Welder Performance Qualification (WPQ) also known as Welder Qualification Test (WQT) or Performance Qualification is a very basic but one of the most important steps before assigning a job to the welder. The welder qualification test (WQT) is performed to determine the skill of a welder, in other words, we can say that the welder performance qualification is carried out to check whether the welder or the welding operator can produce a sound weld or not.
How the performance qualification test is carried out?
First of all a test piece also known as test coupon is prepared as per the requirements of the approved WPS then the welder is asked to weld the test coupon in accordance with the qualified welding procedure specification (WPS). Initial Inspection: Soon after completing the root run, a visual inspection is conducted to check for any signs of lack of fusion, lack of penetration or any surface defects then LPT (DPT or PT) can be performed (if required by the procedure). Proceeding with welding: If the root run passes the inspection, then welder is allowed to proceed further. After completion of the entire welding, which includes the fill-up and final run, another visual inspection is performed, along with Liquid Penetrant Inspection (LPI) or Magnetic Particle Inspection (MPI) as per the requirements of the procedure, If the test coupon is satisfactory then it is sent for RT or DT for final testing. Final Testing: Once the test coupon is finalized, it is sent for further evaluation through Radiography test – RT (or Ultrasonic Test – UT) or Mechanical tests depending on the requirements. After a satisfactory test report, A certificate and Identity card shall be issued to the welder and he may be employed for production welding (or fabrication welding). These are the general steps followed in most of the industries for the qualification of the welders in groove welding.
The 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
- Filler metal/Electrode
Welding Procedure Specification: All 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 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. The thickness of the weld metal deposit and the size of the test coupon: The thickness of the deposited weld metal is very important because of the following two things;
- It determines the performance qualification thickness range i.e. up to what thickness the welder can weld. AWS D1.1 and ASME BPVC Section IX are two widely used welding codes. In ASME BPVC Section IX the performance qualification thickness limit for groove weld is given in Table QW452.1(b), and the outside diameter range for groove weld is given in Table QW452.3. The thickness range is explained later in this article.
- The length and width of the test coupon shall be sufficient enough for the final test (i.e. Radiography or Mechanical test).
Thickness Range or thickness limit for welders:
The qualified thickness limit is specified in Table QW 452.1 (b) of ASME Section IX. This table outlines the maximum thickness range that a welder is permitted to weld, based on the amount of weld metal deposited during their qualification test. A simplified version of Table QW 452.1 (b) is given below;
| Thickness "t" of Weld Metal in the Coupon in mm (in.) | Thickness of Weld metal Qualified |
|---|---|
| All | 2t |
| 13 mm (1 /2 in.) and over with a minimum of three layers | Maximum to be welded |
Note: Here the word “Maximum” means, the welder can weld up to any thickness but not beyond the range specified in the welding procedure specification.
Based on the information provided in the table, three important points can be highlighted:
- Maximum Weldable Thickness: A welder is allowed to weld a maximum thickness of 2T, where T represents the thickness of the weld metal deposited on the test coupon by that welder during the qualification test.
- Minimum Thickness Criteria: There are no specified criteria for minimum thickness.
- Qualification for Unlimited Thickness: If a welder deposits weld metal that is 13 mm or thicker (with a minimum of three layers), they qualify for unlimited thickness. However, the maximum thickness they can weld must not exceed the limits specified in the Welding Procedure Specification (WPS) range.
Important Notes:
- When using multiple welders, processes, or variables, measure and record each weld metal thickness individually to determine the qualified thickness.
- Use multiple pipe test coupons with varying thicknesses to establish the maximum qualified weld metal thickness, which can be applied to production welds meeting the diameter requirements in Table QW-452.3.
- For test coupons 3/4 in. (19 mm) or thicker, a combination of three or more welders can take qualification test using the same or different processes.
Diameter limits (OD) for welders:
The qualified outside diameter (OD) limit for groove welding in pipes is specified in Table QW 452.3 of ASME Section IX. A simplified version of that table is given below;
| S.N. | Outside diameter (OD) of the test coupon in mm (inches) | Qualified Outside diameter (OD) in mm {inches) | |
|---|---|---|---|
| Minimum OD | Maximum OD | ||
| 1 | OD Less than 25 mm (1") | Size welded | Unlimited |
| 2 | 25 mm (1") to 73 mm (2-7/8") | 25mm (1") | Unlimited |
| 3 | More than 73 mm (2-7 /8") | 73mm (2-7 /8") | Unlimited |
Position of the test coupon:
For plate welding, we have four different welding test positions flat, horizontal, vertical & overhead 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 the 2G position then he can weld in horizontal (2G) and flat (1G) positions 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 positions the welder needs to weld in 3G and 4G positions only. For the Limitation on positions, one can refer to Table QW 461.9 of ASME Section IX. Welder Qualification Test in 6G Position:
In the 6G test position, the test coupon is made up of pipe and it is kept at an angle of 45 degrees from the horizontal line. The test coupon remains fixed (at 45 degrees) and the welder moves in all directions to complete this welding. It is one of the toughest qualification tests for welders and If a welder successfully completes this test then he/she shall be qualified in all positions. Hence a 6G qualified welder can be employed for all position welding.