Welder Performance qualification (WPQ) is also known as welder qualification test (WQT) or Performance qualification test. Welder qualification test is a very basic and most important step before assigning the job to a welder. The welder qualification test (WQT) is done to determine whether the welder or the welding operator can produce a sound weld or not. Each welder or welding operator shall be qualified for each welding process to be used in production (or fabrication) welding. The welder is required to weld a test coupon in accordance with the qualified welding procedure specification (WPS), the test coupon is then send for Radiography test or Mechanical test (as per the requirements of the applicable code). After satisfactory test report the welder may be employed for the production welding (or fabrication welding). Following important factors shall always be considered before conducting the welder qualification test (WQT);
- Welding Procedure Specification (WPS)
- Welding Process
- Size of test coupon
- Position of the test coupon
Welding Procedure Specification: All the welding parameters viz. welding current, voltage, base metal, filler/electrode etc. shall be in accordance with the qualified welding procedure specification.
Welding Process: For each welding process a welder has to be qualified separately. Suppose if a welder qualifies for SMAW then he shall be employed only for SMAW welding. In case if our requirement is MIG welding then the same welder will have to weld a different test coupon by MIG welding process then only he can be allowed for MIG welding.
Size of the test coupon: Size of the test coupon is very important because of two things:
It determines the performance qualification thickness limits i.e. upto what thickness the welder can weld. For example, if a welder qualifies with a 10” thickness plate then he can weld upto a maximum of 20” thickness (as per AWS D1.1). Two very widely used welding codes are AWS D1.1 and ASME BPVC Section IX. In ASME BPVC Section IX the performance qualification thickness limit for groove weld is given in ASME BPVC 2017 edition, Table QW452.1(b) and outside diameter range for groove weld is given in ASME BPVC 2017 edition, Table QW452.3.
- Length and width of the test coupon shall be sufficient enough for the final test (i.e. Radiography or Mechanical test).
A brief summary of qualified thickness limit for groove welding (as per ASME BPVC Section IX, 2017 edition) is given below;
A brief summary of qualified diameter limit for groove weld in pipe (as per ASME BPVC Section IX, 2017 edition) is given below;
Position of the test coupon: For plate welding we have four different positions such as 1G,2G,3G,4G OR 1F,2F,3F,4F. For pipe welding also we have multiple positions for example 1G,2G,5G,6G OR 1F,2F,4F,5F. If the welder qualifies in 2G position then he can weld horizontal and flat welding only. On the other hand if the welder qualifies in 2G, 3G and 4G positions then he qualifies for all positions (As per ASME Section IX). Please note that there is a slight difference in AWS D1.1, for qualification in all position the welder needs to weld in 3G and 4G positions only. For Limitation of positions for welder qualification test (WQT), one can refer Table QW 461.9 of ASME Section IX, 2017 edition. To learn more about welding positions, please click here.
In addition to the above factors some more points shall be taken care of during welder qualification test (WQT):
- Preheating and post heating shall be as per the Welding Procedure Specification. The temperature shall be checked before starting the welding. To check the temperature one can use Pyrometer or Temperature chalk.
- Voltage and Amperage shall be maintained strictly as per the WPS, during the welder qualification test (WQT). To check the Voltage and Amperage we can use a Clamp meter.
- The Root run may be checked visually (or by using Dye Penetrent Test). If the welder qualifies the root run then only he can be permitted for further welding
After satisfactory radiography (or Mechanical test) report of the test coupon, A certificate and an Identity card shall be issued to the welder and the welder shall keep the Identity card with him and he shall show his Identity card if asked by the welding Inspector.
Also read: Welding Symbols
Also read: Welding Positions
Also read: P-number, F-number and A-number in welding