130460129-General-Specification-Offshore-Platforms-Offshore-Structures-Construction.pdf

Eni S.p.A. Divisione Agip

GENERAL SPECIFICATION

OFFSHORE PLATFORMS PLATFORMS

OFFSHORE STRUCTURES CONSTRUCTION

08833.STR.MET.SPC Rev. 5 December 2001

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


08833.STR.MET.SPC Rev. 5 December 2001 Pag. 2 di 89

PREFAZIONE Rev. 0 December 1992 Total pages n. 107 Issue Rev.1 February 1993 Modify sheets 37, 38, 44, 45, 79, 91, 101 Rev.2 September 1993 Total pages n. 107 Modify sheets 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 1993 Total pages n. 120 RINA comments are included. General revision. Rev.4 October 1995 Total pages n. 120 General revision. Rev.5 December 2001 Total pages n. 89 Steels with yield strength of 460MPa and steels fabricated with thermomechanical rolling process are considered, 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 draft committee 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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Divisione Agip

CONTENTS 1 1.1 1.2 1.3 1.4 1.5 1.6

GENERAL SCOPE OF THE WORK APPLICABLE DOCUMENTS TERMS AND DEFINITIONS REPORTING STRUCTURAL CLASSES AND TYPICAL ELEMENTS MATERIALS

5 5 5 6 7 7 7

2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

WELDING GENERAL DEFINITIONS WELD CLASS WELDING PROCESSES CONSUMABLES STORAGE AND HANDLING OF CONSUMABLES INITIAL DOCUMENTATION WELDING BOOK

8 8 8 8 9 10 11 13 14

3 3.1 3.2 3.3 3.4 3.5 3.6 3.7

WELDING PROCEDURES GENERAL WELDING PROCEDURE SPECIFICATIONS QUALIFICATION OF WELDING PROCEDURES (WPAR) QUALIFIED PRINCIPAL POSITIONS VALIDITY OF WELDING PROCEDURES (ESSENTIAL VARIABLES) T E S T I NG SPECIAL TESTS

16 16 17 18 18 18 21 24

4 4.1 4.2 4.3

WELDERS AND WELDING OPERATORS GENERAL QUALIFICATIONS RETESTS

26 26 27 28

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8

PRODUCTION WELDS GENERAL W ELDING SEQUENCES TEMPERATURE REPAIRS CLOSURE WELDS STRESS RELIEVING POST WELD HEAT TREATMENT PRODUCTION TESTING COUPONS WELDING PARAMETER CHECKING

29 29 33 33 34 36 37 39 40

6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8

FABRICATION GENERAL FORMING WELDED ATTACHMENTS SITE ASSEMBLY ACTIVITIES MANUFACTURED AND MISCELLANEOUS ITEMS FINISHING OF SURFACES RAT HOLES BOLTED CONNECTIONS

42 42 42 45 45 46 46 46 47

7 7.1 7.2 7.3 7.4

PREFABRICATED ITEMS TOLERANCES FABRICATED TUBULARS, NODES AND CONES ROLLED OR FABRICATED BEAM STIFFENED PLATE PANELS OTHER FABRICATION DETAILS

48 48 50 51 52



8 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12 8.13 8.14

FINAL FABRICATION TOLERANCES POSITION OF NODES JACKET LEGS HORIZONTAL AND DIAGONAL MEMBERS STRAIGHTNESS JACKET CENTERING GUIDE TUBES JACKET SLEEVES AND SHEAR PLATES DECK PLANS PILES BUOYANCY TANKS CONDUCTORS J TUBES SUPPORTS CAISSON / RISER / J-TUBES ANODES HANDRAILS WALKWAYS, LANDINGS AND STAIRWAYS TEMPLATE DOCKING PILES CENTRING SYSTEM

53 53 53 53 53 54 55 55 56 56 57 57 57 57 58

9 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 9.10 9.11 9.12 9.13 9.14

INSPECTION OF WELDMENTS GENERAL DEFINITIONS REFERENCE STANDARDS METHODS OF NDT EXTENT OF NDT EDGE INSPECTION QUALIFICATION OF NDT PROCEDURES QUALIFICATION OF NDT PERSONNEL VISUAL INSPECTION EXECUTION RADIOGRAPHIC TESTING EXECUTION ULTRASONIC TESTING EXECUTION MAGNETIC PARTICLE INSPECTION EXECUTION STANDARDS OF ACCEPTABILITY REPORTS

59 59 59 59 60 61 62 62 64 65 65 65 67 68 70

10 10.1 10.2 10.3 10.4 10.5

TESTING OF FIELD INSTALLED COMPONENTS PREASSEMBLY TESTING RISER PNEUMATIC TESTING PNEUMATIC TESTING OF BUOYANCY TANKS AND JACKET LEGS TESTING OF BALLASTING AND GROUTING SYSTEMS TESTING OF PACKERS SYSTEM

72 72 72 72 72 72

11

APPENDIX 1: STRUCTURAL CLASSES

74

12

APPENDIX 2: FIGURES

75

Eni S.p.A.


Divisione Agip 1

GENERAL

1.1

SCOPE OF THE WORK This specification covers the minimum requirements for fabrication and construction of jackets, decks and modules of the offshore platforms of ENI Division AGIP spa. This specification contains general requirements: construction drawings shall prevail over this specification.

1.2

APPLICABLE DOCUMENTS

1.2.1

Referred Codes For items not specially covered by this specification, the latest editions (at the time of contract 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 Fixed Offshore 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 International Association 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 NDT personnel", (Para. 9), 10025 "Hot rolled products of non-alloy structural steels and their technical delivery conditions" production weld (Para. 5), 462 "Non-Desstructive testing - Image quality of radiograph -Image quality indicators", 970 "Non-Destructive examination of fusion welds -Visual

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Divisione Agip

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 offshore structural 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 the relevant codes of the Certifying Authority.

1.2.3

Associated Specifications AGIP 08832-STR-MME-SPC "Purchase of offshore stru ctural 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: CONTRACTOR

Sub-CONTRACTOR: SUPPLIER: EXAMINER or APPROVED BODY:

1.3.2

ENI Division AGIP or its Authorised Representative. The Company responsible for the fabrication and construction who has awarded the contract from Client. The Company Sub-Contractor to Contractor, approved by Client. The Company who receives the purchase order for supplying of materials or equipment. Person or Society, accepted by the Client, committed to certify: - procedures, materials and welding operators, - procedures, equipment and NDT personnel.

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 of work. Construction drawings together with other specifications define the necessary Contractor information for fabrication drawings built up and relevant engineering detail. Fabrication Drawings: drawings issued by Contractor that contain all the necessary information required to fabricate items at shop and yard level. Assembly sequence drawings and temporary support drawings are considered fabrication drawings As built Drawings: fabrication drawings, issued by Contractor, on which are reported all the information on how the construction has been actually built.



Assembly sequence drawings and temporary support drawings need no to be issued in "as-built" version, except that all attachments left onto the structure shall be reported on as built drawings. Structural Element Class: level of importance of each structural element due to its loading condition 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: thikness NDT: 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 tubulars after row roll-up. Insert: structural element part with the same diagonal dimension section in which it is fitted.

1.4

REPORTING Reports required throughout this specification shall conform to the applicable Contractor guarantee quality formats which shall contain, at least, the information listed in the relevant paragraphs of this specification.

1.5

STRUCTURAL CLASSES AND TYPICAL ELEMENTS For the scope of this document the structural elements of the off-shore installations are subdivided in classes. The definition of the structural classes is reported in Appendix 1 with the definition of structural 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 platform installation (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-SPC rev.7 requirements. Materials substitution and handling shall be in accordance with sections 3.4 and 6.5 of standard EEMUA 158.

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Divisione Agip 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 in accordance 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;

2.3

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).

WELD CLASS The welds to be executed are grouped in classes, corresponding to the structural element classes, of which they maintain the same name. Different requirements on applicable welding processes, mechanical characteristics, NDT type and percentage, defects acceptability combinations are defined for each weld class. In welded joints between elements of different structural classes the higher structural element class shall govern.

Eni S.p.A.


Divisione Agip 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

st

GS/SSFCAW (1)

SAW SMAW GSFCAW (1)

T butt st

GTAW

1 run SAW SMAW GSFCAW

Fillet

Closure st

1 run Seal

na

d

e

SAW SMAW GS/SSFCAW (1) GTAW SMAW

Butt 1 run

c

SAW SAW SMAW GS/SSFCAW (1)

SMAW

SMAW

GS/SSFCAW

SAW SMAW GS/SSFCAW GMAW SMAW SMAW GSFCAW GS/SSFCAW GTAW SMAW SMAW GS/SSFCAW GMAW

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 GMAW process 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. In this case full details about the process, the consumables, the NDT techniques, the relevant applications 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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Divisione Agip

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:

2.5

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 exceeding 3 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.

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 yield strength not lower than the base material. Consumables to be used for welded joints between steels having different yield strength shall be those applicable to the higher strength steel. The use of filler metals giving a low diffusible hydrogen deposit (less than 5 cm³ per 100g of weld deposit, carried out with mercury measurement method, or humidity equal to 0.2% of the weld metal weight, according to AWS D1.1.) is compulsory when one of the following conditions 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 greater than 275MPa. Electrodes in sealed boxes shall have the hydrogen level certified. Electrodes classification shall conform to AWS. Electrodes classified conform to other specifications or codes are accepted provided correspondence and in that case the WPQ has in the name anessential variable All electrodes, according to the reference code or specification, shall be marked.

Eni S.p.A. Divisione Agip 2.5.1


SMAW Electrodes for SMAW shall conform to AWS specification A5.5 classification E7015-A1, or E7016-A1, E7018-A1, E8016-C3, E8018-C3, E9018-M and AWS A5.1 classification E7015, E7016, E7018 ed E7028 (the last one for fillet weld only).

2.5.2

SAW Wires and fluxes for SAW shall conform to AWS specification A5.17 classification F6XXEXXX or F7XX-EXXX or F6XX-EXXX or AWS specification A5.23 classification F7XXEXXX-A1 or F8XX-EXXX-A1.

2.5.3

GTAW Rods for GTAW shall conform to AWS specification A5.18 and electrodes shall conform to AWS specification A5.12.

2.5.4

GMAW GMAW consumables shall be in accordance with AWS specification A5.18 (classes ER 70S2, ER 70S3, ER 70S6, ER 70S7). Processes with 100% CO 2 are not allowed; gas mixtures with 80% Ar and 20% CO 2 are acceptable.

2.5.5

GSFCAW and SSFCAW Consumables shall be in accordance with AWS specification A5.20 (classes E70/71-T6 E70/71-T8) and AWS A 5.29 (class E81T1-Ni1-Ni2). Gas mixture normally used is that with 80% Ar and 20% CO 2. Other type of gas mixture may be applied after Client approval.

2.5.6

Gases CO2 is to have a purity grade not lower than 99.8% and a dew point not higher than 45°C below zero. Argon and Helium are to have a purity grade not lower than 99.99% and a dew point not higher than 45°C below zero. Gases are to be supplied in bottles where type is to be clearly indicated. Fixed distribution networks are to be clearly identified in their content. Heaters for CO 2 are to be used.

2.6

STORAGE AND HANDLING OF CONSUMABLES All consumables shall be supplied in sealed moisture proof containers capable of maintaining the consumables free from moisture for at least six months.



Unopened containers shall be stored in a dry location where the temperature shall not be less than 20°C and the relative humidity shall not exceed 50%. Electrodes, fluxes and wires that have been contaminated by water, oil, grease, or all other deemed 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 he considers 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 AWS specification A5.5, may be carried out at Client's discretion. Samples shall be taken from ovens where electrodes and fluxes are stored, ready for production use. The maximum moisture content by weight for low hydrogen consumables shall be 0.2% for electrodes and 0.1% for fluxes. Client reserves the right to verify the consumables chemical and mechanical characteristics by destructive testing.

2.6.1

Electrodes Low hydrogen electrodes shall be baked for 2 hours at 350/450°C, unless otherwise recommended by the supplier. Thermocouple, which shall be previously calibrated shall be placed at midheight owen. Initial drying may be omitted in case the electrodes are supplied in fully sealed packs with a guaranteed hydrogen level content. After withdrawing from ovens for use, electrodes shall be contained in heated portable quivers at a temperature not lower than 70°C and shall be used within 4 hours. Electrodes not used within above time limit may be rebaked, provided they are in good conditions. Redrying is generally acceptable to a maximum of 2 times. Electrodes that shall not immediatly applied may be stored in ovens at a temperature not lower than 100°C after baking. In alternative electrodes characterized by a low hydrogen level maintainment after box opening may be used. Those electrodes are commercially available in packages equal to a workday or half workday. Anyway Client may require a test to verify the characteristical performance of those electrodes. If these electrode types are used, those unemployed, at the day end, shall not be employed again.

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 to eliminate 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.


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 from grease 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 wire moisture contamination.

2.7

INITIAL DOCUMENTATION Prior to begin fabrication and for all welding processes Contractor shall submit to Client's approval: 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 cutting drawings; 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 above listed All the documents listed above shall be in accordance with the provisions given in following sections.


2.8


WELDING BOOK Before the beginning of the works, the Contractor shall prepare a welding book covering all the 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 thicknesses and covered diameters together with maximum CEV and Pcm qualified for steels with Re > 275MPa;  the welding procedure qualification records, with the testing record certificates and inspection, during fabrication, certificates of the base and filler metals;  the chemical composition and the carbon equivalent CEV / Pcm of the test pieces (for steels 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 initially foreseen on the drawings, this shall be indicated);  the joint configuration before and after welding (size and tolerance); passes number; if a 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-automatic or an automatic process;  the welding position;  the consumables used (standard name, trade name, diameter);



 welding parameters with tolerances (voltage, speed of travel, current, heat input, flow rate and type of gas);  welding technique detailing polarity and nature of current; welding direction; type of protection (gas); weave bead or stringer bead; whether or not back welding is carried out after gouging and/or grinding.

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Divisione Agip 3

WELDING PROCEDURES

3.1

GENERAL Welding of weld classes "a, b, c" shall be carried out in accordance with approved and qualified welding procedures only. All welding procedures applied shall be qualified unless Contractor pr ocedures have already been 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 is carried out as production welding begins. Welding of weld class "d" may be executed with procedure previously qualified by Contractor, without the need of new qualification. Welding of weld class "e" may be carried out with pre-qualify processes without new qualifications (see section 3.3). Prior to beginning work, the Contractor shall qualify all the required welding procedures for the various materials and welded seams of the structures to be fabricated. The Approved Body committed to certify the welding procedures shall be accepted by the Client. The information indicated on each WPS shall be consistent and shall not leave the welder to choose within different combinations of parameters.

3.1.1

Preheating and Interpass Tacking and welding shall be carried out with preheating temperatures ranges stated in table 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)

CEV t < 20mm (check analisys) < 0.39 20 < 0.41 20 < 0.43 20 < 0.45 50 (20) Note: values in brackets refer to SAW only.

Weld thickness (t) t < 30mm

t > 30mm

20 20 50 (20) 100 (75)

50 (20) 75 (50) 100 (75) 125 (100)

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 at both sides. Working interpass temperature shall not be lower than preheating one, nor higher than 250°C. Preheating and interpass values differing from the above stated may be used provided measured during the execution of welding procedure qualification. The requirements of section 5.1.1 shall apply.

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Divisione Agip

3.1.2

Heat input Welding heat input shall be calculated with one of the following formulas: HI = 0.006 VA / s HI = 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 than those considered in paragraph 2.4.2, provided adequate welding procedure qualification demonstrates 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 addition to 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 pipe diameter (when applicable) used for procedure qualification;  sketch of joint showing plate edge preparation (specifying if oxygen cutting or machining) 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. Any pretreatment 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 and welding parameters for each joint zone;  for each run: the current type, polarity, arc current and voltage, welding speed, or electrode 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 waving amplitude;  post weld heat treatments (for avoiding hydrogen cracking and for stress relieving) if applicable;



 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 as specified 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 value of 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 process to that used for weld body, the procedure test plate shall be similarly tack welded and one macro 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 D1.12000.

3.5

VALIDITY OF WELDING PROCEDURES (ESSENTIAL VARIABLES) A qualified welding procedure is to be used within the limitation of essential variables as stated below. The changes described below are to be considered essential and are to initiate a new procedure qualification test. When a combination of welding processes is used, the essential variables applicable to each 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 CEV above 0.02% (for Re > 300MPa only), and Pcm above 0.01% of maximum nominal value of steel 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 accepted also for TM materials, and not viceversa. Change of microalloy elements or manufacturing procedure for steels with minimum specify yield strength of 460MPa.



Groove preparation: presence of bevels protective coat. Oxycutting without grinding to sound 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° weld processes are to be qualified by the test of TKY joints. The bevel angle in this test is to be the smallest used in fabrication. Root face and root gap: changes of root face and root gap shall be in accordance with AWS D1.1-2000, 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 other and 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 or 10%t on single sided joints. Misalignment of 2mm is permitted, regardless of other parameters. 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 are considered equivalent on condition that they belong to the same certification class and are approved 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 nominal preheat temperature applied at the start of the welding procedure test, with a tolerance of 10°/+50°C. For interpass the upper limit of approval is the nominal interpass temperature reached 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% or beyond in gas composition; change +27% or -10% in flow rate.



Grinding: if grinding between passes is omitted. Back-gouging: each reduction in depth of back-gouging in comparison with the qualified one for 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 measured during 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 a change beyond 15%. Where heat inputs in two positions are different, qualification in both positions 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 intermediate run out lengths. Core diameter of an electrode used for capping passes is reduced. All passes in the cap of the 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.


3.5.8


Specific for FCAW (GS and SS) If the mean voltage for any pass deposited by other automatic or semi-automatic process is changed 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-destructive testing and mechanical testing on test samples. Type and number of tests are those specified in table 7.7. of RINA Codes. If different welding consumables or welding processes are applied for the same joint, impact tests 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 of 8mm. 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 rolling direction 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 parallel to the rolling direction; for materials of other quality the welding direction can be perpendicular to the rolling direction. (fig. 3.1) Test conditions shall be a realistic simulation of the actual conditions that will be experienced. When PWHT of nodes or other sub-assemblies is required, all relevant procedures qualifications 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 section 7.2. When plate thickness to be tested is over 36mm or the power of tensile testing machine is not sufficient, tensile specimens may be cut into a number of approximately equal strips not exceeding 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 results averaged.

3.6.2

Acceptance Criteria The welding procedure is qualified when the soundness and mechanical properties comply with the requirements hereafter indicated:

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Divisione Agip

Non-destructive tests: Welded joints soundness is to comply with the prescriptions of section 9.13. NDT shall be carried out not prior than 48 hours from weld completion and in any case after PWHT when applicable. 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 with EN 288-3 paragraph 7.4.1; in case of welding between steels of different grades the tensile strength shall be equal to the lower steel grade. All weld metal tensile test: specimens shall be taken out from full weld metal, and shall take the 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 288-3 paragraph 7.4.2; bending angle test shall be of 180°. Toughness tests: the average and minimum Charpy V-notch energy absorption recorded at each specified position in WM and HAZ shall comply with the requirements stated in tables 3.2, 3.3 and 3.4: TABLE 3.2: IMPACT TEST TEMPERATURE °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 Structural Test temperature element class a -20°C

b

c

-20°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 (1)

D E Note:

Impact test not required

not applicable

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

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Divisione Agip

T ABLE 3.3 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 value obtained by a single specimen must be greater than 70% of the average value required TABLE 3.4 IMPACT TEST LOCATION Thickness

Note:

Location

Double and single side welding t < 45mm Cap WM + HAZ root none t > 45mm Cap WM + HAZ root WM + HAZ - Cap: 2mm +/- 0.5mm 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+2mm, FL+5mm.

Macro section: EN 288-3 paragraph 7.4.3, test condition and acceptability shall be applied. Hardness: the maximum hardness in any part across the welded joint shall not exceed 325 HV10.

3.6.3

Retesting Retesting shall be in accordance with EN 288-3, paragraph 7.5 with the following amendements. Tensile: when the failure, on one or both the specimen, occurs for a load value that is less than 95% of the tensile strength, the procedure will be rejected. When the failure, on one or both the specimen, occurs for a load value that is between 95% and 100% of the tensile strength, two additional tests will be carried out for the interested specimen. Bends: two other specimens of similar type (face, root or side), located as near as possible to the failed specimen, shall meet specification. Macro and hardness: the surveys on two more sections of the coupon have to meet specification. Toughness: in case one specimen tested gives an energy value below the specified minimum single, or more than one value is lower than the minimum average, one further set shall be tested from the same location. The new set shall meet the specified minimum values and conditions, and in addition the mean value of all the two tested sets (the new and the failed) shall attain the specified minimum average value. In case of any additional failure the welding procedure shall be rejected.

Eni S.p.A. Divisione Agip 3.7

SPECIAL TESTS

3.7.1

TKY Joints


The joint qualification shall be carried out in accordance with EN 288-3 paragraph 6.2.4. The can shall be positioned with vertical axis and brace acute angle downward (fig. 3.2). Welding shall be carried out with a qualified T-butt procedure, or with a qualified butt weld procedure. In this case the required mechanicals to qualify the T-butt procedure shall be carried out. Testing shall be 100% NDT, WM and HAZ thoughness at 12 and 3 o'clock positions, macro and hardnesses at 12, 3 and 6 o'clock positions. Acceptability shall be in accordance with applicable requirements of this specification.

3.7.2

Welding Repair Special qualification for repair of excavated welds is required in case the repair process differs from the filling used. The qualification shall be carried out in the worse position, through the utilisation of parameteres which are worse than the expected ones. HAZ of both parent material and original weld shall be tested. The Contractor shall issue standard WPQ repair that may be applied in various cases, including the applied methodology, length and maximum excavation depth, cleaning and NDT methods, preheat temperature and weld re shaping, if any. The previous methodology shall be exactly applied. The requirements of section 5.4 shall apply.

3.7.3

Buttering Buttering procedure carried out with the same process and parameters as for the filling weld need not to be qualified. In case buttering is done with a different welding process, or with same process but different parameters, from main weld, the buttered area and HAZ shall be tested as for a different process weld. Both HAZ on base material induced by buttering and HAZ on buttered area induced by main weld shall be KCV tested. In case one KCV set position coincides with another KCV set, one may be superseded. Welding procedure shall be carried out with maximum allowed root gap conditions. Buttering thickness shall be 4mm and at least 3mm width on each bevel; normally buttering shall apply only to weldments having thickness 15mm and above. Buttering area shall be MT inspected. The requirements of section 5.5 shall apply in case of use of buttering in closure welds.


3.7.4


Permanent Backing Strip Welds Contractor may apply this technique providing a special WPQ including the insertion of steel backing strip into the fit-up joint and its tightening against bevel root, first passes, filling passes and relevant NDT execution. This procedure is not applied in stub-can joints. The test is carried out by welding a joint, at scale 1:1, built up by two tubulars pieces with diameter equal to the minus on which the process is intended to be applied (fig.3.3). A macrographic examination shall be executed on the weld root. Tacking shall be carried out inside the bevel all over the weld root: tacking shall never be done outside bevel. Air gap between the bevel root and backing strip shall be the minimum, before root welding starts. A special UT procedure shall be defined and applied to verify the bevel fusion, the absence of tacking between base material and backing strip, and to recognize the root discontinuity caused by backing strip. The actual bevel inclination shall be considered for choosing UT probes. The procedure shall include the execution of an identification mark on base material at 100mm from joint, to verify the root gap dimensions and the centre of backing strip in every point before weld execution. "Backing strip" welds shall be indicated on "as built" drawings. Maximum root gap variation in backing strip welds shall not exceed 6mm the root gap used during qualification. Backing strip weld is allowed with root gap values higher than 12mm but not exceeding 20mm. Overall procedure produced by Contractor shall be approved by the Client before its application. The requirements of section 5.5 shall apply in case of use of permanent backing strip in closure welds.

3.7.5

Grout Beads Mechanical tests required on grout weld beads shall be two macros, with hardness survey on fusion line and HAZ under bead, one KCV set in HAZ and WM as shown in figure 3.4. KCV temperature test shall be equal to the test temperature utilised for the parent material and shall conform with the minimum energy requirements for this last one.

Eni S.p.A. Divisione Agip 4

WELDERS AND WELDING OPERATORS

4.1

GENERAL


All welding on the structures shall be performed by welders or operators qualified by an Approved Body accepted by the Client. All qualified welder shall have a certification that witnesses the qualification. The certification shall be in accordance with EN 287 code or EN1418 code in case of weld operators. The purpose of welder performance tests is to verify that the welders may produce welds in accordance with this specification requirements using a qualified welding procedure. Welder qualification tests shall be carried out to an approved welding procedure specification. Welders having successfully performed the welds of qualification tests of a qualified process are automatically qualified for the same procedure. All welders shall be qualified with at least one of the qualification tests indicated in table 7 of EN 287-1 1997 "Approval testing of welders - Fusion welding - Part1: Steels" All welds using SMAW process are to be conducted with low hydrogen electrodes. During qualification at least one stop/start has to be produced in each run. The welders are generally to be qualified for all positions butt welding. For welding occurring only in one or limited number of positions, performance test may, after agreement with Client, be performed only in this (these) position(s). Welders, to be qualified for GSFCAW/SSFCAW or GMAW fillet, are to be qualified in all positions The welder can be qualified for mixed welding process by only one test, or by two tests as for EN 287-1 ch. 6.2. Semi killed or fully killed C-Mn steels are normally to be used for welder qualification tests.

4.1.1

Certification Validity The certification validity shall be submitted to the Client approval when fabrication starts, and it shall be in accordance with EN 287-1 with the following amendements. A welder or welding operator may be required to be re qualified if inspection during fabrication reveals that extensive repairs are due to poor performance. This shall be done following a period of supervised retraining. The length of this period shall be at Client discretion but shall be not less than one week. The Contractor shall record details of retraining. Client may review existing welder qualification meeting the requirements of this specification: existing qualifications may be accepted at his solely discretion.

4.1.2

Categories of qualification and test requirement The fundamental categories that the Client will recognise are listed in the following paragraphs of this section.



The coupons to be welded are indicated in the same paragraphs. The coupons shall be checked in accordance with table 8 of EN 287-1. NDT acceptability shall be as per more stringent requirements of this specification. Requalification is necessary if a different welding AWS classification consumable is used. It shall be in compliance with EN 287-1 paragraph 6.5.

4.2

QUALIFICATIONS All the qualifications listed in EN 287-1 page 11,paragraph 6.3, will be applied. The extensions of the welders qualifications shall be in compliance with table 3 of EN 287-1

4.2.1

Automatic welding Welding operators using the submerged automatic arc welding (SAW) process shall be qualified as per AWS D1.1/2000 Chapter 4 Part C (or EN1418) and shall mark their welds for identification purposes. Qualification with more than one wire qualifies one wire weld according to codes.

4.2.2

Manual double-side welding WPQ test welds shall be carried out in accordance with EN 287-1, table 7.

4.2.3

Manual single-side welding WPQ test welds shall be carried out in accordance with EN 287-1, table 7.

4.2.4

Closure Butt Welds This qualification is required for all welders using the closure butt weld procedure. The qualification requirements are the same as per manual single side welding, except that the root gap value shall be as per relevant WPQ. The strong-backs shall be sufficiently strong so that the gap between bevels does not reduce significantly during welding. The extension of the qualification is ruled by EN 287-1, table 3.

4.2.5

Fillet welds Fillet welder qualification shall be carried out according to EN 287.


4.2.6


Carbon arcair gougers Manual welders are acceptable as Carbon arcair gougers. Carbon arcair gougers, for structural class "a, b", shall demonstrate their ability to remove metal to a uniform depth in a workmanlike manner. An up-dated register of approved arc-air gougers shall be keep.

4.2.7

Tackers Tackers, for structural class "a, b", shall be qualified as per AWS D1.1/2000 section 4 part C unless already qualified for manual welding.

4.3

RETESTS Retest applicability requirements shall be in accordance with EN 287-1 paragraph 9 requirements. Welders failing tests shall follow a congruous training period before retest. Such a training must be proved by documents.


PRODUCTION WELDS

5.1

GENERAL

5.1.1

Technique


The width of individual deposited weld beads in flat, horizontal and overhead position, with GMAW and SMAW process, shall not exceed three times the electrode wire diameter or 16mm, whichever is the less. In vertical position the width shall not exceed 15mm. For SAW tandem process only fill beads may be 24mm. Vertical down welding is an acceptable technique only for GSFCAW and SSFCAW process, for weld class "e". Run-out tabs for SAW are recommended to have a length greater than 150mm or 200mm, depending if single wire or twin wire technique is used. Such tabs shall be positioned on both sides of each longitudinal weld. The arc shall only be struck on the bevel faces only and not on base material. Each run of weld metal shall be thoroughly cleaned from flux, spatter and all slag removed, by brush, prior to deposit the next run. For double side buttweld the second side shall be cleaned to sound metal prior to deposit the second side runs. Should carbon arc air gouging be used, carbon and other residual debris shall be completely removed by grinding or other approved mechanical methods. The welding procedure for a single side butt weld shall provide 100% fusion of the root and be such that distortion or contraction of the weld metal is minimized. Peening of welds shall not be permitted. Preheating temperature shall be raised by 50°C above that qualified, for fillet and T butt welds with root gap exceeding 20mm. Welding joints shall be fully protected by shelters from the effects of inclement weather (wind, air draughts or chimney effects). Gas metal arc welding (GMAW) shall be permitted in workshop only and special care shall be exercised to protect the weld arc from air draughts. Two adjacent weld toes distance shall not be lower than 51mm, unless there are geometrical problems. In this last case weld classes "a, b, c, d" shall be ground smooth before NDT execution.

5.1.2

Preparation and Fit-up Surfaces to be joined by welding and extended adjacent areas shall be thoroughly cleaned to remove all material or substance detrimental to welding. Whenever practicable, clamps, magnets, holding devices or other setting-up fixtures shall be used in assembling structural members in order to avoid tack welding. Mechanical grinding and NDT of oxycut surfaces to be welded is required (see also Section 9.6). Arc gouging to open tight grooves are permitted on double side welding only, provided is followed by grinding to bright metal.



Before welding the stub to node can, the relevant welding area on the can shall be 100% UT to detect for laminations. When beam shall be welded on flange beam, the flange beam area subjected to weld shall be UT tested to verify the laminations absence. A similar control shall be performed on plates in the position of joint between pad-eyes and main beams.

5.1.3

Tack Welding Otherwise spacers shall be employed prior to tack welding to ensure correct root gap spacing. Tacking shall be done within the bevels. Tack welding shall be performed by qualified tack welders and an approved qualified welding procedure, including preheating requirements. Steel bars tacked inside the bevel shall be permitted if their position is clearly marked on base material and that Client may verify their removal. Steel bar material shall be similar to base material type or lower grade. All tack welds, on structural class "a, b, c", shall have a minimum length of 4 times the weld thickness, with a minimum of 100mm; all other structural classes the minimum length is 2 times the weld thickness or 50mm whichever are the major. Tack welds may be incorporated into double side main butt welds provided they are sound, have been executed by qualified welders (not tack welders), and have their ends grounded and feathered. Tack welds with a length of 50mm or greater that have shown cracks and when the crack is believed to extend to the bevels, shall be MT on all the interested areas after removal of defective points and before commence welding.

5.1.4

Weld Interruption Welding shall be a continuous operation as far as practical. For components of class "a, b, c" very constrained and for mud-mats, preheating shall never be discontinued before at least 1/3 of the joint thickness has been welded. When the above limit is reached the weld joint may be allowed to cool down to room temperature: the cooling rate shall be minimized by wrapping the weld areas with dry insulating blankets. After any interruption and before continuation of welding, the weld is to be inspected visually for defects and cracks and, if necessary or required by the Client, tested by MT.

5.1.5

Weld Profiles As a minimum, weld profiles and weld finish shall comply with A.W.S. D1.1/2000 Para 5.24 and 6.9; in the case of lack of fusion, incomplete penetration or for marginal indentation, the values shown in section 9.13 of this specification shall not be exceeded. The external and internal weld reinforcement must not exceed 3mm for welding thicknesses up to 25mm, 4mm for thicknesses up to 50mm and 5mm for thicknesses over 50mm. The excess penetration in root welding, with GTAW process, shall not exceed 2mm Weld profiles shall not interfere with the NDT technique specified: reshaping shall be carried out to this purpose, if necessary. Weld profiles shall not be re shaped by use of a gas torch, or by other unapproved means to change their appearance. When specified on the Project Drawings the weld toes shall satisfied API RP2A sect.11 requirements. If necessary, the weld toe can be grinded to obtain the required profile. In that

Eni S.p.A.


Divisione Agip

case a rotary burr grinder (no disc grinder) shall be used, as shown figure 5.1. Grinding shall produce a smooth concave profile at the weld toe with the depth of depression penetrating into the plate surface to at least 0.5mm below the bottom of any undercut, but not deeper than 2mm or 5% of the thickness, whatever the bigger, below the surface. Localized unacceptable undercuts at the weld toe region of any stub to node can welds shall be removed by the technique mentioned above.

5.1.6

Double side welding Double side welding shall be carried out whenever possible. In particular:

 in longitudinal and circumferential joints of tubulars and node cans having diameter 800mm and greater. Limitations to this statement are permitted only in case of non accessibility to back side of the weld;  in T butt welds of nodal joints when construction drawings show the presence of stub. 5.1.7

Welding Grooves Contractor is to prepare his own standard weld joint groove preparation in accordance with the indications given on the fabrication drawings and WPS qualified. Where the joint is accessible from both sides, double side groove preparation, X or K type, shall be used to join members with thickness greater than 25mm; one side groove preparation, V or 1/2 K, may be used to join members with thickness 25mm or less. Contractor may choose a desired welding groove provided all full penetration requirements are fulfilled. Bevel inspection shall be in accordance with paragraph 9.6. Root back gouging is always required in double side joints.

5.1.8

Mismatch The butt joint mismatch of welded plate, pipe, or structural shape edges shall not exceed the table 5.1 values: TABLE 5.1: MISMATCH VALUES

Joint type Double side Single side

Longitudinal Circumferential Longitudinal Circumferential

Mismatch: the lesser of 0.1t or: 4 mm 3 mm 3 mm 3 mm

When members of unequal size are joined, the larger member shall be prepared with a 1/4 tapered transition. The requirements apply both to thickness and width (e.g. beams flanges) dimensions. Worked taper in double sided joints are not required when thickness difference is 1.15t or less.


Spacing between welds

5.1.9.1

Longitudinal seams


When tubular members are fabricated from two or more welded barrels, the longitudinal seams axes of adjacent sections shall be staggered at least 300mm.

5.1.9.2

Node can welds intersecting stubs Longitudinal and circumferential chord welds shall be separated from stub to chord welds as indicated in construction drawings, typical node. Otherwise the following requirements are to be fulfilled.

 flush grinding of the outside area of chord welds intersecting the stub, extended for 150mm at least on both stub sides;  MT and UT on ground area;  stress relieving of the complete node. Circumferential node can weld between two stubs is not allowed. The distance between longitudinal stub seam and any node can seam type measured between weld toe and weld toe shall be in any case not less than 51mm.

5.1.9.3

Node can welds and ring stiffeners The distance between ring stiffeners welds toe and circumferential chord weld toe is to be at least the chord thickness or 75mm, whichever is greater.

5.1.9.4

Cones Circumferential welds within cone are not allowed, unless approved by Client or specified on the construction drawings. All cones shall be right conic frustum.

5.1.9.5

Pipe and node splices The minimum distance between two circumferential welds shall be 1m or one diameter, whichever is greater. Nodes can with length minor or equal than 3m shall be supply in one piece only. Nodes can with length greater than 3m may be supply made in two pieces. In this case the minimum length of the single piece shall be not less than 1m and the circumferential weld between the two pieces shall comply with the following:

 To be not located between two stubs;  Satisfy the requirements reported in the project drawings for the circumferential welds of the nodes In any case the location of the circumferential weld in the node can shall be submitted to Client for approval.



There shall not be more than 2 splices in any 4m of pipe.

5.1.9.6

Beam splices In cantilever beams no splice shall be located closer to the point of support than 1/2 of the cantilever length. In beams with two or more supports there shall not be splices in following positions (fig.5.2):

 in the middle 1/4 of the span;  in the 1/8 of the span nearest to any supports;  not closer than 1m to any support or node.

5.2

WELDING SEQUENCES Contractor shall develop welding sequences to control tolerances within specification and prevent the build-up of excessive residual internal stresses in the structure. No welding shall be carried out between pretensioned parts. Postheating of 300°C for 2 to 4 hours may be applied to reduce the risk of hydrogen induced cracking in welds of complex items, according to the thickness, if it need or it is required by the Client. Welding sequences are to be defined, to the Client's approval, for complex items (e.g. nodes with four or more stubs, pile clusters, etc.) including:

 WPS to apply;  sequence of items welding and welding direction and way;  number and location of welders at each stage of assembly;  position of preheaters and shelters;  postheating (if applied).

5.3

TEMPERATURE Welding is not allowed if weldment temperature is lower than 5°C. In these cases preheating is mandatory to the required minimum temperature prior to begin welding. Preheating shall be applied to an area of 100mm minimum from bevel borders. Definite methods and procedures shall be established for all operations involving preheat and interpass temperature control. Thermic crayons shall be used only outside the weld bevel. Temperature check or measurements shall be done at 50mm minimum from bevel borders and on back side where accessible; temperature reading on weld bead is for interpass temperature measurement only.


5.4


REPAIRS Contractor shall prepare a written repair weld procedure, for each repair, including details of removal methods, weld area preparation, etc. Repair shall be carried out as per qualified procedures only. Defects removal for repair shall be carried out by any method foreseen by this specification and shall produce a clean uncontaminated surface for the repair weld execution.

5.4.1

Repair of finished welds Defects in weld metal may be repaired without Client's approval provided the repair procedure is qualified. A register shall be kept by Contractor that details the location of all repairs, the defects, the names of the original welders, dates and repair procedures. Contractor shall have a relevant NDT documentation to identify the exact defect position. Minimum excavation length shall be 100mm. Excavations closer than 100mm shall be linked into a single excavation. Serious failures, like cracks, will be treated in a proper way. When detected, they will be examined in order to establish the originating reasons; then they will be repaired. The crack shall be removed by either grinding or arcair gouging plus grinding to sound metal; grinding shall be carried out in a 50mm area from both ends of the crack, which is determinated by MT or PT. The MT shall be extended to base material surface to detect possible propagation. UT shall be used to assure defect removal. All NDT shall be carried out in optimum conditions of accessibility. Preheating temperature for repairs shall be 50°C higher than the relevant WPS temperature requirement. Re inspection shall be as per the original inspection technique and shall include all weld metal within 100mm of the repair. The areas interested to the cracks, after the repair, shall be UT detected. All weld repairs shall be executed prior to any stress relieving heat treatment, when required. In case that, after repair completion, NDT shows the presence of new unacceptable defects, the reasons are to be cleared up and reported to the Client prior to proceed with the new repair. In any case the excavation for the new repair is to be widened in order to reduce residual stress concentrations. Client reserves the right to ask for PWHT on multiple repaired joints. Cosmetics grinding for eliminating shape defects on cap layers are permitted only if necessary, but are not considered repairs.

5.4.2

Bevel Repairs



Local grinding may be used to remove notches up to 5mm deep in order to give an even profile. Notches deeper than 5mm shall be ground out and the face buttered according to the applicable requirements of this specification.

5.4.3

Buttering Buttering shall be applied as a corrective action only. Buttering shall be done using qualified welding procedure. Following buttering bevel preparations shall be re established by grinding or machining to the acceptable limits. Buttered area of double side welding shall be 100% MT prior the execution of root pass, if applicable. Buttering on stub to can node welds may be applied to the node can side instead of stub side. The exact root opening shall allow the closure with a single pass by the qualified procedure. The requirements of section 3.7.3 shall apply.

5.4.4

Base Metal Repairs All corrective action shall be in accordance with the approved procedure. All boundaries of cavities resulting from removal of detrimental defects shall be faired to a slope of at least 4 to 1. The repair of failures by grinding shall follows the procedures set in EN10163 rules with the following limitations:

 the residual thickness after grinding shall be not less than 93% of the nominal thickness;  the maximum depth of the grinded area shall not be greater than 3 mm;  the depressions shall be radiused to the other surfaces;  the maximum extension of the grinded area shall not be greater than 5% for each m² of surface. To verify the complete removal of discontinuities, the grinded areas shall be MTI tested. The repair by welding is allowed only if previously authorised by the Client and if executed in conformity with EN10163, with the following limitations:

 the repair by welding is carried out by qualified welders and in accordance with qualified procedures. Reference is made to Cap. 3. and 4. for what concerns the qualification of procedures and welders;  the weld is MTI and UT tested. The acceptance criteria of the UT test are as described in paragraph 9.13.3. For Z quality products no repair is accepted.

Eni S.p.A.


Divisione Agip 5.5

CLOSURE WELDS Qualified root gap values, including qualified tolerance, may be difficult to be reached during assembly phase. In this case only class "a, b" closure welds shall be carried out in accordance with the following requirements. WPS to apply shall be chosen by the Contractor considering actual situations and bevel mismatch and Client shall be informed on the choice. Special and limit situations shall be approved by Client. Weld process used for class "a, b" closure welds can be used for welds in other structural classes in case of high root gap. Considered welds are single side only. These welds shall be carried out with a special WPQ considering a greater root gap, or with a different WPQ. When the root gap exceeds qualified value the following possibilities apply:

 3mm buttering on each bevel with root gap values between 4mm and 12mm as maximum (see paragraph 3.7.3.); otherwise GTAW process may be used both for buttering and air closure. In this case only Charpy-V test, in root region, 1mm under surface is required;  permanent backing strip with root gap values higher than 12mm up to 20mm (paragraph3.7.4.)  with root gap higher than 20mm an insert is required, following the tolerance values indicated in paragraph 5.1.9.5 and 5.1.9.6. The above described conditions are reported in the following table 5.2 in function of the element thickness: TABLE .5.2: HIGH ROOT GAP

Element thickness (mm) t < 20 t >20 Limit root gap values (mm) 4 4 10 12 18 20 > 18 > 20

Actions Normal Buttering Backing strip Insert

Welders qualification for first pass shall be carried out accordingly, following the relevant requirements 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 and GTAW process may be used to carry out the first two passes. GTAW root process used both for buttering and filling, follows mixed process requirements including 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.


5.5.2


Permanent backing strip In this case the following requirements shall be fulfilled (see fig. 3.3):

 backing strip shall not be tack welded to member outside of bevel, otherwise joint shall be cut, even if completed;  backing strip dimension should not be greater than 4mm thickness and 40mm wide. Strip interruptions shall not be wider than 1mm. For a girth weld a maximum of three continuous strips may be used. Backing strip material shall be EN 10025 S235JR, or equivalent, in as rolled conditions. No KCV are required on base material.

5.6

STRESS RELIEVING POST WELD HEAT TREATMENT Stress relieving is to be performed in accordance with a PWHT procedure specification. This specification is to detail heating and cooling rates, temperature gradients, soaking temperature range and time, heating facilities, insulation, control devices and recording equipment. The procedure is to be submitted to the Client's approval. For every application procedure shall include a drawing of the items, supporting method and location of all thermocouples. Support positioning shall be defined assuming a yield strength of 35MPa at soaking temperature. Additional temporary stiffeners shall be used to avoid any final distortion of the items free ends when D/t ratio is above 40. No welds, or part thereof, shall be heat treated more than once. If it is necessary to repeat the heat treatment Contractor shall demonstrate, with additional qualification tests, that weld joint mechanical properties satisfy the requirements of this specification also after repeated heat treatment. All temperature charts shall be signed, dated at both start and finish points, marked with a clear identification, and filed The stress relieving post weld heat treatment is required in the following cases: Welds in tubular nodal joints of classes "a" and "b":

 The whole fabricated node if chord wall thickness is greater than 60mm, or if any of the stubs has wall thickness greater than 40mm Welds in regions other than the above

 Any welds on structural element of any class having wall thickness greater than 65mm Additional areas requiring P WHT and areas where PWHT may be omitted shall be indicated on construction drawings. In the latter case additional requirements may be required For TM steels Contractor shall seek the advice of steel-maker before starting PWHT. Contractor can propose, to Client for approval, a detail procedure for the use of failure mechanical assessment (FMA) in alternative to PWHT.

5.6.1

Heat treatment conditions



Soaking temperature is to be within the range 590°C ±10°C: therefore temperature all over the 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 soaking temperature range. The heat treatment may be done introducing the item in the furnace, or in local manner; this choice 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 300°C. The same may not be taken out from furnace if its temperature is over 300°C. Cooling down below 300°C shall be in air. Item temperature shall be recorded from introduction in the furnace until taking out. Rate of increasing and decreasing temperature is to be 55°C per hour maximum for temperatures above 300°C. The temperature difference on the item, during heating and cooling phases, measured along symmetry lines and planes shall not exceed 50°C; between the outside and the inside surface is not to exceed 50°C; between any point of the item far not less than 4500mm shall not exceed 150°C. Temperature shall be recorded continuously and automatically. Thermocouple locations shall be selected to ensure that the whole item, or item part, being treated is within the range 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 as to avoid excessive oxidation of the surface of the item. There shall be no direct impingement of flame on the item. No parts of the item shall be closer than 200mm from furnace sole plate, 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 to take in case of temperature difference exceeding the above values and in case of any thermocouple damage. Any local stress relieving heat treatment is subject to Client's approval. 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 the temperature at the edge of the heated band is not less than half the peak temperature. The adjacent portion of the item outside the heated zone shall be thermally insulated such that the temperature gradient is in accordance with above paragraph. A minimum total insulated band width of 10 √(Dt/2) is recommended for this purpose.

Eni S.p.A.


Divisione Agip 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 be accepted.

The requirements and acceptable limits foreseen for the procedure qualification apply. Production testing coupon welding shall be carried out by the same equipment and steel used in production at that time, and samples shall be representative of different base material casts and different welding consumables batches throughout production. If production testing coupon presents defects not acceptable to this specification the WPS becomes suspect: causes are to be determined and submitted to Client. All production joints represented by this production testing coupon shall be 100% UT to demonstrate are free from the same unacceptable defects. Otherwise all represented production welds shall be subjected to the Client's approval. The production testing coupon shall be taken in accordance with a proper plan submitted by the Contractor for the Client's approval This plan will take into account any similar condition for 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 maximum of 25 circumferential or longitudinal welds.  class "c" welds: a production testing coupon for every 150 m welds, with a maximum of 25 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 recent qualification of the procedure is available (see section 3.1). Production weld test coupons for butt welds shall not be considered representative for fillet and 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. In any case the coupon length shall be not less than 150mm for thickness up to 20mm, and 200mm for greater thicknesses. All coupons shall be 100% UT and 100% MT as per this specification; RT shall be performed in addition in questionable interpretation.



Contractor shall present to the Client approval a detailed programme of execution of production testing coupon, including the represented welds identification. At the time of the tests 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 end of the longitudinal seam being fabricated and welded to form a continuous seam. For circumferential welds the coupon shall be prepared by a simulation of production welding to be welded in location very close to one of the represented production joints and at same production welding time. For circumferential welds with horizontal fixed axis, coupons shall be carried out in vertical position. For thickness > 45 mm impact test shall be carry out also on root region (as foreseen at section 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 a test 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 angle corresponding 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 by the coupon shall be rejected.

5.8

WELDING PARAMETER CHECKING



Welding parameter check may be applied after to have verified the first production coupon weld soundness. Before starting fabrication Contractor shall submit to Client's approval the procedure and checking 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 coupon whenever he considers necessary. Acceptability of welding parameter checking procedure is solely to Client.


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 or when particular conditions prevent adequate inspection. Fabrication shall proceed on a flat and level surface and frequent checks shall be made on the supports and blocking, and any movement out of the level shall be immediately rectified by appropriate shimming to re establish a level plane. The Contractor shall survey and control dimensions before fit-up for welding of additional components and sections. Dimensions shall be checked at each stage in accordance with the fabrication procedure, tolerances (if given) and the final survey shall meet the defined tolerances. The Contractor shall submit his dimensional control procedures indicating proposed methods of monitoring dimensions, their tolerances compatibility and construction method 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 longitudinal axis of the plate (plate rolling direction). Tubular may be re rolled after welding in order to reduce deformations. In this case WPQ mechanical testing shall be performed in the same final condition, in order to demonstrate that the joint is not impaired by the re rolling process. Re rolling carried out with an equipment 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 calibration process, 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 450°C or above 800°C. TM steel shall not be hot formed, i.e. above 600°C. For TM steels Contractor shall seek the advice of the steel-maker before start any warm forming activity.

6.2.3

Surface preparation Plates having surface condition that may impair the forming operation or which may have scale 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.



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 through the ageing test foreseen in the specification 08832 STR-MME-SPC " OFFSHORE PLATFORMS - Steel for structure" Rev.7 and the true deformation is higher, the plate shall be submitted to a new ageing test with a strain value not less than the real one, or to a thermal relieving treatment. For assembled elements, the relieving treatment can be executed just before the start of operations. When the cold forming is executed on a plate which has not been submitted to any ageing test, and the actual diameter/thickness ratio is less than 30, one plate for eache heat / steel quality and thickness shall be submitted to an ageing test with a deformation value not less than the real value; as an alternative, the item shall be submitted to a thermal relieving treatment 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 450°C up to 600°C shall be considered as "warm forming".

6.2.6

Hot forming Hot forming is carried out beyond 600°C up to 800°C. TM steels should not be hot formed. Forming process shall be followed by normalization heating treatment to restore the mechanical steel characteristics All forming processes, heat treatment included, shall be carried out according to a procedure 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 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 300mm 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 be less than 1m. From the sample coupon shall be obtained in order to carried out the tests indicated in table 6.1.

Eni S.p.A.


Divisione Agip 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 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. (2) Test shall be carried out on base material and HAZ with at least three readings for each test The tests and requisite conditions shall be the same as those described in paragraph 3.6 for the 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 beyond the tested value;  same calender process.

6.2.9

Hot Straightening Hot straightening may be applied to recover excessive deformations caused by welding or stress relieving. All class "a" elements, jacket legs, deck legs, jacket nodes and padeyes shall not be submitted to hot straightening in any care. Hot straightening shall be carried out to 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 550°C and shall be kept under full control at least by means of portable contact thermocouple;



 steels with 500MPa tensile strength, or higher, shall not be fast cooled, by water or other 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 limit the 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. The qualification 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 be permitted except for temporary and non-structural attachments. In this last case too they must 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 requirements and 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 cutting 5mm from the base material, followed by smoothing corners. Flush grinding is required for structural elements of classes "a", "b" and "c" and where paint is foreseen. The interested areas shall be carefully examined by MPI and the results shall be reported. Attachments shall not be removed by hammering or any other method that may cause mechanical damage to the surface.

6.4

SITE ASSEMBLY ACTIVITIES Contractor shall consider, during site assembly, all temporary erection loads imposed on the structure 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 weight and environmental loads. These include scaffolding, staging, temporary cranes, welding shelters and temporary works, at each stage of the structure assembly.



Contractor shall provide during the assembly phase storage for all items, to prevent their damage from environmental. Contractor shall make provision for alignment correction at each stage of the structure assembly 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 the induced 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 either tack welding or bolting. If tack welded, each bar shall be pressed in firm contact with the underlying structure and secured with a minimum 50mm line tack weld. The tack weld, the surrounding heated area of zinc galvanised bar grating and the bar grating cuts shall be touched-up according with the 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 floor plate under-side shall be 100% seal welded to deck stringers and other supporting, to seal all 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 1200mm length gouge.

6.6

FINISHING OF SURFACES As fabrication of various items or portions of the structure is completed, the Contractor shall remove all welds, burrs, tack welds and other marks made by scaffolds or temporary bracing 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 MPI and the results shall be reported.

6.7

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



penetration weld joint). In this case only Contractor shall define the relevant solution, with Client's approval. When not otherwise indicated on the design drawings, dimensions of rat holes shall be the follows (+/- 3mm): Stiffener thickness (t) in mm Rat hole radius (R ) in mm t < 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 are permitted 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 on stiffener corner in order to shape it onto weldment and facilitate complete stiffener fillet welding. 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. Sealing shall be made with a thin steel plate, about 5mm thickness, fillet welded; otherwise iron mastic approved by Client may be applied. In these cases the use of rat holes shall be minimized.

6.8

BOLTED CONNECTIONS Bolt holes shall be drilled at right angles to the metal surface and shall have at least a diameter 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 and nuts shall rest squarely against the metal surface. All bolts shall be of a length such that they will extend entirely through but no more than 6mm 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 on construction drawings.

Eni S.p.A.


Divisione Agip 7

PREFABRICATED ITEMS TOLERANCES The Contractor shall provide personnel with qualified surveyors, equipment and instruments, with current valid calibration certificates, necessary for monitoring and controlling dimensions and tolerances. The following sections give the admitted tolerances for every measurable dimension and shape 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% of nominal circumference or 10mm, whichever is less. The measurement shall be carried out at 600mm from any tubular splice and at tubular ends. 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 by this specification.

7.1.2

Ring stiffeners out of circularity For each ring stiffener shall be checked the difference between the actual radius and the average 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 various position, 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 circumferential seam, and at midway between two ring stiffeners. The following table 7.1 applies. TABLE 7.1: OVALITY VALUES AND MEASUREMENT NUMBERS

Diameter (mm) ≤ 600 ≤ 2000 > 2000

Value 1% of diameter greater of 6mm or 0.75% D greater of 15mm or 0.5% D

Nr. of measures (*) two diameters four diameters six diameters

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

Eni S.p.A.


Divisione Agip

Measuring method, with more than two diameters, may be equally spaced instead of maximum 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 theoretical tubular 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 be carried 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 greater than 2000mm or with nominal outside diameter/wall thickness ratio greater than 65. The check shall be either on the inside or outside, and the positions shall be those indicated in table 7.2 along all tubular element. TABLE 7.2: LOCAL OUT OF STRAIGHTNESS

Type of joint Unstiffened tubular Stiffened tubular node barrels Manways after welding

7.1.6

Check location 45° intervals of arc with template L = 3000mm 20° intervals of arc with template L = distance between stiffeners or 3000mm in other uses at the centre and manway quarter points with template L = 1000mm

Out of straightness Structural classes "a, b, c" members out of straightness tolerance is the greater of 0.1%L or 3mm, 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 with weld 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.



Actual stub centre line is intended as the intersection of two orthogonal diameters at both ends 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 position shown 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 of ±1/3 stiffener thickness but not more 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 web depth but not more than 6mm. For ring stiffeners in nodes and in node cones the same tolerance 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% of the nominal web depth, but not more than 3mm. The deviation of the flange edge, of an internal or external ring stiffener, from the diameter measured 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 buttwelds mismatch 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 paragraph 5.23.1 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, section 6.2.2.1.

7.2.1

Global tolerances Structural class "a, b" members, no hollow sections, out of straightness and verticality is the greater 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 is the 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 roof shape 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)

Eni S.p.A.


Divisione Agip

Web girder twisting shall be equal to (1+0.01h)mm, but not greater than 10mm, where h is the web height in millimetre. Web bow shall be equal to 0.01h with maximum value equal to 0.5t, where t is the web thickness.

7.2.3

Web stiffener Web stiffeners location between girders flanges shall be within tolerances values. Web stiffeners shall be fitted with respect to their theoretical location to an accuracy of half stiffener thickness, but not greater than 6mm. Web stiffener out of straightness shall be within 0.15% L, but not more than 3mm (fig. 7.4). The outstand of web stiffener under load bearing surfaces shall be within 0.5% of the maximum web height but not more than 3mm of a perpendicular set out from two girders flanges3mm (fig. 7.4).

7.2.4

Fillet welds execution Weld passes shall be continuous to prevent any risk of crevice corrosion. Welds shall be returned through the rat hole, when present.

7.3

STIFFENED PLATE PANELS The following apply, with reference to fig. 7.5: TABLE 7.3: TOLERANCES FOR PLATE PANEL

Tolerance type Plane out of position Global lateral deflection between principal stiffeners Global lateral deflection between secondary stiffeners

Tolerance value 0.3% L 0.5% L1

Limiting value(mm) 10 10

0.15% L

15

TABLE 7.4: TOLERANCES FOR PLATE PANEL STIFFENER

Tolerance type Inclination ay Out of position py Nodal out of position py Out of straightness sy both orthogonal and

Tolerance value 2.5% h

Limiting value(mm)

5% h

10

5% h

3

0.5% L1

5

lateral to the plate plane Where: L1 is the distance between two consecutive stiffeners h is the height of the stiffeners.

5

Eni S.p.A.


Divisione Agip

7.3.1

Stiffeners forming cruciform arrangements Where a combination of stiffeners (ring, diaphragm, web) from a cruciform arrangement with other member or stiffener the mismatch of the alignment through the joint shall be according to table 7.5. TABLE 7.5: MISMATCH VALUE

Thickness t3 > t1 and > t2

Mismatch t3 / 2; max 10mm

t2 > t3 and > t1

t2 / 2; max 6mm

for t1 , t2 and t3 identification see fig. 7.6. As built dimensions shall be used to align members. UT check shall be performed where external 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. The weld beads pitch is to be constant throughout the zone where weld beads are required and are to be kept equal between sleeves and piles. Tolerance on position of each weld bead is ±5mm with respect to what required on fabrication 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 into account the above requirements. However not more than one weld bead per sleeve may be out 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 theoretical dimensions. See fig.7.7 for indication.

Eni S.p.A.


Divisione Agip 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 Jacket and deck matching nodes Other leg nodes Other nodes

Tolerance 6mm 10mm 15mm

Table 8.2 shows the tolerance values of some structural dimensions, as an example of said above. TABLE 8.2: DISTANCE TOLERANCES

Measures Length between first and last node working points on jacket legs Distance between working point not involving one leg nodes placed on the same plane involving one leg nodes Distance between abutting jacket and deck node working point

8.2

Tolerance (±) 16mm 30mm 25mm 12mm

JACKET LEGS HORIZONTAL AND DIAGONAL MEMBERS STRAIGHTNESS Overall out of straightness of final structure axis, checked in at least two perpendicular planes 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 6mm radius 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-way of these positions. The out of roundness measurements shall be as per paragraph 7.1.4 only 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 shims mid-way positions the measurement method and the tolerance values shall be as per paragraph 7.1.4.

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Divisione Agip

The completed pile sleeves centrelines taken at shim location shall be within 6mm from their best 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 horizontal connecting plates to the legs. Position of shear plate joints onto leg and sleeve shall be within 6mm from the theoretical vertical 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 Bow of straight free borders Horizontal stiffener between leg and sleeve Vertical stiffener straightness Planarity of sub-panel Planarity of full panel

8.5

DECK PLANS

8.5.1

Deck section columns

Value (± mm) 3 4 2 5 10

The columns intersections centre (item axes intersection centre) measured on the structure shall be within the error sphere, whose radius is indicated in table 8.4, relevant to theoretical fabrication drawings position. TABLE 8.4: HEADER POSITION

Header Beams on column Beams on stringer Beams on principal beams

Error sphere radius 6mm

As said above, table 8.5 gives, as an example, the overall distances and elevations tolerances measured on structure. TABLE 8.5: STRUCTURE MEASUREMENT

Measurements Column distance Header distance Header elevation difference

Tolerances ± mm 12mm 12mm 12mm

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


8.5.2


Deck section plate Plates on deck beams shall not have sags higher than ±3mm relevant to theoretical bearings 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 reference point. The maximum number of water collectors shall be defined on construction drawing and Client 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 ±75mm relevant to the theoretical distance, from head, indicated on fabrication drawings. The checking straightness method by a taut wire along the pipe length is considered acceptable. 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 surface perpendicular to pile centreline with maximum tolerance value of 0.01 gon. Longitudinal seams, between two consecutive barrels shall be separated by a minimum of 100 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= weld thickness). Distance between longitudinal seams shall be 300mm at least. The minimum distance between two circumferential seams shall be 0.4 buoyancy tanks outside diameter at least. Out of roundness shall be checked at each ring stiffener and in between two adjacent ring stiffeners 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 the wall thickness, whichever is the less. Local deviation from straight generator is:

Eni S.p.A.


Divisione Agip ∆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 fabrication drawings. 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 shall perform 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 one relevant to construction phase.

8.8

CONDUCTORS Conductors shall be fabricated to a total tolerance of ±300mm from the length indicated on fabrication drawings. A minimum of 900mm over length shall be provided at top extremity, unless otherwise shown 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 tube tolerance 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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Divisione Agip

Completed J tubes are to be pigged on site to ensure they are clear with no internal weld protrusions 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 theoretical location shown on fabrication drawings.

8.11

ANODES Anodes positioning shall be done according to relevant fabrication drawings with respect to a uniform distribution throughout the jacket. In case of interferences experienced with other welded items, longitudinal or circumferential welds of tubulars, or similar, the following may be 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 fabrication drawings, provided the angle between two successive anodes is not changed more than 45° from that shown on fabrication drawings. Distance among structural weld toes is not less than 150mm both on longitudinal and circumferential joint. Location of anodes shall be as close as possible to the lesser local dihedral angle of each stub-chord intersection. All cases of impracticable solution as per above requirement shall be decided on a case by case 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 be level 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 to the fabrication drawings. TABLE 8.6: TOLERANCE FOR LANDING AND STAIRWAY

Elevation Planarity Planimetric position

± 12mm ± 6mm each 3m length ± 12mm

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


8.14


TEMPLATE DOCKING PILES CENTRING SYSTEM Template docking piles centring system shall be rected after having verified the actual engagement distances and verticality of the erected template docking piles The location of each pile centring cone measuring centre shall be within 12mm of the theoretical location shown on construction drawings.

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Divisione Agip 9

INSPECTION OF WELDMENTS

9.1

GENERAL All welds are to be subjected to non destructive examination (NDT)as fabrication and construction proceed, as per a proper schedule and relevant drawings supplied by the Contractor. 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 offshore welds Contractor shall supply for approval a detail NDT procedure that shall include wait time, 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 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. All NDT reports are to include all data that allows to repeat the examination in the same conditions. Contractor shall formulate a quality control plan that shall contain mandatory NDT inspection and the time when they shall be done. This plan shall be submitted to Client's approval.

9.2

DEFINITIONS The following definitions are used:

9.3

NDT:

Non Destructive Testing.

VI:

Visual Inspection.

MT:

Magnetic Particles Inspection.

PT:

Dye Penetrant Inspection.

UT:

Ultrasonic Testing.

RT:

Radiographic Testing.

DAC:

Distance Amplitude Correction.

HD:

Maximum Amplitude of Flaw Echo Height.

REFERENCE STANDARDS The standards and codes of practice called up by this specification are considered at the latest edition at time of contract award. They are:

 API RP 2X  API Standard 1104  EN 462  EN 970

Eni S.p.A.


Divisione Agip  BS 6072  EN 473

Contractor shall equip themselves with copies of all the standards and codes referred to in this specification and shall make them readily available to all inspection personnel involved on work.

9.4

METHODS OF NDT Accepted NDT methods are RT, UT, MT and PT. Their applicability shall conform to the following table. TABLE 9.1: NDT APPLICABILITY

Weld Classes Joint Butt

t ≤12mm RT MT

a, b, c, d 12
t >38mm UT + 10%RT

e all thicknesses MT

MT T-butt Fillet

MT

UT MT

PT

MT

Table shall be integrated with the following requirements. The indicated thicknesses are those referred to welding thickness. RT For thickness greater than 38mm, in addition to UT control, 10% of welds (one each ten examined) chosen at Client discretion shall be 100% RT. Obtained results, other than to be in compliance with the requirements of this specification, shall be compared with the results of UT control. UT shall be carried out for deck and modules beams, when the joint geometry issuch that RT is unappropriate. Thickness limits are relevant to complete one crossed by rays. RT in shop are to be preferably executed by X ray equipment. Gamma rays may be applied on yard only or on large prefabricated items. Following isotopes do not require Client's approval: Yt up to t=12mm; Ir for thickness from 10mm to 19mm with qualification of the procedure test; Ir and Yt up to t=38mm; X rays for thickness above 38mm. The use of Co 60 is generally not acceptable. UT UT shall be applied also for chevron cracks checks on SAW welds with thickness above 25mm. UT shall be applied when RT inspection is not possible (i.e. T joints) or for offshore welds. In any case UT can not substitute RT for thicknesses lower than 10mm. New UT procedures that permit both to correlate echoes with position on piece through scanner use and to record on magnetic support, may be submitted to Client's approval. Change of NDT procedure based on these new techniques is solely at Client acceptance.

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Divisione Agip

MT MT is the reference surface NDT methods for all welds of classes "a, b, c, d". The substitution with PT for parent materials with minimum yield strength not greater than 275MPa requires Client's approval. For weld class "e" and all classes bevel inspection, PT may substitute MT without approval.

9.5

EXTENT OF NDT Extent of NDT shall be as per following table. TABLE

VI UT/RT MT PT Note 1:

a 100% 100% 100% -

10.2: EXTENTION OF NDT ON WELD CLASSES b, c 100% 100% 20%(1) 100%

d 100% 20% 20% -

e 100% 20%

The MT test for joints and closure welds adjacent to nodes shall be 100%.

Table shall be integrated with the following requirements. SAW All longitudinal SAW welds class "b, c", except nodes and buoyancy tanks, may be RT/UT inspected as follows:

 100% inspection on the first three welded elements from every welding machine;  20% inspection for the following elements from the same welding machine, with minimum inspection length of 1m, and 100% inspection on one element every 10 welded elements, selected by the Contractor. Welds class "a, b, c" cruciform joints and start/stop points shall be RT inspected for a 300mm all around area. UT inspection to check chevron cracks shall be carried out even if RT inspection is standard method. The percentage extension shall be the same for main inspection. Other requirements For weld class "d" joints RT/UT percentage inspection shall be 20% on yard and 10% on shop. Fillet welds class "a, b, c" mainly submitted to tensile stress, shall be UT inspected against lamellar tears and to verify the weld discontinuity; test percentage shall be 100%. The NDT control of sea fastening shall comply in any case with the code and the requirements of the Certifying Society in charge of the transport certification The percentages indicated on table 9.2 refer to the total length of each weld. For welds with a length less than 1m, the required indicated percentages may refer to the percentage of the completed joints of the same type to be inspected (i.e. 20% means 1 weld over 5 to be 100% examined). Where unacceptable flaws are detected in partially inspected seams the NDT percentage shall be doubled and extended to both adjacent sides of the defective area. In case other unacceptable flaws are found in the new area the extension shall become 100%.



If severe flaws (i.e. cracks and other planar flaw, excessive slag lines and cluster porosities) occur repeatedly to Client opinion, all welds made with the same welding procedure during the period in question, may be additionally tested up to 100%, after Client's request. In case the defective weld length, in joints with NDT percentage less than 100%, is greater than 1% of the inspected length the Client reserves the right to increase NDT percentage up to 100%. Welds of all classes except "e" that become inaccessible during item fabrication shall be 100% NDT. 9.6

EDGE INSPECTION Prior to assembly for welding, all edges shall be inspected to find any eventual defects. The inspection of the bevel edges shall be carried out with VI integrated with MT or PT when necessary to show defect. The extension of flaw behind the bevel shall be checked by appropriate UT examination using compression probes, or by grinding to verify the laminated area depth. Any discontinuity extending 5mm and above shall be repaired. The requirements of section 5.1.2 shall apply for laminations defects check before the stub to node can and beam to flange welding.

9.7

QUALIFICATION OF NDT PROCEDURES The Contractor shall prepare procedures for each of the NDT techniques he proposes to use, and submit these to the Client's approval prior to commence any testing. Client may require the qualification of some or all of the procedures, by demonstration of their capability to detect known flaws.

9.7.1

Radiographic Testing (RT) The procedure specification for the radiographic testing is to include at least the following information:

 radiation source (X-rays or gamma rays. If gamma rays, type of isotope);  technique (equipment rating in voltage or curie, external or internal equipment single wall, double wall/single image, double wall/double image);  geometric relationships (film focus distance, object film distance, radiation angle with respect to weld and film, focal spot);  film type (trade name and designation);  intensifying screens (front and/or back material, thickness);  exposure conditions (kV, mA, min, Bequerel, min);



 processing (developing time and temperature, stopbath, fixation, washing, drying, etc.);  image Quality Indicator sensitivities in percent of the wall weld metal thickness based on sources and film side indicators respectively;  density (the radiographs density measured on the sound weld metal image);  film coverage. The representative radiographic procedures are to be qualified by making two radiographic exposures of a welded joint with the same or typical configuration and dimensions, on a material equal to or similar to that which is to be used in the structure. In order to check the sensitivity, the above requirements apply images.

9.7.2

also for double walls

Ultrasonic Testing (UT) A procedure specification for the ultrasonic testing according API RP 2X is to be established, which is at least to include the following information:

 type of instrument;  type of transducer;  frequencies;  calibration details;  surface requirements;  type of couplants;  scanning techniques;  recording details;  reference to applicable welding procedures;  material thickness and curvature range;  check of calibration,  temperature range The qualification test is to be performed under normal working conditions and at Client presence. The test pieces are to be available as reference all over the inspection work. UT carried out by automatic equipment is generally acceptable, but submitted to Client's approval. In this case the requirements of section 9.4 shall apply

9.7.3

Magnetic Particle Inspection (MT)



A procedure specification for the magnetic particle testing is to be established which is to include at least the following information:

 materials and dimensions;  type of equipment;  surface preparation including background paint;  wet or dry method;  make and type of magnetic particle and contrast paint;  magnetizing current (for prod magnetizing: the prod type and spacing are to be stated).  temperature range No special procedure qualification test is required. The procedure is considered qualified based on approval of the testing procedure specification.

9.8

QUALIFICATION OF NDT PERSONNEL Radiographic, ultrasonic, and magnetic particle operators shall be qualified to EN 473 or an equivalent rule. Moreover all ultrasonic operators shall be especially qualified in accordance with API RP 2X paragraph 2.3. A scheme for qualification of operators conform to EN 473 or an equivalent rule shall be established by Contractor. Contractor is responsible for manufacturing suitable test joints, including artificial and natural flaws, representative of the construction configuration that must be carried out. Operators shall examine the number of test plates defined by the above scheme and shall set a written examination. The internal qualification of NDT personnelshall comply with EN 473. EN 473 or equivalent level III, as supervisor, is required within the project and within yard or shop organization. If the qualification of the personnel is in doubt, the Client may require their interdiction to production activities until their ability has been satisfactorily demonstrated. UT operators shall have up to date certification in accordance with ASNT-TC-1A and are to be capable of:

 calibrating the equipment;  performing an operational test under production conditions;  interpreting the screen display;  evaluating size and location of reflectors;  classifying reflectors as planar, cylindrical or spherical. RT operators are to be fully capable of performing an operational test using the qualified radiographic procedure.



Operators performing MT testing are to be capable of performing an operational test, using the test method or technique that is to be applied in production.

9.9

VISUAL INSPECTION EXECUTION Visual Inspection shall be carried out in accordance with EN 970. The stub to node weld inspection shall be carried out with the aid of clipped disk.

9.10

RADIOGRAPHIC TESTING EXECUTION

9.10.1

General Contractor shall prepare a document in which he indicates the radiation source (X and isotopes) he intends to use in function of thickness ranges, worksite locations (yard, shops) and relevant to the whole job conditions. The film type utilised shall be as per ISO 5579. Only lead reinforced screens are to be used. The execution procedures for the radiographic control must be qualified when the source is not accessible during the production control.

9.10.2

Examination Image quality indicators shall be of the wire type as recommended by IIW/IIS 62-60 or ISO Standard and are to be placed on the source side. In case that the source side is inaccessible during production radiography, only film side penetameters are required, but shall be marked with an "F" and the procedure shall be qualified. The image quality indicators are to be clearly identified, and the sensitivity of the source side indicator is to be equal to or better than the requirements given in for "single wall technique". For "double wall technique" the IQI sensitivity shall be calculated putting the total weld thickness penetrated, i.e. two times the plate thickness plus the two weld reinforcements, at the denominator of the formula. In this case the permissible IQI values shall be double of those indicated (ref. EN 462). Radiographs are to have a density at the weld metal image in the range 2.6 to 3.8 for the double images with a minimum of 1.3. For single images the density shall be in the range 2.0 to 3.0 . If the multiple exposure technique is used, at least one penetrameter is to be recorded on each film. If the panorama technique is used to include 100% of tubular girth weld in one exposure, a minimum of three penetrameters are to be equally spaced around the circumference, at 120° one from eachother. The maximum acceptable film lengths are defined by the film references.

9.11

ULTRASONIC TESTING EXECUTION

9.11.1

Equipment



The equipment used for ultrasonic testing is to:

 be applicable for the pulse echo technique and for the double probe technique;  cover the frequency range from 2 to 6 MHz;  have a flat screen accessible from the front for direction plotting of reference curves;  allow echoes with amplitudes of 5% of full screen amplitude to be clearly detectable under test conditions;  include straight beam transducers, and angle beam transducers of 45°; 60° and 70°;  satisfy vertical linearity according to ASME V and horizontal linearity in accordance with ASTM.

9.11.2

Calibration Calibration shall be in accordance with API RP 2X requirements. For portable testing equipment the IIW/ISO calibration block is to be used. For echo amplitude evaluation, a DAC reference curve is to be established and plotted on the instrument screen. The reference block for gain calibration and construction of DAC is to be manufactured from the actual production material and be in accordance with the requirements of API RP2X for Level A. DAC curve construction shall be in accordance with the indications of API RP2X. Equipment horizontal and vertical linearity shall be always calibrated before the any examination beginning. Calibration of the ultrasonic equipment is to be carried out whenever it has been out of function for any reason, and whenever there is any doubt concerning proper functioning of the equipment. UT equipment shall be left warming up before initiating the testing.

9.11.3

Examination Ultrasonic testing of production welds, shall be carried out in accordance with API RP 2X and with the following requirements. The weld is to be examined from at least two sides. T-butt welds are to be examined also from through member opposite face. SAW welds shall be examined for transverse (chevron) cracking by weld cap scanning, using a 45° 4 MHz probe. The weld shall be ground as necessary to facilitate this inspection. For SMAW welds the separate probes for transmitter and receiver method shall be applied when surface conditions are detrimental to correct inspection. Tandem technique keeping constant the inclination angle relevant to the weld seam axis may be applied. Flaw width shall be evaluated with the 6dB technique, flaw length shall be evaluated with the "half-value-drop" method.



The use of beam path lengths longer than 200mm is not allowed. Inspection for acceptance of butt welds over 60mm thick, to which access is limited to one side only, shall include unrestricted scanning from the surface of the weld. Surface shall be grind to an appropriate standard for the inspection purpose. For butt welds with bevel angle between 0° and 10°, and with thickness above 40mm the tandem technique shall be used.

9.12

MAGNETIC PARTICLE INSPECTION EXECUTION

9.12.1

Equipment Only AC equipment or DC equipment with current obtained through half wave rectifier) may be used for testing. Other DC equipment, permanent magnets or equipment which introduce current directly in the item shall not be used. The equipment used for magnetic particle testing is to establish a field strength among 2400 A/m (30 Oersted) and 4000 A/m (50 Oersted). The magnetic field adjustment shall be verified by a relevant instrument. This need not be proven by measurement in case of coil or prod magnetizing, provided the following requirements are met:

 AC electromagnetic yoke is to have a lifting power of at least 5 kg at the pole working spacing;  the coil magnetising current is to be chosen depending on the number of turns of the coil. The ratio between the ampere turns and the diameter of the pipe work piece to be tested is to be 8 to 16 ampere turns per each mm;  AC electromagnetic yoke is to have a lifting power at least 4.5kg with 300mm prode spacing, for surface defects only.  for sections with thickness 20mm or more, the prod spacing is within the range 75200mm with a current of 5-6A for each millimeter;  for sections with thickness less than 20mm, the current is to be 3.5 to 4.5 A per each mm prod spacing, with prode spacing within the range 75-200mm. Prods tipped with lead, or "soft prods" are required. Equipment and calibration blocks applied to verify the above requirements shall be available to NDT personnel and to the Client.

9.12.2

Examination The surface of the parts subjected to test is to be clean and dry, free from any dirt that may interfere with the examination. To ensure detection of discontinuities having axes in any direction, the examination is to be performed with the magnetic field shifted in at least two directions on each area.

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Divisione Agip

Non-fluorescent wet or dry particles are to provide adequate contrast with the background of the surface being examined. Surface painting shall be used to improve the detection of flaws: white background paint is preferred. Magnetic particle examination is not to be performed on parts with surface temperature exceeding 300°C. Wet magnetic particle examination is not to be performed on parts with surface temperature exceeding 60°C. Care is to be taken to avoid local heating of the test surface. All prod burns shall be ground out and PT. Demagnetization shall be provided, when necessary. 9.12.3

Magnetic fluorescent particles This control type shall be done in a darkened room using an ultraviolet radiation light with wavelength within the range 3200/3800 Angstrom. Before starting the testing the operator shall remain for 5 minutes to accustom his eyes to low luminosity. Glasses and contact lens shall not be photosensitive. Before light intensity measurement, it is necessary to wait 5 minutes for a correct heating and for a correct operation. Ultraviolet radiation light shall be measured by a particular instrument. There shall be 800 microwatt/cm² on the examined surface. Ultraviolet radiation light intensity shall be measured each 8 hour or whatever the working position is changed. Wet particles shall be applied on smooth welding surface only.

9.13

STANDARDS OF ACCEPTABILITY Any weld imperfection that prevents the sizing of, or may prevent the detection of, a weld flaw is itself a flaw and shall be repaired. Cracks and lamellar tears found by any of the NDT methods are not admitted in any case and for any weld classes. All this type of discontinuities shall be inspected to find out the originating cause. All detected defects that are higher than the following acceptability limits shall be repaired, the weld restored and a new NDT inspection carried out all over the interested area.

9.13.1

Visual Inspection Acceptance Standard All the outside and inside welds whenever accessible shall be visually inspected. Abutting porosities, gas cavities, and slag inclusions are to be repaired. Acceptable undercuts are as follows: TABLE 9.3: ACCEPTABLE UNDERCUTS

Weld Classes Depth mm Length mm

a 0.25 Intermittent

b, c 0.5 10

d 0.5 20

e 1 40

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Divisione Agip

9.13.2

RT Acceptance Standard Flaws on films appearing to meet the acceptance standards limits, but having darkness density giving a doubt on their depth shall be re examined with UT technique. The lengths of acceptable volumetric flaws are as follows: TABLE 9.4: ACCEPTABLE RT FLAWS

Defect type Gas Cavities Linear Porosity individual cumulative Slag Inclusions individual cumulative Lack of fusion individual cumulative Incom. root penetr. individual cumulative

a, b t/3 or 6mm

c t/3 or 6mm

d t/3 or 6mm

0.75t

1.5t

3t 12t or 150mm

1.5t or 6mm t or 20mm

1.5t or 6mm 2t or 30mm

6mm 2.5t or 60mm

not admitted

not admitted

10mm 1.5t over 12t

not admitted

not admitted

10mm 1.5t over 12t

Two gas cavities are treated like a linear porosity when the distance between them is less than 6 times the diameter of the biggest porosity. The lack of fusion and incomplete penetration acceptance standard for weld class "d" may be applied to longitudinal double welds class "b, c" as diagonals, deck beams and bracings. All other elements as nodes, padeyes, buoyancy tanks and their supports are excluded.

9.13.3

UT Acceptance Standard Any flaw from which echo height exceeds the DAC by 6db shall be repaired and reexamined, regardless of size. All flaws classified as planar, like cracks or lamellar tears, shall be repaired whichever is their echo height. All echoes that exceed 50% DAC shall be classified and evaluated in size, in accordance with table 9.5. All transverse defects are to be regarded as defects requiring repair. This requirement does not apply, where indication can be unequivocally correlated to longitudinal defects. The lengths of acceptable volumetric flaws are as follows: TABLE 9.5: NON PLANAR ACCEPTABLE UT FLAWS

Maximum HD and DAC a, b HD > DAC (100%) 10mm HD > DAC/2 (50%) 20mm HD = maximum amplitude defect echo.

c 30mm 45mm

d 40mm 60mm

Planar defects, clearly detected as lack of fusion and incomplete root penetration may be accepted for weld class "d" as per table 9.6.

Eni S.p.A.


Divisione Agip TABLE

Flaw type Lack of fusion Incomplete root penetration

9.6: FLAW ACCEPTABILITY FOR WELD CLASS "b, c,d " Depth (mm) 1.5 1.5

Length (mm) t/2 1.5t

Max Individual 10mm 10mm

length cumulative 1.5t over 12t 1.5t over 12t

The lack of fusion and incomplete penetration acceptance standard for weld class "d" may be applied to longitudinal double welds class "b, c" in diagonals, deck beams and bracings. All other elements as nodes, padeyes, buoyancy tanks and their supports are excluded. Two gas cavities are treated like a linear porosity when the distance between them is less than 6 times the diameter of the biggest porosity.

9.13.4

MT Acceptance Standard Detected rounded indications shall be classified as elliptical shape if the length is equal to or less than three times the width, or as circular shape in other cases. Linear indications are the remainders. All surfaces to be examined shall be free from linear and rounded indications caused by weld defect, not weld geometry, having the limits indicated below:

 linear indications are not acceptable whichever their dimensions;  acceptable rounded indications shall not be greater than 4mm, and there shall not be more than three indications in line, separated by 1.5mm or less from edge to edge.

9.14

REPORTS Operator shall formalise, in the following 24 hours after test completion, the testing results. The report is to indicate if the weld quality meets the acceptance standard limits of this specification, and indicate the flaws to be repaired. The minimum requirements shown in a NDT report shall be the following:

 procedure qualification informations;  weld identification number;  sketch of the welded joint and probable flaw location;  flaw description and dimensions;  repair flaws;  any remark. The report shall clearly show the type of flaw detected (i.e. lack of fusion, incomplete penetration, porosity and slag) including a repairing flaws location sketch from a particular point choosen as reference.


RT reports The report shall show, beyond general requirements, the following:

 film identification number;  film location.

9.14.2

UT reports The report shall show, beyond general requirements, the following:

 planar and not planar flaw evaluation.

9.14.3

MT reports The report shall show, beyond general requirements, the following:

 tested surface conditions;  black light intensity;  powder and solvent types used.



TESTING OF FIELD INSTALLED COMPONENTS

10.1

PREASSEMBLY TESTING


When large and complex assembly items shall be joined offshore, Contractor shall carry out a yard assembly test in order to verify the correct fit. Handrail sections or other similar items shall be stamped or metal tagged so that it is possible easily to restore their exact position during offshore assembly. Items such as bolt or pin shall be assembled, fitted and welded so that the connection can be easily installed or removed.

10.2

RISER PRESSURE TESTING Pressure test of risers shall be carry out in accordance with the requirements of the applicable project specifications.

10.3

PNEUMATIC TESTING OF BUOYANCY TANKS AND JACKET LEGS Members that are designated to provide buoyancy shall be pneumatically tested prior to load-out. The air pressure shall be set to 0.2-0.3 bars and the variations measured over a period of 2 hours with a well-type manometer. During testing flanged manways shall be tested with soap solution technique.

10.4

TESTING OF BALLASTING AND GROUTING SYSTEMS All equipment, components and piping of jacket ballasting and grouting system shall be tested both by pressure test and in working conditions, before the load-out. Testing shall be done according to relevant line service conditions (1.5 times the design pressure). Pressure testing shall be done in conditions of minimum temperature variation as per applicable piping specification. Pressure shall be maintained at least for one hour. Flooding values shall be hydrotested to detect leaks either from body or trim, and to verify for their smooth and free operability. The leak test shall be done by hydrotest at the maximum working pressure. Reach-rods and flooding valves, when present, operability shall be tested while flooding lines are under pressure. Flooding valves are to be lubrificated and checked before load out to ensure that they are in the closed position, and that protective caps or other obstructions are not present that would prevent proper valve operation.

10.5

TESTING OF PACKERS SYSTEM

10.5.1

Testing of line



All air lines shall be isolated from the grout packers, to prevent damage to grout packers, before this testing to be done prior to load out. Test pressure shall be 1.5 times the design pressure and shall be held for one hour. There shall be no pressure drop and no leaks. After testing of all lines, they shall be completely drained, dried and re-connected to the grout packers.

10.5.2

Testing of packers When packers are already inside the barrels, the purchaser shall give a certification relevant to the acceptance test. Contractor shall apply purchaser requirements for acceptance test when previous certification is not available.

Eni S.p.A.


Divisione Agip 11

APPENDIX 1: STRUCTURAL CLASSES Structural Classes

Module and Deck

Jacket

Not typical nodes with complex geometry

Not typical nodes with complex geometry

Structural elements essential for the global safety of the platform

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 structure

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

a

b

c

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

Foundation piles; Buoyancy tanks; Risers supports, pin piles

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

Eni S.p.A.


Divisione Agip 12

APPENDIX 2: FIGURES 3.1

Beam weld, WPQ test samples

3.2

Special test for TKY joints

3.3

Permanent backing strip weld

3.4

Charpy-V set for grout bead

5.1

Improved weld profile

5.2

Beam splices

7.1

Node working point position

7.2

Ring stiffeners

7.3

Roof shape

7.4

Web stiffener

7.5

Stiffened plate panel

7.6

Mismatch on cruciform joints

7.7

Opening and penetration

8.1

Mismatch between centering guide

Eni S.p.A.


Divisione Agip

Fig 3.1

Beam weld, WPQ test sample

Weld bead Beam web

Beam web

Weld bead

MATERIAL QUALITY NOT Z

MATERIAL QUALITY Z

Eni S.p.A.


Divisione Agip Fig 3.2

Special test for TKY joints

CAN VERTICAL AXIS

BRACE ACUTE ANGLE DOWNWARD

300mm min

Eni S.p.A.



Permanent backing strip weld

< 60°

YES TACK

4 mm NO TACK

40 mm

1mm MAX

Eni S.p.A.



Charpy-V set grout bead

= =

Eni S.p.A.



Improved weld profile

STUB

WELD R 8 min

*

CAN

6 min

* 0.5mm UNDER ANY VISIBLE UNDERCUT BUT NOT GREATER THAN 2mm OR 0.05T WHICHEVER IS THE LESS. TOE GRINDING: IS TO BE PERFORMED AROUND THE STUB TO CHORD WELD WHERE INDICATED ON DRAWINGS SO TO PRESENT SMOOTH SURFACE, WITHOUT EDGER OR SIGNIFICANT GROOVES, WITH BURR ROTATION DIRECTION PERPENDICULAR TO THE WELD LENGTH.

Eni S.p.A.



Beam splices

ZONES IN WHICH SPLICES ARE ALLOWED

L/8

L/4

L/2

L/2

L

L/4

L/8

Eni S.p.A.



Node working point

ACTUAL WORK POINT

TRUE WORK POINT ANYWHERE IN SPHERE OF ERROR

RADIUS OF ERROR SPHERE

Eni S.p.A.



Ring stiffener

DESIGN POSITION

t h

OUT OF

OUTSTAND

LOCATION 0.01 h 6mm MAX

b

0.05 b

h

WEB BOW

FLANGE 0.01 h 3mm MAX

DEVIATION

Eni S.p.A.



Roof shape

6mm max

Eni S.p.A. Divisione Agip Fig 7.4


Web stiffener

h

0.5% h

Eni S.p.A.



Stiffened plate panels

TRANSVERSE STIFFENERS

L

LENGTH BETWEEN GIRDERS

LONGITUDINAL STIFFENERS

sy py L1 LENGTH BETWEEN STIFFENER

ay

Eni S.p.A.



Mismatch on cruciform joints

t3

t1 t2

Eni S.p.A. Divisione Agip Fig 7.7

Openings and penetrations

CENTRELINE OF OPENING AND PENETRATION


130460129-General-Specification-Offshore-Platforms-Offshore-Structures-Construction.pdf

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