General Specification of Offshore platforms

Eni S.p.A.

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GENERAL SPECIFICATION

OFFSHORE PLATFORMS

STEEL FOR STRUCTURES

08832.STR.MME.SPC Rev.7 December 2001

ENGINEERING COMPANY STANDARD Documento riservato di proprietà di Eni S.p.A. Divisione Agip. Esso non sar à 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.

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08832.STR.MME.SPC Rev.7 December 2001 Pag. 2 di 25

FOREWARD Rev. 0

December 1992 Sheet N. 40 Issue

Rev. 1

February 1993 Sheet N. 40 Some modifications

Rev. 2

July 1993 Sheet N. 40 Modified 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 1994 Sheet N. 43 RINA comments are included. Steel designation has been changed according to EN10027.

Rev. 4

October 1995 Sheets N. 38 Some 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 1998 Sheets N. 26 General revision with changes of the paragraphs

Rev.7

December 2001 Sheets N. 25 This revision include: steels with 460MPa SMYS, steels according to prEN10225, steels produced with thermomechanical 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 data collected.

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TABLE OF CONTENTS

1. 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

GENERAL .........................................................................................................................4 INTRODUCTION ...............................................................................................................4 DEFINITION ......................................................................................................................4 APPLICABLE STANDARD................................................................................................5 DOCUMENTS AND TESTING ..........................................................................................5 MARKING ..........................................................................................................................7 IMPACT TEST OF MATERIALS .......................................................................................8 WELDING ..........................................................................................................................9 NON DESTRUCTIVE EXAMINATION ..............................................................................9

2. 2.1 2.2 2.3

PLATES AND HOT ROLLED SECTIONS......................................................................11 GENERAL........................................................................................................................11 TESTING .........................................................................................................................11 REPAIRS .........................................................................................................................12

3. 3.1 3.2 3.3

API PIPE..........................................................................................................................13 GENERAL........................................................................................................................13 CHEMICAL COMPOSITION ...........................................................................................13 NON DESTRUCTIVE TESTING AND DIMENSIONAL TOLERANCES .........................13

4. 4.1 4.2 4.3 4.4

FABRICATION OF STRUCTURAL STEEL TUBES ......................................................15 GENERAL........................................................................................................................15 QUALIFICATION OF THE FORMING PROCEDURE.....................................................15 WELDING ........................................................................................................................16 CONTROLS AND REPAIRS ...........................................................................................16

5. 5.1 5.2 5.3 5.4

FABRICATION OF STRUCTURAL STEEL SECTIONS FROM PLATES.....................17 GENERAL........................................................................................................................17 FABRICATION ................................................................................................................17 DIMENSION AND TOLERANCES ..................................................................................17 INSPECTION AND REPAIR............................................................................................17

6. 6.1 6.2 6.3

MATERIALS FROM STOCK ..........................................................................................19 GENERAL........................................................................................................................19 TEST................................................................................................................................19 NON DESTRUCTIVE EXAMINATION ............................................................................19

7. 7.1

MISCELLANEA...............................................................................................................21 BOLTS .............................................................................................................................21

8. 8.1 8.2 8.3

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

9. 9.1 9.2

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

10.

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

11.

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

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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 rolled sections, 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 when necessary. 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 compliance with the minimum requirements of this specification and of the referenced standards. Supply of materials produced with thermomechanical rolling process is allowed upon condition 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 elements as 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 with thickness equal or more than 45 mm and for all Z quality plates, before starting the production weldability data of the material shall be provided to the Client, in accord to tests similar to these indicated in Appendix A "Production Qualification". In case of materials manufacturer can not produce weldability data, or does not have any experience in producing the materials required by this specification, a production qualification shall be carry out according to appendix A. In addition to the requirements of the above paragraph the production qualification shall be carry out when expressly indicated in the order. The material described in this specification can be acquired to the steel manufacturer or by stock. In any case, required documents and certificates shall be available for the Client before using 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 CERTIFYING Person or Society accepted by the Client , which for SOCIETY 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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1.3


CTOD

Crack Tip Opening Displacement referred to BS 7448-1

Unit test

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

APPLICABLE STANDARD The standards that are listed here below forms an integral part of this specification, in the whole or only the mentioned paragraphs, and with the modifications or additions indicated by 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 and dimensions", 10025-95 "Hot rolled products of non-alloy structural steels and their technical delivery conditions", 10027 “Designation systems for steel”, 10029 "Hot rolled steel plates 3mm thick or above - Tolerances on dimensions, shape and mass", 10113-94 "Hot rolled products in weldable fine grain structural steels", 10160 "Ultrasonic testing of steel flat products of 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 hollow sections of non-alloy and fine grain structural steels", pr10219 "Cold formed structural hollow sections of non-alloy and fine grain structural steels", 10164 “Steel products with improved deformation properties perpendicular to the surface of the product. Technical delivery conditions 10204 “Metallic products. Types of inspection documents”, pr10225-99 “Weldable structural steels for fixed offshore structures”

EU

103 "Determinazione micrografica della grossezza del grano ferritico o austenitico degli acciai", 168 "Prodotti siderurgici-Documenti di controlloContenuti", 186 "Ultrasonic testing of broad flanged beams with parallel flanges and IPE beams"

API

RP 2Z "Recommended practice for preproduction qualification for steel plates 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 strain fracture 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 edition shall 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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TABLE A - TYPE OF CERTIFICATE Structural element class a, b, c d e

Document referred to EN 10204 3.1.C 3.1.B 2.2

Documents shall have to be endorsed by an Examiner or Certifying Society approved by the Client. True copy of the original documents issued by the quality department of the steel manufacturer is considered equivalent to the original document. Copy of documents which do not fall within the previous case may be accepted as substitutive of the original only if authenticated by an Examiner or Certifying Society approved by the Client. In any case the documents of the sea fastening materials shall be also in compliance with the code and the requirements of the Certifying Society in charge of the transport certification At Client request, tests shall be carried out at the presence of a Client Representatives. The testing record shall contain at least the following information: Table B - Minimum information in the test documents Type Identific ation

Composition

Heat treatment (only for normalised and quenched and tempered steels) Mechanical properties

Other

Description mill location

EU168 code A01

the purchaser's order and item number method of steel manufacture heat or cast number supply condition dimensions grade of steel ladle analysis product analysis (where applicable) carbon equivalent Pcm details of heat treatment stating temperature, soaking times and cooling method

A07 C70 B07 B04 B11/B13 B02 C71/C92

yield strength, tensile strength, yield/tensile strengths ratio, elongation impact test results through thickness tensile test results, if required Strain age test where applicable Nominal or actual mass non destructive test results Caption "CONFORM WITH AGIP SPECIFICATION 08832-STR-MME-SPC- Rev 7

C11/C12/C13/C 60 C42/C43 C60/C99 D02-99

C71/C92 C96/C99 B05

D02/C69

If during mechanical testing unexpected defects detrimental to the employment of the materials are verified, the plates, sections or pipes on which the samples have been taken, shall be submitted for verification by means of additional controls to clarify the nature and extent of the defects. Above examinations shall be extended to all the products that constitute the test unit. If the results of these controls confirm the dimension and extension

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of defects detrimental to the product application, all the products of the test units shall be discarded 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 shall be 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 marking shall be positioned at two opposite angles of the plates and at the two ends of the beams and 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:

1.5.2



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.

Die stamping Die stamping shall be carried out on material having thickness equal to or greater than 6 mm with punch having letters 8 mm high at least. The die stamped markings shall be ringed with 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 with their combination give immediately visual information about the plate characteristic. Each pipe shall be painted with colour code stripes located on its internal surfaces and on thickness at both ends. Each sections shall be painted on its web with colour code stripes located at both ends. The width of each stripe for plates, sections and pipes shall be at least 50 mm, and the distance between the stripes shall be 100 mm for plates and 50 mm for tubular and sections.

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Table C - Colour Code Colour White Orange Yellow Blue Green Silver Red

1.6

Type S275 S355 S460 -

t°C KCV 0 -20 > -40 -

Properties Z

IMPACT TEST OF MATERIALS Materials to be supply according to this specification shall be submitted to Charpy-V impact test 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 < t < 50,8 mm < t < 25,4 mm 50,8 mm 70 mm °Tp > +5 °C t < 15 mm 15 mm < t < 30 mm < t < 50,8 mm < t < 30 mm 50,8 mm 70 mm Test temperature Structural Element Class a -20°C

b

-20°C

c

0°C

70 mm < t < 100 mm 70 mm < t < 100 mm

100 mm < t < 150mm 100 mm < t < 150 mm

-40°C

0°C (2)

d e Note:

1.6.2

Impact test not required

not applicable

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

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Table E - adsorbed energy Nominal yeld strength (Ry)

Average adsorbed energy on base material (J)

> 450 Mpa 350
60 50 40

Average adsorbed energy on weld metal and heat affected zone (J) 45 36 27

Minimum adsorbed energy on weld metal and heat affected zone (J) 32 26 19

Minimum adsorbed energy of impact test single piece of base material shall be greater than 70% of the average required energy. 1.7

WELDING The welding for the fabrication of pipes and sections shall be in accord with the requirements 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 08833STR.MET.SPC " Offshore Structures Construction " Welders shall be qualified according to EN287 and EN1418 by Examiner or Certifying Society approved by the Client. Each welding process shall be qualified according to EN288 by Examiner or Certifying Society approved by the Client. The welding procedure qualification test and the production weld test coupon shall include hardness 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

t < 45 mm

cap root cap root

t > 45 mm

Double and singleside welding WM + HAZ none WM + HAZ WM + HAZ

Note: Cap: 2 mm +/- 0.5 mm below external weld cap surface. Root: in root region of back welding. 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 24 hours after welding completion. Inspection and NDT prior to PWHT shall be at the Contractor discretion and shall not avoid further tests.

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All bevels shall be 100% visually inspected and those relevant to component “a, b, c” shall be 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 that originates them. Ultrasonic test shall be performed by operators certified at least level II according to EN473 or 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 as foreseen in the procedures. The UT shall be used for search hot, cold and chevron cracks. UT automatic equipment is accepted. 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 reexamined, 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 specification may be left unprepared.  Echo indications of transverse defects are in any case to be regarded as defects requiring repair: this does not apply where indication can be unequivocally correlate to longitudinal defects. The length of acceptable volumetric flaws are as per following table. Table G - UT acceptable limits (mm) Max HD e DAC HD > DAC HD > DAC/2 HD = maximum echo amplitude

a, b 10 20

c 30 45

d 40 60

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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 supplementary requirements defined in this sections. For all the products that are relative to the standard EN10025-95, all the options foreseen in its 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 in its 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 and only 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 standard EN10113-94 for thickness <40mm. The plates and sections of Z quality shall be additionally inspected and tested in accordance with and conforms to the requirements of the standard EN10164 - Class Z35 with sample of 10 mm diameter for all the thickness. For products of Z quality that are relative 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 vacuum degassed, 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 relative to 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 to 0.008%.  The limited values for CEV as contained in standard EN10113-94 shall also be applied to the steel associated to EN10025-95 having the same yield values. For all steels with carbon content < 0,12% the carbon equivalent shall be calculated both with the IIW formula (CEV) and the Ito-Bessyo formula (Pcm) included in standard prEN10225-99 Maximum allowable value of Pcm for steels of grade S275 relative to standards EN10025-95 and EN10113-94 is 0,22%, while for steels of grades S355 relative to standards EN10025-95 and EN10113-94 and steels of grade S460 relative to standards 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, For EN10113-94 steels, (V+Nb+Ti) < 0,11%

2.2

S

<

0.01%

and

P

<

0.025%.

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

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Impact test One or two sets depending upon the thickness and the structural element class as reported in the following table. Table H - Number of impact tests Element Class a, b c d

1 set t < 40 mm t < 60 mm t < 60 mm

2 set t > 40 mm t > 60 mm na

The first set shall be taken at 2 mm below (outer) surface, while the second shall be taken at 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, the requested 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 with diameter/thickness ratio less than 30 and greater than 20, if an heat treatment is not performed, shall be to strain ageing test according to the option 12 of standard prEN1022599. In case of diameter/thickness ratio is equal or less than 20 the test shall be carry out using 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 minimum requirements 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 standard EN10160, 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 the standard prEN10225-99 and the standard requirements still apply (section 8.4 of standard prEN10225-99). 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 be inspected 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 qualified welders in accordance with the requirements of Appendix A;



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

For products of Z quality no repairs are allowed.

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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 seamless or 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 requirement SR5B 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 this specification. The mechanical properties on finished products shall conform to the API 5L-00 specification and 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 standard EN288 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-00 specification 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 Re < 255 MPa 255 < Re < 355 MPa 355 MPa < Re

Thickness t < 20 mm 20 < t < 50 mm t < 50 mm t < 50 mm

CEV % 0.41 0.39 0.43 0.43

Pcm % 0.22 0.22 0.22 0.23

For all structural classes the following limit on heat chemical analysis shall apply C 0.20% max Further limitations for the chemical analysis for structural classes "b, c" are as follows: Cu 0.40% max V 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 at distance of 150 mm. Seamless pipes, with exception of A25grade, shall be controlled with UT 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 section 7.8 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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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 Specification 2B, 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 ageing test 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 quality of steel according to the proposed procedure, subsequent welded according to that foreseen 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 qualified value shall require new qualification. The length of the sample shall be equal to the diameter of the tube used and can not less than 1 m. Qualification tests shall be as per following table. Table J - Mechanical tests Thickness < 16 mm

Type and number of tests 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 surface with axis perpendicular to the longitudinal tube axis. Specimen shall be taken on base material close to the welding. First specimens set shall be taken from the outer 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 three readings 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 not beyond 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 the requirement S-2, referring to the standard EN288 and the requirements of chapter 1 of this specification. Production weld test coupon shall be carried out, starting the welding with a first coupon test and continuing every 120 m. Production weld test coupon shall be welded with same welding procedure and material used 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-down bend 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 shall be 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 requirements given 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 be carried 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 may have scale incorporated into its surface shall be blasted before forming.  Dents, marks or other surface damages that may appear after forming shall not exceed 3 mm in depth.  In any case superficial defects shall not have sharp corners and shall jointed with a 1 to 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 this specification. The sections are intended to be without stiffeners. The fabrication shall be done in accordance with the provisions set out in API 2B with the additional 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 the requirement 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 the indications of the drawings supplied with the purchase order. Tack weld, root passes and repair welding may be carried out with SMAW or GMAW processes. Root tack weld may be continuos. Production weld test coupon shall be carried out, starting the welding with a first coupon test and continuing every 120 m. Production weld test coupon shall be welded with same welding procedure and material used 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 shall be welded after 240 m from that point onwards. The requirements of the paragraph API 2B 5.2 apply, but the requirements of the Charpy Vnotch shall be in accordance section 1.6 of this specification. Welding Procedure Qualifications 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 TOLERANCES Tilt 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 is flange width and t is flange thickness. Twisting of web shall be not greater than (1+0.01h)mm with 10 mm maximum; bow of web shall be not greater than 0.01h with 0.5t as maximum value, where h is web height and t is web thickness.

5.4

INSPECTION AND REPAIR The 100% of each longitudinal full penetration weld shall be UT tested with the requirements 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 have scale 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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Divisione Agip 6.

MATERIALS FROM STOCK

6.1

GENERAL


Material shall be supplied with required certificates endorsed by Examiner or Certifying Society approved by the Client and satisfying the requirements of this specification Such certificates shall be original or true copies of the originals issued by the quality department of the steel manufacturer. Copy of documents which do not fall within the previous cases may be accepted as substitutive of the original only if authenticated by an Examiner or Certifying Society approved by the Client. If at the beginning the certificates were endorsed by Examiner or Certifying Society approved by the Client or with certificates not satisfying the requirements of this specification, materials cannot be considered acceptable. The correspondence between material and its certificate shall be verified by checking the quality control plan of supplier or by means of the repetition the mechanical tests and chemical analysis on one element of the unit test. The limits for the chemical composition and for the carbon equivalent values (CEV and Pcm) shall be applied also to the material from stock. In case of welded pipes, welding processes may be accepted if only they are qualified in accordance to standards approved by the Client upon the condition that comply with impact test requirements of section 1.6 of this specification. Welded pipes, in the absence of production testing coupons, shall be submitted to tests through specimens taken in accordance with procedures and requirements set out by this specification. The number of tests shall be agreed with the Client. Weldability of stock materials, where required (see section 1.1 of this specification), shall be demonstrated with data referred to previous productions. Data shall comply with the applicable limits requirements of appendix A of this specification. For stock materials of quality Z having thickness equal or greater than 50mm a sulphur content < 0.005% is acceptable in alternative to: vacuum degassing, sulphur refining, calcium or rare earth treating (required at section 2.1 of this specification). 6.2

TEST Any non-conformance to the above reference requirements for material from stock shall be reported to the Client, with whom a proper inspection and test programme will be agreed. This programme will normally contain the complete test of the items in compliance with the content of this specification. In case of non conformance, when the properties are outside the reference standard and specification limits, the material may be used only after repetition of mechanical tests and chemical analysis of each item. In case of API 5L-00 pipes, for every test unit a hardness control shall be carried out on a pipe chosen by the Client. If a part of a pipe presents a hardness greater than 327 BRINELL 2 for a total area > 500mm ,the pipe shall be rejected and the hardness test shall be repeated on other three pipes chosen by the Client on the same test unit. In case that on one of the new tested pipes the measured hardness is greater the allowable limit the hardness test shall be carry out on all the pipes of the test unit, otherwise the entire test unit shall be rejected.

6.3

NON DESTRUCTIVE EXAMINATION Steel plates, pipes and sections from stock shall have satisfied non destructive examination required by this specification.

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On plates in absence of documents relevant to those inspections, plates with thickness greater or equal to 20 mm shall be UT inspected along lines perpendicular to the rolling direction 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 each element. 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 3 shapes 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 the heat. The acceptance criteria for UT test shall be those of this specification.

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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, UNI 3740 Class 10.9;  For submerged bolts, the strength class shall not exceed ISO 898 8.8, ASTM A 320 Grade 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. alloy 625) shall be used. It shall be verified that the materials have acceptable mechanical properties 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 galvanizing shall be followed by post baking. For subsea installations the use of poly tetra fluor ethylene (PTFE) based coatings can be used provided electrical continuity is verified by measurements. Cadmium plating shall not be used.

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Divisione Agip 8.


APPENDIX A: PRODUCTION QUALIFICATION The qualification of the production consists of a series of tests including all the production test and a number of special tests and CTOD test to be carried out only one time and before starting the steel production.

8.1

SPECIAL TESTS On the materials subject to supply, the following test for the assessment of the weldability properties 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 prEN10225-99 according 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 the qualification conditions specified below. The transition curve shall be carried out with at least 8 sets to be tested: one at the project temperature and the other seven at temperatures differing between them 10°C, two above and 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. Second transition 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 be submitted, 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 and 5kJ/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 shall be 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 are valid 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 a requalification: 

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 chemical analysis 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.

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Divisione Agip 9.

APPENDIX B: MATERIALS REFERRED TO OTHER STANDARDS In addition to the standard prEN10225-99, EN10025-95, EN10113-94 and API 5L-00, that are referred by this specification, the Purchaser may use other reference standards for the fabrication and qualification of steel, provided that the minimum requirements of this specification and the referred standards are satisfied. To this purpose, the Purchaser shall demonstrate the equivalence of the proposed material, by means of documents additional to the inspection documents and test results that show the differences between the standards. Some alternative standards are listed below.

9.1

EN10210 AND EN10219 PIPES Pipes supplied with these standards are applicable for thickness less than 50 mm. They shall be in compliance with standards EN10210 and EN10219 with the option 1 to 9. Arc-welded pipes are not accepted. The welding procedures for longitudinally welded pipes shall be qualified in compliance with the requirements of chapter 4. Test and non destructive examination shall be in compliance with the requirements given in the chapter 2.

9.2

ASTM PIPES Material referred to ASTM specification and equivalent to the type indicated in this specification may be applied as follows, including in particular the requirements API 5L-00 SR4 (NDT tests) and API 5L-00 SR5 (impact test) as emended by this specification: Table K - Alternative materials for pipes Structural element class b, c, d

e

ASTM standard A333 GR.6 A334 GR.6 A106 GR.B A524 GR.I e II A53 GR.B A500 GR.A e B A139 GR.B

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APPENDIX C: STRUCTURAL CLASSES Table L - structural classes

Structural Classes

a

b

Definition Structural elements essential for the safety of the platform with low structural redundancy, complex shape and stresses concentration not easily foreseeable

Structural elements essential for the global safety of the platform

Module and Deck

Jacket

Not typical nodes with complex geometry

Not typical nodes with complex geometry

Typical nodes with simple geometry; Lifting padeyes and their connection to the deck; Legs; Tubular and beam elements situated between two legs; Crane columns; Flare and supports bridges

Typical nodes with simple geometry; Lifting padeye of jackets and templates and elements connected to; Legs; bracings; Sleeves; Launchways and relevant attachments; Supports and reinforcements of floatation tanks.

Essential structural elements for the total structure safety with simple geometry and with fatigue stress not dimensioning

Beams with height higher or equal to 300 mm or thickness higher than 15 mm; structural walls; bridge structure and flare

d

Significant structural elements for the local safety of the structure

Beams with height lower than 300 mm and thickness up to 15 mm; Diagonal braces, sea fastening

e

Unimportant structural elements and nonstructural elements

Chequered plates; Stairs and walkways, Not structural walls; Draining system

c

Foundation piles; Buoyancy tanks; Risers supports, pin piles

Conductor guide frames; Mud mats; Boat landings; Fenders; Water tight diaphragms; Padeyes for pile and conductors, sea fastening, predrilling template and conductors installation guides Pumps casing; Grouting, flood and air system; Stairs and walkways; Anode core; Blow down

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APPENDIX D: GRADE AND APPLICATION Table M - plates and hot rolled sections (1)

°Tp > -5 t <12,5 12,5 mm< t < 25,0 mm 25,0 mm < t < 50,8 mm 50,8 mm < t < 70 °C mm mm °Tp > +5 t <15 15 mm < t < 30 mm 30 mm < t < 50,8 mm 50,8 mm < t < 70 °C mm mm Structural Applicable grade and quality Element Class a EN10113-94 S355/ EN10113-94 (2) S355L, S275/ S275L S355L, S275L, S460/S460L S460L EN10025-95 S355K2G3 b EN10113-94 S355/ PrEN10225-99 (3) S355L, S275/ S275L S355G8+M/N, S460/S460L S355G10+M/N, EN10025-95 S355K2G3 S460G2+Q/M c EN10025-95 S355J0, S275J0 EN10113-94 S460 d e

Note:

EN10025-95 S355JR, S275JR, S235JR, S185

70mm < t < 100mm 70mm < t < 100mm

100 mm < t < 150mm 100 mm < t < 150 mm

PrEN10225-99 PrEN10225-99 S355G8+M/N, S355G8+N, S355G10+M/N S355G10+N

S460G2+Q/M

not applicable

1) Impact properties of materials shall comply with requirements of section 1.6 of this specification 2) For material with thickness equal or greater than 25.4 mm supplementary requirement Z for chemical and mechanical properties shall apply. For thickness lower than 25.4 mm only supplementary requirement Z for chemical properties shall apply. 3) Only for material used in nodal joints for cans and for uninterrupted stubs having thickness equal to or greater than 25 mm supplementary requirement Z apply for chemical and mechanical properties Table N - API pipes (1) (2)

°Tp > -5 °C

t < 12,5 mm

°Tp > +5 °C Structural Element Class a

t < 15 mm

12,5 mm< t < 25,0 25,0 mm < t < 50,8 50,8 mm < t < 70 mm mm mm 15 mm < t < 30 mm 30 mm < t < 50,8 mm 50,8 mm < t < 70 mm Applicable grade and quality not applicable

b (3) c

API 5L-00 X 52 PSL2 SR5B; API 5L-00 X 42 PSL2 SR5B, API 5L-00 X65 PSL2 SR5B

d e Note:

API 5L-00 PSL2 GR B ; API 5L-00 A25

(1) Impact properties of materials shall comply with requirements of section 1.6 of this specification. (2) All pipes with thickness greater than 12mm shall have SR4 requirements (3) Excluded cans with thickness greater than 20mm

General Specification of Offshore platforms

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