w-p-ss-011

SPECIFICATION FOR WELDING AND WELDING INSPECTION OF SHOP AND FIELD FABRICATED PIPING

0

02-02-2002 Approved Issue

Rev.

date

Description/issued for prepared authorised client: ADWEA project: STANDARD SPECIFICATIONS FOR WATER WORKS title: SPECIFICATION FOR WELDING AND WELDING INSPECTION OF SHOP AND FIELD

FABRICATED PIPING tender:

project:

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Table of Contents 1.

SCOPE...................................................................................................3

2.

APPLICABLE STANDARDS AND CODES ..........................................3

3.

SITE CONDITIONS................................................................................4

4.

Design Consideration ..........................................................................4

5.

WELDING REQUIREMENTS ................................................................4 5.1 Approved Welding Processes .....................................................4 5.2 Welding Procedure Qualification .................................................5 5.3 Welder and Welding Operator Performance Qualifications .......10 5.4 Production Welding Requirements ............................................11

6.

INSPECTION AND TESTING ..............................................................24 6.1 General......................................................................................24 6.2 Visual Examination ....................................................................26 6.3 Radiographic Examination.........................................................27 6.4 Ultrasonic Examination..............................................................28 6.5 Magnetic Particle/Dye-Penetrant Examination ..........................29 6.6 Ultrasonic Thickness Measurement...........................................30 6.7 Extent of Non-Destructive Examination .....................................30 6.8 NDE Personnel Qualifications ...................................................30 6.9 Repair of Defects.......................................................................30

7.

VENDOR DOCUMENTATION .............................................................32

Client Project: Title:

tender:

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ADWEA STANDARD SPECIFICATIONS FOR WATER WORKS SPECIFICATION FOR WELDING AND WELDING INSPECTION OF SHOP AND FIELD FABRICATED PIPING project:


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1.

SCOPE This specification prescribes the minimum requirements for welding, welding inspection and Non-Destructive Examination of shop fabricated and field fabricated steel piping (carbon steel and stainless steel). The requirements apply to pipework associated with vendor supplied equipment packages, longitudinal seam welds of bulk purchased piping components such as pipes, tees and elbows, pipework fabricated as part of a contractual fabrication and field erected piping. This specification shall apply to the main CONTRACTOR and to all his sub-contractors.

2.

APPLICABLE STANDARDS AND CODES All materials and work manship shall comply with the latest edition of applicable standards and codes which shall include but not be limited to the following. API 5L

Specification for Line Pipe

API 1104

Welding Pipelines and related facilities.

BS 4504 Sect 3.1

Circular Flanges for Pipes, Valves and Fittings (PN designated) Specification for steel flanges.

ASME B31.3

Process Piping

ASME Section II Part C

Welding Rods, Electrodes and Filler Metals

ASME Section V

non-destructive Examination

ASME Section VIII Div. 1

Pressure Vessels

ASME Section IX

Welding and Brazing Qualifications

ASTM A 312

Seamless and welded austenitic stainless steel pipe

ASTM A 106

Seamless carbon steel pipe for high temperature service.

ASTM E110

Indentation Hardness of Metallic Materials by Portable Hardness Testers

ASTM E92

Vickers Hardness of Metallic Materials

ASTM E94

Standard Recommended Practice for Radiographic Testing

ASTM A 370

Mechanical Testing of Steel Products


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3.

SITE CONDITIONS For site and climate condition refer General Technical requirements document.

4.

Design Consideration The design, fabrication and inspection of pipework shall comply with the requirements of ASME B31.3 except as modified herein. Welding procedure specification (WPS), Procedure qualification records (PQR) and Welders performance tests shall be carried out as per ASME Sect IX code.

5.

WELDING REQUIREMENTS All welding and quality control of welding fabrication shall be done by the CONTRACTOR in accordance with the requirements of this Specification. Weld metal composition shall be compatible with the parent metal. The CONTRACTOR shall comply with ADWEA/ENGINEER Safety Regulations. All welding shall be as specified by the CONTRACTOR on the drawings and the isometric drawings showing all welds, each marked with a unique identification number.

5.1

Approved Welding Processes The following processes are approved for use on pipework : a)

Shielded Metal Arc Welding (SMAW)

b)

Gas Tungsten Arc Welding (GTAW, or TIG)

c)

Gas Metal Arc Welding (GMAW or MIG/MAG)

d)

Submerged Arc Welding (SAW)

e)

Electric Resistance Welding - high frequency process (for longitudinal seams only)

The selection of the welding process, electrodes, shielding gas etc. depend on the materials properties of the pipes to be welded in accordance with the welding code's requirement. Manual GTAW (TIG) welding must be done with the addition of filler metal and high frequency starting unit. It is limited to a thickness range of 3 mm to 6 mm for carbon steel. Short circuiting arc (MIG, MAG or GMAW) welding, Gas Shielded Flux-Cored Arc or Plasma Arc Welding may be used only upon specific approval by ADWEA/ENGINEER. Self shielded flux-cored arc welding shall not be permitted. The root pass welding of pipework of all materials for pipes of nominal diameter less than or equal to DN 50 mm (2" NB) shall be done by GTAW process.


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Full welding of pipework of all materials for pipes of nominal diameter less than or equal to DN 50 mm (2" NB) and wall thickness less than 6 mm shall be done by GTAW process.

5.2

Welding Procedure Qualification

5.2.1

Welding Procedure Specifications (WPS) Prior to the commencement of production welding, the CONTRACTOR shall submit to ADWEA/ENGINEER for approval, proposed welding procedure specifications (WPS) and repair weld procedures for each material, diameter and thickness range as determined by the essential variables and defined in ASME Sec. IX. Welding procedure specifications and repair weld procedures are required to cover all circumferential butt welds, any longitudinal butt welds and attachment welds including branch, weldolet, sockolet and pipe support welds. All welding procedures should be submitted for approval on Form QW-482 of ASME Sec. IX. The proposed WPS shall include but not be limited to the following : a)

CONTRACTOR's name

b)

WPS number, revision and date

c)

Welding process and type (manual, automatic, etc)

d)

Joint design and sketch and sequence of passes

e)

Base material P number and group number

f)

Material type and grade

g)

Pipe diameter and thickness range

h)

Welding consumables - AWS classification, manufacturer, brand name, F number, A number, size, etc.

i)

Welding positions

j)

Welding progression

k)

Preheat temperature, minimum

l)

Interpass temperature, minimum and maximum

m) Method of preheat application and measurement n)

Post weld heat treatment, holding temperature and time, heating rate, cooling rate and method of application.


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o)

Type of current and polarity

p)

Method of edge preparation

g)

Method of back grinding

r)

Gas shielding - flow rate and composition

s)

Gas backing - initial duration of purging, flow rate, composition and duration

t)

Current, voltage and welding speed for each layer.

The welding procedure specifications shall be clearly identified and the CONTRACTOR shall give precise details of which welds are covered by WPS, e.g. pipe size and service/application. Unless specified otherwise, all welding procedure specifications shall be qualified by the CONTRACTOR and duly, witnessed and approved by ADWEA/ENGINEER. Written approval by ADWEA/ENGINEER is required prior to the use of any pre-qualified WPS.

5.2.2

Procedure Qualification Records (PQR) When the welding procedure specifications of the CONTRACTOR have been accepted by ADWEA/ENGINEER and prior to the commencement of production welding, procedure qualification tests shall be carried out under the surveillance of ADWEA/ENGINEER. Welding procedure qualification tests shall be conducted in accordance with ASME Section IX except as modified by this specification. The results of the qualification tests along with the test reports shall be submitted in the approved format, as recommended by ASME Sect. IX Code by the CONTRACTOR as Procedure Qualification Record (PQR). The procedure Qualification Record (PQR) shall include the following: a)

CONTRACTOR's name

b)

PQR number and date

c)

WPS number, revision and date

d)

Welding process

e)

Type (manual, automatic, semi-automatic)

f)

Joint design and sequence of passes

g)

Base material specification, grade, carbon equivalent, thickness and pipe diameter.


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h)

Filler metal AWS classification, size, manufacturer, brand name, A. No. and F. No.

i)

Welding position and progression

j)

Preheat temperature, method of application and measurement.

k)

Interpass temperature

l)

Post weld heat treatment, holding temperature, holding time, heating and cooling rates

m) Shielding gas, composition and flow rate n)

Backing gas composition and flow rate

o)

Current type and polarity

p)

Tungsten electrode type and size (for GTAW )

q)

Orifice or gas cup size (for GTAW & GMAW)

r)

Method of cleaning

s)

Method of back grinding

t)

Welding current, arc voltage, welding speed and heat input as per sect 6.3.7 for each pass.

The CONTRACTOR shall submit all welding procedures and Qualification Records (PQR) with the following back up certificates/reports for ADWEA/ENGINEER approval prior to the commencement of production welding : a)

Welding procedure specifications (WPS), and Procedure Qualification Records (PQR) revised if necessary.

b)

Mill certificates of the test piece sample metal used.

c)

Batch test certificates of the welding consumables.

d)

Heat treatment charts, where applicable.

e)

Non-destructive examination reports.

f)

Mechanical test reports including photo micrographs.

g)

Welding consumable control/electrode redrying procedure.

Documentation for previously qualified welding procedures may be submitted for approval to ADWEA/ENGINEER to support welding procedure specifications. Where it is considered that such documentation adequately proves the suitability of the welding procedures and meets


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the requirements of this specification, requalification may be waived or the number of tests reduced solely at the discretion of ADWEA/ENGINEER. Welding procedure qualification tests shall be performed under conditions simulating site conditions expected during production welding. NDE and mechanical testing shall be conducted after post weld heat treatment where applicable. NDE shall be conducted by American Society of Non Destructive Testing (ASNT) Level II or equivalent certified personnel. Mechanical testing shall be carried out in accordance with ASME Sec. IX in an approved testing laboratory using calibrated instruments. Welding procedure qualifications will be approved by ADWEA/ENGINEER based on satisfactory NDE and Mechanical testing and submission of documentation. Only ADWEA/ENGINEER approved and qualified welding procedure specifications shall be used for production welding.

5.2.3

Essential Variables Essential, supplementary and non-essential variables shall be defined and listed for each Welding process as per ASME Sec. IX. Requalification of a welding procedure shall be required when any of the essential variables changes. Where notch toughness is required as part of the mechanical tests for procedure qualification, a change in any supplementary essential variable shall call for requalification of the welding procedure. The following variables shall be treated as essential variables in addition to those listed in ASME Sec. IX.

5.2.3.1

Base Material Qualification shall be limited to P number as per ASME IX, with the exception of those cases where impact properties are required. Where impact tests are required, qualification is limited to the P number and Group number combinations of the test piece. Base materials not listed in ASME specifications but having equivalent chemical and mechanical properties may be classified in a listed P number and, where applicable, Group number subject to the approval of ADWEA/ENGINEER. Each base metal within a given P number or Group number having nominally different chemical or mechanical properties (as designated by Table QW-422 of ASME Sec. IX) require: a)

Separate welding procedure specification (WPS)

b)

Separate procedure qualification whenever a welding operation satisfactory for one base material is, in the opinion of ADWEA/ENGINEER, unsatisfactory for another base material within the same P or Group number.


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5.2.3.2

Welding Process Any change in welding process, addition, deletion or combination of welding processes.

5.2.3.3

5.2.3.4

Joint Design a)

A change from double sided weld to a single sided weld but not vice versa.

b)

An increase of more than 20° or a decrease of more than 10° in the included angle.

Base Material Thickness The maximum thickness qualified shall be limited to twice the thickness of the test pipe.

5.2.3.5

Welding Consumable The following will require procedure requalification : a)

Change in wire chemistry for ferritic steels from one AWS (American Welding Society) classification to another or to a chemical composition not covered by AWS filler metal specifications.

b)

A change in filler metal from one specific make and type designated under AWS classification 'G' to any other manufacture or manufacturer's designation.

c)

A change in submerged arc welding flux from one manufacturer to another or from one manufacturer's grade to another grade (equivalency on the basis of AWS A5.17 or A5.23 is not acceptable).

d)

Changes in the chemical composition of the weld deposit from one A number to any other A number in QW-442 of ASME Section IX including a change from A-1 to A-2 and vice versa.

Where impact tests are required, all low hydrogen type electrode sizes having no impact test requirements according to the applicable AWS filler metal specification must be certified by one of the following methods: The next largest size of the same manufacturer's electrode grade meets the AWS impact requirements. The specific size of the same manufacturer's electrode grade meets the AWS impact requirements for the applicable electrode classification. 5.2.3.6

Welding Position Any change in welding position except that qualification in the 6G position or 2G plus 5G positions will qualify for all positions.


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5.2.3.7

Welding Parameters Any change in the parameters affecting heat input (current, voltage and welding speed) outside ± 15% of those qualified for root, fill and capping passes. Heat Input (KJ/cm)

=

(current in amps x volts x 60) (welding speed (cm/min) x 1000)

5.2.4

Qualification Tests

5.2.4.1

Non-destructive Examination The test weld shall be 100% visually examined. After satisfactory visual examination, butt welds shall be subjected to 100% radiographic examination. Fillet welds shall be examined by magnetic particle inspection (MPI) for magnetic materials and dye penetrant (DP) examination for non-magnetic materials. The acceptance criteria shall be ASME B31.3, Table 341.3.2 except as modified by this specification.

5.2.4.2

Destructive Tests The type, number and location of specimens to be removed from the test weld shall be in accordance with ASME Sec. IX. Unless otherwise specified, test specimen dimensions, testing procedure and evaluation of tests shall be in accordance with ASME Sec. IX. All mechanical tests shall be conducted after post weld treatment wherever applicable.

5.3

Welder and Welding Operator Performance Qualifications

5.3.1

General Considerations Welders and welding operators shall be qualified in accordance with ASME Section IX. and the requirements stated hereunder. Automatic MIG/MAG/GMAW welding operators shall be qualified by radiography and guided bend tests. All welders and welding operators shall be qualified for all welding positions in which they will carry out production welding. All welds executed by unqualified welders shall be rejected. No welder shall be qualified on production welds. A welder or welding operator who fails the performance qualification test of this specification, may be granted an immediate retest in accordance with ASME Sec. IX (QW-321 solely at ADWEA/ENGINEER discretion. If the welder or welding operator fails in the retest, he may be


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given only one further test in accordance with QW-321.3 but only after he has received adequate training to the satisfaction of ADWEA/ENGINEER.

5.3.2

Qualification Validity Welder and welding operator qualifications are valid indefinitely provided the CONTRACTOR can show to ADWEA/ENGINEER's satisfaction that the welder or welding operator has been continuously engaged on work of a similar nature with the specific welding process since successful qualification. A break in continuity of more than 3 months (90 days) shall require requalification. When a welder or welding operator's work is judged unsatisfactory by ADWEA/ENGINEER, that welder or welding operator shall immediately be removed from the work, and his last shifts work 100% radiographically examined.

5.3.3

Identification of Welders All welders and welding operators qualified for production welding shall be assigned a unique identification number or symbol which shall be marked by crayon adjacent to each of their production welds (marking crayons shall be free from chloride and sulphur). All the welders identification badges shall be counter singed by ADWEA/ENGINEER and these badges shall be worn by the welders during welding. ASME Section IX, Form QW-484 along with the welder's photograph shall be used for each performance certification. Such records showing the date and the results of qualification tests completed by each welder or welding operator with the identification numbers/symbols assigned to them shall be available for scrutiny by ADWEA/ENGINEER at all times.

5.4

Production Welding Requirements

5.4.1

General The CONTRACTOR shall carry out all production welding and quality control at his sole cost, in accordance with the requirements of this specification.

5.4.2

Welding Equipment All welding equipment shall be of sufficient capacity for the work to be performed and shall be capable of producing welds of acceptable quality. All equipment shall be maintained in good working condition by the CONTRACTOR. Any equipment which does not meet these requirements shall be replaced. All welding machines should be in a good working condition. inspection at any time by ADWEA/ENGINEER.

They will be subject to

All welding equipment and accessories shall meet the safety regulations of the relevant international specifications (such as NEMA) and shall be safe to operate.


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When using the GTAW process, a high frequency (HF) arc initiation unit, a controlled current delay device (to eliminate crater) and suitable pre-end post-gas flow device (to eliminate porosity and air entrapment) shall be used.

5.4.3

Welding Processes Only approved welding processes shall be used for production welding. The selection of welding processes shall be governed by Section 5.1 of this specification.

5.4.4

Weather Protection The CONTRACTOR shall provide adequate shelter to the satisfaction of ADWEA/ENGINEER to protect the welding environment from inclement weather and drafts. All surfaces to be welded and the adjoining area of the material shall be warm and dry to the touch with a minimum metal temperature as specified by the approved welding procedure specification (WPS). Where the surfaces to be welded are covered by moisture and where there is no requirement of preheat by the applicable WPS, the surfaces should be completely dried and warmed up by a hydrocarbon torch using a soft flame before starting to weld. The use of oxy-acetylene torches shall not be permitted. No welding shall be carried out when the weld surfaces are wet or dirty and if inadequate provision has been made for weather protection.

5.4.5

Parent Materials All materials used for ADWEA/ENGINEER work shall be stored in a proper manner and protected from weather conditions. The material storage areas shall be separated by material type such as carbon steel, stainless steel and non-ferrous materials. Materials separation shall be maintained throughout the entire time of fabrication. Prior to fabrication, the CONTRACTOR shall submit for ADWEA/ENGINEER approval a proposed material storage and control procedure to assure the separation of such areas. Manufacturer's material identification marks on all pipes and fittings shall be maintained on all components and shall be verified and fully documented by Mill Test certificates which shall be made available to ADWEA/ENGINEER. All spools shall be duly identified by painting or writing by crayon the Isometric number, spool, etc. Materials which do not have proper identification including valid mill test certificates shall be rejected at CONTRACTOR's sole cost.


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5.4.6

Welding Consumables Electrodes, filler wires and fluxes shall conform to the requirements of ASME Boiler and Pressure Vessel Code Section II Part C. The proposed brands shall have the approval of Lloyd's Register of Shipping, DNV, BV, ABS or any internationally recognised controlling/inspecting body. Gases, both combustible and inert, shall meet the requirements of American Welding Society or any other standard acceptable to ADWEA/ENGINEER. All welding consumables shall be subject to ADWEA/ENGINEER approval and shall be selected such that the deposited weld metal exhibits mechanical properties equal to or in excess of the minimum specified values of the base material. The CONTRACTOR shall prepare and submit to ADWEA/ENGINEER a list of welding consumables to be used on the project showing type, manufacturer, brand and the manufacturer's recommended storage and drying procedure for each. The CONTRACTOR shall prepare and submit to ADWEA/ENGINEER a detailed procedure for storage, inspection, control and monitoring of welding consumables to assure adherence to job and manufacturer's requirements. The procedure when approved by ADWEA/ENGINEER shall be mandatory. Storage and control of welding consumables shall be in accordance with the following : -

All electrodes shall be stored in fully sealed packages and stored in dry storage rooms. The electrodes should be properly identifiable upto the time of usage.

-

All electrodes which are damaged, wet, rusty or otherwise contaminated with oil, grease, dirt etc. shall be scrapped. Electrodes with visible stains as well as partly used electrodes shall not be used.

-

The CONTRACTOR shall provide separate ovens for baking and storing of low hydrogen welding consumables.

-

Heating ovens with automatic heat controls and temperature read out equipment shall be provided to heat and store the low hydrogen electrodes at the required temperature.

-

SMAW electrodes of different weld metal compositions or having different flux type covering shall not be stored or baked together in the same oven.

-

Low hydrogen electrodes shall be baked at 300°C for at least one hour or as per manufacturer's recommendations so as to deposit weld metal with a diffusible hydrogen content of not greater than 10ml per 100gm weld metal. After this, the oven temperature shall be brought down to 120°C. Thereafter the electrodes may be transferred to an intermediate storage cabinet at 120°C - 150°C and maintained at that temperature before they are issued for welding. Welders shall remove from the ovens only enough electrode that will be utilised within four (4) hours. These electrodes shall be carried in quivers or portable heaters maintained at a minimum temperature of 70°C and used with in four Client Project: Title:

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hours. Welders shall ensure that their quivers are in working condition and that quiver lids are closed after removal of electrodes. Electrodes shall not be baked in layers greater than 3. Electrodes shall not be baked more than once. Cellulose coated SMAW electrodes shall be kept in a dry and dust free enclosure after opening of the factory container. These electrodes shall not be held at an oven temperature above 65 °C as the coating and weldability of these electrodes may be impaired. Cellulose coated SMAW electrodes that have become wet, rusty or damaged shall be discarded.

-

Filler wires and bare electrodes shall be stored in sealed, dirt and moisture proof containers within a dry, dust-free enclosure. Filler wires withdrawn from the container and not used shall be returned to their container and the container resealed. Filler wires that have rusted or are contaminated with oil, grease, dirt etc. shall be discarded. Fluxes shall be stored in sealed, dirt and moisture proof containers or bags within a dry, dustfree enclosure. Contaminated fluxes shall be removed from the site and discarded. Only fused type fluxes shall be used and they should be dried according to manufacturer's recommendation. If agglomerated fluxes are used, they shall be baked at a temperature of 250°C - 300°C for a minimum of two hours and kept in drying ovens at all times. For carbon steel materials, the SAW process shall not utilise an active (Mn-Si) flux nor EHXX (high manganese) wires. Only low hydrogen electrodes shall be used for the following cases with SMAW : (a) Welding and/or installing hot-tap connections on pipes containing flammable liquids, gas or combustible materials. (b) For the repair of all welds in carbon steel plates. (c) Full penetration double-groove joints. (d) Fill and cap passes of all other applications for all carbon steels for all thicknesses. With the exception of low hydrogen electrodes, (a) through (c), cellulose coated electrodes may be used only for the root passes of carbon steels with prior written permission of ADWEA/ENGINEER. Welding electrodes kept in the drying oven shall be consumed on "first in - first out" basis. 5.4.6.13 Electrode Size (a) The maximum electrode diameter for all single sided welding using the SMAW process shall be 3.2mm for the root pass and 5mm for the fill and cap passes. b)

The maximum electrode diameter for double sided welds using SMAW shall be 4mm for the root pass and 5mm for the fill and cap passes.


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5.4.6.14 Shielding Gases The shielding gases are used for the protection of the electrode and the weld pool from the surrounding air. Depending on the welding process adopted, parent material, weld configuration and shielding gas shall be selected. (a) For the GTAW process purity of Argon is 99.99%. Oxidising element such as Oxygen shall not be permitted, as it will cause oxidisation of the tungsten electrode. Gas mixtures consisting Argon and hydrogen (95/5 % or 90/10 % can also be applied to achieve higher penetration and a lower weld pool viscosity. It is limited to horizontal weld position. (b) For the GMAW, the filler wires shall be compatible with the type of gas. De-oxidising elements shall present in the filler wire when above gases like CO2 is used. For reducing the surface tension of the filler metal, slight amount of O2 and CO2 can be used. (c) When welding the root end and the first pass the back side of the weld can be protected to prevent oxidation, Nitrogen/Hydrogen gas mixtures in composition of 95/5 to 85/15 % volume can be used.

5.4.7

Cutting and Weld Joint Preparation Preparation and cutting of carbon steels may be done by machining, grinding, machine guided gas torch or plasma arc cuttings. Gas torch and plasma arc cutting shall only be used where it is not practicable to use mechanical methods. Thermal cutting is acceptable for carbon and low alloy steels. For plates less than 25 mm thick, cold shearing may be used. For plates between 11 mm to 25 mm thick the cut edges shall be dressed back atleast 2 mm by machining or grinding. The edges shall be inspected by MP or DP method. For stainless steel material, flame cutting is not allowed but plasma cutting may be applied. End profiles of pipes and fittings which are to be butt welded shall be in accordance with ASME B 16.25. Pipes for socket weld joints shall be cut square. All cut surfaces shall be finally prepared by grinding or machining to clean, bright metal. After the edges have been prepared for welding, they shall be visually examined to confirm that the preparations are smooth and uniform and free from tears, cracks, gouges and other discontinuities which might affect the weld quality. Further the prepared welding ends shall be examined by ultrasonics for a distance of 50mm back from the bevelled edge to ensure freedom from laminations, and magnetic particle inspection on bevels. The use of arc air gouging shall not be permitted. Branch connection cut outs shall be carefully bevelled and accurately matched to form a suitable groove for welding and to permit complete penetration of the welds at all points.

5.4.8

Cleaning Requirements All surfaces to be welded and the surrounding areas shall be clean and free of paint, oil dirt, rust , oxides or any other foreign matter which could interfere with welding, prior to the


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application of preheat or welding. The deemed surface shall extend at least 25 mm beyond the substrate actually touched by the arc.

5.4.9

Edge Preparation and Joint Alignment The edge preparation for butt joints shall be as indicated below: a)

For piping with thickness upto 26 mm the preparation shall be 'V' type, with 370 30' + 20 30' bevelling.

b)

For piping with thickness over 26 mm, the preparation shall conform to ASME B31-3, or shall be of another type approved by ADWEA/ENGINEER.

For butt welding of all piping components, pipe ends, fittings and welding neck flanges, a uniform root opening its required as shown:
1.5 mm

DN 50 to DN 250 mm

1.5 to 2.5 mm

>DN 250 mm

2.5 to 3.5 mm

Butt weld alignment shall satisfy the requirement of ASME B31.3 and the conditions stated below. Internal misalignment of pipework shall not exceed 1.0mm in order to facilitate welding of the root pass. When a GTAW root pass is to be used the maximum misalignment shall not exceed 0.8mm Misalignment may be reduced by the use of hydraulic or screw type of clamps. Hammering heating and buttering of weld shall not be permitted. In case of pipes/components with different thickness misalignment upto 3.2 mm may be improved by internal machining provided the taper does not exceed 1 in 4 max. However the minimum required wall thickness shall be maintained. Grinding shall not be used. Correction of misalignment by use of cold working shall not be permitted. Where internal pipe aligners are used, they shall not be removed until the root pass has been completed. Where external lineup clamps are used, the clamp may be removed when the root bead is at least 50% completed. The root bead should be spaced evenly around the circumference. The longitudinal welds of adjacent pipes shall be staggered by at least 100mm.

5.4.10

Tack Welds All tack welds shall be made by qualified welders using approved electrodes and pre-heat, as specified by the approved welding procedures.


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Tack welds to assist alignment shall have a minimum length of 25mm and shall be of sufficient size to maintain joint alignment until production welding begins. All tacks welds which will be part of the main welds shall be cleaned, ground to a feather edge at both ends and visually inspected prior to welding of the root pass. Any defective tack shall be completely removed by grinding prior to welding of the root pass. When tack welds are removed, the CONTRACTOR shall ensure that the root preparation is correctly maintained for the subsequent pass. Tack welds not incorporated in the final weld shall be removed by grinding or other mechanical means to achieve smooth surface without reduction in wall thickness, followed by Non destructive test inspection.

5.4.11

Joint Backing Requirements Permanent backing rings or backing plates shall not be used. The use of consumable inserts for root passes shall not be permitted.

5.4.12

Preheat Requirements Preheating of the parent metal prior to any welding, tack welding and thermal cutting can be necessary to minimise the detrimental effects of high temperature and severe thermal gradients inherent in welding.

5.4.12.1 Preheat Temperatures The minimum pre-heat temperature for welding, flame cutting and arc cutting shall be as specified below. Where welding procedure specification (WPS) indicates that a higher preheat temperature is necessary, this shall be used for production welding. Materials

Minimum Temperature

Carbon steels upto 25mm thick

10 Deg C (50 Deg F)

Carbon steels above 25mm thick

79 Deg C (175 Deg F)

Austenitic stainless steel (all thickness)

10 Deg C (50 Deg F)

The determination of pre-heat temperature for carbon steel production welds should be based upon ASME Section 1X Code after consideration of specific heat input, joint thickness metal composition, welding process and welding consumables. Unless notified otherwise by ADWEA/ENGINEER the following criteria should be used to determine preheat levels : (1) The relevant carbon equivalent (CE) should be calculated from the maximum CE allowed by the material specification. Client Project: Title:

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(2) Consideration should be given to joint restraint as in case of branch connections (weldolets, sockolets and nippolets). When the base metal temperature is below 21 deg.C for carbon steels, the material shall be preheated to 50 deg.C prior to welding. Whenever material is wet or contains surface moisture or condensate, it shall be dried by heating. The fusion faces and 100 mm on each side of the welds shall be preheated up to 50 deg.C. 5.4.12.2 Application of Preheat Preheat shall be applied by electrical resistance methods. Preheating methods with hydrocarbon gases shall only be used with prior written approval of ADWEA/ENGINEER. The use of oxy-acetylene torch for preheating is prohibited. Preheat shall be applied in a gradual and uniform manner and shall be maintained throughout the welding operation. The minimum preheat temperature shall be established on both sides of the joint preparation for a minimum distance of 75 mm or 3 times the material thickness whichever is greater. If possible, the preheat temperature shall be measured on the opposite face to that being heated. Where access to only one face is possible, the heat source shall be turned off to allow for temperature equalization (one minute for each 25mm of wall thickness) before measuring the preheat temperature. The preheat temperature shall be held for at least 5 minutes before welding is commenced and shall be checked before and during welding by thermo-couples, contact pyrometer or by temperature indicating crayons. (colour charging crayons shall not be used)

5.4.13

Interpass Temperature Interposes temperature is the temperature at which the weld area must be before the next pass is started. The maximum interpass temperature shall not exceed the following limits unless stated in ADWEA/ENGINEER approved welding procedure specifications (WPS): (a) Carbon Steels

:

250 0C

(b) Austenitic Stainless Steel

:

175 0C

The minimum interpass temperature shall be the minimum preheat temperature specified in ADWEA/ENGINEER approved welding procedure specification. The interpass temperature shall be measured at a distance of about 12.5mm from the bevel ends and shall be measured by contact pryrometer, thermo-couples or temperature indicating crayons. (colour changing crayons shall not be used)


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5.4.14

Interruption Of Welding Welding of each joint should be a continuous operation. No weld shall be allowed to cool unless at least 3 runs have been deposited and 50% of wall thickness is deposited. If for any reason welding is discontinued, the following criteria shall apply: a)

If 3 runs, and 50% wall thickness has not been deposited, then the weld should be cut out and recommenced from a new preparation.

b)

If 3 runs, and 50% wall thickness have been deposited then the welding operation may commence provided the following conditions (c) and (d) are met:

c)

The weld on interruption shall be allowed to cool slowly from welding temperature to room temperature (this may be done by wrapping the weld with insulation and allowing the joint to cool in still air.)

d)

Before welding is resumed the weld shall be preheated to the specified temp, after a close visual or MPI as required by ADWEA/ENGINEER.

Root runs and second passes (hot passes) shall be made without interruption other than for changing electrodes or filler wires or to allow welders to reposition themselves. The second pass (hot pass) of carbon steel pipe welds shall be deposited immediately after the root pass in order to prevent "cold cracking' in the root area due to shrinkage stresses and joint restraint.

5.4.15

Weld Bead Sequence Weld bead deposition shall be established during welding procedure qualification and shall be indicated on the joint design of the Procedure Qualification Record (PQR). The specified welding sequence shall be adhered to during production welding. Adjacent weld beads shall be staggered and not started from the same location. Welding shall be carried out in a sequence which will minimize distortion. All welds shall be full penetration welds apart from the following: a)

Socket welds which may be used on pipe of nominal size DN 40 mm and less, as defined in the contract drawings.

b)

Pipe support attachment welds.

c)

Fillet welds, as specified, which shall be continuous.

Where access permits, pipework with nominal size over DN 600 mm shall be welded from both sides. Double sided welds shall be back-gouged to sound metal and ground smooth prior to welding from the second side. However the CONTRACTOR shall ensure safe working atmosphere like ventilation/fume extraction/respirators etc. is provided in order for the welder to perform the welding. Client Project: Title:

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All pressure containing welds shall have a minimum of three passes with overlaps of starts and stops. This shall include seal welds of threaded connections and socket welds. Longitudinal butt-welded pipe fittings are not allowed without written approval of ADWEA/ENGINEER.

5.4.16

Interpass Cleaning After each welding pass, the weld shall be cleaned of all flux, slag and spatter by power wire brush, grinding or hand chipping tools. In case of root pass the weld shall be ground. Every welding pass shall be visually examined by the welder to ensure that the weld is free from slag, porosity and uneven contour before the start of the next pass. Any defects found shall be removed or repaired prior to the start of the next pass. Any cracks found shall be brought to ADWEA/ENGINEER's notice before removal and restart of work. Upon completion of the weld, the adjacent surfaces shall be cleaned of all spatter, slag, flux, soot and other foreign materials.

5.4.17

Peening No weld peening of any sort shall be permitted.

5.4.18

Seal and Socket Welding Sealing compound or Teflon tape shall not be used on joints which are to be seal welded. Seal welding of threaded connections shall cover all exposed threads. Seal welds shall contain a minimum of two passes and shall extend from the outer diameter of the fitting smoothly to the nipple surface without any undercut. Seal welding shall be carried out using a low heat-input welding process such as GTAW or SMAW. When SMAW process is used, the electrode size shall not exceed 3.2 mm in diameter. During socket welding, the inserted end of the pipe nipple shall not come in contact with the bottom of the socket. A minimum clearance of 1.6mm shall be given prior to welding. Use of contraction rings to achieve minimum clearance are not allowed without written approval of ADWEA/ENGINEER.

5.4.19

Attachment Welds Fillet welds used for attachments shall be carried out by qualified welders using approved electrodes and preheat as specified by ADWEA/ENGINEER approved welding procedure. Fillet welds shall have proper fusion and penetration at the root of the joint. Fillet welds shall fuse gradually into the pipe and be free from marked irregularities, convexity/concavity and undercut.


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Temporary attachments welded to pipework to facilitate fabrication shall be permitted with the prior approval of ADWEA/ENGINEER. All temporary attachments shall be completely and carefully removed checked by DP/MPI test prior to any post weld heat treatment. Removal of temporary attachments by hammering or bending is not permitted.

5.4.20

Weld Spacing Distances between welds shall be measured between the adjacent edges of the cap passes. Weld joints shall not be arranged so close to each other. Sufficient weld clearance shall be maintained to prevent thermal stresses near the joint. Circumferential butt welds on the pipeline shall be separated by maximum possible distance. Longitudinal butt welds of adjacent pipes shall be separated by at least 100 mm or 5 times the thickness of the thicker pipes whichever is greater. Should the site conditions warrant, short pipe lengths between fittings can be used and its butt welds shall not be closer than 75 mm or 5 times the thickness of the thicker pipes whichever is greater. Branch/nozzle and other pressure attachment welds shall not be closer than 75mm to adjacent pressure welds. Cases which fail to meet this criteria shall be referred to ADWEA/ENGINEER for approval prior to the commencement of fabrication. Non-pressure containing attachment welds, such as pipe support welds shall be at a minimum distance of 50mm from any pressure containing welds. Where pup sections are to be inserted, the length of such insert pup sections for both new and existing fabrication shall not be less than three pipe diameters, or 150mm whichever is greater.

5.4.21

Workmanship and Weld Finish The welding arc shall be struck inside the joint groove or where the weld is to be made. Arc strikes, gouges and other indications of careless workmanship outside the weld arc shall be carefully removed by grinding and the ground area shall be examined by MPI or Dyepenetrant test, and ultrasonics to ensure min. wall thickness is maintained. Arc strikes, gouges etc. outside the fusion face shall be limited to one per pipe and one per joint. Repair of Arc strikes shall be at the discretion of ADWEA/ENGINEER. If resultant wall thickness after grinding is less than the minimum design thickness, the position of pipe containing arc burn shall be removed as a cylinder. Insert patching and rewelding to increase the wall thickness shall not be permitted.


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Coated surfaces shall be protected from the welding arc and the associated weld spatter. Weld reinforcement and internal weld protrusion shall be as required by ASME B31.3 but in no case shall the height exceed the weld crown. Excessive internal weld protrusions on accessible joints shall be removed by grinding. Welds having excessive protrusions on inaccessible joints shall be cut and re-welded. Welds which are to be examined by non-destructive testing shall be appropriately surface finished to facilitate easy interpretation of results. External weld undercutting shall not be permitted. The acceptability of fillet welds shall be established by suitable gauges or templates. The minimum required size of each fillet weld shall be as specified in the applicable drawing. Where leg length is specified, the throat thickness for a 1 x 1 fillet weld shall be from 0.7 to 1 times the required leg length. The throat thickness for a 1 x 2 fillet weld shall be 0.7 to 1.2 times the size of the shorter leg.

5.4.22

Welding Technique Wherever possible, welding should be carried out with minimum weaving. The width of weave during production welding shall be within acceptable limits of ADWEA/ENGINEER approved and qualified welding procedure. In no case shall the width of weaving exceed three times the core wire diameter or 12 mm whichever is less for SMAW. For SAW process, welding shall be done without any weaving (oscillation.) All pressure containing welds shall have at least two passes with overlapping starts and stops. Only single electrode processes shall be used. Use of multiple electrodes shall require prior ADWEA/ENGINEER approval. Welding of all pressure containing welds shall be done with direct current unless otherwise previously approved by ADWEA/ENGINEER. All vertical welding shall be done uphill. Downhill ('stove-pipe') welding of pressure containing welds shall not be permitted.

5.4.23

Post Weld Heat Treatment Post Weld Heat Treatment shall be required under the following conditions: a)

All carbon steel pipework when the material thickness through a butt weld joint exceeds 19mm.

b)

Carbon steel pipework subject to vibration, such as compressor piping, when the material thickness through the butt weld joint exceeds 12.7mm.


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c)

Carbon Steel branch connections when the thickness in any plane through the branch weld exceeds thickness requirements as indicated in ASME B31.3 para 331.1.3.

d)

Wherever required for the fabrication of fittings as applicable.

Post weld heat treatment shall be carried out as soon as possible after completion of welding and shall be conducted in accordance with ASME B31.3 except as modified by this specification. The temperature controls during heating and cooling shall meet the requirements of ASME Sec. VIII Division 1. A post weld heat treatment (PWHT) procedure shall be submitted for ADWEA/ENGINEER approval prior to any PWHT being conducted. Only ADWEA/ENGINEER approved procedures shall be limited to the temperature at which the part is loaded into the furnace (for furnace heating), rate of heating up to the holding temperature, holding temperature, holding time at maximum temperature, rate of cooling from the maximum temperature, the number, location and method of attachment of thermocouples to the part to be heat treated. Wherever possible PWHT shall be conducted in an enclosed furnace. For site or field welds, local PWHT by electrical resistance method shall be conducted. The use of manually operated gas torches or gas rings or proprietary exothermic kits shall not be permitted. Where Local PWHT is done, the weld being post-weld heat treated shall be in the centre of the heated band. The heated band shall be sufficiently wide such that a band at least 25mm on each side of the weld edges reaches the specified temperature range. There shall be sufficient insulation to avoid an undesirable temperature gradient. During furnace or local post-weld heat treatment, there shall be a minimum of 4 thermocouples (or as otherwise approved by ADWEA/ENGINEER) used to ensure that thermal gradients outside the requirements of this specification do not occur during the heat treatment cycle. Thermocouples shall be positioned at a distance of 25mm from the weld edges on each side of the weld. The minimum number of thermocouples required may be decreased only with prior ADWEA/ENGINEER approval. A time temperature chart recording the thermal history of the part heat treated shall be provided by the CONTRACTOR. The chart shall be clearly identified with the drawing/ISO number, part and weld number an signed by the CONTRACTOR and certifying authority where applicable. The chart shall be included in the project record work/"As-built" documentation. Thermocouples shall, if possible, be placed on the inside for objects being heated from the outside, and vice-versa, if internally heated. The method and placement of thermocouple attachment to pipework shall be subject to ADWEA/ENGINEER approval. For local PWHT, only one butt weld joint shall be recorded on any one chart. Additional charts, shall be used on any other joints.


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Thermocouples and temperature recording equipment shall be calibrated prior to use and shall have a valid certification by a reputed certifying authority. Welding shall be avoided on any post-weld heat treated material. If any welding is to be carried out on any post weld heat treated material, this shall be referred to ADWEA/ENGINEER. Failure to do so will call for repeating heat treatment All machined surfaces such as pipe ends, flange faces and threads shall be suitably protected during the PWHT cycle. NDT of welds, where applicable, shall be conducted after PWHT for final acceptance.

5.4.24

Weld Identification Each weld shall be uniquely identified with a weld number and ISO/drawing number and the same must be represented on the weld identification/NDT drawings. After the completion of each weld and prior to its visual examination, the weld and welder identifications shall be marked adjacent to the weld at a distance of about 50mm from the weld using paint or indelible crayons. This identification shall remain on the pipe till the completion of all NDT for any verification by ADWEA/ENGINEER.

6.

INSPECTION AND TESTING

6.1

General CONTRACTOR to include the provision of service by a ADWEA/ENGINEER approved third party inspection (TPI) subcontractor to cover inspection activities in addition to CONTRACTOR's own inspection. As part of CONTRACTOR organisation, the CONTRACTOR ADWEA/ENGINEER his proposed QA/QC/Inspection organisation.

shall

submit

to

The CONTRACTOR shall submit detailed non-destructive examination (NDE) procedures for ADWEA/ENGINEER approval. All NDE shall be carried out in accordance with the procedures approved by ADWEA/ENGINEER. The radiographic inspection procedures shall include film-processing procedures to be used for non-destructive examination (NDE). The CONTRACTOR shall demonstrate, to the satisfaction of ADWEA/ENGINEER nondestructive testing production technique of exposure, film screen combination, use of lead screens, and film processing and handling are satisfactory and meet this specification. The resultant radiographic procedure shall be considered the Standard Test Radiographic Procedure. The production radiographs shall, as a minimum, be the same quality as the Standard Test Radiograph. The radiographic inspection procedure shall be submitted to ADWEA/ENGINEER for approval.


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The Standard Test Radiograph shall be repeated at the option of ADWEA/ENGINEER whenever any change has been made in the operation procedure or whenever production films vary appreciably in details, contract or density, from the Standard Test Radiograph. Radiographic inspection shall be conducted by the use X-rays. Gamma ray examination may only be used with the approval of the ADWEA/ENGINEER. Radiographic sources and procedures shall be subject to the approval of ADWEA/ENGINEER. The CONTRACTOR shall submit detailed radiation safety procedures which comply with ADWEA safety regulations. Radiographic inspection shall comply with the relevant safety codes and radiation control procedures. Special attention is drawn to the necessity for audible and visual warning devices and for regular monitoring of radiation levels. Radiographic procedures shall be qualified using both source and film side penetrameter. Each radiographic film shall contain the following identification information: •

Project identification

•

Weld number

•

Welder number

•

Pipe diameter and wall thickness

•

Date

•

Film location markers related to the area of weld that the radiographic covers

•

NDE Contractor's symbol

•

Weld thickness

•

Image Quality Indicator

The zero datum shall be top dead centre of the pipe. Defect location shall be in metric units system. Each radiograph shall have reference markers at 10 cm intervals. The letter "R" shall appear on all radiographs of weld repairs in addition to the above information. The RT films shall be stored and kept by the CONTRACTOR until final handing over, and shall be available at anytime for ADWEA/ENGINEER review. The CONTRACTOR shall provide easy access to the jobs for inspection and NDE and shall provide full co-operation and all assistance that ADWEA/ENGINEER may request.


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Prior to the commencement of work, the CONTRACTOR shall establish an identification system such that each assembly, each component and each weld can be uniquely and fully identified with welder/welding operator, welding procedure specification (WPS), NDE procedure/technique, extent of NDE and NDE results. Procedures for radiography, ultrasonic, magnetic particle and dye-penetrant examination shall all be conducted in accordance with ASME Section V. All personnel performing NDE shall have ASNT Level II or equivalent certification as approved by ADWEA/ENGINEER prior to the commencement of work. The CONTRACTOR must submit weld map showing NDE system for ADWEA/ENGINEER and written ADWEA/ENGINEER approval is required prior to the commencement of fabrication.

6.1.1

Reduced Percentage Examination For any examination frequency less than 100%, say 'X' percent examination (X may be 5, 10 or 25%), the following rules shall apply: (a) At least 'X' percent of the total number of welds within the specified line class shall be examined for 100% of their length (circumference). (b) At least 'X' percent of the total number of welds on each isometric shall be examined and shall not be less then one weld per isometric. (c) At least 'X' percent of the total number of welds made by each welder shall be examined for 100% of their length. At least one complete weld shall be examined for each welder. (d) Examinations shall be representative of the entire range of pipe sizes and joints that have been welded. (e) Where reduced percentage examination is required and the resulting test shows defects, then additional examinations as required by ASME B 31.3 para 341.3.4 shall apply regardless of the examination process used. (f)

Defect acceptance criteria for all reduced percentage examinations shall be the same as for 100% examination.

(g) 'X' percent shall be determined by ADWEA/ENGINEER and shall be specified for each piping class.

6.2

Visual Examination Prior to visual examination, welds and the adjoining areas shall be thoroughly cleaned free of all slag, mill scale, dirt, weld spatter, paint, oil, flux, stub ends and other foreign matter. The CONTRACTOR shall provide easy access to the pipework for inspection. This will include the provisions of ladders and scaffolding when required.


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The workmanship and weld finish shall be as per this specification. Weld acceptance criteria for visual examination shall be as per ASME B31.3, Table 341.3.2 except as modified by this specification.

6.3

Radiographic Examination Radiographic procedures shall be in accordance with the methods described in ASME Section V Article 2 except as modified by this section. Radiographs should be evaluated in accordance with ASME B31.3, Table 341.3.2, except as modified by this specification. Only fine grain, high contrast film or ultra fine grain high contrast film shall be used. Type 1 film (AGFA, structurix D4 or equivalent) of ASTM E94 shall be used for gamma ray radiography of pipes with wall thicknesses below 10mm. Gamma radiography shall only be used if it can be proven that the required sensitivity can be achieved. Wherever possible, DIN penetrameters (wire type Image Quality Indicators) shall be used. Radiographic sensitivity shall be 1.8% or better. Where film side IQI's are used, correlation of sensitivity with source side IQI'S shall be established before proceeding with inspection Only lead intensifying screens shall be used. The radiographic density in the diagnostic area shall be between 2.0 and 3.5 All burn-through shall not be permitted. Radiography shall be conducted after any required PWHT for final acceptance.

6.3.1

Reporting The radiography report shall include the following information: -

Contract number

-

Project title

-

Name of the component

-

Source type (X-ray/Ir-192)

-

Source strength (mA/curies)

-

Focal spot size

-

Technique (SWSI/DWDI/DWSI/PANAROMIC)

-

Film type and size


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6.4

-

Penetrameter type and number

-

Exposure time

-

Developing time and temperature

-

Density

-

Sensitivity

-

Lead screens (front and back)

-

Specification (ASME B31.3)

-

Weld identifications

-

Pipe diameter and wall thickness

-

Welder identification

-

Interpretation

-

Remarks (Accept/Reject)

-

Radiographer's name and signature

-

Date of exposure

Ultrasonic Examination The CONTRACTOR shall submit an ultrasonic examination procedure for all full penetration butt and branch welds for ADWEA/ENGINEER approval prior to the commencement of examination of production welds. Ultrasonic examination shall be carried out in accordance with ASME Section V Article 5, except as modified by this section and the results shall be evaluated in accordance with ASME B31.3 Table 341.3.2. The ultrasonic equipment shall be checked for linearity, db attenuation etc. and a valid calibration certificate shall be submitted for ADWEA/ENGINEER review, prior to use. As a minimum requirement, ultrasonic examination shall be conducted using a minimum of three transducers, one 0° compression and two angle beam transducers with a frequency of 1 to 5 MHZ. Where access permits, ultrasonic examination shall be conducted from both sides of the joint. Prior to conducting ultrasonic examination, the CONTRACTOR shall ensure that the weld and the surrounding area are sufficiently smooth to avoid false or misleading indications. Transfer correction should be applied to accommodate surface curvature and roughness.


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Branch connections that include a reinforcing pad plate shall be examined after welding the branch to the header and again after welding on the reinforcing plate. The test report should outline the technique employed, type and size and frequency of probes used, and defects discovered and shall contain the following information as a minimum: (a) Weld identification and welder number (b) Weld procedure used (c) Size of reportable defect (d) Depth of reportable defect (e) Location and orientation of reportable defect (with a sketch) (f)

Weld acceptable/not acceptable.

(g) Specification (h) Inspector's name and signature (i)

Date of Examination

(j)

Scanning Diagram.

Ultrasonic examination of welds shall be conducted after PWHT that may be required for final acceptance.

6.5

Magnetic Particle/Dye-Penetrant Examination Magnetic particle examination shall be carried out on magnetic materials. Dye-penetrant examination shall be carried out on non-magnetic materials (stainless steels and non-ferrous materials). Weld areas to be examined by magnetic particle/dye-penetrant examination shall be sufficiently smooth to avoid spurious indications that may result from irregular weld surfaces. All magnetic particle examination shall be carried out by alternating current yoke method with a white background and black magnetic ink. Magnetic particle examination shall be carried out in accordance with ASME Section V Article 7. Dye-penetrant examination shall be carried out in accordance with ASME Section V Article 6. The acceptance criteria shall be as per ASME B31.3 and Table 341.3.2. Where PWHT is required, magnetic particle/dye-penetrant examination shall be conducted after PWHT for final acceptance. Examination shall be conducted before PWHT for any repair/rectification that may be required before PWHT.


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6.6

Ultrasonic Thickness Measurement Ultrasonic thickness measurements, where required by the ASME B31.3 code, and/or by ADWEA/ENGINEER, it shall be done with Ultrasonic Flaw Detectors. The use of D-Meters is not permitted for thickness measurements. Where specified by ADWEA/ENGINEER, ultrasonic thickness measurements shall be made on both sides of welds at a distance of 25mm from the weld edges. The thickness readings shall be recorded on NDE spool drawings.

6.7

Extent of Non-Destructive Examination The minimum requirements of non-destructive examination of welds shall be as per ASME B31.3 code. More stringent NDE may be specified based upon materials of construction, service severity and/or testing limitations.

6.8

NDE Personnel Qualifications Welding inspectors shall be certified to AWS or equivalent. All personnel carrying out non-destructive examination (radiography, ultrasonic, magnetic particle and dye-penetrant examination) shall be ASNT Level II certified or equivalent. Where the NDE technician is certified by the CONTRACTOR himself, the qualification shall be in accordance with CONTRACTOR's written procedures which shall use ASNT'S recommended practice No. SNT-TC-1A, as a guide. This written procedure shall be made available to ADWEA/ENGINEER whenever required and shall be subject to ADWEA/ENGINEER approval. New qualification tests may be required if a technician's performance indicates deficiencies. The CONTRACTOR shall bear all costs for qualifying technicians and ADWEA/ENGINEER Inspector will have the option to witness any qualification tests. The CONTRACTOR shall have records of qualifications and certificates for each technician available for review by ADWEA/ENGINEER prior to the commencement of work by the technician. Any technician may be disqualified by ADWEA/ENGINEER upon proof of unethical practices, negligence, non-compliance with procedures or poor performance.

6.9

Repair of Defects

6.9.1

General Prior to carrying out any repairs involving welding, the CONTRACTOR shall submit a written repair welding procedure to ADWEA/ENGINEER for approval. This shall include details of the type and extent of defects, method of removal, preparation of area to be welded, method of application of preheat, reference welding procedure specification and NDE procedures.


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The CONTRACTOR shall report all repair work to ADWEA/ENGINEER and repair work shall only proceed with ADWEA/ENGINEER authorisation. Acceptance of all repair work shall be subject to ADWEA/ENGINEER approval.

6.9.2

Minor Surface Repairs Minor surface imperfections may be removed by grinding provided that the wall thickness is not reduced locally by more than 12.5% of the nominal value specified or the minimum design thickness whichever is greater and the minimum wall thickness is maintained, which will be verified by ultrasonic thickness survey. The ground area shall be dressed to a uniform and smooth profile with no sharp corners or notches. The ground area shall be examined by MPI or dye-penetrant examination to ensure that the defects have been completely removed.

6.9.3

Repairs Involving Welding Any defect that cannot be removed by surface grinding shall be repaired by welding. Any defect exceeding acceptance criteria of this specification shall be carefully removed by grinding. The excavation shall extend at least 25mm beyond both extremities of the defect without substantial removal of the base metal and shall be done in such a manner that the remaining weld or base metal is not nicked or undercut. The grooves shall be free from scale, have a smooth contour to facilitate welding. Surface should be ground to a smooth, bright metal surface. The ground area shall be carefully examined visually and then by MPI or dye-penetrant examination prior to commencement of re-welding to ensure that the defect has been completely removed. The area to be repaired shall be pre-heated to at least 50 deg.C above the temperature specified in the corresponding initial welding procedure but shall not exceed the maximum interpass temperature. Repair welding shall be carried out using the approved repair welding procedure. The CONTRACTOR shall take appropriate care such as proper weld sequencing, control of interpass temperature etc. to minimize residual stresses. All repair welding shall be carried out by qualified welders. If any repairs are carried out after PWHT or hydrostatic test, the PWHT and hydrostatic test shall be repeated. Planar defects such as cracks etc. shall not be permitted. Such joints containing cracks shall be cut out.


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6.9.4

NDE of Repair Welds All areas repaired by welding shall be thoroughly cleaned free of slag, spatter etc. and ground to a smooth contour with the parent material and existing weld taking care that over-grinding does not occur. The repaired weld shall be subject to 100% visual examination and then NDE by the same techniques used for the original examination. The acceptance criteria shall be the same as for the original welds. A weld with defects may be only repaired twice. If the repair is not acceptable after the second repair, the complete weld shall be removed, rebevelled, re-welded and re-examined.

6.9.5

Limitations on Repairs Repairs shall be limited to 30% of the weld length. For internal repairs or external repairs which open the root, only 20% of the weld length shall be repaired. Repairs opening the root shall only be carried out in the presence of ADWEA/ENGINEER. The minimum length of a repair area shall be 25 mm. If the repairs cannot be carried out without exceeding these limitations, or not carried out successfully, the weld shall be cut out.

6.9.6

Additional Acceptance Criteria Defect Acceptance levels shall be as per ASME B31.3 Hollow bead porosity and concave root shall not be permitted. Visual Acceptance standard for undercutting length shall be as per API 1104, Section 6.7 The CONTRACTOR shall have the various inspection stages witnessed and reports reviewed by ADWEA/ENGINEER. "Acceptance" by ADWEA/ENGINEER does not relieve the CONTRACTOR of his responsibility to fulfill his contractual obligations.

7.

VENDOR DOCUMENTATION The as-built QC dossier shall include the following: (a) Material identification/traceability reports for each item in the contract drawings. (b) Mill certificates of all materials giving the chemical composition and mechanical properties. (c) ADWEA/ENGINEER approved procedure specifications (WPS) (d) ADWEA/ENGINEER approved Procedure Qualification Records (PQR) along with backup NDE and mechanical test reports. (e) List of Qualified Welders and Welder Performance of Notification Certificates. Client Project: Title:

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(f)

NDT reports.

(g) As-built drawings. (h) Weld identification drawings. (i)

NDT summary control sheets, which show weld numbers, type and extent of NDT for each weld, report numbers for each weld identification drawing and welding date.

(j)

Heat treatment reports and charts.

(k) Dimensional inspection reports. (l)

Hydrotest reports.

(m) Blasting and painting reports.


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