This procedure gives instruction for repair of weld that might be found defective and to be removed before welding in fabricating of vessel, structural & piping systems.
2. REFERENCE DOCUMENTS
- Project specification
- AWS D1.1 (*): Structural Welding Code – Steel
- ASME V (*): Nondestructive Examination
- ASME VIII DIV. 1 (*) : Rules for Construction of Pressure Vessel
- ASME IX (*): Qualification standard for welding and brazing procedures, welders, brazers, and welding and brazing operators
- ASME B31.3 (*) : Process Piping
- ASME B31.1 (*): Power Piping
(*) current edition.
- QC inspector who is in-charge of welding inspection shall notify the Production Supervisor who is in charge of production for the necessarily of repair of any defective weld.
- The Production Supervisor shall arrange to perform the required repair, and shall inform the QC Inspector for inspection of the completed repair.
- The QC Inspector shall arrange for inspection of the repair with same method and scope as for original weld.
- Either the QC Inspector or Production Supervisor may request QA/QC Manager to give more instruction for the repair when there is any doubt.
4. WORKING PROCEDURE
QC Inspector shall identify and mark the location of the defects. All defects shall be classified in the category of major or minor defects as follows:
MAJOR DEFECTS: All cracks of weld metal, planar defects or volumetric defects except crater crack.
a. Area of crack, planar defects or volumetric defects shall be excavated by grinding or gouging.
b. Only crack defects may drill both end of indication to stop developing expansion to other locations. An excavated area shall be at least 25mm beyond each end of the crack.
c. Excavated groove shall visually inspect to ensure that the defects had removed out. MT or PT methods may also support to detect the defect.
d. Welding procedure specification (WPS) shall be applied the same as original weld product or approval WPS by Client prior to repairing work.
e. Two-time repair attempts are allowed for (one) defect area. No further attempt to repair this area shall be performed without obtaining Client approval.
f. The repair area shall accomplish by the qualified welders.
g. The repair welding shall be subjected to test the same method as for the original weld product.
h. The second repaired location may be applied hardness test to mark sure the product welds do not except allowance hardness.
MINOR DEFECTS: Irregular surface by grinding, weld defects found during welding which can immediately repair.
a. Surface defects may be blend by grinding to provide that the joint component thickness is reduced by no more than the smaller of 1.0 mm or 10% of nominal thickness. Transition between the repaired areas and adjacent areas shall be smoothly required.
b. After completion of repair, the locations may be examined by PT or MT to ensure that the defects have been completely removed.
The repaired product welds shall update in the visual examination form or welding summaries form for traceable. Identification of repairing traceable by means “R1” – first repair, “R2” – second repair, “RW” – re-weld.