Welding Inspection Handbook PDF

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WELDING INSPECTION HANDBOOK

Introduction Duties of the Welding Inspector Welder Qualifications Procedure Qualification Records Welding Consumables Pre-Heat and Post Heat Treatment Fabrication Welding Gases Welding Symbols Safety in Welding Conversion Tables & General Information

2 3 15 36 50 63 79 90 92 96 100

Quality Department 1

Duties of the Welding Inspector Introduction This handbook has been prepared to provide PEC welding QC and construction personnel with a set of general inspection guidelines and technical information to ensure a consistent Quality of construction works on all E&C projects.

It is the duty of the welding inspector to ensure that all operations concerning welding are carried out in accordance with written, approved procedures and specifications. The responsibilities of a welding inspector are given below: Read and interpret all applicable welding drawings and specifications. Check purchase orders to ensure that welding materials and consumables have been properly specified. Check and identify materials as they are received against the purchase specifications Check the chemical compositions and mechanical properties shown on mill test reports against specified requirements. Check storage condition of filler materials Check equipment being used (calibration status, visible condition...) Check weld joint preparations Verify the maintenance of welding parameters (current/voltage/heat input as applicable) at random. Check joint fit-up Verify application of approved welding procedure

Received By: ………………………………….. Date: …………………………………………….

Verify qualifications of welders and welding operators Select production test samples as applicable Evaluate test results- Destructive & Non-Destructive Maintain records Prepare reports

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3

Duties of the Welding Inspector Knowledge of drawings & specifications: • Advance study of drawings & specifications, construction in detail, MOC, welding procedure, heat treatment • Obtain necessary clarification/details from Design/Project engineer

Duties of the Welding Inspector Storage of filler material & welding equipment check: • Check storage conditions, e.g. Low Hydrogen Electrode baking / holding • Check welding machine type, its capability, calibration of ammeter, voltmeter Weld joint preparation:

This will help in: • Precise interpretation & decision during inspection • A Permitting or rejecting deviations observed • Decide feasibility of correcting error/deviation for large component • Determining specifications which are not defined. Material Verification:

• Check edge preparation for joint for: - Probable lamination - Bevel angle, root face - Preferable to have gauges • Cleanliness (free of oxidation, oil/grease) Qualification of Procedure & Welders:

• Advance study of drawings & specifications, construction in detail, MOC, welding procedure, heat treatment. • The specification for raw material e.g. ASTM A 106 Grade? • Consumable like electrode e.g. E 70 XX • Shielding gas, backing material • As far as possible ensure that original markings are preserved • Transfer identification marks before cutting, when required • Sometimes may be necessary to preserve electrode cases packets with original batch number.

• Establish written welding procedure specifications • Qualify procedures based on various WPS • Qualify welders based on various WPS • Verify records of validity • Interpret qualification ranges

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5

Duties of the Welding Inspector

Duties of the Welding Inspector Documentation

Inspection before Welding: Safety Ensure that all operations are carried out in compliance with local, company or National Safety regulations. If he sees unsafe practices he should stop the work and report the incident. Documentation • Read and understand the project specifications and relevant codes. If in doubt ask your superior. • Check that the correct revision of the drawing is used. • Check WPS’s and welder qualifications for approval. • Welding and related equipment has required calibration certificates, stickers. • Inspection instruments are calibrated as required. • Incoming materials, piping, fittings, welding consumables are the correct type and grade. They are stored correctly and have the required certification. • Material composition & condition of material • Type of edge preparation, method and finish

6

• Consumable types i.e. electrodes, filler wires, fluxes, shielding and backing gases (composition) and special drying requirements for electrodes. • Welding processes • Cutting, Bevelling and Fit-up. • Check correct revision of drawing. • Heat no’s material and colour codes are transferred and recorded as required. • Correct method of cutting (pre-heat may be required prior to cutting). • Correct joint geometry as per the WPS. • Required pre-heat prior to tack welding. • Correct distortion precautions, number of tacks, jigs, line up clamps. • Qualified welder for tacking. Inspection during Welding: • Qualified welder for tacking. • Welding process • Weather conditions, is the weldment suitably protected from the elements. • Correct pre-heat and inter-pass application and maintenance. 7

Duties of the Welding Inspector Inspection during Welding: • • • • •

• •

• • •

Duties of the Welding Inspector Inspection after Welding:

Joint preparation Filler metals Control of distortion Qualified welder. Welding consumables are the correct type, not damaged and are stored correctly i.e. heated quivers or Vacuum packs. Welding and/or purging gas (type, flow rate, control method). In process inspection, welding parameters comply with WPS (volts, amps, travel speed, heat input for impact tested steels). Inter run cleaning, dedicated tools for corrosion resistant alloys. Maximum or minimum inter pass temperature, temperature and control method. Compliance with weld procedure sheet and applicable standard.

• Visual inspection of acceptable joint as per the appropriate specification. • Dimensional accuracy & conformity to drawings and specifications Inspection after Welding: • Weld is correctly numbered. • Welder(s) have marked the joint with his/there stamp numbers. • NDE as required (method, technician qualified, executed correctly) • Identify repairs from review of visual and NDE reports. • Repair area is marked correctly and welded with an approved welder and WPS. • Re-inspect after repair with visual and NDE. • Post weld heat treatment (PWHT), approved procedure. • Re-inspect with NDE after PWHT if required. • Collate reports and log the results.

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Duties of the Welding Inspector

Duties of the Welding Inspector

Summary of Weld Defects-Causes & Prevention

2- Porosity:

1- Cracks:

Causes:

Causes: • Hydrogen in the weld metal and/or heat affected zone introduced either through moisture in the welding consumable or shielding gas. Poor preparation of the base metal prior to welding, all rust, grease, mill scale should be removed and the weld preparation cleaned to bright sound metal. • Insufficient weld size. • High levels of joint restraint. • Poor joint design and/or preparation. • Rapid cooling rates. Prevention: • Make sure that consumables are correctly treated and stored. • Make sure the weldment is clean prior to welding. • Increase the weld size to part thickness. • Reduce joint restraint through proper design. • A more ductile weld metal may be required. • Slow down the cooling rate, by use of pre-heat and thermal insulation after welding. 10

• • • • • • •

Weldment is not cleaned correctly. Arc length is too long. Welding current is too high. Travel speed is too high. Loss of gas shielding. Damp or incorrectly treated electrodes. High solidification rate

Prevention: • Make sure the weldment is clean prior to welding. • Maintain proper arc length. • Use proper welding current for the size of consumable used, as specified on the WPS. • Reduce travel speed, as specified on the WPS. • Check the weldment is protected from wind and draughts. • Check shielding gas flow rate is in compliance with the WPS. • Check consumables are treated and stored required by an approved procedure. • Pre-heat or increase heat input to optimum

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Duties of the Welding Inspector

Duties of the Welding Inspector

3- Undercutting:

4- Lack of Fusion/Lack of root fusion:

Causes:

Causes:

• • • • • •

Amperage too high. Arc length is too long. Travel speed too high. Poor electrode manipulation. Inter pass temperature is too high. Arc blow with DC current.

Prevention: • Use proper welding current for the size of consumable used, as specified on the WPS. • Maintain proper arc length. • Reduce travel speed, as specified on the WPS. • Correct technique especially when weaving, qualified welder. • Use the max interpass temperature as specified on the WPS. • Make sure earth return lead is connected directly to the weldment.

• Travel speed to high • Amperage too low • Faulty joint preparation, root face too wide, root gap too small • Too large an electrode diameter • Loss of shield gas • Wrong electrode angle • Arc blow 11

Prevention: • Use correct travel speed as specified on the WPS. • Use proper welding current for the size of consumable used, as specified on the WPS. • Check joint geometry as specified on the WPS prior to welding. • Use the correct diameter electrode. • Check shield gas flow rate; make sure the welding area is protected from the elements. • Use proper technique and qualified welders. • Make sure earth return lead is connected directly to the weldment.

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Duties of the Welding Inspector

Duties of the Welding Inspector

5- Slag Inclusions:

6- Excess Penetration/Burn Through:

Causes:

Prevention:

• • • • •

Poor interpass cleaning. Excessive weaving. Erratic travel speed. Poor joint geometry. Uneven weld surfaces with sharp crevices

• Root gap as specified on the WPS • Root face as specified on the WPS • Correct amperage as per the WPS • Correct travel speed as per WPS • Welder training and qualification

Prevention: • • • • •

Proper cleaning methods between passes. Keep bead width to that specified on the WPS. Keep travel speeds in compliance with WPS. Make sure bevel angles are as specified on the WPS. Make the surface of smooth contour and grind uneven bead

6- Excess Penetration/Burn Through: Causes: • • • • •

Welder Qualifications Welder performance qualification tests are intended to determine the ability of welders and welding operators to make sound welds using an approved welding procedure. Required tests and ranges of qualification are dependent on the construction code used. Summarized below are the requirements of the two most commonly used Codes, ASME Section IX and API 1104. These requirements may be supplemented by additional project specification requirements.

Root gap too wide Root face too narrow Amperage too high Travel speed too low Poor technique 14

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Essential Variables Manual & Semi Automatic GTAW

ASME IX Welder Qualification Summary Essential Variables SMAW Para QW-402 Joints QW-403 Base Metal

QW-404 Filler Metal

QW-405 Positions

Para

Brief of Variables .4

QW-402 Joints

Backing

-

.16

Change in Pipe Dia.

.18

Change in P-No.

.15

Change in F-No.

QW-403 Base Metal

QW-404 Filler Metal

.30

Change in t weld deposits

.1

+ Position

.3

Change

QW-405 Positions QW-408 Gas QW-409 Electrical

Brief of Variables - Backing

.4 .16

Change in Pipe Dia.

.18

Change in P-No.

.14

+/- Filler

.15

Change in F-No.

.22

+/- Inserts

.23

Change from solid or metal cored to flux cored.

.30

Change of t weld deposit.

.1

+ Position

.3

Change

.8

- Inert Backing

.4

Change in Current or Polarity

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QW-452 Performance Qualification Thickness Limits & Test Specimens

QW-452 Performance Qualification Thickness Limits & Test Specimens

Type and Number of Examinations and Test Specimens Required

Thickness of Weld Metal in (mm)

Visual Examination QW-302.4

Less than 3/8 (10)

X

Side Bend QW462.2 Note 1

Face Bend QW462.3(a) or QW462.3(b) Notes 1 & 2

Root Bend QW462.3(a) or QW462.3(b) Notes 1 & 2

1

1

General Note: The “Thickness of weld metal is the total weld metal thickness deposited by all welders and all processes in the test coupon exclusive of the weld reinforcement. Notes: • To qualify using 5G or 6G, a total of four bend specimens are required. To qualify using a combination of 2G and 5G in a single test coupon, a total of six bend specimens are required. See QW-302.3. The type of bend test shall be based on the weld metal thickness. • Coupons tested by face and root bends shall be limited to weld deposits made by one welder with one or two processes or two welders with one process each. Weld deposit by each welder and each process shall be present on the convex surface of the appropriate bent specimen.

3/8 (10) to less than ¾ (19)

X

2 Note 3

¾ (19) and over

X

2

• One face and root bend may be substituted for the two side bends.

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19

Note 3

Note 3

QW-452.1(b) Thickness of Weld Metal Qualified Thickness t of weld metal in the coupon, in (mm) Notes 1 & 2

Thickness of weld metal qualified Note 3

• Thickness of test coupon of ¾” (19mm) or over shall be used for qualifying a combination of three or more welders each of whom may use the same or a different welding process.

All

2t

QW-452.3 Groove Weld Diameter Limits

½ (13) and over with a maximum of three layers

Maximum to be welded

Notes: • When more than one welder and/or more than one process and more than one filler metal F-No is used to deposit weld metal in a coupon, the thickness t, of the weld metal in the coupon deposited by each welder with each process and each filler metal F-No in accordance with the applicable variables under QW-404 shall be determined and used individually in the: Thickness t of Weld Metal in the Coupon” column to determine the “Thickness of Weld Metal Qualified”.

Outside Diameter Qualified in (mm) Outside Diameter of Test Coupon in (mm)

Minimum

Maximum

Less than 1 (25)

Size Welded

Unlimited

1 (25) to 2 7/8 (73)

1 (25)

Unlimited

Over 2 7/8 (73)

2 7/8 (73)

Unlimited

General Notes:

• Two or more pipe test coupons with different weld metal thickness may be used to determine the weld metal thickness qualified and that thickness may be applied to production welds to the smallest diameter for which the welder is qualified in accordance with QW-452.3.

• Type and number of tests required shall be in accordance with QW-452.1 • 2 7/8 in (73) OD is equivalent of NPS 2 ½ (DN65). • Based on the above diameter limits a NPS 2” test coupon qualifies for a min diameter of NPS ¾”.

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QW-452.6 Fillet Qualification by Groove Weld Test

QW-452.5 Fillet Weld Test (Performance)

Type of Joint

Any Groove

Thickness of Test Coupon as Welded in (mm)

Qualified Range

Type and No. of Test Required

All

Fillet welds are qualified when a welder/operator qualifies on a groove weld test

All Thicknesses

Type of Joint

Thickness of Coupon as Welded in (mm)

3/16-3/8 (5-8) Tee Fillet Less than 3/16 (5)

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Qualified Range

All base material thicknesses, fillet sizes and diameters 2 7/8 (73) OD and over. Note 1 T to 2T base material thickness, T max fillet size and all diameters 2 7/8 (73) OD and over. Note1

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Type and Number of Test Required QW-462.4(b) or QW-462.4(c) Macro

Fracture

1

1

1

1

QW-452.5 Fillet Weld Test (Performance) General Note: • Production assembly mockups may be substituted in accordance with QW-181.2.1. When production assembly mockups are used, range qualified shall be limited to the fillet size, base metal thicknesses and configuration of the mockup. Note: • 2 7/8 in. (73mm) O.D. Is considered the equivalent of NPS 2 ½ (DN65). For smaller diameter qualifications, refer to QW-452.4 or QW -452.6. • ASME Section IX permits welders and welding operators to be qualified by radiography as an alternative to visual examination and mechanical testing, provided the following conditions are met.

QW-302.2 Radiographic Examination • When the welder or welding operator is qualified by radiographic examination, as permitted in QW-304 for welders and QW-305 for welding operators, the minimum length of coupon(s) to be examined shall be 6 inches (150mm) and shall include the entire weld circumference for pipe(s), except that for small diameter pipe, multiple coupons may be required, but the number need not exceed four consecutively made test coupons. The RT technique and acceptance criteria shall be in accordance with QW191. QW-304 Welders • Except for the special requirements of QW-380, each welder who welds under the rules of the Code shall have passed the mechanical and visual examination prescribed in QW-302.1 and QW-302.4 respectively. Alternatively welders making a groove weld using SMAW, SAW, GTAW, PAW and GMAW (except short circuiting mode) or a combination of these processes, may be qualified by radiographic examination, except for P21 through P25, P51 through P53 and P61 through P62 metals. Welders making groove welds in P21 through P25 and P51 through P53 metals with the GTAW process may also be qualified by radiographic examination. The radiographic examination shall be in accordance with QW-302.2.

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QW-321 Retests

QW321.3 Immediate Retest Using Radiography

• A welder or welding operator who fails one or more of the tests prescribed in QW-304 or QW-305, as applicable, may be retested under the following conditions.

• When the qualification coupon has failed the radiographic examination of QW-302.2 the immediate retest shall be by the radiographic examination method.

QW-321.1 Immediate Retest Using Visual Examination • When the qualification coupon has failed the visual examination of QW-302.4, retesting shall be by visual examination before conducting the mechanical testing. When an immediate retest is made, the welder or welding operator shall make two consecutive test coupons for each position which he has failed, all of which shall pass the visual examination requirements. The examiner may select one of the successful test coupons from each set of retest coupo...