Quality System & Welding System
0.1 WELDING AND WELDING PROCESS CONTROL.
0.5.1 Welding Equipment: All the welding machines viz. welding generators, rectifiers, transformer details, are mentioned in "RESOURCES" attached.
0.5.2 Electrode Storage
Welding electrodes and wires are stored on platforms/racks off the floor in dry and ventilated covered storage to check deterioration.
0.5.3 weld Procedure Specifications (WPS) and Procedure Qualification Record (PQR) For individual fabricated and welded jobs, WPS is prepared as per ASME-SEC-IX/AWS D 1.1 Code after approval of WPS by competent authority/Client . Qualifying Tests are conducted on test samples prepared accordingly and PQR is maintained for the same. Competent authority of approval of WPS may be Customer, if required as per contract or QC dept. Of CORE FAB.
0.5.4 Welder Performance Qualification (WPQ) Qualified welders as per approved WPS do production welds. Qualification tests are conducted as per ASME Sec-IX / other applicable code. If required as per contract, tests are witnessed by Customer's representative.
0.5.5 Redrying of Electrodes. Low Hydrogen and other special electrodes require re-drying prior to production weld.Redrying is carried out at the temperature, as recommended by electrode manufacturers.CORE FAB has four nos. Portable dryers& one storage type baking oven.
0.5.6 Controlling the Welding Quality. Production welds in CORE FAB are done following qualified WPS and approved QAP. Welding process and welding quality at all stages during manufacturing as per acceptance criteria specified in the technical specification (TS) approved drawings, WPS and approved QAP. For information general check stages of welding are indicated below.
i) Pre Welding
- Checking of cabling voltage & current output of welding equipment as per requirement of the job.
- Raw materials preparation i.e., circularity, flatness straightness of the components to be welded.
- Edge preparation & joint fit-up i.e., angle, gap etc, as per approved drawings.
- Checking of re-drying of electrodes as required.
- Pre-heating temperature of job as per qualified WPS. If any. Also preheating checked by thermo pen.
ii) During Welding.
- Controlling inter-pass temperature as per WPS.
- Peening of heat affected zone (except root run final weld run) for relieve of residual stress.
- Root-pass Grinding/Back gouging.
- Dye penetration test, if required as per Qualified WPS.
- Checking of weld-heads by wire-brushing/chipping/grinding.
- Visual checking of finished Welding as per acceptance criteria of approved QAP and removal/rectification of spatter, undercut, pinholes or other surface flaws weld contours and sizes are also checked. Final welding Inspection (Visual) is to be checked as per Inspection parameter and procedure indicated in Annexure-1
- NDE of weld joints viz. Radiography testing (RT) Ultrasonic testing (UT) etc, as Required as per TC/approved QAP.
- Rectification of weld defects area, if any and rechecking by NDE method for Soundness.
- NDE of welding i.e., RT/UT/PT/MPT are all done by level-II qualified personnel as Per requirement of SNT-TC-1A of ASNT.
- Applicable procedure and acceptance standard of NDE of weld joints followed by CORE FAB are as mentioned in TC/Approved QAP/ Approved drawings.
Rectification of welds.
- Defective welds rectified as per repair procedure approved by Customer / Inspection agency or in absenceCORE FAB follows their own repair procedure indicated in Annexure-ii
5.7 Final Inspection.
Final Inspection of fabrication items mainly dimension checked on layout or control assembly condition as per approved customers drawings. Layout and dimension measured by calibrated measuring instruments.
FINAL WELDING INSPECTION (VISUAL)
1.0 Type of defects/ flaws :
1.1 Parent metal damage: Chipping of damage of parent metal due to removal of welded brackets/edges or by gas flame. These are to be spot-welded and grind smooth.
1.2 Cleaning of weld: Removal of slag and spatters to be done.
1.3 Surface crack: In the weld metal or in the parent metal adjacent to it.
1.4 Surface Flaws: Pin holes, undercut, UN fused welds, and excessive weld reinforcement.
1.5 Size /contours and finished under/oversize welds and convexity / concavity, uneven welds, unfilled crate, incompletely filled groove, unequal leg lengths, welding not done centrally.
2.0 Sizes of welds are to be checked by welding gauges. Acceptance criteria of weld size / surface flaws shall be as per drawing / technical specification or in absence, applicable standards viz. AWS 1.1 /IS 2825/ASME SEC-VIII and API 1104 etc.
REPAIR PROCEDURE OF WELD DEFECTS
1.1 Weld defects observed during visual inspection / pressure tests / NDT , shall be rectified by removing the defective materials by grinding/chipping/machining/flame gouging upto the sound metal. Adequate care is taken so that the above process of defective materials does not penetrate the parent metal to any substantial amount beyond the depth of weld penetration unless cracks or other defects exist in the parent metal. A crack or any other defects like lack of fusion/ lack of penetration etc , is removed throughout its length , to ensure that the whole of defect is removed. Material beyond 25 mm of each end is removed.
1.2 Weld of repaired portion after removal of complete defective material and ensuring by D P Test that the groove profile has reached the sound metal. Re welding is done following approved welding WPS