Welding Procedure and performance qualification – ASME Section IX
Welding Procedure Specification (WPS)
A Welding Procedure Specification (WPS) is a written document that provides detailed instructions to the welder for making production welds in accordance with code requirements. Every WPS must be qualified by the manufacturer. It outlines the conditions (ranges) under which welding must be performed, known as variables. The WPS addresses essential, supplementary essential, and non-essential variables.
Purpose of WPS Qualification
The purpose of WPS qualification is to ensure that the weldment can provide the required properties for its intended application. WPS establishes the properties of the weldment, rather than evaluating the skill of the welder.
Procedure Qualification Record (PQR)
A Procedure Qualification Record (PQR) documents what occurred during the welding of the test coupon and the results obtained from it. The PQR records the essential variables, specific information, and results of the required testing. Additionally, when notch toughness is required for procedure qualification, the applicable supplementary essential variables must be recorded.
A PQR is a record of the welding data used to weld a test coupon and also contains the test results. A completed PQR must document all essential variables, including their ranges. The PQR must be certified as accurate and cannot be subcontracted. If more than one welding process is used, the weld deposit thickness for each process and the filler metal must be recorded.
Multiple WPSs and PQRs
Several WPSs can be derived from a single PQR. For example, a 1G plate PQR can support WPSs for 2G, 3G, 4G, pipe 5G, and 6G, as long as other parameters remain the same. Conversely, a single WPS can cover multiple PQRs. For instance, a WPS might cover a thickness range of 1.6 mm to 32 mm if there are PQRs for the ranges 1.6 to 4.8 mm and 4.8 to 32 mm.
Weld Orientation
- Plate Groove Positions: 1G, 2G, 3G, 4G
- Pipe Groove Positions: 1G, 2G, 5G, 6G
- Plate Fillet Positions: 1F, 2F, 3F, 4F
- Pipe Fillet Positions: 1F, 2F, 2FR, 4F, 5F
- 1F: 0° to 30°
- 2F: +15° to -10° with respect to 45°
- 4F: 0° to 125°
- 3F: 125° to 235°
Base Metal Classification
P numbers are based on composition, weldability, and mechanical properties. Group numbers categorize metals within P numbers for procedure qualification when notch toughness requirements are specified. However, base metals cannot be substituted indiscriminately.
Conclusion
In summary, the qualification and documentation of Welding Procedure Specifications (WPS) and Procedure Qualification Records (PQR) are critical steps in ensuring the quality and reliability of weldments for their intended applications. WPSs provide clear guidance to welders and define the essential variables for welding processes, while PQRs record the welding data and test results to confirm that the required properties are achieved. The ability to derive multiple WPSs from a single PQR, and to cover multiple PQRs with a single WPS, offers flexibility and efficiency in welding operations. This comprehensive approach ensures that weldments meet the necessary standards and perform as expected in their designated roles.
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