NORSOK Structural Steel Fabrication M-101

NORSOK STANDARD

STRUCTURAL STEEL FABRICATION

M-101 Rev.4. Dec. 2000

This NORSOK standard is developed by NTS with broad industry participation. Please note that whilst every effort has been made to ensure the accuracy of this standard, neither OLF nor TBL or any of their members will assume liability for any use thereof. NTS is responsible for the administration and publication of this standard. Norwegian Technology Center Oscarsgt. 20, Postbox 7072 Majorstua N-0306 Oslo, NORWAY Telephone: + 47 22 59 01 00 Fax: + 47 22 59 01 29 Email: [email protected] Website: http://www.nts.no/norsok Copyrights reserved

Structural steel fabrication

M-101 Rev. 4, Dec. 2000

CONTENTS FOREWORD INTRODUCTION

3 3

1 SCOPE

4

2 NORMATIVE REFERENCES

4

3 DEFINITIONS AND ABBREVIATIONS 3.1 Definitions 3.2 Abbreviations

5 5 5

4 SELECTION OF STEELS 4.1 Design classes 4.2 Selection of steel quality level

6 6 6

5 QUALIFICATION OF WELDING PROCEDURES AND WELDERS 5.1 Welding procedure specification (WPS) 5.2 Qualification of welding procedures 5.3 Welding procedure approval record (WPAR) - Range of approval 5.4 Examination of the test weld 5.5 Welder and welding operators qualifications

6 6 6 7 8 11

6 FABRICATION AND WELDING REQUIREMENTS 6.1 General 6.2 Forming 6.3 Assembly 6.4 Preparation for coatings 6.5 Preparation and fit-up of weld bevels 6.6 Welding processes 6.7 Welding consumables 6.8 Preheat and interpass temperature 6.9 Production welding 6.10 Post weld heat treatment (PWHT) 6.11 Grinding 6.12 Peening

11 11 11 12 13 13 13 14 14 15 16 16 16

7 PRODUCTION TESTS

17

8 FABRICATION TOLERANCES

17

9 NON-DESTRUCTIVE TESTING (NDT) 9.1 General 9.2 Qualification of inspectors and NDT-operators 9.3 Extent of visual examination and NDT 9.4 Visual examination and finish of welds 9.5 Radiographic testing 9.6 Ultrasonic testing 9.7 Magnetic particle and Penetrant testing 9.8 Acceptance criteria

17 17 18 19 21 21 21 22 22

10

REPAIR

28

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Structural steel fabrication 10.1 10.2 10.3 10.4 10.5

M-101 Rev. 4, Dec. 2000

Definitions Correction of welds containing defects Repair by welding Repair welding procedure Correction of distortion

28 28 28 29 29

ANNEX A 1 - TYPICAL GRINDING DETAILS FOR HIGH FATIGUE UTILISATION (INFORMATIVE)

30

ANNEX A 2 - TYPICAL PEENING DETAILS FOR HIGH FATIGUE UTILISATION (INFORMATIVE)

31

ANNEX B - CORRELATION BETWEEN STEEL QUALITY LEVEL, MDS NUMBER AND STEEL GRADE/DESIGNATIONS (NORMATIVE) 33 ANNEX C - QUALIFICATION OF WELDING CONSUMABLES BY DATA SHEETS (NORMATIVE)

34

ANNEX D - WELDING CONSUMABLE DOCUMENTED BY BATCH TESTING (NORMATIVE) ANNEX E FABRICATION TOLERANCES (NORMATIVE)

36 37

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M-101 Rev. 4, Dec. 2000

FOREWORD NORSOK (The competitive standing of the Norwegian offshore sector) is the industry initiative to add value, reduce cost and lead time and eliminate 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 supported by OLF (The Norwegian Oil Industry Association) and TBL (Federation of Norwegian Manufacturing Industries). NORSOK standards are administered and issued by NTS (Norwegian Technology Center). The purpose of NORSOK standards is to contribute to meet the NORSOK goals, e.g. to develop standards that ensure adequate safety, value adding and cost effectiveness and thus are used in existing and future petroleum industry developments. The NORSOK standards make extensive references to international standards. Where relevant, the contents of a NORSOK standard will be used to provide input to the international standardisation process. Subject to implementation into international standards, the NORSOK standard will be withdrawn. Annex A is informative. Annexes B, C, D and E are normative.

INTRODUCTION Revision 4 of this standard has been necessary due to regulations in new design standard N 004 and new designation of steel grades. In addition a steel grade with SMYS 690 is introduced with additional requirements to fabrication.

NORSOK standard

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1

M-101 Rev. 4, Dec. 2000

SCOPE

This standard covers the requirements for fabrication and inspection of offshore steel structures with SMYS < 500 MPa and with a minimum design temperature down to -14°C. For special application steels with SMYS up to 690 MPa may be used. Note: For highly fatigue utilized structures, more severe requirements may apply, and these will be shown on the design drawings.

2

NORMATIVE REFERENCES

The 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 otherwise agreed. Other recognized standards may be used provided it can be shown that they meet or exceed the requirements of the standards referenced below. API 2B API RP 2X ASME, Section V

Specification for fabricated structural steel pipe. Ultrasonic examination of offshore structural fabrications. Non-destructive testing.

BS 7448, Part 1 BS 7910

Fracture mechanics toughness tests. Guide on methods for assessing the acceptability of flaws in fusion welded structures.

DNV RP D404

Unstable fracture.

EN 287-1 EN 288-series

Approval testing of welders - Fusion welding. Specification and qualification of welding procedures for metallic materials. NDT - General principles for radiographic examination of metallic materials by X-rays and gamma rays. NDT - Image quality of radiographs. Qualification and certification of NDT personnel - General principles. Welding coordination - Tasks and responsibilities. Quality requirements for welding - Fusion welding of metallic materials. Welding - Welded joints in metallic materials - Specimen location and notch orientation for impact tests. Welding - Visual examination of fusion welded joints. Welding - Recommendation for welding of metallic materials, relevant parts. Non destructive examination of welds - Penetrant testing of welds Acceptance levels. NDT of welds - Magnetic particle examination of welds - .

EN 444 EN 462-series EN 473 EN 719 EN 729-series EN 875 EN 970 EN 1011-series EN 1289 EN 1290

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Structural steel fabrication EN 1291 EN 1418 EN 1435 EN 1597-1 EN 1714 EN 10204 prEN 10225 EN 26847 ISO 3690

M-101 Rev. 4, Dec. 2000 NDT of welds - Magnetic particle examination of welds - Acceptance levels. Welding personnel - Approval testing for fully mechanised and automatic welding. Non destructive examination of welds - Radiographic examination of welded joints. Welding consumables - Test methods - Part 1: Test piece for all weld metal test specimens in steel, nickel and nickel alloys. Non destructive examination of welds - Ultrasonic examination of welded joints. Metallic products - Types of inspection documents. Weldable structural steels for fixed offshore structures. Covered electrodes for manual metal arc welding. Deposition of a weld pad for chemical analysis.

ISO 5817 (=EN 25817)

Welding - Determination of hydrogen indeposited weld metal arising from the use of covered electrodes for welding mild and low alloy steels. Arc welded joints in steel - Guidance on quality levels for imperfections.

NORSOK M-001 NORSOK M-120 NORSOK N-001 NORSOK N-004 NS 477

Material selection Material data sheets for structural steel Structural design Design of steel structures Welding. Rules for approval of welding inspectors.

3

DEFINITIONS AND ABBREVIATIONS

3.1 Definitions Normative references Informative references Shall Should May Can

Shall mean normative in the application of NORSOK standards. Shall mean informative in the application of NORSOK standards. Shall is an absolute requirement which shall be followed strictly in order to conform with the standard. Should is a recommendation. Alternative solutions having the same functionality and quality are acceptable. May indicates a course of action that is permissible within the limits of the standard (a permission). Can is conditional and indicates a possibility open to the user of the standard.

3.2 Abbreviations AWS American Welding Society BS British Standard CE Carbon Equivalent equation CTOD Crack Tip Opening Displacement DAC Distance Amplitude Curve DC Design Class DIN Deutsche Institut für Normung NORSOK standard

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Structural steel fabrication DNV EN (pr EN) FCAW FSH HAZ HDM IIW ISO NDT MDS MSF Pcm PWHT SAW SMYS SQL WPS WPAR

4

M-101 Rev. 4, Dec. 2000 Det Norske Veritas European Standard (proposal for EN) Flux Cored Arc Welding Full Screen Height Heat Affected Zone Hydrogen content, deposit metal International Institute of Welding International Organization for Standardization Non Destructive Testing Material Data Sheet Module Support Frame Carbon equivalent (Parameter for crack, modified) Post Weld Heat Treatment Submerged Arc Welding Specified Minimum Yield Strength Steel Quality Level Welding Procedure Specification Welding Procedure Approval Record

SELECTION OF STEELS

4.1 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-004. 4.2 Selection of steel quality level The steel quality level will be decided by the designer in compliance with N-004. 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-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.

5

QUALIFICATION OF WELDING PROCEDURES AND WELDERS

5.1 Welding procedure specification (WPS) WPS shall be established in accordance with EN 288 part 2. 5.2 Qualification of welding procedures Welding procedures used for structures requiring steel quality level I and II for all strength levels and steel quality level III for SMYS ≥ 355 MPa shall be qualified in accordance with 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. NORSOK standard

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Structural steel fabrication 5.3

M-101 Rev. 4, Dec. 2000

Welding procedure approval record (WPAR) - Range of approval

5.3.1 For welding of steels with SMYS ≤500 MPa 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 testing have 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 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 groove angle more than +20 deg./-10 deg. g) A qualification of fillet welds carried out on plate thickness equal to or greater than 30 mm, applies for all plate and throat thicknesses. Single layer fillet welds qualifies multi-layer, but not the converse. h) CTOD testing shall be included in the qualification of welding procedures for weldments with a plate thickness above 50 mm for all strength levels for steel quality level I and II and for SMYS >400 MPa for steel quality level III. CTOD testing shall be included in the qualification of welding procedures for weldments with a plate thickness below and equal 50 mm if requested by the designer for the specified steel quality level. Testing shall be executed from as welded and PWHT weld assemblies as applicable, covering the following combined conditions: • • •

Full penetration buttweld with K-, or half V -groove as deemed most representative for the actual 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 manufacturer, welding process and welding consumable (brand) used, except welding consumables used for root passes only, provided these are removed completely by gouging and grinding. 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 manufacturer for relevant thicknesses and heat input ranges. If sufficient documentation from the steel manufacturer 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.

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M-101 Rev. 4, Dec. 2000

5.3.2 For welding of steels with SMYS >500MPa In addition to the requirements given in 5.3.1 the following additional requirements apply for welding of steels with SMYS >500 MPa a) b) c) d)

5.4

A change in steel manufacturer. CTOD testing as described in 5.3.1 h) shall be executed for thicknesses above 30 mm Stress relieving if required/specified by designer When the steel to be welded has a Pcm ≥ 0,21 or a carbon content ≥ 0,13, then an increase of more than 0,03 Pcm or 0,04 carbon equivalent units (IIW formula) over the value of the approval test shall require a new qualification test. Examination of the test weld

5.4.1 General The type and number of tests shall be in accordance with table 5.1. 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 9.

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M-101 Rev. 4, Dec. 2000

Table 5.1 Type and number of tests

Joint configuration Buttwelds (Tubulars and plates) T-joints (plates) 4) Tubular joints

Joint thickness (mm) t<50 t≥50

4)

Fillet welds

t<50 t≥50 t<50 t≥50 All

Mechanical testing Tensile Bend test tests 1) 2 2

2 2

3) 3) 3) 3)

Charpy V-notch tests 4 sets 6 sets

Hardness and macro 5) 1 1

4 sets 2) 6 sets 4 sets 2) 6 sets

2 2 2 2 2

CTOD Ref. 5.3.1h and 5.4.4

Notes: 1. Bend tests shall consist of 1 face and 1 root bend specimen for t < 20 mm and 2 side bend specimens for t ≥ 20 mm 2. If the dimensions of the joint does not allow Charpy V-notch testing, the Charpy Vnotch 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. 3. It shall be documented on a butt weld test that the welding consumable used will have sufficient tensile strength. 4. T-joints on plates qualify for tubular joints, and vice versa. 5. For welds on submerged structures with cathodic protection, the hardness limits in NORSOK M-001 (i.e. max 350 HV10) shall apply in addition to the requirements of EN 288. For SMYS 690 MPa max 400 HV10 shall apply. 5.4.2 Charpy V-notch testing Sampling of Charpy V-notch impact tests shall be carried out in accordance with EN 875, with the 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 EN 875). • • • •

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

For welds with a joint thickness of 50 mm 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/b) • Notch in fusion line (VHT 0/b) The test temperature and energy requirements shall comply with table 5.2.

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Structural steel fabrication Table 5.2

M-101 Rev. 4, Dec. 2000

Charpy impact test temperatures and energy requirements for welding procedure qualifications.

Material thickness mm

t ≤ 12 12 < t ≤ 25 25 < t ≤ 50 t > 50 Energy Requirement 1)

Steel quality level I SMYS 400< ≤400 SMYS≤ 500 0°C -20°C -20°C -40°C -40°C -40°C -40°C -40°C 36J 42J

SMYS >500

SMYS ≤400

-20°C -40°C -40°C -40°C 60J

0°C 0°C -20°C -40°C 27J

II 400< SMYS≤ 500 -0°C -20°C -40°C -40°C 42J

III SMYS >500 -20°C -40°C -40°C -40°C 60J

355≤ SMYS ≤500 -0°C 0°C -20°C -40°C 27J

SMYS >500 0°C -20°C -40°C -40°C 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 specimens shall be: 7,5 mm - 5/6 and 5 mm - 2/3. 5.4.3 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/HAZ). 5.4.4 CTOD testing The CTOD- technique with the Bx2B through-thickness notched type specimen according to BS 7448 Part 1 should be used. Three valid test specimens shall be obtained for each test position. CTOD-testing of welds shall be carried out with the fatigue notch tip positioned in the coarse grained region of the heat affected zone and in the weld metal. For HAZ, determination of the actual location of the fatigue crack tip shall be performed after testing. Ref. is made to prEN 10225. Note: Test assemblies may be given hydrogen diffusion treatment prior to testing, and specimens may be precompressed. If not specified otherwise, the test temperature for design temperature down to -14 °C shall be: -10 °C for splash zone or above. 0 °C for submerged parts. Other test temperature may be prescribed by the designer. Three (3) valid test specimens shall be obtained for each notch location. The requirement for minimum CTOD value shall be prescribed by the designer. If not specified, the requirement for minimum CTOD value shall be as for the steel purchase order. CTOD-testing of HAZ can be omitted if relevant CTOD properties in HAZ have been documented previously in accordance with requirements in this standard, provided the requirements for the essential variables are met.

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M-101 Rev. 4, Dec. 2000

CTOD-testing of weld metal can be omitted if relevant CTOD properties in WM have been documented previously in accordance with requirements in this standard, provided the requirements for the essential variables are met. The required fracture toughness level shall be decided in design for joints when steel quality level I and II are required. Testing is normally not requested for structures with plate thickness below 40 mm for SMYS≤500 MPa or for structures with plate thicknes below 25 mm for SMYS>500 MPa. 5.5 Welder and welding operators qualifications The welders, welding operators and tack welders shall be qualified in accordance with EN 287, EN 1418 or equivalent. For tack welders, an internal test may be used. For welding of single sided acute angled tubular joints with α < 70º, welders shall be qualified with a realistic joint, representing the minimum angle α to be used in production. For welding of joints where steel quality level IV is selected, a certificate for welding of plates in position PE is sufficient for welding all product forms.

6

FABRICATION AND WELDING REQUIREMENTS

6.1 General All welding work shall be according to recommendations given in relevant part of EN 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. 6.2 Forming Cold forming of steel (i.e. forming below 250°C) 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 250°C 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 portion of 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.

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M-101 Rev. 4, Dec. 2000

If forming is performed at temperature above 250°C, 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: Percent strain = 6.3

Wall thickness x 100% Forming mid thickness diameter

Assembly

6.3.1 General In tubular joints, circumferential and longitudinal weld joints should not be placed in the shaded areas shown in fig. 6.1, unless otherwise shown on design drawings. W1

W1

W1

W1

W2

W2

W2

W2

W

3

D

Longitudinal welds

Circumferential welds

W1 = 75 mm or min. 2 times chord thickness W2 = 150 mm or min. D/4 W3 = 600 mm or min. D Fig. 6.1 Prohibited location of welds in tubular joints. Longitudinal respectively circumferential welds shall not be located in shaded area. 6.3.2 Splices Splices shall not be located in areas, noted as restricted on design drawings. 6.3.3 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. NORSOK standard

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M-101 Rev. 4, Dec. 2000

6.3.4 Bolting connection Bolting 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 from the outside atmosphere. Seal welds shall have a throat thickness of at least 3 mm. Where steel items shall be hot dip galvanised, hollow sections shall be ventilated. 6.3.6 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 100 mm. 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. 6.3.7 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. 6.3.8 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. 6.4 Preparation for coatings Edges of plates and structural shapes which are intended to be coated shall be rounded to approximately 2 mm radius, unless otherwise indicated on design drawings. 6.5 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. Buttering in excess of 20 mm shall be avoided. 6.6 Welding processes The welding processes listed in EN 288-3 are acceptable.

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M-101 Rev. 4, Dec. 2000

6.7 Welding consumables The manufacturers shall ensure that welding consumables applied for joints where steel quality level I, II and III 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. • For steels with SMYS ≥ 500 MPa Annex D is mandatory Except for solid wires such consumables shall be classified by the supplier as extra low hydrogen, i.e. HDM ≤ 5ml/100g weld metal. For self shielded flux cored wire HDM ≤ 8ml/100g may be accepted, provided preheating temperature and post weld holding temperature and time is assessed to avoid hydrogen cracking. Hydrogen testing shall be according to ISO 3690 or equivalent. For all steels with SMYS ≥ 500 MPa special precautions shall be taken to verify that selected consumables comply with hydrogen requirements. Stricter requirements than given above may be relevant. Prequalification with mock-up structures shall apply if there is a risk for high restraint in welding or erection. Consumables for joints in steel quality level III (with SMYS <355MPa) and IV and for joining stainless to carbon steel shall be selected with due consideration of base material properties, thickness and weldability, to ensure sufficient 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, including a statement of compliance with the Welding Consumable Data Sheet and the chemical composition of the weld deposit (elements of the data sheet). Welding fluxes shall be supplied with a test report (EN 10204 type 2.2), declaring conformity with the approved product type. 6.8 Preheat and interpass temperature Preheating above 50ºC should be achieved by electric heating elements. Cutting torches are not allowed for preheating. The minimum interpass temperature shall not drop below the minimum required preheat temperature. If not otherwise stated in the WPS, and qualified by the WPAR, the maximum interpass temperature shall not exceed 250°C measured at the edge of the groove. For C- and C/Mnsteels, a maximum interpass temperature of 250ºC may be used, even if a lower temperature was recorded on the WPAR. The preheat temperatures used during repair welding should be minimum 50°C higher than the preheat used for the original weld. NORSOK standard

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M-101 Rev. 4, Dec. 2000

Note: Production welding of high strength steels with SMYS>500 MPa is normally more sensitive to hydrogen cracking than experienced during welding for qualification. Special precautions, including preheating temperature, minimum holding temperature and extended post weld holding temperature for 24 hours or more, shall be taken into consideration. 6.9

Production welding

6.9.1 General Welding shall be carried out in accordance with the WPS and applicable drawings. Butt welds in joints where steel quality level I and II for all strength levels, or steel quality level III for SMYS > 400 MPa are required shall, whenever possible, be welded from both sides. If any welding is conducted after PWHT, the PWHT shall be repeated. For joints in inspection category A, the ”straight” edges of K- and 1/2V-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.) Any occurrence of cracking during production welding shall be investigated. Welding should be suspended until the cause of cracks and defects has been identified and measures taken to prevent their reoccurrence. Cracks or other persistent weld defects may lead to revision and requalification of the WPS. 6.9.2 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 cut minimum 3 mm from the base metal and ground. The ground area shall be visually examined and magnetic particle/penetrant tested (as relevant) in accordance with the inspection category in question. 6.9.3 Stainless steel components Permanent or temporary structural elements, attachments or penetration sleeves in stainless steel materials may be selected for various purposes. Requirements for welding and testing of stainless outfitting structures shall follow similar classification principles as for other structural steel elements. All welding and testing of welds to carbon steel structures shall as a minimum comply with the requirements for the structure to which they are attached. Unless other requirements apply higher alloyed consumables than given for the relevant stainless component shall be selected for tacking and final welding.

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M-101 Rev. 4, Dec. 2000

6.10 Post weld heat treatment (PWHT) PWHT shall be required for structural welds in steel quality level I or II, or quality level III with Re>400MPa, when the nominal thickness (as defined in EN 288-3, section 8.3.2.1) exceeds 50 mm, 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 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 time and temperature shall be as recommended by the steel manufacturer The temperature difference between different parts of the structure during soaking time shall not exceed 30°C within the heated area. Double sided heating shall be used as far as possible. The temperatures shall be continuously and automatically recorded on a chart. 6.11 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. 6.12 Peening Weld improvement by peening shall be performed in accordance with detailed procedures. Normally pregrinding of a groove will be required to assure correct location of peening area. Tools for grinding and peening, surface roughness and profile of grinding as well as peening shall be specified. Tools for check and measurements shall be described and shall be available during operations. Documentation of correct performance shall include macrophotography. Typical examples of requirements for peening of joints are given in Annex A.

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M-101 Rev. 4, Dec. 2000

PRODUCTION TESTS

Production tests shall be selected on weldments in critical regions to verify that the specified requirements 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 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.

8

FABRICATION TOLERANCES

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

9

NON-DESTRUCTIVE TESTING (NDT)

9.1 General The inspection category shall be decided by the designer in accordance with NORSOK N-004, and shall 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/or welding consumables in question. When PWHT is performed, the final NDT shall be carried out when all heat treatment have been completed. Prior to fabrication start-up, contractor shall implement a system for recording of weld defect rates. The defect rates shall be recorded on a weekly basis from each production area (geographically split in production areas at the same yard) and shall be reported together with the accumulated defect rate. The defect rate statistics shall be used as a tool in weld quality control. Causes for defects shall immediately be investigated and corrective actions shall be taken to prevent further occurrence. Cracks detected with any NDT method shall require documented investigation/action by the responsible welding engineer. At a weekly high defect rate or at repeated occurrence of planar defects, two trigger levels apply for extended NDT for welds in inspection category B, C and D. Two steps of actions apply within trigger level 2.

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M-101 Rev. 4, Dec. 2000

Trigger level 1 If a defect rate for any method exceed 10 % for a single week the extent shall be increased to 100 % for all welds in question irrelevant of the required inspection category for the welds. Trigger level 2 If a defect rate for any method of 5 - 10 % for a single week is observed the following two steps of extended NDT shall apply: Step 1. A defect rate for any NDT method exceeding 5 % (1% for MT) for a single week require doubling of the extent of NDT according to the inspection category. Spot extent shall be increased to 20 %. Step 2. If the defect rate for the weld length where the extended NDT is taken in accordance with Step 1 above exceed 5 %, the extent shall be increased to 100 % for all welds in question irrelevant of the required inspection category for the welds. The increased NDT extent shall cover welds of the same inspection categories, welded in the same period of time when the high defect rate was produced, to assure that the weld quality is maintained also with the lower extent of NDT. Unless the causes for defects found leads to immediate and documented preventive actions, the higher level of extent of NDT shall be maintained until the weekly defect rate is well below 5 %. Generally, if the defect rate approaches 10 % during any stage in production welding, further welding should be held until investigations are completed and corrective actions implemented. A low defect rate may be used as basis for a reduction in the extent of NDT for inspection categories B, C and D, provided that a correct defect rate identification is prepared for each weld method, each NDT method and each production area. See Note 2 in Table 9.1. 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. 9.2 Qualification of inspectors and NDT-operators Personnel responsible for welding inspection - welding inspectors - shall be qualified in accordance with NS 477 or equivalent scheme. Personnel performing visual inspections of welded joints shall be qualified in accordance with relevant part of EN 473/NORDTEST. Personnel responsible for all NDT activities shall be qualified according to EN 473/NORDTEST Level 3 or equivalent. The NDT operators shall be qualified according to EN 473/NORDTEST Level 2 or equivalent.

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M-101 Rev. 4, Dec. 2000

Operators simply producing radiographs and not performing evaluation, do not require level 2, but shall have sufficient training. In undertaking testing of castings or forgings the NDT operator should also document experience with forged and cast products. 9.3 Extent of visual examination and NDT The required minimum extent of examination/testing is given in table 9.1. Design drawings may show areas of welds where testing is mandatory. Testing performed shall be representative for the weld quality. Partial NDT shall normally be planed for on all shop drawings. 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 testing shall be performed on minimum 5% of welds in inspection category A and B for SAW (12) and FCAW (131 and 136)

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M-101 Rev. 4, Dec. 2000

Table 9.1 Minimum extent (in %) of non-destructive testing for structural welds. Inspection category A B1) C1) D1) E

Type of connection Buttw. T-conn. Fillet/partial Buttw. T-conn. Fillet/partial Buttw. T-conn. Fillet/partial All conn. All conn.

Visual examination 100 100 100 100 100 100 100 100 100 100 100

Extent of testing RT 10 Spot -

UT 100 100 50 2) 50 2) 20 2) 20 2) -

MT 100 100 100 100 2) 100 2) 100 2) 20 2) 20 2) 20 2) spot -

Legend RT = Radiographic testing UT = Ultrasonic testing MT = Magnetic particle testing Spot means 2 - 5%.

Note: 1. The extent of NDT shall be increased for Inspection categories B, C and D if repeated occurrence of planar defects are revealed or if the weekly defect rate for any NDT method, including all types of defects, are as given for the limits below. Trigger level 1 - Defect rate exceeding 10 %: The extent shall be increased to 100 % irrelevant of inspection category. Trigger level 2 - Defect rate of 10 % and below calls for stepwise increase in extent: Step 1 - Defect rate exceeding 5 % ( MT exceeding 1%): The original extent shall be doubled. Spot extent shall be increased to 20 %. Step 2 - Defect rate for the extended testing under Step 1 exceed 5 %: The extent shall be increased to 100 % of the weld lengths in question for all inspection categories. The required level of increased extent shall be maintained until a defect rate below 5 % is re-established and documented. 2. The extent may be reduced to 50% of the specified extent, based on experience and documented records with similar joints, provided the defect rate (see clause 10.1 and 11.1) for UT/RT is <2.0% and for MT is <0.2% during the last 100m of weld. The last 100m shall be continuously updated every week. If the defect rate exceeds the limits given above, the normal extent of NDT shall apply again. A possible reduction in the extent of NDT shall be considered separately for each welding method and each production area.

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M-101 Rev. 4, Dec. 2000

When partial testing is defined for welds in an area, the testing shall be spread such that the most essential members and nodes are included in the inspection, and such that areas of welds most susceptible to weld defects are covered. The specified percentage to be tested in table 9.1 refers to the total length of welds in each inspection category. All WPS's used and welds representing all welding personnel involved in the fabrication shall be subject to NDT. During the initial fabrication the extent of UT and MT of inspection category B and C welds shall be intensified, normally to twice the level given in table 9.1. This extent shall be maintained for a weld and test length sufficient to conclude that the weld repair percentage is at a reasonable level. The increased initial testing may be accounted for in the overall extent provided the initial testing confirms consistent good workmanship. 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 of defects is deemed to be most harmful, shall be tested. c) Ultrasonic and radiographic testing shall not overlap, except when 100% UT is specified. However, ambiguous imperfections revealed by UT shall in addition be tested by RT. d) Ultrasonic testing is normally not applicable for thicknesses less than 10 mm. For such thicknesses, UT 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 or as required by the designer. 9.4 Visual examination and finish of welds The visual examination shall be carried out in accordance with EN 970. 9.5 Radiographic testing Radiographic testing shall be carried out in accordance with EN 1435, Class A. 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 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. 9.6 Ultrasonic testing Ultrasonic testing of welds in plate and tubular butt welds and double side welded tubular joints shall be performed in accordance with EN 1714, examination level C. Reference blocks shall be made with thickness and side-drilled holes in accordance with table 9.2. DAC reference curves shall be established.

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M-101 Rev. 4, Dec. 2000

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, reference blocks shall be produced both perpendicular to, and parallel to, the direction of rolling. The rolling direction shall be clearly identified. The actual refracted angle for each probe measured from the reference block or as measured on the 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. 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 acceptance criteria shall be reported, unless more stringent requirements are given in table 9.5. The examination record shall include the position, the echo height, length, depth and type of indication. 9.7 Magnetic particle and Penetrant 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. For non-magnetic materials penetrant testing in accordance with EN 1289 should be used. 9.8

Acceptance criteria

9.8.1 General All welds shall comply with the requirements given below, in 9.8.2 - 9.8.5. 9.8.2 Visual examination All welds shall show evidence of good workmanship. The quality shall comply with the requirements of table 9.3. 9.8.3 Radiographs The soundness of the welded joint shall comply with the requirements of table 9.4. 9.8.4 Ultrasonic testing acceptance criteria The acceptance criteria for welds shall comply with table 9.5 unless more stringent requirements are specified by the designer.

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M-101 Rev. 4, Dec. 2000

9.8.5 Magnetic particle testing Linear indications (i.e. indications with a length/width ratio above 3 and length above 1.5 mm ) are not acceptable. Any linear indications shall be ground and re-examined. Rounded indications shall be evaluated in accordance with the requirements of table 9.3. The same acceptance criteria applies for penetrant testing. 9.8.6 All methods All defects shall be repaired according to clause 10. 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 BS 7910 , DNV RP D404 or other recognised methods. Table 9.2

Calibration reference block requirements

Thickness of material to be examined (mm) 10 < t < 50 50 < t < 100 100 < t < 150 150 < t < 200 200 < t < 250 t > 250

NORSOK standard

Thickness of block

Diameter of hole

40 or t 75 or t 125 or t 175 or t 225 or t 275 or t

Ø 3 mm +/-0.2 mm Ø 6 mm +/-0.2 mm

Distance of hole from one surface

t/2 and t/4. Additional holes are allowed and recommended

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Structural steel fabrication Table 9.3

M-101 Rev. 4, Dec. 2000

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

Welding Type of defect Cracks Incomplete penetration or lack of fusion Undercut

Surface porosity Exposed slag

Concave root Excessive pen. 1) Roughness of weld (fig. 1) Misalignment of butt welds (fig. 2) Reinforcement of butt welds (fig. 3) 1) Reinforcement of fillet/partial pen. welds (fig.4) 1)

Symmetry of fillet welds (fig. 5) Grinding arc strikes etc. Removal of temporary attachments 2) Sharp edges

NORSOK standard

Insp. cat. A, B Not acceptable Not acceptable

Max depth 0.5 mm Continuous undercut is not permitted Not acceptable

Acceptance criteria Inspection category C, D, E Not acceptable Single - side weld: Length < t/2, max 10 mm Defects shall be regarded as a continuous defect if the distance between them is < t. Maximum depth 0.75 mm Continuous undercut is not permitted

Not acceptable. However, the following defects may be acceptable if it does not conflict with surface treatment requirements: Accumulated pore diameters in any area of 10 x 150 mm is not to exceed 15 mm. Max. size of a single pore is t/4 or 4 mm, whichever is the smaller. Max. concavity 0.5 mm if the transition is smoothly formed. Max. 3 mm “U” shall be less than 2.5 mm. Weld surface shall be smooth, without sharp transitions. The bottom of roughness in butt welds shall not be below the base material surface. Max. misalignment (M), 0.15 x t or max. 4 mm, whichever is the smaller. “t” less or equal to 10 Max reinforcement “C” 2 mm “t” greater than 10, up to 25 Max reinforcement “C” 3 mm “t” greater than 25, up to 50 Max reinforcement “C” 4 mm “t” greater than 50 Max reinforcement “C” 5 mm “a” less or equal to 10 Max reinforcement “C” 2 mm “a” greater than 10, up to 15 Max reinforcement “C” 3 mm “a” greater than 15, up to 25 Max reinforcement “C” 4 mm “a” greater than 25 Max reinforcement “C” 5 mm “a” less or equal to 6 Max difference, b - h: 3 mm “a” greater than 6, up to 13 Max difference, b - h: 5 mm “a” greater than 13 Max difference, b - h: 8 mm Grinding of base material shall not exceed 7% of the wall thickness or max. 3 mm. Repair welding and inspection shall be performed if removal of the base metal exceeds the specified requirements. Minimum 2 mm radius (Ref. 6.4)

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M-101 Rev. 4, Dec. 2000

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

U

U

t

t

c

Fig. 1 Roughness of weld

M

Fig. 2 Misalignment of butt weld

Fig.3 Reinforcement of butt weld b

Fig. 4a Reinforcement of fillet weld

NORSOK standard

Fig. 4b Reinforcement of partial pen. weld

a

a

a

c

c

h

Fig. 5 Symmetry of fillet weld

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M-101 Rev. 4, Dec. 2000

Table 9.4 Structural steel welds, RT acceptance criteria Type of defect

Inspection category A, B

C, D, E

Internal porosity (Note 1) Isolated: Pore diameter Cluster: Pore diameter Scattered: Accumulated pore diameters in any 10x150 mm area of weld Slag inclusions, or piping porosity (Note 2) Width Length (Note 3) Incomplete penetration, lack of fusion Length (Note 2) Cracks

max t/4, but max.6 mm

max t/3, but max. 6 mm

max. 3 mm

max. 4 mm

max. 20 mm

max. 25 mm

t/4, max .6 mm 2t, max 50 mm

t/3, max. 6 mm 4t, max. 100 mm

t, max. 25 mm Not acceptable

2t, max 50 mm 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 <20 mm.

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Structural steel fabrication Table 9.5 Description General

Cracks Lack of fusion or incomplete penetration

Slag inclusions Porosity

M-101 Rev. 4, Dec. 2000

Structural steel welds. UT acceptance criteria. Inspection category Inspection category A+B C, D, E If the type of defect can not be ascertained with certainty the defect shall be repaired when the length exceeds 10 mm and the echo height exceeds the reference curve. Unambiguous cracks are unacceptable regardless of size or amplitude. Internal defects : I: The echo height exceeds the reference curve: Max length t, Max length 2t, max 25 mm max 50 mm II: The echo height is between 50 and 100% of the reference curve: Max length 2t, Max length 4t, max 50 mm max 100 mm Surface defects are not acceptable except: For root defects in single sided welds , the max length for which the echo height exceeds the reference curve shall be: Max length t, Max length 2t, max 25 mm max 50 mm When echo height exceeds the reference curve: Max length 2t, Max length 4t, max 50 mm max 100 mm Repair is required if porosity may mask for other defects.

Notes 1 2 3 4

1 2 3 4 5

1 2 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 length 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 defects smaller than the beam). 4. With UT performed from only one side of the weld with only one surface accessible, the acceptable 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 the nearest 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.

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10

M-101 Rev. 4, Dec. 2000

REPAIR

10.1 Definitions 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 9 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 the discretion of the fabricator. Weld defect: Discontinuity with a size and/or density that exceeds the acceptance criteria defined in clause 9. 10.2 Correction of welds containing defects All repairs shall be carried out in accordance with established procedures. Welds containing cracks shall not be repaired, until the reason for the cracking has been determined. 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. 10.3

Repair by welding

10.3.1 Repair and re-repair welding Before repair welding, the defect shall be completely removed. The excavated area shall have smooth transitions to the metal surface and allow good access for both NDT after excavation and subsequent repair welding. After excavation, complete removal of the 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 50 mm long, measured at defect depth even if the defect itself 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. NORSOK standard

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M-101 Rev. 4, Dec. 2000

10.3.2 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. 10.4 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. For repairs using a different process, and/or consumable, a separate WPS shall be qualified if required by 5.2. 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. 10.5 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 6.

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M-101 Rev. 4, Dec. 2000

ANNEX A 1 - TYPICAL GRINDING DETAILS FOR HIGH FATIGUE UTILISATION (INFORMATIVE) TYPICAL GRINDING DETAILS FOR HIGH FATIGUE UTILISATION

T3

T4= 2mm or 0,05 x T3 max. (wichever is less)

T4

Rotary burr grinder Remove sharp edges Weld rad.

S UT O

E ID

E AC BR

Remove sharp edges

L AL W

T1

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

TYP. TUBULAR JOINT GRINDING DETAIL Blend out to remove edge on undercut

Grinding direct ion

Maximum depth below plate surface for blend is not to exceed 1,5mm

Remove ov erlap flush with plate surface

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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M-101 Rev. 4, Dec. 2000

ANNEX A 2 - TYPICAL PEENING DETAILS FOR HIGH FATIGUE UTILISATION (INFORMATIVE) A.2.1

General

Peening of local area as weld toe or weld trasition is an acceptable method to improve fatigue life of structures. Peening is applied together with grinding where grinding serves the purposes to remove stress risers such as surface defects and to define a steering grove for the tool in the area to be peened. Both grinding and peening require skills and preparations not normally available in fabrication yards. Due to the dependancy of correct performance specific precautions shall be taken when peening is planned for. A.2.2

Requirements for application

When peening is planned for the following preparations are required : • • • • • • • • ! ! ! ! ! • •

Nomination of responsible engineer for preparations, performance and documentation A complete responsibility and personnel matrix Statement on expected or required improvements Detailed work instructions Documentation on operators experience, skill or training Selection of peening methods to be applied Detailed mark up drawings showing all areas of application Detailed stepwise procedure for the work, including: grinding details as tools, radius, depth and direction tools to be used for peening method, intensity and extent of peening quality control measures documentation of performance and results Verification of performance such as experiments, tests or other relevant information As built record index for the final DFI resume

As preparation for peening the surface shall be dressed in a way that makes lack of coverage detectable, preferably by stone grinding. Applicable tool for grinding is normally a rotary burr or stone of 6 to 8 mm diameter when a single tool hammer is used and 10 to 12 mm when a needle hammer is used. The depth of the groove is approximately 0.5 mm below the original surface. All surface defects shall be removed by grinding prior to peening. Applicable tool for peening is normally pneumatic hammers. A needle hammer is normally used when a wider area shall be covered. For local toe peening a single tool hammer is recommended. Correct tool is essential to maintain correct peening in compliance with requirements. Special tools with adjusted curvature shall be prepared in accordance with weld geometry. Needle peening shall be applied with a coverage of minimum 200 %. Single hammer peening shall result in a fully covered hammered groove where the surface is smooth with uniform indentation. All traces from previous grinding shall be completely removed.

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M-101 Rev. 4, Dec. 2000

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

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M-101 Rev. 4, Dec. 2000

ANNEX B - CORRELATION BETWEEN STEEL QUALITY LEVEL, MDS NUMBER AND STEEL GRADE/DESIGNATIONS (NORMATIVE) Steel NORSOK quality MDS No. level Note 1 Y20 Y21 Y22 Y30 Y31 Y32 I Y40 Y41 Y42 Y50 Y51 Y52 Y70 Y25 Y26 Y27 Y28 Y35 Y36 Y37 Y45 II Y46 Y47 Y55 Y56 Y57 Y70 Y05 Y06 III Y07 Y08 Y15 Y16

Rev. Reference No. standard

Product type

3 3 3 3 3 3 3 3 3 3 3 3

Plates Rolled sections Seamless tubulars Plates Rolled sections Seamless tubulars Plates Rolled sections Seamless tubulars Plates Rolled sections Seamless tubulars Plates Plates Rolled sections Seamless tubulars Welded tubulars Plates Rolled sections Seamless tubulars Plates Rolled sections Seamless tubulars Plates Rolled sections Seamless tubulars Plates Plates and sections Tubulars Hot finished tubulars Cold formed tubulars Plates and sections Cold formed tubulars

prEN 10225

3 3 3 3 3 3 3 3 3 3 3 3

prEN 10225

EN 10113 prEN 10225 EN 10210 EN 10219 En 10113 EN 10219 EN 10025

IV

Y01

3

EN 10210 EN 10219

Steel grade

S355G10+N/G10+M S355G12+N/G12+M S355G15+Q/G15+N S420G2+Q/G2+M S420G4+M S420G6+Q(mod) S460G2+Q/G2+M S460G4+M S460G6+Q(mod) S500G2+Q/G2+M S500G4+M S500G6+Q(mod) S690+Q S355G9+N/G9+M S355G11+N/G11+M S355G14+Q/G14+N S355G13+N S420G1+Q/G1+M S420G3+M S420G6+Q S460G1+Q/G1+M S460G3+M S460G6+Q S500G1+Q/G1+M S500G3+M S500G6+Q S690+Q S355NL/ML S355G1+N S355NH S355MLH S420NL/ML S420MLH S235JRG2 Plates and sections S275JR S355J0 S235JRH Hot finished tubulars S275J0H S355J0H S235JRH Cold formed tubulars S275J0H S355J2H

Former Steel grade S355N4z/M4z S355N3z/M3z S355Q3z/N3z S420Q3z/M3z S420M3z S420Q3 (z mod) S460Q3zM3z S460M3z S460Q3(z-mod) S500Q3z/M3z S500M3z S500Q3(z-mod) S355N4/M4 S355N3/M3 S355Q3/N3 S420Q3/M3 S420M3 S420Q3 S460Q3/M3 S460M3 S460Q3 S500Q3/M3 S500M3 S500Q3

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

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M-101 Rev. 4, Dec. 2000

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. Specifically this shall include, as applicable: • Chemical analysis limits for solid wires and metal powders. For information also typical weld metal analysis, using a relevant shielding gas or flux. • Chemical analysis limits of weld metal from coated electrodes and cored wires, deposited according to EN 26847. For information also specified limits for S, P and N in the core wire or strip. The analysis shall include limits for all elements specified in the relevant classification standard and/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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M-101 Rev. 4, Dec. 2000

• Mechanical properties (range or/and guaranteed minimum) of the weld, deposited and tested according to prEN 1597 part 1 and including tensile strength, yield strength elongation, notch toughness Charpy-V at -40ºC. For information also typical properties of a relevant butt weld should be added. • Diffusible hydrogen content HDM max., including any information on drying, restricted welding parameters etc. required to ensure this value in practice. • When relevant for the product, basic information about CTOD properties, to be supported by separate test reports as required and agreed. Data sheets shall also contain product classification according to recognised standards, relevant approvals 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 nonspecific 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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M-101 Rev. 4, Dec. 2000

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 for solid 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 -40ºC, 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.

NORSOK standard

Page 36 of 36


M-101 Rev. 4, Nov. 2000

ANNEX E - FABRICATION TOLERANCES (NORMATIVE)

CONTENTS E.1

SCOPE AND OBJECTIVES

38

E.2

CODES, STANDARDS AND SPECIFICATIONS

38

E.3

DEFINITIONS

38

E.4 E.4.1 E.4.2 E.4.3 E.4.4 E.4.5 E.4.6 E.4.7 E.4.8

GENERAL REQUIREMENTS Implementation policy of requirements Procedures and documents Qualification of inspectors Instrument reliability Reference temperature Control methods Interface criteria’s Alignment Requirement

39 39 40 40 40 40 41 43 43

E.5 FABRICATION TOLERANCES FOR STRUCTURAL COMPONENTS E.5.1 I / H- Girders E.5.2 Box Girders E.5.3 Tubulars E.5.4 Panels E.5.5 Girder Nodes E.5.6 Box Nodes E.5.7 Tubular Nodes E.5.8 Cast and Forged Elements E.5.9 Curved and cylindrical shell E.5.10 Conical transitions

44 44 45 46 49 50 52 53 55 56 56

E.6 E.6.1 E.6.2 E.6.3 E.6.4

ASSEMBLY TOLERANCES Topsides and modules Jacket and other tubular frame structures Floating production units Subsea structures

57 57 58 63 64

E.7 E.7.1 E.7.2 E.7.3 E.7.4 E.7.5 E.7.6

FABRICATION TOLERANCES FOR SPECIAL ITEMS Crane Pedestal Skid Beams Outfitting Structure Installation Aids Grillages Cranes

65 65 65 65 65 65 65

NORSOK standard

Page 37 of 65


E.1

M-101 Rev. 4, Nov. 2000

SCOPE AND OBJECTIVES

This annex defines the maximum allowable dimensional tolerances for offshore steel items and structures. The Designer may, however, specify stricter tolerances and additional tolerances. These will, in case take presedence over this annex. Note: It should be observed that the requirement to fabrication tolerances in this annex may be more strict than the manufacturing tolerances for steel products according to M-120. The intention of this annex is to give dimensional tolerances which will ascertain that: • The calculated strength and fatigue resistance is present in the structures • Items and structures can be assembled without dimensional rework • All parts of the structures are suitable for their intended use • The structures are thrustworthy relative to measurements given on the structural drawings • The relevant components tolerances are achieved and maintained after the components final incorporation in the completed structure(s)

E.2

CODES, STANDARDS AND SPECIFICATIONS

Reference standards for this annex are: ISO-8062 Castings - System of dimensional tolerances and machining ENV 1090-1 1995 for Cranes. Execution of steel structures - Part 1: General

E.3

DEFINITIONS

Terminology used in conjunction with this annex: AFC drawing: Engineering drawings formally approved for construction. Centreline: A real or imaginary line that is equidistant from the surface or sides of the (measured) object. Deflection: Load imposed curves, bends, angles or irregularities from an unloaded structure. Note: Opposed to straightness deviation. Flatness: Flatness is here defined as vertical offset at any point from a plane parallel with the surveyed object.

NORSOK standard

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M-101 Rev. 4, Nov. 2000

Grid System: The grid system is defined as the design reference system for all parts, components and elements of a 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 by elastic deformation. Survey Reference System A reference system constituting of fixed and coordinate determined points, from where surveys can be performed, and where the location and elevation of the fixed points are identifiable relative to the grid 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 single elements to be parts of complex structures, specification of detailed and more stringent tolerances for each fabrication and erection sequence may be necessary in order to meet the requirements 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 also be 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 unacceptable deviation for the finished section or complete structure. NORSOK standard

Page 39 of 65


M-101 Rev. 4, Nov. 2000

If tolerances given for individual sections and components are conflicting, those tolerances representing 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 assure that 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 the extent of exceeding the allowable tolerance for the complete structure. Dimensional inspection procedures relevant for the structures and any additional specifications needed to those included in this document, subject drawings or other regulations/guidelines for the structural 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 submitted on request. Final documentation shall be prepared in correspondence with the requirements for as built documentation and fabrication record. E.4.3

Qualification of inspectors

Personnel responsible for dimensional control activities shall have a minimum background of at least 5 years relevant experience in industrial surveying. Personnel monitoring dimensions and tolerances shall have relevant training in use and understanding of instruments, and subsequent calculations, enabling them to perform all necessary controls of own work performance. E.4.4

Instrument reliability

All instruments used shall be in accurate permanent adjustment, have current valid control certificates and be subject to a programme of periodic checking. E.4.5

Reference temperature

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

Page 40 of 65


M-101 Rev. 4, Nov. 2000

The field work temperature shall as a minimum be noted on all dimensional reports, when this is necessary 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 the reference 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. The survey reference system shall use the same numerical values, and the same orientation directions of the 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 adjusted to 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 of the 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 reference system 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 permanent survey stations are established. All additional or rechecked surveys shall be properly documented.

NORSOK standard

Page 41 of 65


Fig. E.4.6-1

M-101 Rev. 4, Nov. 2000

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 the methods chosen for controls. E.4.6.2 Marking criteria’s During layout and assembly of each structural item all work points and centrelines, which are relevant 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 to ensure 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 engineering surveying techniques consistent with the tolerances required by this annex. All girders, boxes, nodes and 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 achievement of a survey accuracy better than the specified tolerances. The methods and equipment used must enable verification of the survey accuracy.

NORSOK standard

Page 42 of 65


M-101 Rev. 4, Nov. 2000

All activities related to measurement and inspection of dimensions and tolerances shall take into account the effects of self weight while the structure is under fabrication. E.4.7

Interface criteria’s

All non-adjustable interfaces and interfaces deemed critical prior to erection shall be surveyed and documented. A comparison of the interface results prior to erection shall be performed and necessary 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 as follows: a) Butt-joints Reference is made to table 9.3. b) Cruciform Joints Eccentricity of non-continuous plating in cruciform joints shall not exceed the following requirements, (ref. figure 4.8-1) e e t1 t2 t3

≤ t1/2 (mm), maximum 5 mm, for t2 ≤ 20 mm ≤ t1/2 (mm), maximum 8 mm, for t2 > 20 mm = smaller thickness in mm of non-continuous plate = thickness in mm of continuous plate = larger thickness in mm of non-continuous plate

e = 2m + t3 - t1 2 m = misalignment e = eccentricity

Fig. E.4.8-1

Cruciform joints

NORSOK standard

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M-101 Rev. 4, Nov. 2000

E.5

FABRICATION TOLERANCES FOR STRUCTURAL COMPONENTS

E.5.1

I / H- Girders

Type of deviation

Figure 5.1-1A

Notation f

Ref. Length L

Allow % of ref. length ±0.15

Max. Deviation mm ±10

Lateral or vertical deflection Length

5.1-1A

L

L

±0.25

±3

Height Width Inclination of web

5.1-1B 5.1-1B 5.1-1B

H B V

H B H

±0.3 ±0.8

±3 ±3 ±10

Eccentricity of web 5.1-1B on flange Buckling of web 5.1-1B

V1

H

±1.0

±3

V3

H

±0.75

±10

Curvature/rotation 5.1-1B flange Twisting of section 5.1-1C

V2

B/2

±2.5

±3

d5

L

±0.10

±10

Fig. E.5.1-1

I-/H-Girders tolerance references

NORSOK standard

Page 44 of 65


E.5.2

M-101 Rev. 4, Nov. 2000

Box Girders

Type of deviation

Figure

Notation

Ref. Length

Allow % of ref. Length -

Max Dev. mm ±3

Position deviation at end/interface section Length Height Width Out of straightness

5.2-1A

d1

5.1-1A 5.1-1B 5.1-1B 5.2-1B

L H B d2

Ref. Centre Lines L H B L

±0.25 ±0.3 ±0.15

±3 ±3 ±3 ±10

Buckling of plates

5.2-1C

d3

H, W

±0.5

±10

Pos. deviation of load bearing stiffeners inclusive inclination Twisting

5.2-1D

d4

Ref. Centre Lines

-

±5

5.2-1E

d5

H

±0,5

±6

Fig. E.5.2-1 Box Girders tolerance references NORSOK standard

Page 45 of 65


E.5.3

M-101 Rev. 4, Nov. 2000

Tubulars

The allowable tolerance given for individual tubular segments shall not be cumulative for the finished tubular. a)

Circumference:

The external circumference shall not depart from the nominal external circumference by more than the 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 is the 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 than 0.25% 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 mm deviation for lengths up to 12 m. Above 12 m length max. allowable deviation is 12 mm. Out of straightness 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: • Bevelled ends: NORSOK standard

5 mm 3 mm Page 46 of 65


g)

M-101 Rev. 4, Nov. 2000

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 20° of 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 wall thickness. Local straightness shall be checked on the inside or outside of tubulars with a nominal external diameter greater than 2000 mm or with a nominal external diameter to nominal wall thickness ratio greater than 65. These checks shall be carried out at 45° intervals 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

NORSOK standard

Page 47 of 65


Fig. E.5.3-3

M-101 Rev. 4, Nov. 2000

Tubulars - Local out-of roundness references

NORSOK standard

Page 48 of 65


E.5.4

M-101 Rev. 4, Nov. 2000

Panels

Type of deviation Figure PANEL SHEET: Out of plane straightness, sagging/hogging, between 5.4-1 girders Local buckles between stiffeners 5.4-1 GIRDERS/ STIFFENERS: Out of straightness in X and Y direction Position deviation Inclination Out of straightness of web normal to web (web buckles)

Fig. E.5.4-1

5.4-1 5.4-1

Notation

Ref.

Allow. %

Max. dev. mm

p1

W

±0.15

±15

p2

W1

±0,5

±5

g1 g2

0.15%

±10

±0.8

±10 ±10

±0.75

±10

5.4-1

g3

W Grid system Hg

5.4-1

g4

Hg , W1

Deck panels tolerance references

NORSOK standard

Page 49 of 65


E.5.5

M-101 Rev. 4, Nov. 2000

Girder Nodes

Type of deviation

Figure

Notation

Ref. length

Position deviation of interfaces Lateral and vertical straightness of node Lateral and vertical straightness of stiffeners Height of node

5.5-1B, 5.5-1C 5.5-1A

d1 f

Ref. Centre Line L

5.5-1A

f1

5.5-1B

Pos. deviation stiffeners inclusive inclination Position deviation column interfaces Baseplate flatness /rotation rel.to Z axis Pos.deviation baseplate relative to Z axis

Fig. E.5.5-1

Allow % of ref. length -

Max. deviation mm ±5

±0.15

±5

L,H

±0.1

±5

s

-

-

±5

5.5-1B, 5.5-1C 5.5-1C

d2

-

±5

-

±5

5.5-1A, 5.5-1B 5.5-1B

b1

Ref. Centre Line Ref.Centre Line Ref. Centre Line Ref.Centre Line

-

±2

-

±3

d3

d4

Girder nodes tolerance references

NORSOK standard

Page 50 of 65


Fig. E.5.5-1

M-101 Rev. 4, Nov. 2000

Girder nodes tolerances

NORSOK standard

Page 51 of 65


E.5.6

M-101 Rev. 4, Nov. 2000

Box Nodes

Type of deviation

Figure

Notation

Ref. Length

Position deviation of main box interface Out of straightness

5.6-1A

d1

5.6-1B

d2

Ref. Centre Line L

Buckling of plates

5.6-1C

d3

Radial and tangential stub end deviation Pos. deviation of load bearing stiffeners incl. inclination Offset of centrelines at centre of node

5.6-1C, 5.6-1E 5.6-1D

d4

Fig. E.5.6.1

5.6-1E, 5.6-1F

d5 d6

Allow of ref. length -


± 0,10%

±10

H, W

±0,5%

±10

Ref. Centre Line Ref. Centre line Ref. Centre Line

-

±5

-

±5

-

±5

Box nodes tolerance references

NORSOK standard

Page 52 of 65


E.5.7

M-101 Rev. 4, Nov. 2000

Tubular Nodes

Type of deviation

Figure

Notation

Ref. length Allow of ref. length

Overlength of stub

5.7-1A

l2

L2

Overlength of node can barrel

5.7-1A

l1

L1

Stub ends perpendicularity

5.7-1A

p

-

Radial and tangential stub end/ node cans position Position of intersection point node can / stub

5.7-2

V ∆α

5.7-2

E

Grid system Grid system

5.7-1A 5.7-1B 5.7-1B 5.7-1C 5.7-1B

P M B N

Internal stiffeners -Position -Inclination of web -Flange width -Bow of web -Rotation of flange -Eccentricity of flange on web -Height of stiffeners Local straightness of stubs/barrel Straightness of barrel

h b

5.7-1A

1,0% 1,5% 1,0%

Wall thickness L

±6 ±6

Lx

5.7-1B 5.7-1B 5.7-1A

0.2° of arc

Max. deviation mm +25 -0 +10 -0 ±3

±5 ±5 ±3 ±6 ±6

25%

±6 +10/-3 8

1/1200

10

The centre line of stub shall be within 0.2° from 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

NORSOK standard

Page 53 of 65


M-101 Rev. 4, Nov. 2000

Fig. A

Fig. B (tolerance references)

Fig. C (tolerance references - internal stiffeners)

Fig. E.5.7-1

Tubular nodes

NORSOK standard

Page 54 of 65


Fig. E.5.7-2 E.5.8

M-101 Rev. 4, Nov. 2000

Node stub location

Cast and Forged Elements

All relevant tolerances regarding these elements’ geometry i.e. hole positions, flatness, web and rib positions 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.

NORSOK standard

Page 55 of 65


M-101 Rev. 4, Nov. 2000

During installation of cast and forged items, special care shall be taken that the parent plate edges are 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 submersible’s pontoons) special dimensional procedures shall be implemented for measurement and computing. Sylindrical shells. The maximum deviation from the nominal radius, measured at ringstiffeners or at bulkheads shall not exceed the value: δ ra r

= = =

| ra - r| <= 0,005 r actual distance from the cylinder axis to the shell wall nominal radius of the shell

Components defined as Cylindrical Shell to be specified on design drawings. E.5.10 Conical transitions At both ends of a cone, the maximum deviation from the nominal radius shall not exceed the value: δ=| ra - r| <= 0,005 r where ra= Actual distance from the cylinder axis to the cone wall r = Nominal radius at cone end Requirements for internal stiffeners shall be in accordance with table 5.7.

NORSOK standard

Page 56 of 65


M-101 Rev. 4, Nov. 2000

E.6

ASSEMBLY TOLERANCES

E.6.1

Topsides and modules

Type of deviation

Figure

Notation

Ref.

Position of any point of main steel Position of support node 2)

6.1-1

X1,Y1

Grid system


6.1-1

Grid system

±6

Position of lifting node

6.1-1

Grid system

±10

Elevation of decks and mezz. decks sag./hog. Footings deviation from elevation reference 1)

6.1-1

X2, Y2, Z2 X2, Y2, Z2 H1, H2, H3 H

Grid system

±10

Grid system

±5

6.1-1

Allowable % of ref. length

For truss frames without any defined support points the elevation reference should be based on a mean 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

NORSOK standard

Page 57 of 65


E.6.2

M-101 Rev. 4, Nov. 2000

Jacket and other tubular frame structures

E.6.2.1 Assembly tolerances Type of deviation Position deviation of centre of nodes Rotation of node Distance deviation between two nodes Diagonal distance between coloumn in each hor. plane Position of leg ring stiffeners and diaphragms Inclination of ringstiffeners Straightness of legs / chords Straightness of braces Position of intersecting braces

Figure 6.2.1-A 6.2.1-A 6.2.1-A

Notation ∆x, ∆y

Ref. Grid system

S

Max. dev. mm ±12 ±6 ±20 12

±6 6 6.2.1-B/C

∆f

L

X±10

6.2.1-C

∆f

L

X±L/1000

Grid system

±15

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

NORSOK standard

Page 58 of 65


Fig. E.6.2-1

M-101 Rev. 4, Nov. 2000

Jacket and tubular frame structures - assembly tolerances

NORSOK standard

Page 59 of 65


M-101 Rev. 4, Nov. 2000

E.6.2.2 Final Tolerances for Jacket, Interface Jacket/MSF Type of deviation

Figure

Notation

Reference

Max. dev. mm

Horizontal position deviation of centre of stab-in cans

6.2.2

Vx, Vy V= √ (Vx²+Vy²)

Grid system 1)

±6 ±8

F

L

±12

Grid system 2)

±3

L

±6

Jacket: 6.2.2 Distance between centre of column to centre of any column at stab-in cans Jacket: Mating surface level at stab-in MSF: 6.2.2 Distance between centre of column to centre of any column at stab-in cans

F

Ovality of stab-in can

As in section E.5.3b

Horizontal position deviation of caissons, risers, J-tube NOTES:

Grid system

±6

1) The position of the stab-in cans shall, if the situation allowes, be related to the topside 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. Section E.6.1, the measured deviations shall be considered incorporated when cutting the legs in order to minimise loads due to differential settlements in footings.

NORSOK standard

Page 60 of 65


Fig. E.6.2-2

M-101 Rev. 4, Nov. 2000

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 the coordinate system. Local alignment of sleeves 20 mm. Radius of spacer plates ±5 mm.

NORSOK standard

Page 61 of 65


M-101 Rev. 4, Nov. 2000

E.6.2.4 Piles Type of deviation

Figure

Notation

Length

Ref.

Max. dev. mm. ±100

Diameter between spacerplates

6.2.4

d1

As specified on drawing

Diameter in driving head

6.2.4

d2


End perpendicularity in driving head

6.2.4

P


Pile markings For general tolerances, see E.5.3 Tubulars.

Fig. E.6.2-4

±50

Piles tolerance references

E.6.2.5 Conductor Guides The position deviation of the centre of the conductor guides shall be ±10 mm related to the coordinate system for top el. and ±15 mm for the other elevations related to the same coordinate system. The maximum deviation of any conductor guide from the optimised centreline through all conductor guides, shall not vary more than ±15 mm.

NORSOK standard

Page 62 of 65


M-101 Rev. 4, Nov. 2000

E.6.2.6 Appurtenances Caissons, J-tubes and risers. Type of deviation Length E.6.3

Figure

Notation

Ref.

Max.dev. mm

-

-

-

±25

Floating production units

E.6.3.1 Semi submersibles and tension leg platforms Overall hull / substructure tolerances: Type of deviation Global position of column top / bottom Distance between top / bottom of two columns Local position of column top / bottom

Fig. E.6.3.1-1

Figure 6.3.1-1 6.3.1-2 6.3.1-1 6.3.1-2 6.3.1-3

Ref. Global grid system

Local grid system

Max. dev. mm ±15 ±30 ±5

Semi submerisibles / tension leg platforms. Global tolerance

NORSOK standard

Page 63 of 65


Fig. E.6.3.1-2

Semi submerisibles / tension leg platforms. Global tolerance

Fig. E.6.3.1-3

Semi submerisibles / tension leg platforms. Local tolerance

M-101 Rev. 4, Nov. 2000

E.6.3.2 Ship Ships should be fabricated using a grid system with origo in the aft perpendicular, and in accordance with section E.3 of this annex. Based on the grid system a reference system according to section E.4.6.1 should be permanently marked onboard the ship. E.6.4

Subsea structures

Subsea structures should be fabricated according to tolerances given on drawings.

NORSOK standard

Page 64 of 65


E.7

FABRICATION TOLERANCES FOR SPECIAL ITEMS

E.7.1

Crane Pedestal

M-101 Rev. 4, Nov. 2000

Crane pedestal tolerances shall be specified in a separate document to be prepared by the designer, taking into account the structural aspects as well as the mechanical functional tolerances and equipment interface tolerances. E.7.2

Skid Beams

Skid beam tolerances shall be specified in a separate document to be prepared by the designer, taking into account the structural aspects as well as the mechanical functional tolerances and equipment interface tolerances. E.7.3 • • • • • • • •

Outfitting Structure

This section covers all primary and secondary outfitting structures. The difference in elevation of deck plates and/or grating at joints shall not exceed 2 mm. Plates and gratings shall be without visible warping. Landing and stairway locations shall not deviate more than 25 mm from the dimensions shown on the AFC drawings. Fabrication of handrails shall be performed to such a degree of accuracy that when erected, the toprail shall be continuous, straight, have smooth transitions and be level to the eye. Members in the vertical plane shall not be out of plumb by more than 6 mm on each 3000 mm section and not more than 26 mm over the total height of the structure. Wherever tolerances are not shown on the drawings, or specified elsewhere, fabrication work shall be accurate to within 10 mm of all nominal dimensions. Matching holes for bolted connections shall not exceed 2 mm difference in location.

E.7.4

Installation Aids

Installation aid structures such as primary and secondary guides and bumpers shall be fabricated and installed in accordance with acceptable tolerances for relevant elements/structures defined in this document. Specific tolerance requirements are shown on respective drawings, and shall be mandatory. E.7.5

Grillages

Load out grillage, barge grillage and seafastening shall be fabricated and installed in accordance with acceptable tolerances for relevant structures/elements defined in this document. (Ref. section E.4.8) Specific tolerance requirements shall be shown on respective drawings and shall be mandatory. E.7.6

Cranes

Reference standard: ENV 1090-1 applies.

NORSOK standard

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NORSOK Structural Steel Fabrication M-101

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