration reference block requirementsThickness of material to be

examined (mm)Thickness of

block

Diameter of

holeDistance of hole from one surface

10 < t < 50 40 or t

50 < t < 100 75 or t

3mm +/-

0.2mm

100 < t < 150 125 or t

150 < t < 200 175 or t

200 < t < 250 225 or t

t > 250 275 or t

6mm +/-

0.2mm

t/2 and t/4. Additional holes

areallowed and recommended

Table 10.3 Visual acceptance criteria for structural steel welds

Welding Acceptance criteria

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

Lack of penetration or

lack of fusionNot acceptable

Single - side weld:

Length < t/2, max 10mm

Defects shall be regarded as a continuous

defect if the distance between them is

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Misalignment of butt

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

smaller.

Reinforcement of butt

welds (fig. 3) 1)

"t" less or equal to 10 Max reinforcement "C" 2mm

"t" greater than 10, up to 25 Max reinforcement "C" 3mm

"t" greater than 25, up to 50 Max reinforcement "C" 3mm

"t" greater than 50 Max reinforcement "C" 5mm

Reinforcement of

fillet/partial pen. welds

(fig.4) 1)

"a" less or equal to 10 Max reinforcement "C" 2mm

"a" greater than 10, up to 15 Max reinforcement "C" 3mm

"a" greater than 15, up to 25 Max reinforcement "C" 4mm

"a" greater than 25 Max reinforcement "C" 5mm

Symmetry of fillet welds

(fig. 5)

"a" less or equal to 6 Max difference, b - h: 3mm

"a" greater than 6, up to 13 Max difference, b - h: 5mm

"a" greater than 13 Max difference, b - h: 8mm

Grinding arc strikes etc.

Removal of temporary

attachments 2)

Grinding of base material shall not exceed 7% of the wall thickness or

max. 3mm. Repair welding and inspection shall be performed if

removal of the base metal exceeds the specified requirements.

Sharp edges Minimum 2 mm radius (Ref. 7.5)

Notes:

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

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

3. When required (ref. 7.12), grinding of the surface shall be specified. Typical examples ofgrinding requirements are given in annex A.

Figure 1 Roughness of weld Figure 2 Misaligment of butt weld

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Figure 3 Reinforcement of butt weld Figure 4a Reinforcement of fillet weld

Figure 4b Reinforcement of partial pen weld Figure 5 Symmetri of fillet weld

Table 10.4 Structural steel welds, Radiographic acceptance criteria

Inspection categoryType of defect

A, B C, D, E

Internal porosity (Note 1)

Isolated:Pore diameter

max t/4,butmax.6mm

max t/3, butmax.6mm

Cluster:

Pore diametermax.3mm max .4mm

Piping porosity:

Length of projected areamax.25mm max. 30mm

Scattered:

Accumulated pore diameters in any 10x150mm area

of weldmax.20mm max. 25mm

Slag inclusions (Note 2)Width

t/4, max .6mm2t, max 50mm

t/3, max. 6mm4t, max. 100mm

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Length

Lack of penetration

Length (Note 2)t, max. 25 mm 2t,max 50 mm

Lack of fusion

Length (Note 2) Not acceptable 2t, max.50mm

Cracks Not acceptable Not acceptable

Notes:

1. If more than one pore is located inside a circle of diameter 3 times the pore diameter, thepores are to be considered as a cluster.

2. Defects in a line where the distance between the defect is shorter than the longest defectshall be regarded as one continuous defect.

Table 10.5 Ultrasonic acceptance criteria for weld defects

DescriptionInspection category

A + B

Inspection category

C, D, ENotes

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

shall be repaired when the length exceeds 10mm and the echo height

exceeds the reference curve.

1

2

3

4

Cracks Unambiguous cracks are unacceptable regardless of size or amplitude.

Lack of fusion orincomplete

penetration

Internal defects :

I: The echo height exceeds the reference curve:

Max length t, Max length 2t,

max 25mm max 50mm

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

Max length 2t, Max length 4t,

max 50mm max 100mm

Surface defects are not acceptable except:

For root defects in single sided welds , the max length for which the

echo height exceeds the reference curve shall be:

Max length t, Max length 2t,

max 25mm max 50mm

12

3

4

5

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Slag inclusions When echo height exceeds the reference curve:

Max length 2t, Max length 4t,

max 50mm max 100mm

1

2

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 the welding

process, signal geometry, defect position etc.

2. If elongated defects are situated on line and the distance between them is less than the lengthof 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 (fordefects larger than the beam) or by the maximum amplitude technique (for defects smallerthan 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 6mm from thenearest surface. A defect is classified as a "surface defect" if any part of the defect is located

less than 6 mm or t/4, whichever is smaller, from the nearest surface.

10.8.5 Magnetic particle testing

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

be evaluated in accordance with the requirements of table 10.3.

10.8.6 All methods

All defects shall be repaired according to clause 11.

Defects may be accepted by the relevant parties when repair work is considered detrimental to the

total integrity of the weld. Such acceptance shall be based on a fitness for purpose evaluation in

accordance with BSI PD6493, DnV RP D404 or other recognised methods.

11 REPAIR

11.1 Defintions

Weld discontinuities: Irregularities in the body of the weld or on the weld surface classified as

either weld imperfection or as weld defect.

Weld imperfection: Discontinuities that are within the acceptance criteria defined in clause 10 and

are considered to have no practical limitations on the intended use of the product. Weld

imperfections may be left without remedial work. Cosmetic grinding may be performed at thediscretion of the fabricator.

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

clause 10.

11.2 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. If necessary, the defective part of the weld shall be cut out for further examination.

Crater cracks may be repaired by grinding followed by NDT and subsequent repair welding

according to an accepted 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 the

base material shall be smooth. Removal of defects shall be verified by local visual inspection, aided

by applicable NDT methods. If applicable, the remaining thickness in the ground area shall be

measured. Repair welding is required if the remaining thickness is less than that specified.

11.3 Repair by welding

11.3.1 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 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 for

the original weld.

The excavated groove shall be minimum 50mm long, measured at defect depth even if the defect

itself is smaller. Defects spaced less than 100mm shall be repaired as one continuous defect.

After repair welding the complete weld (i.e. the repaired area plus at least 100mm 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.

11.3.2 Re-welding

Re-welding shall be performed in accordance with the procedures and WPS utilised for the original

weld, and includes complete removal of the original weld and HAZ.

11.4 Repair welding procedure

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

a separately qualified procedure.

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For repairs using a different process, and/or consumable, a separate WPS shall be qualified if

required by 6.2. Mechanical testing may be limited to HAZ Charpy V-notch testing in the original

weld, provided the process/consumable is backed up by other WPAR's.

11.5 Correction of distortion

Improperly 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

requirement in clause 7.

ANNEX A TYPICAL PERFORMANCE FOR GRINDING

OF WELDS (INFORMATIVE)

TYPICAL GRINDING DETAILS FOR HIGH FATIGUE UTILISATION

TYPICAL TUBULAR JOINT GRINDING DETAIL

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TYPICAL 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 andextended below the plate surface in order to remove the toe defects.

2. Grinding should extend below plate surface to a minimum of 0.5mm below the bottom ofany 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 should be inspectedwith 100% visual examination and 100% MP1.

5. Ground surface shall be free of any cracks or cracklike indications, and there shall be noevidence of undercut or overlap.

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ANNEX B CORRELATION BETWEEN STEEL QUALITY

LEVEL, MDS NUMBER AND STEEL

GRADE/DESIGNATIONS (NORMATIVE)

Steel quality

level

NORSOK MDS

No.1)

Reference

standardProduct type Steel grade

I

Y20

Y21

Y22

Y30

Y31

Y32

Y40Y41Y42Y50Y51Y52

prEN 10225

Plates

Rolled sections

Seamless

tubulars

Plates

Rolled sections

Seamless

tubulars

Plates

Rolled sectionsSeamless

tubularsPlatesRolled sectionsSeamless

tubulars

S355NLO5

S355NLO5

S355NLO5

S420QLO4S420QLO4

S420QLO2

(mod.)

S460QLO4

S460QLO4S460QLO2 (mod)

S500QLO4S500QLO4S500QLO4

II

Y25Y26Y27Y35Y36Y37Y45Y46Y47Y55Y56Y57

prEN 10225

PlatesRolled sectionsSeamless




tubulars

S355NLO3S355NLO3S355NLO3S420QLO2S420QLO2S420QLO2S460QLO2S460QLO2S460QLO2S500QLO2S500QLO2S500QLO2

III Y03EN 10025EN 10025

prEN 10225

PlatesRolled sectionsSeamless

tubulars

S355J2G3S355J2G3

NO1

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Y01 EN 10025

PlatesRolled sectionsSeamless tubulars

S235JRG2

IV

Y02 EN 10025 PlatesRolled sectionsSeamless tubulars

S275JR

NORSOK Material data sheets are in NORSOK standard M-CR-120.

ANNEX C QUALIFICATION OF WELDING

CONSUMABLES BY DATA SHEETS (NORMATIVE)

C.1 SCOPE

The purpose of certification is to verify that each batch of consumables has a chemical composition

within 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 the

weld 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 supplier

under one unique 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 (GTAW, GMAW, SAW), originating from the same heat, where one diameter may

represent all.

C.2 DATA SHEET

Each welding consumable or combination of consumables shall have a unique data sheet, issued as

a 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 be

documented in PWHT condition in addition to the as-welded condition.

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Specifically this shall include, as applicable:

Chemical analysis limits for solid wires and metal powders. For information also typicalweld metal 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 wireor strip.

The analysis shall include limits for all elements specified in the relevant classification standard

and/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.

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,

notch toughness Charpy-V at -40C. For information also typical properties of a relevant

butt weld should be added.

Diffusible hydrogen content HDM max., including any information on drying, restrictedwelding parameters etc. required to ensure this value in practice.

When relevant for the product, basic information about CTOD properties, to be supportedby separate 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 a

minimum the specific tested chemical composition of the wire or weld metal, as applicable. The

chemical elements shall conform to those of the data sheets, with a statement "below specified

maximum" 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 the

accepted 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 SCOPE

The purpose of the batch testing is to verify that the consumables remains nominally equivalent to

that 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 supplier

under one unique 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 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,

nominal batch 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, deposited

according 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 tested

according 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.

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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.

Documents

M-CR-101r2