WELDER PERFORMANCE QUALIFICATIONS
Requirement of Welder Qualification
In performance qualification, the basic attempt is to establish the ability of the welder to deposit sound metal. In case of welding operator qualification it is his mechanical ability to operate the welding machine that is tested and acknowledged.
During welder's qualification, only the essential variables (as applicable to welder's skill) are considered and production welds with such altered variables should not be continued without additionally qualifying the welders. A welding machine operator usually gets qualified along with procedure test. Additional qualifications are to be suitably enforced as and when certain essential variables are not meeting.
Codes for Performance Qualifications and Acceptance of Defects
A large number of industrial codes now a days recognise prequalified welding procedures as t he manufacturing firms are able to produce the documentary evidence for such procedures as in vogue in their organisations. The selection, training and qualification of welders are the next few steps. Some of the popular codes to look for, at this juncture are:
- Indian Boiler Regulations - IBR
- ASME Boiler and Pressure Vessel Code - Section IX (Welding, Brazing & Soldering Qualifications)
- DIN 8560 - (Testing of Welders)
- BS 4872 - (Approval Testing of Welders when welding procedure approval is not required.
- ISO
- EN
There are also number of other specifications for welder testing, pertaining to individual codes of construction. A welder's plate test coupon can be maximum 300 mm x 400 mm with appropriate thickness to cover the allowed, specified thickness ranges. Similarly 2 pipes (or tubes) having a maximum of 125 mm length each are joined together for a pipe weld test coupon.
The test coupons are then subjected to radiography testing. Welders are outrightly failed for the following indications in the radiographic film. All other defects are acceptable within limits.
1. Severe root porosites / blow holes
2. Cluster of porosites
3. Cracks
4. Lack of fusion / incomplete penetration
After necessary post weld heat treatment the plates or pipes are marked, stamped, cut and machined into mechanical test specimens. Though, the requirements of the codes are slightly varied, 2 face bend tests and 2 root bend t ests alone are conducted for performance qualifications. In lieu of the above a radiographic evaluation is done.