general specification of offshore platforms

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Eni S.p.A.Divisione Agip

ENGINEERING COMPANY STANDARD

Documento riservato di propriet àdi Eni S.p.A. Divisione Agip. Esso non sarà mostrato a Terzi né utilizzato per scopi diversi da quelli per i quali è stato inviato.This document is property of Eni S.p.A. Divisione Agip. It shall neither be shown to Third Parties not used for purposes other than those for which it has been sent.

GENERAL SPECIFICATION

OFFSHORE PLATFORMS

STEEL FOR STRUCTURES

08832.STR.MME.SPC

Rev.7 December 2001




08832.STR.MME.SPCRev.7 December 2001

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FOREWARD

Rev. 0 December 1992Sheet N. 40Issue

Rev. 1 February 1993Sheet N. 40Some modifications

Rev. 2 July 1993Sheet N. 40Modified sheets: 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 40

Rev. 3 February 1994Sheet N. 43RINA comments are included.Steel designation has been changed according to EN10027.

Rev. 4 October 1995

Sheets N. 38Some subject are defined more precisely, in particular testing documentation, SR4 requirements for API 5L pipes, NDE controls and repairs for plates, sections and pipes, requirements for cold forming.

Rev. 5 Not issued

Rev. 6 March 1998Sheets N. 26General revision with changes of the paragraphs

Rev.7 December 2001Sheets N. 25This revision include: steels with 460MPa SMYS, steels according to prEN10225, steels produced withthermomechanical rolling process, reference to API 5L-00, a dedicated section for impact test in order to take into account recommendations of draft committee for revision of ISO 13819-2, feed back datacollected.





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TABLE OF CONTENTS

1. GENERAL .........................................................................................................................41.1 INTRODUCTION...............................................................................................................41.2 DEFINITION ......................................................................................................................41.3 APPLICABLE STANDARD................................................................................................51.4 DOCUMENTS AND TESTING..........................................................................................51.5 MARKING..........................................................................................................................71.6 IMPACT TEST OF MATERIALS .......................................................................................81.7 WELDING..........................................................................................................................91.8 NON DESTRUCTIVE EXAMINATION ..............................................................................9

2. PLATES AND HOT ROLLED SECTIONS......................................................................112.1 GENERAL........................................................................................................................112.2 TESTING .........................................................................................................................11

2.3 REPAIRS.........................................................................................................................12

3. API PIPE..........................................................................................................................133.1 GENERAL........................................................................................................................133.2 CHEMICAL COMPOSITION ...........................................................................................133.3 NON DESTRUCTIVE TESTING AND DIMENSIONAL TOLERANCES .........................13

4. FABRICATION OF STRUCTURAL STEEL TUBES ......................................................154.1 GENERAL........................................................................................................................154.2 QUALIFICATION OF THE FORMING PROCEDURE.....................................................154.3 WELDING........................................................................................................................164.4 CONTROLS AND REPAIRS ...........................................................................................16

5. FABRICATION OF STRUCTURAL STEEL SECTIONS FROM PLATES.....................17

5.1 GENERAL........................................................................................................................175.2 FABRICATION ................................................................................................................175.3 DIMENSION AND TOLERANCES..................................................................................175.4 INSPECTION AND REPAIR............................................................................................17

6. MATERIALS FROM STOCK ..........................................................................................196.1 GENERAL........................................................................................................................196.2 TEST................................................................................................................................196.3 NON DESTRUCTIVE EXAMINATION ............................................................................19

7. MISCELLANEA...............................................................................................................217.1 BOLTS.............................................................................................................................21

8. APPENDIX A: PRODUCTION QUALIFICATION...........................................................228.1 SPECIAL TESTS.............................................................................................................228.2 CTOD TEST ....................................................................................................................228.3 RESULTS AND VALIDITY OF THE QUALIFICATION TEST.........................................22

9. APPENDIX B: MATERIALS REFERRED TO OTHER STANDARDS...........................239.1 EN10210 AND EN10219 PIPES .....................................................................................239.2 ASTM PIPES ...................................................................................................................23

10. APPENDIX C: STRUCTURAL CLASSES......................................................................24

11. APPENDIX D: GRADE AND APPLICATION.................................................................25





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1. GENERAL

1.1 INTRODUCTION

The present specification defines the supply conditions, at yards and workshops, of

products assigned for the fabrication of offshore structures such as steel plates, hot rolledsections, seamless pipes, pipes and sections assembled by welding.

Whenever possible, the materials are referred to European standards and, in absence of specific standards for offshore construction, additional specifications are introduced whennecessary.For steel plate the reference standards are EN10025-95, EN10113-94 and prEN10225-99.For steel pipe the API 5L-00 specification shall be used as reference standards.Material supplied according to other specification are acceptable, provided their compliancewith the minimum requirements of this specification and of the referenced standards.

Supply of materials produced with thermomechanical rolling process is allowed uponcondition that these materials shall not undergone during fabrication to thermal cycles

having temperature greater than 590 ± 10°C.

Structural components are divided in classes, each of which refers to defined material,depending on the thickness and service temperature.The classification is listed in appendix c: structural classes. The classes of single elementsas indicated on design drawings have priority on the general indication of this specification.

Any cases of uncertainty in the assignment of classes shall be decided by the Client.

For all the plates of quality prEN10225-99, EN10113-94 or EN10025-95 S355K2G3 withthickness equal or more than 45 mm and for all Z quality plates, before starting theproduction weldability data of the material shall be provided to the Client, in accord to testssimilar to these indicated in Appendix A "Production Qualification". In case of materialsmanufacturer can not produce weldability data, or does not have any experience inproducing the materials required by this specification, a production qualification shall becarry out according to appendix A.

In addition to the requirements of the above paragraph the production qualification shall becarry out when expressly indicated in the order.

The material described in this specification can be acquired to the steel manufacturer or bystock.In any case, required documents and certificates shall be available for the Client beforeusing the materials for the building.

1.2 DEFINITION

The following definitions and abbreviations are used in this specification:

CLIENT ENI Division AGIP or its Authorised Representative.

CONTRACTOR Company to whom the contract is given.

MANUFACTURER Company which manufacturers the product.

EXAMINER OR CERTIFYINGSOCIETY

Person or Society accepted by the Client , which for example for some activities may be a member of IACS(International Association of Certification Society)

Z steel EN10164 - Class Z135 steel

M steel Steel produced with thermomechanical rolling process





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CTOD Crack Tip Opening Displacement referred to BS 7448-1

Unit test It is defined in the reference standard. For API pipesreference shall be made to EN10025-95.

1.3 APPLICABLE STANDARD

The standards that are listed here below forms an integral part of this specification, in thewhole or only the mentioned paragraphs, and with the modifications or additions indicatedby the same.

EN 287 "Approval testing of welding procedures for metallic materials", 288"Specification and approval of welding procedures for metallic materials",473 "Qualification and certification of NDT personnel. General principles",10024 "Hot rolled taper flange I section - Tolerances on shape anddimensions", 10025-95 "Hot rolled products of non-alloy structural steelsand their technical delivery conditions", 10027 “Designation systems for steel”, 10029 "Hot rolled steel plates 3mm thick or above - Tolerances ondimensions, shape and mass", 10113-94 "Hot rolled products in weldablefine grain structural steels", 10160 "Ultrasonic testing of steel flat productsof thickness equal or greater than 6mm (refelction method)", 10163

"Delivery requirements for surface conditions of hot-rolled steel plates,sheets, wide flats and sections", pr10210 "Hot finished structural hollowsections of non-alloy and fine grain structural steels", pr10219 "Cold

formed structural hollow sections of non-alloy and fine grain structuralsteels", 10164 “Steel products with improved deformation propertiesperpendicular to the surface of the product. Technical delivery conditions10204 “Metallic products. Types of inspection documents”, pr 10225-99“Weldable structural steels for fixed offshore structures”

EU 103 "Determinazione micrografica della grossezza del grano ferritico oaustenitico degli acciai", 168 "Prodotti siderurgici-Documenti di controllo-Contenuti", 186 "Ultrasonic testing of broad flanged beams with parallel

flanges and IPE beams"

API RP 2Z "Recommended practice for preproduction qualification for steelplates for offshore structures", RP 2X "Recommended practice for ultrasonic examination of offshore structural fabrication and guidelines for qualification of ultrasonic technicians", 5L-00 "Specification for line pipe",2B "Specification for the fabrication of structural steel pipe"

BSI 7448-1 “Fracture toughness test - Method for determination of plane strainfracture toughness, critical tip opening displacement and critical J values of metallic materials”

ISO 5817 “Arc welded joints in steel - Guidance on quality levels for imperfections”

A copy of all listed standards shall be available by the Contractor. The applicable editionshall be the latest at the contract award.

1.4 DOCUMENTS AND TESTING

The required documents for the purchase of material are the followings:





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of defects detrimental to the product application, all the products of the test units shall bediscarded even in the case that there are positive results from other test trials.

For M steel products that have been heat treated above 590 ± 10°C, mechanical tests shallbe repeated on samples that have been heat treated in the same way.

Type and frequency of mechanical test shall be as required for the normal condition test.

1.5 MARKING

All products at the end of testing shall be paint marked and die stamped. Such markingshall be positioned at two opposite angles of the plates and at the two ends of the beamsand tubular. Markings on plates shall be put at 90° with respect to the rolling direction.

1.5.1 Paint marking

The marking shall be done with white paint and letters shall be of height 40 mm at least.The indications to be reported are the following:

purchase order number;

length, width and thickness of the item, or shape type, or diameter and thickness;

steel grade;

manufacturer mark;

rolling direction (with double arrowed line). Excluding hot rolled sections.

1.5.2 Die stamping

Die stamping shall be carried out on material having thickness equal to or greater than 6mm with punch having letters 8 mm high at least. The die stamped markings shall be ringedwith white paint.

The following indications shall be marked:

type of steel and grade;

cast number;

plate or product number;

manufacturer die stamp;

Examiner die stamp.

Subsequent die stamping on semi-worked products shall be carried out with round nose

dies (low stress).1.5.3 Colour code

For each side, the thickness of plates shall be painted with 2/3 colour code stripes that withtheir combination give immediately visual information about the plate characteristic.Each pipe shall be painted with colour code stripes located on its internal surfaces and onthickness at both ends. Each sections shall be painted on its web with colour code stripeslocated at both ends.The width of each stripe for plates, sections and pipes shall be at least 50 mm, and thedistance between the stripes shall be 100 mm for plates and 50 mm for tubular andsections.





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Table C - Colour Code

Colour Type t°C KCV PropertiesWhite S275 - -

Orange S355 - -Yellow S460 - -

Blue - 0 -Green - -20 -Silver - > -40 -Red - - Z

1.6 IMPACT TEST OF MATERIALS

Materials to be supply according to this specification shall be submitted to Charpy-V impacttest in longitudinal direction as specify in this paragraph.

1.6.1 Temperature

Impact test shall be carry out at the following temperature:

Table D- impact test TEMPERATURE(1)

°Tp > -5 °C t < 12,5 mm 12,5 mm< t <25,4 mm

25,4 mm < t <50,8 mm

50,8 mm < t <70 mm

70 mm < t <100 mm

100 mm < t <150mm

°Tp > +5 °C t < 15 mm 15 mm < t <

30 mm30 mm < t <

50,8 mm50,8 mm < t <

70 mm70 mm < t <

100 mm100 mm < t <

150 mm

StructuralElement

Class

Test temperature

a -20°C

b -20°C -40°C

c 0°C 0°C(2)

d

e Impact test not required not applicable

Note: (1) Impact test carry out at temperature lower than those specify in the table are acceptable if the adsorbed energy requirements of section 1.6.2 are fulfilled

(2) Thickness range applicable only for plates to be used for piles fabrication.

1.6.2 Adsorbed energy

The adsorbed energies values during impact test (in Joules) shall be the follow:





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Table E - adsorbed energy

Nominal yeldstrength

(Ry)

Average adsorbedenergy on base

material (J)

Averageadsorbed energy

on weld metaland heat affected

zone (J)

Minimumadsorbed energy

on weld metal andheat affected zone

(J)

> 450 Mpa 60 45 32

350<Ry< 450 MPa 50 36 26

Ry<350 Mpa 40 27 19

Minimum adsorbed energy of impact test single piece of base material shall be greater than70% of the average required energy.

1.7 WELDING

The welding for the fabrication of pipes and sections shall be in accord with therequirements specified in chapters 4 and 5.Post weld heat treatment shall be applied for the cases, and following the prescriptions,reported in section 5.6 " Stress relieving post weld heat treatment" of specification 08833-STR.MET.SPC " Offshore Structures Construction "

Welders shall be qualified according to EN287 and EN1418 by Examiner or CertifyingSociety approved by the Client.Each welding process shall be qualified according to EN288 by Examiner or CertifyingSociety approved by the Client.

The welding procedure qualification test and the production weld test coupon shall includehardness and Charpy V-notch tests according to EN288, with the minimum requirements

indicated in section 1.6 of this specification.Table F - Impact test set location

Thickness Location Double andsingleside welding

t < 45 mm caproot

WM + HAZnone

t > 45 mm caproot

WM + HAZWM + HAZ

Note: Cap: 2 mm +/- 0.5 mm below external weld cap surface. Root: in root region of backwelding. WM: weld metal in the centre of weld. HAZ: heat affected zone. HAZ means: FL,FL+2 mm, FL+5 mm.

1.8 NON DESTRUCTIVE EXAMINATION

All products shall be 100% visually examined.

NDT on weld class "a, b, c" shall be carried out only 48 hours after completion of welding.The same requirement for weld class "d" with thickness higher than 20mm.

NDT on weld class "e" and on all other classes not considered above may be carried out 24hours after welding completion.

Inspection and NDT prior to PWHT shall be at the Contractor discretion and shall not avoidfurther tests.





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All bevels shall be 100% visually inspected and those relevant to component “a, b, c” shallbe inspected with MT and/or UT when defects are found and in any case not less than 20%,with location decided by the Client.

The acceptability for the welding imperfections is defined in ISO 5817, level C (intermediate)

for classes “a, b, c” and level D (moderate) for classes “d, e”. All the grave defects, e.g. cracks, shall be examined in order to establish the causes thatoriginates them.

Ultrasonic test shall be performed by operators certified at least level II according to EN473or similar. They shall be qualified by Examiner or Qualifying Society approved by the Client.In case of automatic ultrasonic inspection the results of the control shall be certified asforeseen in the procedures.The UT shall be used for search hot, cold and chevron cracks. UT automatic equipment isaccepted. UT instrument calibration shall be as per API RP2X-A.

Standard of acceptability shall be as follows.

Any flaw from which echo height exceeds the DAC by 6 db shall be repaired and re-examined, regardless of size.

All flaws classified planar (cracks or lack of fusion) shall be repaired whichever is their echo height.

All echoes that exceed 50% DAC shall be classified and evaluated in size.

Any evaluated not planar flaw not exceeding the limits accepted by this specificationmay be left unprepared.

Echo indications of transverse defects are in any case to be regarded as defectsrequiring repair: this does not apply where indication can be unequivocally correlate tolongitudinal defects.

The length of acceptable volumetric flaws are as per following table.

Table G - UT acceptable limits (mm)

Max HD e DAC a, b c d

HD > DAC 10 30 40HD > DAC/2 20 45 60

HD = maximum echo amplitude





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2. PLATES AND HOT ROLLED SECTIONS

2.1 GENERAL

The plates and hot rolled sections shall conform to the requirements of the standards

prEN10225-99, EN10113-94, EN10025-95 and to the amendments and supplementaryrequirements defined in this sections.

For all the products that are relative to the standard EN10025-95, all the options foreseen inits chapter 11 shall be applied, with exclusion of number 9, 11, 13, 18, 21, 23 and 24. For the option 4 the prescription about the Cu minimum content shall be not considered.

For all the products that are relative to the standard EN10113-94, all the options foreseen inits chapter 11 shall be applied, with the exclusion of numbers 3, 5, 7, 8, 9, 11, 12, 14, 15,17, 18 and 19 of parts 1, 2, 3.

All products that are relative to the standard prEN10225-99 shall be of group 2 and 3 andonly the options 2, 6, 7, 9, 10, 12, 13 (only for Z quality), 21 and 28 shall be applied. After Client approval steels of group 1 can be used in alternative to steels relative to standardEN10113-94 for thickness <40mm.

The plates and sections of Z quality shall be additionally inspected and tested inaccordance with and conforms to the requirements of the standard EN10164 - Class Z35with sample of 10 mm diameter for all the thickness. For products of Z quality that arerelative to the standard prEN10225-99 the option 13 shall be applied.Steel of Z quality having thickness equal to or greater than 50 mm shall be vacuumdegassed, sulphur refined and calcium or rare earth treated.

The applicable tolerances on plates shall be EN10029 type A.The applicable tolerances on sections shall be EN10024.The above mentioned tolerance requirements shall not applied for products that are relativeto the standard prEN10225-99 and the standard requirements shall apply.

The values of the chemical composition shall be in accordance with EN10025-95,EN10113-94 and prEN10225-99 with the additional requirements indicated below.

If Boron content is not indicated in the ladle analysis it shall be considered equal to0.008%.

The limited values for CEV as contained in standard EN10113-94 shall also be appliedto the steel associated to EN10025-95 having the same yield values.For all steels with carbon content < 0,12% the carbon equivalent shall be calculatedboth with the IIW formula (CEV) and the Ito-Bessyo formula (Pcm) included in standardprEN10225-99

Maximum allowable value of Pcm for steels of grade S275 relative to standardsEN10025-95 and EN10113-94 is 0,22%, while for steels of grades S355 relative tostandards EN10025-95 and EN10113-94 and steels of grade S460 relative tostandards EN10225-99 the Pcm maximum allowable values shall be those indicated in

standard prEN10225-99 (table 3) respectively for steels S355G9+M and S460.

For structural class "a" and quality Z, S < 0.01% and P < 0.025%.For EN10113-94 steels, (V+Nb+Ti) < 0,11%

2.2 TESTING

For plates coming from ingots, the samples shall be taken from the end corresponding tothe head of the ingot.





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2.2.1 Impact test

One or two sets depending upon the thickness and the structural element class as reportedin the following table.

Table H - Number of impact tests

Element Class 1 set 2 set

a, b t < 40 mm t > 40 mmc t < 60 mm t > 60 mmd t < 60 mm na

The first set shall be taken at 2 mm below (outer) surface, while the second shall be takenat half thickness. For M steels sets shall be taken at half thickness.Impact test results shall comply with requirements of section 1.6 of this document.If the impact tests are to be carried out on samples of reduced sections 10 x 7.5, therequested average values shall be multiplied by the corrective coefficient of 0.8.

2.2.2 Strain ageing tests for plates:

Plates of structural classes "a, b, c" assigned to the fabrication by cold forming withdiameter/thickness ratio less than 30 and greater than 20, if an heat treatment is notperformed, shall be to strain ageing test according to the option 12 of standard prEN10225-99. In case of diameter/thickness ratio is equal or less than 20 the test shall be carry outusing the actual ratio or in alternative an heat treatment after cold forming shall be carry out.Results of impact test carry out during strain ageing test shall conform to the minimumrequirements for undeformed steel of this specification

2.2.3 Non destructive tests

All plates with thickness greater or equal to 50 mm and Z quality plates of any thickness,shall be ultrasonic inspected on the surface and on edges according to the standardEN10160, considering of class C for Z quality plates and class B for other plates.

The above mentioned requirements shall not apply for products that are relative to thestandard prEN10225-99 and the standard requirements still apply (section 8.4 of standardprEN10225-99).Hot rolled sections shall be controlled according to EU186, with survey extended to

A+B+C+D and quality class for acceptance 12 and 21 for classes “a, b, c” and A+B for classes “d, e”.

2.3 REPAIRS

Correction of minor defects by grinding shall be as per standard EN10163.

In order to check the complete elimination of all minor defects the ground areas shall beinspected with the MT method.Repairs of defects by welding shall be carried out after Client approval and according to

standard EN10163 with the following limitations:

welding repairs shall be carried out with qualified procedure and by qualifiedwelders in accordance with the requirements of Appendix A;

weld shall be checked with MT and UT method. The acceptance limits shall be asforeseen on previous paragraph.

For products of Z quality no repairs are allowed.





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3. API PIPE

3.1 GENERAL

Pipes fabricated according to API 5L-00 may be purchased if they satisfy all the

requirements defined in this chapter.Pipes shall be of quality PSL2 (with exception of grade A25) and may be may be seamlessor longitudinally welded with SAW procedure up to a maximum diameter of 508 mm (20").For conductor pipes the limit of maximum diameter is 762 mm (30”).

Generally all pipes shall have the supplementary requirements API 5L-00 SR4, only for thickness greater than 12mm, and SR5B. In particular the supplementary requirementSR5B shall not apply to pipes to be used in structural element class "e".Welded pipes shall have non destructive examination according to the requirements of thisspecification.

The mechanical properties on finished products shall conform to the API 5L-00 specificationand to the impact test requirements of section 1.6 of this document (for impact properties).

The pipe to be used in structural classes "b” shall be supplied in the normalised condition.UOE process is acceptable. Spiral welded pipes are not allowed.The allowed steel production processes are basic oxygen and basic electric arc furnace.

Welding processes for longitudinally welded pipes shall be qualify according to standardEN288 and requirements of paragraph 1 of this specification.

3.2 CHEMICAL COMPOSITION

The chemical composition shall be in accordance with the requirements of the API 5L-00specification and the following additional requirements.The acceptable limits for carbon equivalent are indicated in the following table

Table I - max values for carbon equivalent

Yield strength Thickness CEV % Pcm %

Re < 255 MPa t < 20 mm 0.41 0.22

20 < t < 50 mm 0.39 0.22

255 < Re < 355 MPa t < 50 mm 0.43 0.22

355 MPa < Re t < 50 mm 0.43 0.23

For all structural classes the following limit on heat chemical analysis shall applyC 0.20% max

Further limitations for the chemical analysis for structural classes "b, c" are as follows:Cu 0.40% maxV 0.1% max

3.3 NON DESTRUCTIVE TESTING AND DIMENSIONAL TOLERANCES

All welding shall be inspected according to API 5L-00 sect.9.7

All welded pipes to be used in structural classes "b, c" shall be controlled with UT system for the entire length along a directrix placed at 90° and along directrices placed each other atdistance of 150 mm. Seamless pipes, with exception of A25grade, shall be controlled withUT system according to requirements of section 9.7.2.6 and SR4 of API 5L-00.

The acceptable defect limits shall conform to those required by standard API 5L-00 section7.8 with the following amendments:

longitudinal defects shall be evaluated on the reference hole of 5% the pipe thickness;





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the pipe shall be free from undulations, folds, chips, cracks, scratches and other detrimental defects;

the lamination defects shall not extended for more than 1000 mm2;

The repair of the defects is acceptable only after Client approval.The repair shall be carried out as per limits and requirements of API 5L-00 appendix B.

Dents shall not be deeper more than 3 mm or 1% of external diameter whichever is the less,with an extension not greater than 25% of the external diameter.





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4. FABRICATION OF STRUCTURAL STEEL TUBES

4.1 GENERAL

This chapter contains the minimum requirements for the fabrication of longitudinally double

side welded tube of any structural class, made in one piece from plate.

The fabrication shall be done in accordance with the provisions set out in API Specification2B, with the requirements of this specification indicated below.The requirements S-2 shall be applied, with the conditions defined in this specification.

Plates to be used for tube fabrication shall comply to the requirements of this specification.In particular when diameter/thickness ratio is less than 30 materials shall be to strain ageingtest or in alternative heat treated after cold forming according to section 2 of this document.

4.2 QUALIFICATION OF THE FORMING PROCEDURE

Each forming process, including cold re-rolling for tube calibration after welding, shall be

qualified with the tube in its final condition.For this purpose, an element of welded tube shall be carried out for every grade and qualityof steel according to the proposed procedure, subsequent welded according to thatforeseen by the fabrication specification and cold sizing, including re rolling where used.The local deformation at weld level shall be measured by a straight gouge 300 mm long,measuring the gap between the weld and gouge itself. Deformations greater than qualifiedvalue shall require new qualification.The length of the sample shall be equal to the diameter of the tube used and can not lessthan 1 m.Qualification tests shall be as per following table.

Table J - Mechanical tests

Thickness Type and number of tests

< 16 mm 1 set for KCV impact test (1)1 tensile test on base material

3 macro and hardness on base material and HAZ (2)

> 16 mm 2 set for KCV impact test (1)1 tensile test on base material

3 macro and hardness on base material and HAZ (2)

Note: (1) Impact test specimen set (KCV) shall be taken at 2 mm under the surfacewith axis perpendicular to the longitudinal tube axis. Specimen shall be taken onbase material close to the welding. First specimens set shall be taken from theouter surface, the second specimens set shall be taken from the inner surface.Impact test shall comply with requirements of section 1.6 of this document.(2) Test shall be carried out on base material and HAZ with at least threereadings for each test. Maximum allowable hardness shall be 350 HV10

The forming procedure is valid under the following conditions:

same fabricator;

steel grade lower than those qualify;

impact properties lower than specify;

same manufacturing process;

D/t ratio greater than the qualification value;

cold expansion rate or deformation after welding restored by the re-rolling notbeyond the tested value;





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same calender process.

Existing qualification accepted by Client avoid new qualification.

4.3 WELDING

The requirements of the paragraph API 2B from 5.2 to 5.4 are applicable with therequirement S-2, referring to the standard EN288 and the requirements of chapter 1 of thisspecification.

Production weld test coupon shall be carried out, starting the welding with a first coupon testand continuing every 120 m.Production weld test coupon shall be welded with same welding procedure and materialused in production and the first coupon shall be checked as per qualification procedure,while for the other one the following test shall be required:

one transverse tensile test

one upright bend test

one upside-down bend test

two side bend tests can be carried out instead of the upright and upside-downbend tests

one impact test in FL + 2 mm

one impact test in weld metal

1 macro test

In case of positive results but after Client approval only, production weld test coupon shallbe welded after 240 m from that point onwards.

4.4 CONTROLS AND REPAIRS

The 100% of each longitudinal weld shall be ultrasonically tested with the requirementsgiven by the chapter 1 of this specification.

One radiography shall be carried out on 350 mm of weld at each tubular ends. The 20% of each weld shall be MT inspected on external surfaces. Wherever possible MT shall becarried out also on the internal surface of the weld.

The requirements of the paragraph API 2B 7.4 apply with the following amendments.

Plates having surface condition that may impair the forming operation or which mayhave scale incorporated into its surface shall be blasted before forming.

Dents, marks or other surface damages that may appear after forming shall not exceed3 mm in depth.

In any case superficial defects shall not have sharp corners and shall jointed with a 1to 4 transition.





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5. FABRICATION OF STRUCTURAL STEEL SECTIONS FROM PLATES

5.1 GENERAL

This chapter contains the minimum requirements for the fabrication of longitudinally welded

sections of any structural class, made from steel plate conform to the requirements of thisspecification.The sections are intended to be without stiffeners.The fabrication shall be done in accordance with the provisions set out in API 2B with theadditional requirements here given and reading “section” instead of “pipe”The requirements S-1 and S-2 shall be applied.

Sections shall be fabricated with their longitudinal axes parallel to the plate rolling direction.

5.2 FABRICATION

The requirements of the paragraph API 2B from 5.2 to 5.4 are applicable with therequirement S-2, referring to the standard EN288 and the requirements of chapter 1 of this

specification.

The welds shall be full double side penetration or double fillet in accordance with theindications of the drawings supplied with the purchase order.Tack weld, root passes and repair welding may be carried out with SMAW or GMAWprocesses. Root tack weld may be continuos.

Production weld test coupon shall be carried out, starting the welding with a first coupon testand continuing every 120 m.Production weld test coupon shall be welded with same welding procedure and materialused in production and the first coupon shall be checked as per qualification procedure,while for the other one the following test shall be required:

one FL+2 mm and WM Charpy-V strength test.

one macro and hardness test.

In case of positive results but subject to Client approval, production weld test coupon shallbe welded after 240 m from that point onwards.

The requirements of the paragraph API 2B 5.2 apply, but the requirements of the Charpy V-notch shall be in accordance section 1.6 of this specification. Welding ProcedureQualifications for fillet welds shall be according to EN288 with macro and hardness test.Welding Procedure Qualifications owned by the fabricator may be submitted to the Client for acceptance without requalification.

5.3 DIMENSION AND TOLERANCESTilt and roof-shape of flanges shall be not greater than (1+0.01b)mm with 6 mm maximum;flange eccentricity shall be not greater than 0.02b with 6 mm as maximum value, where b isflange width and t is flange thickness.

Twisting of web shall be not greater than (1+0.01h)mm with 10 mm maximum; bow of webshall be not greater than 0.01h with 0.5t as maximum value, where h is web height and t isweb thickness.

5.4 INSPECTION AND REPAIR

The 100% of each longitudinal full penetration weld shall be UT tested with therequirements indicated in the chapter 1 of this specification.The 20% of each weld, either complete penetration or fillet, shall be MT inspected.





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Fillet welds and partial penetration welds shall be inspected in accordance with MT 100%for components of classes " a, b," and 20% for classes “c, d” on parts chosen by Client.

Plates having surface condition that may impair the fabrication operation or which may havescale incorporated into its surface shall be blasted before fabrication. Dents, marks or other

surface damages that may appear after fabrication shall not exceed 3 mm in depth.





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On plates in absence of documents relevant to those inspections, plates with thicknessgreater or equal to 20 mm shall be UT inspected along lines perpendicular to the rollingdirection spaced 100m, and 100% of ends on a strip of at least 50 mm width.

For pipes, UT shall be carried out in agreement with the Client, along a grid according to

chapter 3, with extension not less than 30% of the total length including the ends of eachelement.

On rolled shapes available from stock non destructive examination is not required for structural element classes "d" and "e" while for structural element classes "a", "b" and "c"(shape with web equal or greater than 300mm) UT test shall be carry out at least on 3shapes for heat and for type according to section 2.2.3 of this specification. In case one of this test does not give satisfactory result the UT test shall be carry out on all shapes of theheat.

The acceptance criteria for UT test shall be those of this specification.





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7. MISCELLANEA

7.1 BOLTS

Types, dimensions and classes of the bolts and fasteners shall be indicated on the

construction drawings.

Bolting materials for structural applications shall generally be carbon or low alloy steels.

The following limitations shall apply:

For topside applications, the strength class shall not exceed ISO 898 class 10.9, UNI3740 Class 10.9;

For submerged bolts, the strength class shall not exceed ISO 898 8.8, ASTM A 320Grade L7 or A 193 Grade B7 / A 194 2H, UNI 3740 Class 8.8;

All bolts and fasteners < 10mm diameter shall be made of stainless steel;

All bolts and fasteners > 10mm diameter shall be processed by hot dip galvanizing,

minimum 50µ thickness, or equivalent process in accordance with ASTM A 153.

For specific projects of subsea structures where there is no possibility of inspection or maintenance, and cathodic protection cannot be ensured corrosion resistant bolts (e.g. alloy625) shall be used. It shall be verified that the materials have acceptable mechanicalproperties at the actual design temperatures.

For submerged applications, where the dissolution of a thick zinc layer may cause loss of bolt pretension, electrolytic galvanizing or phoshating shall be used. Electrolytic galvanizingshall be followed by post baking.

For subsea installations the use of poly tetra fluor ethylene (PTFE) based coatings can beused provided electrical continuity is verified by measurements.

Cadmium plating shall not be used.





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8. APPENDIX A: PRODUCTION QUALIFICATION

The qualification of the production consists of a series of tests including all the productiontest and a number of special tests and CTOD test to be carried out only one time and beforestarting the steel production.

8.1 SPECIAL TESTS

On the materials subject to supply, the following test for the assessment of the weldabilityproperties shall be carried out:

Bead on Plate according to prEN10225-99 Appendix F;

controlled Thermal Severity according to prEN10225-99 Appendix G;

transition curves of welded joints carried out on Fusion Line, FL+2 mm and FL+5 mm.

Weldability tests only for steels that are relative to the standard prEN10225-99according to prEN10225-99 Appendix E with exception of CTOD test.

All tests shall be carried out on the thickest plate to supply within the validity of thequalification conditions specified below.The transition curve shall be carried out with at least 8 sets to be tested: one at the projecttemperature and the other seven at temperatures differing between them 10°C, two aboveand five below the design temperature. The specimens shall be taken from the flat side of the joint carried out on K bevelled seams welded with heat input of 1.5 kJ/mm. Secondtransition curves shall be carried out for a similar joint welded with an heat input of 5 kJ/mm.

8.2 CTOD TEST

Supply of materials to be used for joint cans with thickness greater than 50 mm shall besubmitted, on the thickest plate of supply and for each structural grade, to CTOD tests in

accordance to the standard BS 7448 to be carry out on butt weld joint, with K bevel and5kJ/mm heat input, previously submitted to simulated post weld heat treatment at 590 ±

10°C. Tests shall be carried out at -10 °C and the munber and position of the samples shallbe in accordance to table E.4 of standard prEN10225-99

8.3 RESULTS AND VALIDITY OF THE QUALIFICATION TEST

The results of all of the tests are subject to Client for approval. The qualification tests arevalid only if carried out in the presence of a Certifying Authority appointed by the Client.The following conditions are essential parameters whose variation implies the necessity of arequalification:

same steel-mill producer;

same elaboration and fabrication process;

same method of deoxidisation;

same heat treatment and supply condition;

chemical composition of the cast not varying with respect to the sample chemicalanalysis exceeding the limits indicated in paragraph 2.4 of standard API RP 2Z;

the material thickness shall not be greater than 20% in relevant to the thickness of the test sample.

general specification of offshore platforms

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