General Specification Offshore Platforms Offshore Structures Construction

7/29/2019 General Specification Offshore Platforms Offshore Structures Construction

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Eni S.p.A.Divisione Agip

ENGINEERING COMPANY STANDARD

Documento riservato di proprietdi Eni S.p.A. Divisione Agip. Esso non sar mostrato a Terzi n utilizzato per scopi diversi da quelli per i quali 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

OFFSHORE STRUCTURES CONSTRUCTION

08833.STR.MET.SPC

Rev. 5 December 2001


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08833.STR.MET.SPCRev. 5 December 2001

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PREFAZIONE

Rev. 0 December 1992Total pages n. 107Issue

Rev.1 February 1993Modify sheets 37, 38, 44, 45, 79, 91, 101

Rev.2 September 1993Total pages n. 107Modify sheets 6, 7, 10, 11, 12, 13, 14, 15, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 36,37, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 51, 52, 54, 56, 57, 58, 60, 61, 62, 63, 64, 66, 67, 69, 70, 71, 72, 73, 74, 75,76, 77, 78, 81

Rev.3 December 1993Total pages n. 120RINA comments are included.General revision.

Rev.4 October 1995Total pages n. 120General revision.

Rev.5 December 2001Total pages n. 89Steels with yield strength of 460MPa and steels fabricated with thermomechanical rolling process areconsidered, check of congruence with specification 08832 STR-MME-SPC Rev.7 has been carried out,extension has been done for offshore welds and sea fastening, standard AWS D1.1/2000 has been considered,a dedicated section for impact test has been included in order to take into account recommendations of draftcommittee for revision of ISO 13819-2, reference has been done to European standards EN462 and EN970,PWHT applicability criteria has been review, specification has been review and simplify where possible.


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CONTENTS

1 GENERAL 51.1 SCOPE OF THE WORK 5

1.2 APPLICABLE DOCUMENTS 51.3 TERMS AND DEFINITIONS 61.4 REPORTING 71.5 STRUCTURAL CLASSES AND TYPICAL ELEMENTS 71.6 MATERIALS 7

2 WELDING 82.1 GENERAL 82.2 DEFINITIONS 82.3 WELD CLASS 82.4 WELDING PROCESSES 92.5 CONSUMABLES 102.6 STORAGE AND HANDLING OF CONSUMABLES 11

2.7 INITIAL DOCUMENTATION 132.8 WELDING BOOK 14

3 WELDING PROCEDURES 163.1 GENERAL 163.2 WELDING PROCEDURE SPECIFICATIONS 173.3 QUALIFICATION OF WELDING PROCEDURES (WPAR) 183.4 QUALIFIED PRINCIPAL POSITIONS 183.5 VALIDITY OF WELDING PROCEDURES (ESSENTIAL VARIABLES) 183.6 TESTING 213.7 SPECIAL TESTS 24

4 WELDERS AND WELDING OPERATORS 264.1 GENERAL 264.2 QUALIFICATIONS 274.3 RETESTS 28

5 PRODUCTION WELDS 295.1 GENERAL 295.2 WELDING SEQUENCES 335.3 TEMPERATURE 335.4 REPAIRS 345.5 CLOSURE WELDS 365.6 STRESS RELIEVING POST WELD HEAT TREATMENT 375.7 PRODUCTION TESTING COUPONS 395.8 WELDING PARAMETER CHECKING 40

6 FABRICATION 426.1 GENERAL 426.2 FORMING 426.3 WELDED ATTACHMENTS 456.4 SITE ASSEMBLY ACTIVITIES 456.5 MANUFACTURED AND MISCELLANEOUS ITEMS 466.6 FINISHING OF SURFACES 466.7 RAT HOLES 466.8 BOLTED CONNECTIONS 47

7 PREFABRICATED ITEMS TOLERANCES 487.1 FABRICATED TUBULARS, NODES AND CONES 487.2 ROLLED OR FABRICATED BEAM 50

7.3 STIFFENED PLATE PANELS 517.4 OTHER FABRICATION DETAILS 52


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8 FINAL FABRICATION TOLERANCES 538.1 POSITION OF NODES 538.2 JACKET LEGS HORIZONTAL AND DIAGONAL MEMBERS STRAIGHTNESS 538.3 JACKET CENTERING GUIDE TUBES 538.4 JACKET SLEEVES AND SHEAR PLATES 53

8.5 DECK PLANS 548.6 PILES 558.7 BUOYANCY TANKS 558.8 CONDUCTORS 568.9 J TUBES 568.10 SUPPORTS CAISSON / RISER / J-TUBES 578.11 ANODES 578.12 HANDRAILS 578.13 WALKWAYS, LANDINGS AND STAIRWAYS 578.14 TEMPLATE DOCKING PILES CENTRING SYSTEM 58

9 INSPECTION OF WELDMENTS 599.1 GENERAL 59

9.2 DEFINITIONS 599.3 REFERENCE STANDARDS 599.4 METHODS OF NDT 609.5 EXTENT OF NDT 619.6 EDGE INSPECTION 629.7 QUALIFICATION OF NDT PROCEDURES 629.8 QUALIFICATION OF NDT PERSONNEL 649.9 VISUAL INSPECTION EXECUTION 659.10 RADIOGRAPHIC TESTING EXECUTION 659.11 ULTRASONIC TESTING EXECUTION 659.12 MAGNETIC PARTICLE INSPECTION EXECUTION 679.13 STANDARDS OF ACCEPTABILITY 689.14 REPORTS 70

10 TESTING OF FIELD INSTALLED COMPONENTS 7210.1 PREASSEMBLY TESTING 7210.2 RISER PNEUMATIC TESTING 7210.3 PNEUMATIC TESTING OF BUOYANCY TANKS AND JACKET LEGS 7210.4 TESTING OF BALLASTING AND GROUTING SYSTEMS 7210.5 TESTING OF PACKERS SYSTEM 72

11 APPENDIX 1: STRUCTURAL CLASSES 74

12 APPENDIX 2: FIGURES 75


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1 GENERAL

1.1 SCOPE OF THE WORK

This specification covers the minimum requirements for fabrication and construction ofjackets, decks and modules of the offshore platforms of ENI Division AGIP spa.

This specification contains general requirements: construction drawings shall prevail overthis specification.

1.2 APPLICABLE DOCUMENTS

1.2.1 Referred Codes

For items not specially covered by this specification, the latest editions (at the time ofcontract award) of the following codes in the order shown below shall be used:

American Welding Society (A.W.S.), Structural Welding Code D1.1 / 2000.

API RP 2A "Recommended Practice for Planning, Designing and Constructing FixedOffshore Platforms".

EEMUA 158 "Construction specification for fixed offshore structures".

American Institute for Steel Construction (AISC), Manual of Steel Construction.

American Welding Society (A.W.S.), Specification for electrodes, wires and fluxes.

RINA "Guide for design, construction and installation of steel fixed off-shore platform".

RINA "List of products approved by RINA according to sections G and H to the rules".

Consumable Classification from Institutes members of the IACS InternationalAssociation Classification.

1.2.2 Referred Norms

The following norms are referred to in this specification:

BSI 709 "Methods of destructive testing fusion welded pressure vessel" welding

procedures (Para. 3)

BSI 5500 "Specification for unfired fusion welded pressure vessel" local out

roundness (Para. 7)

BSI 6072 "Method for magnetic particle flaw detection" NDT (Para. 9)

EN 287 "Approval testing of welders-Fusion welding-Part1" (Para 5), 288

"Specification and approval of welding procedures for metallic material"

(Para. 3), 473 "General principles for qualification and certification of NDTpersonnel", (Para. 9), 10025 "Hot rolled products of non-alloy structuralsteels and their technical delivery conditions" production weld (Para. 5), 462

"Non-Desstructive testing - Image quality of radiograph -Image qualityindicators", 970 "Non-Destructive examination of fusion welds -Visual


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examination", 10163 "Delivery requirements for surface condition of hot

rolled steel plates and sections"

EN 10045 "Charpy impact test on metallic materials", Charpy-V Specimen(Para. 3)

API RP2X "Reccomended practice for ultrasonic examination of offshorestructural fabrication and guidelines for qualification of ultrasonic

technicians", Standard 1104 NDT (Para. 9)

Materials which shall be certified by Certifying Authority shall be in accordance with therelevant codes of the Certifying Authority.

1.2.3 Associated Specifications

AGIP 08832-STR-MME-SPC "Purchase of offshore structural steel" Rev. 7.

1.3 TERMS AND DEFINITIONS

The following definitions are given for terms contained in this specification.

1.3.1 Parties Involved

CLIENT: ENI Division AGIP or its AuthorisedRepresentative.

CONTRACTOR The Company responsible for the fabrication andconstruction who has awarded the contract fromClient.

Sub-CONTRACTOR: The Company Sub-Contractor to Contractor,approved by Client.

SUPPLIER: The Company who receives the purchase order for supplying of materials or equipment.

EXAMINER orAPPROVED BODY:

Person or Society, accepted by the Client,committed to certify:- procedures, materials and welding operators,

- procedures, equipment and NDT personnel.

1.3.2 Definitions and abbreviations

Shall/Is to be: is used where a provision is mandatory.Should: is used where a provision is advisory but preferred.May: is used where a provision is completely discretionary.Construction Drawings: drawings issued by Client and developed to a detail level that may

change from project to project, depending on Contractor scope ofwork. Construction drawings together with other specifications definethe necessary Contractor information for fabrication drawings built upand relevant engineering detail.

Fabrication Drawings: drawings issued by Contractor that contain all the necessaryinformation required to fabricate items at shop and yard level.

Assembly sequence drawings and temporary support drawings areconsidered fabrication drawings

As built Drawings: fabrication drawings, issued by Contractor, on which are reported allthe information on how the construction has been actually built.


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Assembly sequence drawings and temporary support drawings needno to be issued in "as-built" version, except that all attachments leftonto the structure shall be reported on as built drawings.

Structural Element Class: level of importance of each structural element due to its loadingcondition and with respect to the overall integrity of the platform.

Fabrication: built-up of single item, generally executed in a shop.Construction: assembly of several items carried out at yard.na: not applicable.nr: not required.Ry: minimum specified yield strength.Rm: tensile strength.t: thiknessNDT: Non Destructive Test.Closure weld: welds on tubulars with inside diameter of 600 mm or greater without

back gouging; generally they are welds made on diagonal tubularsafter row roll-up.

Insert: structural element part with the same diagonal dimension section inwhich it is fitted.

1.4 REPORTING

Reports required throughout this specification shall conform to the applicable Contractorguarantee quality formats which shall contain, at least, the information listed in the relevantparagraphs of this specification.

1.5 STRUCTURAL CLASSES AND TYPICAL ELEMENTS

For the scope of this document the structural elements of the off-shore installations aresubdivided in classes.

The definition of the structural classes is reported in Appendix 1 with the definition ofstructural element class for typical jackets, decks and modules structural elements.Construction drawings may indicate specific informations about structural element class.

Ambiguous cases relevant to structural element class shall be cleared by Client.

This classification does not consider structural elements that are removed after platforminstallation (platform for lifting lugs, temporary ladders, ecc), but includes those items,although removed, they are fundamental (buoyancy tanks, lifting aids, sea fatening etc.).

1.6 MATERIALS

All building steel to be used shall comply with ENI Division AGIP 08832-STR-MME-SPCrev.7 requirements.

Materials substitution and handling shall be in accordance with sections 3.4 and 6.5 ofstandard EEMUA 158.


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2 WELDING

2.1 GENERAL

All structural welding shall be in accordance with the requirements of this specification.

Steel backing strips, out of closure welds, may be used upon Client's approval only, and inaccordance with paragraph 3.7.4.

2.2 DEFINITIONS

The following definitions are used:

SMAW: shielded metal arc welding (using manual equipment);

SAW: submerged arc welding (using automatic equipment);

GTAW: gas tungsten arc welding (using manual equipment);

GMAW: gas metal arc welding;

GSFCAW: gas shielding flux cored arc welding;

SSFCAW: self shielding flux cored arc welding;

WPS: welding procedure specification;

WPQR: welding procedure qualification record;

HAZ: heat affected zone;

WM: weld metal;

FL: fusion line;

KCV set in HAZ:Charpy V test set, consisting of three (3) groups of three (3) specimens

each from the following lines: fusion line (FL= 50% WM and 50% HAZ), FL

plus 2mm, FL plus 5mm, for a total of 9 specimens;

KCV set in WM:Charpy V test set, consisting of three (3) specimens in weld centreline;

TM: thermomechanically controlled rolled (base material): thermomechanical

rolling process carried out with a rigid control of both plate temperature and

rolling grade;

Q&T: quenched and tempered (base material).

2.3 WELD CLASS

The welds to be executed are grouped in classes, corresponding to the structural elementclasses, of which they maintain the same name.

Different requirements on applicable welding processes, mechanical characteristics, NDTtype and percentage, defects acceptability combinations are defined for each weld class.

In welded joints between elements of different structural classes the higher structuralelement class shall govern.


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2.4 WELDING PROCESSES

2.4.1 Acceptable Welding Processes

The approval is to be obtained prior the use of the process in production begins.

All welding fabrication of structures shall be accomplished with low hydrogen processes.

Welding processes for structural classes of components are listed in table 2.1.

Other welding processes could be employed under Client approval.

TABLE 2.1: JOINT TYPE AND WELD CLASS

Structural element class = Weld class

a b c d e

Butt SAWSMAW

GS/SSFCAW (1)

1st

run GS/SSFCAW(1)

GTAW SMAW SAW

T butt

SAWSMAW

GSFCAW (1)

SAWSMAW

GS/SSFCAW(1)

SMAW

1st

run GTAW SMAW GS/SSFCAW

Fillet SAWSMAW

GSFCAW

SAWSMAW

GS/SSFCAWGMAW

GMAW

ClosureSMAW

GSFCAWSMAW

GS/SSFCAW

1st

run na GTAW SMAW

Seal SMAW GS/SSFCAW GMAW

Note 1: not applicable for steels with minimum specify yield strength of 460MPa.

The use of GTAW shall be limited to the first passes where second side is not accessible.GTAW shall be utilized only with direct current, straight polarity.

First run on principal tubulars longitudinal double side welds may be carried out by GMAWprocess providing it is completed removed prior to back passes are executed.

The use of "narrow gap" welding processes are permitted only upon Client's approval. Inthis case full details about the process, the consumables, the NDT techniques, the relevantapplications and the previous experience are to be documented.

2.4.2 Restrictions of Welding Processes

The following procedures require the following positions:

SMAW: all positions, except vertical down;

SAW: flat position in general, horizontal position for fillet weld only;

GMAW: flat position in general, horizontal position for fillet weld only and with "spray

arc" technique;


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GS/SSFCAW: all positions (except the vertical down for class "e" structures only), under

Client's approval only, after a documented experience is furnished to

Client's satisfaction.

Welding procedures shall not exceed the following limits:

SMAW: for heat input exceeding 3 kJ/mm; bead width exceeding 16mm or 4 times

the core wire diameter;

SAW: for heat input exceeding 5 kJ/mm;

GTAW: when adequate environmental shielding is not provided;

GSFCAW: for heat input exceeding 3 KJ/mm; when adequate environmental shielding

is not provided;

SSFCAW: for heat inputs exceeding 1.5 kJ/mm; with weave beads; vertical up; without

the voltage and wire-feed speed are set and locked;

ALL: welding on materials less than 30mm thickness with a heat input exceeding3 kJ/mm; heat input greater than 3 kJ/mm for steels with minimum specify

yield strength of 460Mpa; square edge butt welds greater than 8mm

thickness; welding on second side of a joint without back gouging except for

SAW procedures using the punch-through technique; single-pass fillet

welds (other than by submerged arc) with a leg length greater than 7mm;

use of ceramic inserts.

2.5 CONSUMABLES

The use of consumables is subject to meeting the welding procedure qualification

requirements.

Consumables to be used shall have chemical composition similar to and have a yieldstrength not lower than the base material.

Consumables to be used for welded joints between steels having different yield strengthshall be those applicable to the higher strength steel.

The use of filler metals giving a low diffusible hydrogen deposit (less than 5 cm per 100g ofweld deposit, carried out with mercury measurement method, or humidity equal to 0.2% ofthe weld metal weight, according to AWS D1.1.) is compulsory when one of the followingconditions is fulfilled:

welds in classes "a, b, c";

weld thickness greater than 10mm;

Specified Minimum Yield Strength of one of the parts to be joined equal to or greaterthan 275MPa.

Electrodes in sealed boxes shall have the hydrogen level certified.

Electrodes classification shall conform to AWS. Electrodes classified conform to otherspecifications or codes are accepted provided correspondence and in that case the WPQhas in the name anessential variable All electrodes, according to the reference code or

specification, shall be marked.


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Unopened containers shall be stored in a dry location where the temperature shall not beless than 20C and the relative humidity shall not exceed 50%.

Electrodes, fluxes and wires that have been contaminated by water, oil, grease, or all otherdeemed unsuitable, or unmarked consumables shall not be employed in the work and shall

be removed from the worksites.

Client may require an additional monthly test (or two months in shop) and whenever heconsiders that the consumable baking and maintaining procedure are applied in wrong way.

On any electrode batch and on any flux lot, a moisture test in accordance with AWSspecification A5.5, may be carried out at Client's discretion. Samples shall be taken fromovens where electrodes and fluxes are stored, ready for production use. The maximummoisture content by weight for low hydrogen consumables shall be 0.2% for electrodes and0.1% for fluxes.

Client reserves the right to verify the consumables chemical and mechanical characteristicsby destructive testing.

2.6.1 Electrodes

Low hydrogen electrodes shall be baked for 2 hours at 350/450C, unless otherwiserecommended by the supplier. Thermocouple, which shall be previously calibrated shall beplaced at midheight owen. Initial drying may be omitted in case the electrodes are suppliedin fully sealed packs with a guaranteed hydrogen level content.

After withdrawing from ovens for use, electrodes shall be contained in heated portablequivers at a temperature not lower than 70C and shall be used within 4 hours.

Electrodes not used within above time limit may be rebaked, provided they are in goodconditions. Redrying is generally acceptable to a maximum of 2 times.

Electrodes that shall not immediatly applied may be stored in ovens at a temperature notlower than 100C after baking.

In alternative electrodes characterized by a low hydrogen level maintainment after boxopening may be used. Those electrodes are commercially available in packages equal to aworkday or half workday. Anyway Client may require a test to verify the characteristicalperformance of those electrodes.

If these electrode types are used, those unemployed, at the day end, shall not be employedagain.

2.6.2 Fluxes

Low hydrogen fluxes storage, usage and rebaking requirements shall be as for electrodes.

The maximum amount of recycled flux used for welding shall not exceed 30% of the total(70% minimum new flux). Fluxes may be recycled aspirating from welding and filtered toeliminate impurity before mixing with new one.

The Contractor shall provide a handling and recycling procedure including details of baking,use of heated hoppers, recovery system and circumstances in which flux is deemed

unsuitable and scrapped.


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2.6.3 Wires

Wires storage, usage and re baking shall be the same as for electrodes.

To avoid porosity, gas holes, hot cracking and low electrical contact, wires shall be free fromgrease and moisture.

Current swing avoidance during welding shall be avoided through a regular coil speed.

At the workday end all the automatic welding coil winders shall be emptied as to avoid wiremoisture contamination.

2.7 INITIAL DOCUMENTATION

Prior to begin fabrication and for all welding processes Contractor shall submit to Client'sapproval:

A. storage and consumables handling procedure;

B. welding procedure specifications list;

C. welding procedure qualifications list;

D. welder/operator qualification list;

E. welding machine calibration certification;

F. fabrication procedures and erection sequences;

G. list of proposed welding consumables and Supplier;

H. procedures for heat treatment;

I. procedures for NDT testing and inspection and associated personnel qualification;

J. cold forming and straightening procedures;

K. identification and control procedures for materials;

L. procedures for dimensional control, control of tolerances during fabrication.

M. fabrication drawings including plate seam arrangement drawings and plate cuttingdrawings;

N. drawings and calculations of temporary works; inclusive of support points, jacking points

and sling points;O. certificates of supply materials;

P. key plans showing member identification and weld marking scheme.

For particular cases Contractor may require derogation for the points M, N, O, P abovelisted

All the documents listed above shall be in accordance with the provisions given in followingsections.


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2.8 WELDING BOOK

Before the beginning of the works, the Contractor shall prepare a welding book covering allthe welding operations to be performed. This book shall be permanently available to the

Client on the site where the welding is to be carried out.It shall comprise:

identification sketches or a list of welded joints per type;

a summary of the accepted welding procedures with their qualifications;

all welding procedure specifications which shall be applied;

destructive and non destructive testing, specifying the technique used for the latter.

WPQ and WPS that shall be carried out during fabrication shall be added to the welding

book.

For each welding procedure qualification (WPAR) shall be indicated:

the references(s) of the qualification certificate(s) specifying the range of thicknessesand covered diameters together with maximum CEV and Pcm qualified for steels withRe > 275MPa;

the welding procedure qualification records, with the testing record certificates andinspection, during fabrication, certificates of the base and filler metals;

the chemical composition and the carbon equivalent CEV / Pcm of the test pieces (forsteels with a minimum specified yield strength higher than or equal to 275MPa only).

For each welding procedure specification (WPS) shall be indicated:

base material grade (when the grade actually used is be different from that initiallyforeseen on the drawings, this shall be indicated);

the joint configuration before and after welding (size and tolerance); passes number; ifa temporary or permanent backing is used; the grade of the backing material, the

precision of the backing fit, the method of removal (if foreseen);

conditions and special measurements, e.g. preheating and postheating temperature(soaking time), maximum interpass temperature;

if stress relieving treatment is foreseen: the procedure, the temperature, the hold time,the heating and cooling rates, and the tolerances for each of these parameters.

For each pass the following indications shall be given:

the welding process specifying, if necessary, whether it is a manual, a semi-automaticor an automatic process;

the welding position;

the consumables used (standard name, trade name, diameter);


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welding parameters with tolerances (voltage, speed of travel, current, heat input, flowrate and type of gas);

welding technique detailing polarity and nature of current; welding direction; type ofprotection (gas); weave bead or stringer bead; whether or not back welding is carried

out after gouging and/or grinding.


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3 WELDING PROCEDURES

3.1 GENERAL

Welding of weld classes "a, b, c" shall be carried out in accordance with approved andqualified welding procedures only.

All welding procedures applied shall be qualified unless Contractor procedures have alreadybeen qualified or Contractor qualifications have been in use in the preceding 12 month.Welding procedure qualified before this period may be applied providing a test coupon iscarried out as production welding begins.

Welding of weld class "d" may be executed with procedure previously qualified byContractor, without the need of new qualification.

Welding of weld class "e" may be carried out with pre-qualify processes without newqualifications (see section 3.3).

Prior to beginning work, the Contractor shall qualify all the required welding procedures forthe various materials and welded seams of the structures to be fabricated.The Approved Body committed to certify the welding procedures shall be accepted by theClient.

The information indicated on each WPS shall be consistent and shall not leave the welder tochoose within different combinations of parameters.

3.1.1 Preheating and Interpass

Tacking and welding shall be carried out with preheating temperatures ranges stated intable 3.1. Carbon Equivalent formula is (IIW):

CEV = C+Mn/6+(Mo+Cr+V)/5+(Ni+Cu)/15

TABLE 3.1: MINIMUM PREHEATING TEMPERATURES (C)

Weld thickness (t)CEV

(check analisys)t < 20mm t < 30mm t > 30mm

< 0.39 20 20 50 (20)< 0.41 20 20 75 (50)< 0.43 20 50 (20) 100 (75)

< 0.45 50 (20) 100 (75) 125 (100)Note: values in brackets refer to SAW only.

Arc air gouging and oxicutting may be carried out without preheating.

Preheating temperature is to be measured on bevels and at 50mm minimum from bevels atboth sides.

Working interpass temperature shall not be lower than preheating one, nor higher than250C.

Preheating and interpass values differing from the above stated may be used providedmeasured during the execution of welding procedure qualification.

The requirements of section 5.1.1 shall apply.


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3.1.2 Heat input

Welding heat input shall be calculated with one of the following formulas:

HI = 0.006 VA / sHI = 0.001 VAT / (ROL)

where:HI= heat input in KJ/mm; V = arc voltage in Volts; A = arc current in Ampere; s =welding speed in cm/min; T = arc time in second; ROL = electrode run-out-length in mm.

Heat input value for filling passes and for any process on TM steel may be higher thanthose considered in paragraph 2.4.2, provided adequate welding procedure qualificationdemonstrates it is not detrimental to the mechanical characteristics of welded joint.

3.2 WELDING PROCEDURE SPECIFICATIONS

Welding procedure specifications (WPS) shall specify the EN 288 requirements in additionto the following information (as recorded on relevant Procedure Qualification Record):

company name and unique WPS number;

welding process, or processes when more than one is used in making a complete joint;

steel type, and whether it is normalised or TM, thickness, length, width and pipediameter (when applicable) used for procedure qualification;

sketch of joint showing plate edge preparation (specifying if oxygen cutting ormachining) and joint fit-up tolerances;

thickness and diameter ranges qualified;

welding position and welding direction (for vertical position);

the make, trade name, classification and size of welding consumable and fluxes. Anypretreatment of electrode/consumable;

name, type and flow rate for gas shielding, and backing if applicable;

sketch showing number of beads, welding sequence and relevant consumables andwelding parameters for each joint zone;

for each run: the current type, polarity, arc current and voltage, welding speed, orelectrode run-out length and relevant burning time;

treatment to second side;

actual preheat and maximum interpass temperature used in the qualification test weld,and those to be used in production; method of temperature measurement;

for semi-automatic processes: torch position, wire protrusion, frequency and wavingamplitude;

post weld heat treatments (for avoiding hydrogen cracking and for stress relieving) ifapplicable;


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any deposition augmentation system used;

tack welding procedure;

removal methods for weld defects.

3.3 QUALIFICATION OF WELDING PROCEDURES (WPAR)

Qualification of welding procedures shall comply with AWS D1.1 or EN 288 or RINA and asspecified in the following.The welding procedures shall be certified by an Approved Body accepted by the Client.

Prequalified joints foreseen by AWS D1.1 apply only to weld class "e".

The qualification of the welding procedures performed may be used for any other workshop

or worksite within the same organization.

The execution of procedure qualifications for SAW shall be done using the maximum valueof the allowable recycled flux percentage (paragraph 2.6.2).

Where tack welds in production will remain in final joint and are done by a different processto that used for weld body, the procedure test plate shall be similarly tack welded and onemacro section taken through a tack location.

3.4 QUALIFIED PRINCIPAL POSITIONS

Qualified principal positions shall be in accordance with table 4.1, page 109, AWS D1.1-2000.

3.5 VALIDITY OF WELDING PROCEDURES (ESSENTIAL VARIABLES)

A qualified welding procedure is to be used within the limitation of essential variables asstated below. The changes described below are to be considered essential and are toinitiate a new procedure qualification test.

When a combination of welding processes is used, the essential variables applicable toeach process shall be applied.

WPQ carried out on base material of quality not "Z" may be applied to other similar steels,including quality "Z", or lower grade.

3.5.1 Material

Base Material: change of grade of steel, change of steel quality. Increase in product CEVabove 0.02% (for Re > 300MPa only), and Pcm above 0.01% of maximum nominal value ofsteel in comparison with the value of WPS. Change in supply condition (as rolled,normalised, TM, Q&T). The qualification obtained for a normalised materials is acceptedalso for TM materials, and not viceversa. Change of microalloy elements or manufacturingprocedure for steels with minimum specify yield strength of 460MPa.


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Groove preparation: presence of bevels protective coat. Oxycutting without grinding tosound metal.

3.5.2 Weld Geometry and Position

Groove angle: change of included angle greater than +10 or -5.

Components angle : where acute angles in the stub to node can welds are below 45 weldprocesses are to be qualified by the test of TKY joints. The bevel angle in this test is to bethe smallest used in fabrication.

Root face and root gap: changes of root face and root gap shall be in accordance with AWSD1.1-2000, either for double side weldings and for single side weldings.

Groove design: change from double side welding to single side welding and vice versa;change in groove weld preparation shape (V groove, U groove, etc. except that a single half

V bevel qualifies a single V, K qualifies X, and 2:1 and 1:1 preparations qualify each otherand all intermediate geometries).

Thickness: outside the qualified range listed in EN 288 -3.

Misalignment: values exceeding the lesser of 5mm or 10%t on double sided joints, 3mm or10%t on single sided joints. Misalignment of 2mm is permitted, regardless of otherparameters.

Diameter: outside the qualified range listed in EN 288 -3.

Welding positions: outside the qualified range listed in table 4.1, page 109, AWS D1.1-2000.

3.5.3 Consumables and Equipment

Welding consumables: change of electrode trade name; electrode and wire type areconsidered equivalent on condition that they belong to the same certification class and areapproved by a Certifying Authority, in that case they do not have to be requalified.

Power: changes are made to pulsed power welding parameters.

Welding parameters: change from AC to DC or vice versa; change in DC polarity.

3.5.4 Procedures

Welding process: any change in welding process.

Preheating/working temperature: for preheating the lower limit of approval is the nominalpreheat temperature applied at the start of the welding procedure test, with a tolerance of -10/+50C. For interpass the upper limit of approval is the nominal interpass temperaturereached in the welding procedure test.

Post weld heat treatment: added or omitted; change beyond specified temperature range;soaking time increased more than 25%; increasing or decreasing speed more than 20%.

Gas shielding: gas type change from active to inert and viceversa; change of 10% orbeyond in gas composition; change +27% or -10% in flow rate.


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Grinding: if grinding between passes is omitted.

Back-gouging: each reduction in depth of back-gouging in comparison with the qualified onefor automatic process; each increase higher than 10mm of qualified depth.

Back welding: if omitted.

Welding direction: change from uphill to downhill, and vice versa.

3.5.4.1 Welding Parameters

Voltage and current: change beyond 10% of mean values.

Bead: if each bead width increase, for any electrode diameter.

Speed: if wire feed speed setting for any pass is changed by more than 5%.

Heat input: change beyond 10% (tolerance applies to mean heats input values measuredduring qualification in root, fill and weld cap passes) for weld class "a" and nodes of class"b". Welding of all other elements of class "b" and of every other class is considered achange beyond 15%. Where heat inputs in two positions are different, qualification in bothpositions qualifies all intermediate heat inputs.

3.5.5 Specific for SMAW

Measured current for any electrode diameter is changed by more than 20%.

Run out length for any electrode size is changed by more than 10%; where the runs out

lengths in two positions are different, qualification in both positions qualifies all intermediaterun out lengths.

Core diameter of an electrode used for capping passes is reduced. All passes in the cap ofthe qualifying weld shall use the same electrode diameter.

3.5.6 Specific for SAW

Number of wires used for any pass is changed.

Separation of tandem arcs, transverse or longitudinal, is changed by more than 10%.

Feeding direction is changed by more than 5 transverse or 3 longitudinal to the weld.

Use of iron powder.

3.5.7 Specific for GTAW

Root gap exceeding 3mm is to be qualified with separate procedure.

Tungsten wire changing diameter.


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3.5.8 Specific for FCAW (GS and SS)

If the mean voltage for any pass deposited by other automatic or semi-automatic process ischanged by more than 10%.

Change of contact tip-to-workpiece distance.

3.6 TESTING

The qualification of welding procedures is based upon visual examination, non-destructivetesting and mechanical testing on test samples. Type and number of tests are thosespecified in table 7.7. of RINA Codes.

If different welding consumables or welding processes are applied for the same joint, impacttests required are to be carried out for the related regions of the weld. If SAW tandem

process is used and fills passes have width over 19mm one KCV set is required at depth of8mm.

Size and shape of specimens and test execution for Charpy-V are to comply with EU10045.

3.6.1 Testing Coupon

The test plates used for procedure qualification (samples location) shall have the rollingdirection parallel to the test weld.

CEV shall be not less than 0,02% and Pcm than 0,01% in comparison with the maximum of

the specification of the steel to be welded.

For Z quality material beams, samples taken for WPQ shall have welding direction parallelto the rolling direction; for materials of other quality the welding direction can beperpendicular to the rolling direction. (fig. 3.1)

Test conditions shall be a realistic simulation of the actual conditions that will beexperienced.

When PWHT of nodes or other sub-assemblies is required, all relevant proceduresqualifications shall include PWHT over the full range of material thickness.

The dimensions of the test plates (coupons) shall be in accordance with EN 288-3,

paragraph 6. Position and cut of test coupons shall be in accordance with EN 288-3 section7.2.

When plate thickness to be tested is over 36mm or the power of tensile testing machine isnot sufficient, tensile specimens may be cut into a number of approximately equal strips notexceeding 36mm (or the machine strength equivalent thickness whichever is the greater)with a minimum overlap of 2 mm. Test shall be performed on each strip and the resultsaveraged.

3.6.2 Acceptance Criteria

The welding procedure is qualified when the soundness and mechanical properties complywith the requirements hereafter indicated:


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Non-destructive tests:Welded joints soundness is to comply with the prescriptions of section 9.13. NDT shall becarried out not prior than 48 hours from weld completion and in any case after PWHT whenapplicable. Repairs are not allowed.

The locations of all imperfections exceeding 50% of the reference level shall be marked,and the cutting of tests pieces shall be arranged to avoid these imperfect regions.

Destructive tests:Transverse tensile tests: the tensile strength of the welded joint is to be in accordance withEN 288-3 paragraph 7.4.1; in case of welding between steels of different grades the tensilestrength shall be equal to the lower steel grade.

All weld metal tensile test: specimens shall be taken out from full weld metal, and shall takethe form of the "reduced transverse test" piece to BS 709; the tensile strength of the welded

joint is to be at least equal to the minimum specified tensile strength.

Bend tests: test conditions and acceptability limits shall be in accordance with EN 288-3paragraph 7.4.2; bending angle test shall be of 180.

Toughness tests: the average and minimum Charpy V-notch energy absorption recorded ateach specified position in WM and HAZ shall comply with the requirements stated in tables3.2, 3.3 and 3.4:

TABLE 3.2: IMPACT TEST TEMPERATURE

Tp > -5 C t < 12,5 mm 12,5 mm< t 20 Actions

Limit root gap values (mm)

4 4 Normal

10 12 Buttering

18 20 Backing strip

> 18 > 20 Insert

Welders qualification for first pass shall be carried out accordingly, following the relevantrequirements of this specification.

Contractor shall identify all closure welds on fabrication drawings, indicating the applied

procedures.

5.5.1 Normal and buttering actions

The requirements are relevant to joints with root gap between 4mm and 12mm. SMAW andGTAW process may be used to carry out the first two passes.

GTAW root process used both for buttering and filling, follows mixed process requirementsincluding KCV test in WM and HAZ, two macro sections, hardness and bends.

Buttering carried out by SMAW process does not require qualification with thickness up to

6mm.First pass with root gap exceeding 4mm, with SMAW process is not allowed.


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Soaking temperature is to be within the range 590C 10C: therefore temperature all overthe points of the item to be treated shall be within this range.

Soaking time is to be 2.5 minutes for each millimetre of thickness of the thickest member in

item, with a minimum of 1.5 hours.

Soaking time begins when the lowest measured temperature value is within soakingtemperature range.

The heat treatment may be done introducing the item in the furnace, or in local manner; thischoice depends by the item dimension only.

5.6.2 Furnace heat treatment

The item may be introduced in the furnace if this has not a temperature over 300C. The

same may not be taken out from furnace if its temperature is over 300C. Cooling downbelow 300C shall be in air.

Item temperature shall be recorded from introduction in the furnace until taking out. Rate ofincreasing and decreasing temperature is to be 55C per hour maximum for temperaturesabove 300C. The temperature difference on the item, during heating and cooling phases,measured along symmetry lines and planes shall not exceed 50C; between the outside andthe inside surface is not to exceed 50C; between any point of the item far not less than4500mm shall not exceed 150C.

Temperature shall be recorded continuously and automatically. Thermocouple locationsshall be selected to ensure that the whole item, or item part, being treated is within therange specified; additional pyrometers should be used to check that undesirable thermal

gradients do not occur.

During the stress relieving heat treatment the furnace atmosphere shall be controlled so asto avoid excessive oxidation of the surface of the item. There shall be no direct impingementof flame on the item. No parts of the item shall be closer than 200mm from furnace soleplate, or closer than 300mm from inside walls.

5.6.3 Local heat treatment

Local heat treatment is to be carried out by electrical heating: resistance or induction.The procedure specification for stress relieving shall contain the calculations of the

necessary heat power and insulation, the temperature measurement point, the actions totake in case of temperature difference exceeding the above values and in case of anythermocouple damage. Any local stress relieving heat treatment is subject to Client'sapproval.

In circumferential seams the width of the heated band shall be not less than 5(Dt/2), with weld in the centre. Sufficient insulation shall be fitted to ensure that thetemperature at the edge of the heated band is not less than half the peak temperature. Theadjacent portion of the item outside the heated zone shall be thermally insulated such thatthe temperature gradient is in accordance with above paragraph. A minimum total insulated

band width of 10(Dt/2) is recommended for this purpose.


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5.7 PRODUCTION TESTING COUPONS

Production weld test coupon shall be tested as follows:

1 transverse tensile stress test

1 straigth bend test

1 back bend test

1 FL + 2 mm Charpy-V strength and welding test.

1 macro and hardness test.

Note: as an alternative to the straigth and back bend tests, two lateral bend tests can beaccepted.

The requirements and acceptable limits foreseen for the procedure qualification apply.

Production testing coupon welding shall be carried out by the same equipment and steelused in production at that time, and samples shall be representative of different basematerial casts and different welding consumables batches throughout production.

If production testing coupon presents defects not acceptable to this specification the WPSbecomes suspect: causes are to be determined and submitted to Client. All production jointsrepresented by this production testing coupon shall be 100% UT to demonstrate are freefrom the same unacceptable defects. Otherwise all represented production welds shall besubjected to the Client's approval.

The production testing coupon shall be taken in accordance with a proper plan submitted bythe Contractor for the Client's approval This plan will take into account any similar conditionfor any type of joint, thickness or process. The following frequency shall be used:

class "a, b" welds: a production testing coupon for every 100 m welds, with a maximumof 25 circumferential or longitudinal welds.

class "c" welds: a production testing coupon for every 150 m welds, with a maximum of25 circumferential or longitudinal welds.

class "d" welds: a production testing coupon for every 200 m welds.

Client may allow reduction of frequency after initial satisfactory results.

For stress relieved joints, the production testing coupon shall be tested after the same heat

treatment, performed in furnace together with relevant joint.

The first production testing coupon shall be taken at the start of production, if no recentqualification of the procedure is available (see section 3.1).

Production weld test coupons for butt welds shall not be considered representative for filletand T butt welds, even if carried out with the same WPS.

The coupon size shall be sufficient to obtain the required type and number of specimens. Inany case the coupon length shall be not less than 150mm for thickness up to 20mm, and200mm for greater thicknesses. All coupons shall be 100% UT and 100% MT as per thisspecification; RT shall be performed in addition in questionable interpretation.


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Contractor shall present to the Client approval a detailed programme of execution ofproduction testing coupon, including the represented welds identification. At the time of thetests Contractor shall record at least:

data required on PQR during weld procedure qualification;

date and time;

location of test;

corresponding production weld number;

welder or welding operator identification number;

identification numbers of equipment used;

consumable batch numbers and identification number of represented weld.

5.7.1 Butt welds

For longitudinal seams the coupon shall be prepared from a test coupon attached to the endof the longitudinal seam being fabricated and welded to form a continuous seam.

For circumferential welds the coupon shall be prepared by a simulation of productionwelding to be welded in location very close to one of the represented production joints andat same production welding time.

For circumferential welds with horizontal fixed axis, coupons shall be carried out in verticalposition.

For thickness > 45 mm impact test shall be carry out also on root region (as foreseen atsection 3.6.2 for the test of the welding procedure)

5.7.2 Tee butt joints

The coupon shall be prepared from a test coupon cut from an excess length of a piece, or atest coupon attached to the end of the piece and welded to form a continuous seam.

5.7.3 Tubular joints (TKY welds)

The coupon shall consist of three T butt joints with edge preparation and dihedral anglecorresponding to the values applied during welding procedure qualification.

5.7.4 Retest

In case of failure of one test the provisions indicated in section 3.6.3 apply.If the retest fail production test coupon shall be rejected all the welded joints represented bythe coupon shall be rejected.

5.8 WELDING PARAMETER CHECKING


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Welding parameter check may be applied after to have verified the first production couponweld soundness.

Before starting fabrication Contractor shall submit to Client's approval the procedure andchecking methods that he intends to use to this purpose. Welding parameters checks shall

be continuous all over the production. Client anyway may require a production test couponwhenever he considers necessary.

Acceptability of welding parameter checking procedure is solely to Client.


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6 FABRICATION

6.1 GENERAL

All fabrication and erection shall be in accordance with these specification requirements.

Work shall not be performed when weather does not permit satisfactory workmanship orwhen particular conditions prevent adequate inspection.

Fabrication shall proceed on a flat and level surface and frequent checks shall be made onthe supports and blocking, and any movement out of the level shall be immediately rectifiedby appropriate shimming to re establish a level plane.

The Contractor shall survey and control dimensions before fit-up for welding of additionalcomponents and sections. Dimensions shall be checked at each stage in accordance withthe fabrication procedure, tolerances (if given) and the final survey shall meet the definedtolerances. The Contractor shall submit his dimensional control procedures indicatingproposed methods of monitoring dimensions, their tolerances compatibility and constructionmethod philosophy to the Client before commencing fabrication.

6.2 FORMING

6.2.1 Tubular fabrication

Tubular may be formed with calendar rolls axis both parallel or orthogonal to the longitudinalaxis of the plate (plate rolling direction).

Tubular may be re rolled after welding in order to reduce deformations. In this case WPQmechanical testing shall be performed in the same final condition, in order to demonstratethat the joint is not impaired by the re rolling process. Re rolling carried out with anequipment type different from that used for forming shall be subject to Client's approval.

6.2.2 General

Contractor is to qualify each complete forming process, including final re forming calibrationprocess, when forseen.

Qualification shall be carried out within the terms and as specified in paragraph 6.2.7.The forming shall be not carried out in the temperature range from 200 to 450C or above800C. TM steel shall not be hot formed, i.e. above 600C.

For TM steels Contractor shall seek the advice of the steel-maker before start any warmforming activity.

6.2.3 Surface preparation

Plates having surface condition that may impair the forming operation or which may havescale incorporated into its surface shall be restored by blasting, SA 2 level, before forming.

All defects that may appear after forming shall not exceed 3mm in depth.


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6.2.4 Cold forming

Cold forming is considered the forming carried out at ambient temperature.

When the cold forming is executed on plates which have already pass successfully throughthe ageing test foreseen in the specification 08832 STR-MME-SPC " OFFSHOREPLATFORMS - Steel for structure" Rev.7 and the true deformation is higher, the plate shallbe submitted to a new ageing test with a strain value not less than the real one, or to athermal relieving treatment. For assembled elements, the relieving treatment can beexecuted just before the start of operations.

When the cold forming is executed on a plate which has not been submitted to any ageingtest, and the actual diameter/thickness ratio is less than 30, one plate for eache heat / steelquality and thickness shall be submitted to an ageing test with a deformation value not lessthan the real value; as an alternative, the item shall be submitted to a thermal relievingtreatment before the start of operations.

In all the other cases, cold forming can be carried out on plates without any additional test.

6.2.5 Warm forming

Forming processes carried out from 450C up to 600C shall be considered as "warmforming".

6.2.6 Hot forming

Hot forming is carried out beyond 600C up to 800C.

TM steels should not be hot formed.

Forming process shall be followed by normalization heating treatment to restore themechanical steel characteristics

All forming processes, heat treatment included, shall be carried out according to aprocedure previously approved by the Client.

6.2.7 Qualification of the forming procedure

Each forming process, including cold re rolling for tube calibration after welding, shall bequalified 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 300mm 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 beless than 1m.

From the sample coupon shall be obtained in order to carried out the tests indicated in table6.1.


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TABLE 6.1: TYPE AND TEST NUMBER

Thickness Type and number of tests

< 16 mm 1 set for KCV impact test (1)

1 tensile test on base material3 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.(2) Test shall be carried out on base material and HAZ with at least threereadings for each test

The tests and requisite conditions shall be the same as those described in paragraph 3.6 forthe grade and quality steel on test.

Previous qualifications accepted by Client avoid new qualification.

6.2.8 Validity limits of forming qualifications procedure

The forming procedure is valid within the following limits:

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 beyondthe tested value;

same calender process.

6.2.9 Hot Straightening

Hot straightening may be applied to recover excessive deformations caused by welding orstress relieving. All class "a" elements, jacket legs, deck legs, jacket nodes and padeyesshall not be submitted to hot straightening in any care. Hot straightening shall be carried outto a Client's approved procedure.

The following requirements shall be fulfilled:

gas torch may be used, but heated areas shall not be larger than 60mm;

maximum temperature shall not be greater than 550C and shall be kept under fullcontrol at least by means of portable contact thermocouple;


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steels with 500MPa tensile strength, or higher, shall not be fast cooled, by water orother means.

Follow the advice (recommended practice) provided by the steel manufacturer;

The heating should be rapid, in order to introduce as little heat as possible, and to limitthe amount of heat that is conducted away from the zone to be heated;

If possible utilize mechanised equipment to moving of the heat source;

The depth of the visible HAZ in a transverse macrosection should not exceed 2.5 mm;

Conduct a qualification test of the flame straightening procedure in question. Thequalification test should incorporate:- metallographic examination,- hardness measurements,- impact test ,- tensile test.

All hot straightening operations shall be witnessed by Client.

6.3 WELDED ATTACHMENTS

Welded attachments to the structure not shown on the construction drawings shall not bepermitted except for temporary and non-structural attachments. In this last case too theymust be maintained at a minimum number.

In these cases welding shall be allowed, provided that the attachment thickness is not

greater than 20mm and the welds location are not closer than 51mm from any weld.

All attachments shall be welded to the structure according to this specification requirementsand approved procedures.

Temporary attachments welding to nodes or PWHT elements are not allowed.

After the structure completion, all welded attachments shall be removed by flame cutting5mm from the base material, followed by smoothing corners.

Flush grinding is required for structural elements of classes "a", "b" and "c" and where paintis foreseen. The interested areas shall be carefully examined by MPI and the results shallbe reported.

Attachments shall not be removed by hammering or any other method that may causemechanical damage to the surface.

6.4 SITE ASSEMBLY ACTIVITIES

Contractor shall consider, during site assembly, all temporary erection loads imposed on thestructure from supports, jacking and slinging at each stage of the structure assembly.

Contractor shall consider, during site assembly, the local or overall stability from self weightand environmental loads. These include scaffolding, staging, temporary cranes, welding

shelters and temporary works, at each stage of the structure assembly.


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Contractor shall provide during the assembly phase storage for all items, to prevent theirdamage from environmental.

Contractor shall make provision for alignment correction at each stage of the structureassembly provided he demonstrates to Client satisfaction that the induced stresses in the

items are lower than the admissible value (ref. API RP 2A).

The welding of forced members shall not be allowed unless Contractor shows that theinduced stresses are lower than those of design.

6.5 MANUFACTURED AND MISCELLANEOUS ITEMS

6.5.1 Bar grating

Bar grating shall be cut to dimension and installed as shown on the construction drawings.

Unless otherwise restricted by construction drawings, bar grating may be attached by eithertack welding or bolting.

If tack welded, each bar shall be pressed in firm contact with the underlying structure andsecured with a minimum 50mm line tack weld. The tack weld, the surrounding heated areaof zinc galvanised bar grating and the bar grating cuts shall be touched-up according withthe relevant painting specification or as per procedure.

6.5.2 Steel floor plate

All butt type joints shall be double welded to produce an 85% fused joint minimum. All floorplate under-side shall be 100% seal welded to deck stringers and other supporting, to sealall facing surfaces from corrosion. Seal fillet welds shall have a minimum leg length of 4mm.

Seal welds and butt joints shall be staggered at least 50mm.

Steel floor plate shall not present subsidence higher than 3mm measured with a 1200mmlength gouge.

6.6 FINISHING OF SURFACES

As fabrication of various items or portions of the structure is completed, the Contractor shallremove all welds, burrs, tack welds and other marks made by scaffolds or temporarybracing used in the fabrication procedure.

All arc-strikes and burn marks shall be ground smooth, visual and PT inspected.

The areas of components "a, b and c" interested shall be carefully examined visual and MPIand the results shall be reported.

6.7 RAT HOLES

Rat holes are required when shown on construction drawings and whatever they arenecessary to full penetration weld execution (e.g. when a stiffener weld crosses a full


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penetration weld joint). In this case only Contractor shall define the relevant solution, withClient's approval.

When not otherwise indicated on the design drawings, dimensions of rat holes shall be thefollows (+/- 3mm):

Stiffener thickness (t) in mm Rat hole radius (R ) in mmt < 20mm R = t + 15 mm

t < 35mm R = t + 10 mm

t > 35mm R = t + 5 mm

The surfaces of the holes shall be smooth and without any indentation. No rat holes arepermitted on tubular members.

Full penetration welded stiffeners shall blend onto parent material inside rat hole.

Fillet weld shall be returned through the rat hole.

When weld joint crossed is fillet welded, a 45 clip of sufficient width may be provided onstiffener corner in order to shape it onto weldment and facilitate complete stiffener filletwelding.

Rat holes in structural elements to be painted but which are not accessible to back side(e.g. box beam, boxed support, etc.) shall be seal closed before paint is applied. Sealingshall be made with a thin steel plate, about 5mm thickness, fillet welded; otherwise ironmastic approved by Client may be applied. In these cases the use of rat holes shall beminimized.

6.8 BOLTED CONNECTIONS

Bolt holes shall be drilled at right angles to the metal surface and shall have at least adiameter 1.5mm larger than the bolt diameter.

No bolt holes shall be enlarged by burning or flame cutting.

Bolts shall be freely insertable into the holes without damage to the thread. Bolt heads andnuts shall rest squarely against the metal surface.

All bolts shall be of a length such that they will extend entirely through but no more than6mm beyond the nut and locknut.

After final tightening, nuts shall be locked by tab washer, cotter pin or locknut.

Equipments, bolt material and tightening torque shall meet the requirements specified onconstruction drawings.


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7 PREFABRICATED ITEMS TOLERANCES

The Contractor shall provide personnel with qualified surveyors, equipment andinstruments, with current valid calibration certificates, necessary for monitoring andcontrolling dimensions and tolerances.

The following sections give the admitted tolerances for every measurable dimension andshape of structural elements.

7.1 FABRICATED TUBULARS, NODES AND CONES

7.1.1 Circumference

Circumference measured with tape shall not differ from theoretical value more than 1% ofnominal circumference or 10mm, whichever is less.

The measurement shall be carried out at 600mm from any tubular splice and at tubularends. Intermediate measured values shall not differ more than 1.5 times the above.

The circumferential tolerance shall not be reason for increasing the mismatch tolerated bythis specification.

7.1.2 Ring stiffeners out of circularity

For each ring stiffener shall be checked the difference between the actual radius and theaverage radius, in different points.

This difference shall not be greater than 0.25% of the external ring stiffener diameter.

The average radius defined by optimum centre and the radius measurements, in variousposition, relevant to the optimum centre shall be calculated in accordance with a procedure,approved by Client, based on EEMUA 158 optimum centre out of circularity.

7.1.3 Ovality (General)

Ovality is intended as the difference between the maximum and the minimum diameters,measured either internally or externally, at the same section.

Ovality shall be checked at each item end, at each 3m interval, at each circumferentialseam, and at midway between two ring stiffeners.

The following table 7.1 applies.

TABLE 7.1: OVALITY VALUES AND MEASUREMENT NUMBERS

Diameter (mm) Value Nr. of measures (*)

600 1% of diameter two diameters

2000 greater of 6mm or 0.75% D four diameters

> 2000 greater of 15mm or 0.5% D six diameters

Two diameter measurements may not be at 90 between them, but carried out in theposition with maximum and minimum value.


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Measuring method, with more than two diameters, may be equally spaced instead ofmaximum and minimum position.

7.1.4 Local out of roundness

Local out of roundness shall be measured by means of a 20 gauge having a theoreticaltubular form, and the measurement is verified all over the circumference (360).

Local out of roundness shall not be greater than 0,4% of the diameter. This control shall becarried out on tubular elements with diameter greater or equal than 1000mm.

7.1.5 Local out of straightness

Local out of straightness is the deviation of the shell plate from its axis.

This value shall not exceed 20% of the wall thickness.

Local out of straightness shall be checked on tubes with nominal outside diameter greaterthan 2000mm or with nominal outside diameter/wall thickness ratio greater than 65. Thecheck shall be either on the inside or outside, and the positions shall be those indicated intable 7.2 along all tubular element.

TABLE 7.2: LOCAL OUT OF STRAIGHTNESS

Type of joint Check location

Unstiffened tubular 45 intervals of arc with template L = 3000mm

Stiffened tubularnode barrels 20 intervals of arc with template L = distancebetween stiffeners or 3000mm in other uses

Manways after welding at the centre and manway quarter points withtemplate L = 1000mm

7.1.6 Out of straightness

Structural classes "a, b, c" members out of straightness tolerance is the greater of 0.1%L or3mm, but not greater than 12mm.

Straightness shall be checked in at least two perpendicular planes.

7.1.7 Ends perpendicularity

Ends perpendicularity shall be held within 3mm. This tolerance shall not be cumulated withweld root gap tolerance

7.1.8 Prefabricated nodes

Length tolerance of node cans, stubs and cones shall be within - 0 + 100mm from length

shown on fabrication drawings.


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Actual stub centre line is intended as the intersection of two orthogonal diameters at bothends of the stub; one of the diameters is parallel to the longitudinal axis of the node chord.

Each actual stub centre line shall be kept within 10mm cylinder from its theoretical positionshown on the fabrication drawings (fig 7.1).

7.1.9 Ring stiffeners

Rings stiffeners in node cans and cones shall be fitted, with respect to their theoretical

location shown on fabrication drawings to an accuracy of1/3 stiffener thickness but notmore than 6mm. Stiffeners in tubulars shall be fitted with an accuracy of 12mm.

The internal or external ring stiffeners inclination shall be within 1% of the nominal webdepth but not more than 6mm. For ring stiffeners in nodes and in node cones the sametolerance is 0.5%h with maximum value of 3mm.

The maximum bow in the web of an internal or external ring stiffener shall be within 1% ofthe nominal web depth, but not more than 3mm.

The deviation of the flange edge, of an internal or external ring stiffener, from the diametermeasured at the flange centreline shall be within 5% of the nominal flange width.

If ring stiffener is fabricated in two or more pieces and if flange is required the buttweldsmismatch shall not exceed 0.1 stiffener web or flange thickness nor 3mm.

For more explanation see fig 7.2.

7.2 ROLLED OR FABRICATED BEAM

Fabricated structural steel section tolerances shall comply with section 5.23 from paragraph5.23.1 to paragraph 5.23.9 of AWS D1.1 / 2000 Code.

For permissible variations from flatness of web see AWS D1.1 / 2000 paragraph 5.23.6.

All other tolerances not considered here shall be in accordance with EEMUA 158, section6.2.2.1.

7.2.1 Global tolerances

Structural class "a, b" members, no hollow sections, out of straightness and verticality is thegreater of 0.1%L or 3mm, but not greater than 12mm.

The out of straightness and verticality tolerance for girder and beam with hollow section isthe greater of 0.2%L or 5mm but not greater than 25mm.

7.2.2 Local tolerances

Flange eccentricity shall be equal to 0.02b, with maximum value equal to 6mm. Tilt and roofshape shall be equal to (1+0.01b)mm but not greater than 6mm, with b is the flange width

and t the thickness. (fig. 7.3)


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7.3.1 Stiffeners forming cruciform arrangements

Where a combination of stiffeners (ring, diaphragm, web) from a cruciform arrangement withother member or stiffener the mismatch of the alignment through the joint shall be according

to table 7.5.

TABLE 7.5: MISMATCH VALUE

Thickness Mismatch

t3> t1 and > t2 t3 / 2; max 10mm

t2> t3 and > t1 t2 / 2; max 6mm

for t1, t2and t3identification see fig. 7.6.

As built dimensions shall be used to align members. UT check shall be performed whereexternal measurement can not guarantee the alignment.

7.4 OTHER FABRICATION DETAILS

7.4.1 Weld beads for grouting

Weld beads position and size shall be in accordance with the construction drawings. Theweld beads pitch is to be constant throughout the zone where weld beads are required andare to be kept equal between sleeves and piles.

Tolerance on position of each weld bead is 5mm with respect to what required onfabrication drawings.

The height of the bead shall to be a tolerance of -0 to +2mm.

Weld beads distance from circumferential barrels butt welds shall not be less than 51mm,measured at weld toes. The barrels length shall therefore be defined also taking intoaccount the above requirements. However not more than one weld bead per sleeve may beout of pitch.

7.4.2 Opening and penetration holes

The centreline point of any opening and penetration shall be within a tolerance of 10mm of

the theoretical central point.

The actual size of any opening shall be within a tolerance of 2mm of the theoreticaldimensions.

See fig.7.7 for indication.


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8 FINAL FABRICATION TOLERANCES

Final fabrication tolerances shall be within the tolerance values specified here below.

8.1 POSITION OF NODES

The node working point (intersection point among items axis measured on structure) (fig.8.1) shall be positioned within the error sphere whose radius is indicated in table 8.1,relevant to the theoretical position shown on fabrication drawings.

TABLE 8.1: NODES POSITIONS

Node type Tolerance

Jacket and deck matching nodes 6mm

Other leg nodes 10mm

Other nodes 15mm

Table 8.2 shows the tolerance values of some structural dimensions, as an example of saidabove.

TABLE 8.2: DISTANCE TOLERANCES

Measures Tolerance ()

Length between first and last node working points on jacket legs 16mm

Distance between working point not involving oneleg nodes

30mm

placed on the same plane involving one legnodes

25mm

Distance between abutting jacket and deck node working point 12mm

8.2 JACKET LEGS HORIZONTAL AND DIAGONAL MEMBERS STRAIGHTNESS

Overall out of straightness of final structure axis, checked in at least two perpendicularplanes shall not exceed 1/1000 of measured length with maximum value of 10mm.

8.3 JACKET CENTERING GUIDE TUBES

Conductor support centre, measured on the structure shall be within a circle with 6mmradius centred in the drawing position.

The actual centre shall not be far more than 12mm from best fit line, obtained as per fig.8.1.

8.4 JACKET SLEEVES AND SHEAR PLATES

Completed pile sleeves out of roundness shall be measured at shims location and mid-wayof these positions. The out of roundness measurements shall be as per paragraph 7.1.4only at top and bottom shim location. At mid shim location six diameters shall be taken in

correspondence to the shims: the design value is to be respected as a minimum. At shimsmid-way positions the measurement method and the tolerance values shall be as perparagraph 7.1.4.


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The completed pile sleeves centrelines taken at shim location shall be within 6mm from theirbest fit line.

Centreline of each sleeve shall be located within 12mm of the relevant column best fit line.

The measurements shall be undertaken at the intersections of the sleeve with the horizontalconnecting plates to the legs.

Position of shear plate joints onto leg and sleeve shall be within 6mm from the theoreticalvertical plane containing leg axis and sleeve axis.

Shear plate details out of plane shall be in accordance with table 8.3.

TABLE 8.3: SHEAR PLATE OUT OF PLANE

Position Value ( mm)

Bow of straight free borders 3

Horizontal stiffener between leg and sleeve 4Vertical stiffener straightness 2

Planarity of sub-panel 5

Planarity of full panel 10

8.5 DECK PLANS

8.5.1 Deck section columns

The columns intersections centre (item axes intersection centre) measured on the structureshall be within the error sphere, whose radius is indicated in table 8.4, relevant to theoreticalfabrication drawings position.

TABLE 8.4: HEADER POSITION

Header Error sphere radius

Beams on columnBeams on stringer

Beams on principal beams6mm

As said above, table 8.5 gives, as an example, the overall distances and elevationstolerances measured on structure.

TABLE 8.5: STRUCTURE MEASUREMENT

Measurements Tolerances mm

Column distance 12mm

Header distance 12mm

Header elevation difference 12mm

Indicated tolerance shall not be higher than bevel mismatch. Tolerance among same levelcolumn shall not be higher than planarity and bevels mismatch limit.


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8.5.2 Deck section plate

Plates on deck beams shall not have sags higher than 3mm relevant to theoreticalbearings level.

8.5.3 Working plane position

Deck and modules working plane position shall have a vertical outstand lower than R/500,with 9mm as maximum, relevant to the theoretical plane; R is the distance from referencepoint.

The maximum number of water collectors shall be defined on construction drawing andClient shall define their position after welding of steel floor plates.

8.6 PILES

Overall piles length tolerance shall be 300mm relevant to the fabrication drawing value.

Different wall thickness and/or diameter pile section positions shall be within 75mmrelevant to the theoretical distance, from head, indicated on fabrication drawings.

The checking straightness method by a taut wire along the pipe length is consideredacceptable. Measurement shall be repeated at a minimum of three radial points.

Out of straightness shall not exceed 0.1% of any measured length.

The ovality shall not exceed the greater of 10mm and 0.5% of diameter.

The driving head face shall be worked (machined or grinded) to present a square surfaceperpendicular to pile centreline with maximum tolerance value of 0.01 gon.

Longitudinal seams, between two consecutive barrels shall be separated by a minimum of100 gon.

Inserts or barrels of every pile shall never have length lower than 2m

8.7 BUOYANCY TANKS

The butt joint mismatch shall not exceed 0.1t nor 3mm whichever is the less (t= weldthickness).

Distance between longitudinal seams shall be 300mm at least.

The minimum distance between two circumferential seams shall be 0.4 buoyancy tanksoutside diameter at least.

Out of roundness shall be checked at each ring stiffener and in between two adjacent ringstiffeners and shall not exceed the 0.5% of the nominal external radius.

Local out of roundness shall not be greater than 0.2% of the outside diameter or 25% of thewall thickness, whichever is the less. Local deviation from straight generator is:


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g= Lg/120

where Lg is the gage length to be used which shall be:

Lg= 4(Rt)

where: R = shell radius; t = shell thickness

The circumference tolerance shall be + 25mm or - 5mm.

The length tolerance shall be within 50mm of theoretical length shown on fabricationdrawings.

Conical head section length shall be within 10mm of their theoretical length.

The measured distance between the actual centrelines of the lower and upper supports

shall be within 10mm of their theoretical dimensions.

Additional requirements shall be specified on fabrication drawings.

Ring stiffeners tolerances shall be in accordance with relevant sections.

8.7.1 Same buoyancy tanks reutilization for more than one launching

Whenever buoyancy tanks have already been applied in several launchs, Contractor shallperform the following inspections:

100% visual inspection all over the structure;

100% MT of high stress areas (padeyes and attachments);

100% UT on padeyes, comparing the new inspection certificate with the previous onerelevant to construction phase.

8.8 CONDUCTORS

Conductors shall be fabricated to a total tolerance of300mm from the length indicated onfabrication drawings.

A minimum of 900mm over length shall be provided at top extremity, unless otherwiseshown on fabrication drawings.

Straigthness shall be in accordance with paragraph 8.6.

8.9 J TUBES

J tubes bends may be obtained either by hot forming or by cold forming processes. J tubetolerance shall be in accordance with API 5L specification.

Bend radius tolerance shall be within 2% of nominal radius, but not more than 50mm;

bend angle shall be within 0.5 of theoretical value.


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Completed J tubes are to be pigged on site to ensure they are clear with no internal weldprotrusions that may damage umbilicals and risers, prior the messenger wire installation.

8.10 SUPPORTS CAISSON / RISER / J-TUBES

Caisson/riser/j-tubes supports shall be located in such a way that the centreline of

caisson/riser/j-tube at each horizontal frame is within 25mm with respect to theoreticallocation shown on fabrication drawings.

8.11 ANODES

Anodes positioning shall be done according to relevant fabrication drawings with respect toa uniform distribution throughout the jacket. In case of interferences experienced with other

welded items, longitudinal or circumferential welds of tubulars, or similar, the following maybe applied:

anode translation from the defined position plus or minus one anode length;

anode rotation of 90 each side relevant to the position shown on the fabricationdrawings, provided the angle between two successive anodes is not changed morethan 45 from that shown on fabrication drawings.

Distance among structural weld toes is not less than 150mm both on longitudinal andcircumferential joint.

Location of anodes shall be as close as possible to the lesser local dihedral angle of eachstub-chord intersection.

All cases of impracticable solution as per above requirement shall be decided on a case bycase basis, by Client.

Welds onto nodes (stubs or chords) are not allowed in any case.

8.12 HANDRAILS

Fabrication and erection shall be performed to a degree of accuracy that the top rail shall belevel to the eye, and the handrail shall be plumb.

8.13 WALKWAYS, LANDINGS AND STAIRWAYS

Walkways, landing and stairway shall be located within the following tolerances, relevant tothe fabrication drawings.

TABLE 8.6: TOLERANCE FOR LANDING AND STAIRWAY

Elevation 12mm

Planarity 6mm each 3m length

Planimetric position 12mm

Distance among steps shall not be more than 3mm from theoretical position.


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8.14 TEMPLATE DOCKING PILES CENTRING SYSTEM

Template docking piles centring system shall be rected after having verified the actualengagement distances and verticality of the erected template docking piles

The location of each pile centring cone measuring centre shall be within 12mm of thetheoretical location shown on construction drawings.


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9 INSPECTION OF WELDMENTS

9.1 GENERAL

All welds are to be subjected to non destructive examination (NDT)as fabrication andconstruction proceed, as per a proper schedule and relevant drawings supplied by theContractor.

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. For offshorewelds Contractor shall supply for approval a detail NDT procedure that shall include waittime, after welding, before NDT and possible accelerated cooling procedures of the welds.

NDT on weld class "e" and on all other classes not considered above

General Specification Offshore Platforms Offshore Structures Construction

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