A welded construction applies, quality prescriptions concerning design production and use. Therefore clients in Petro and chemical industry claims approved welding procedures. Welding requires skill. Determining "how to weld" requires knowledge regarding the materials being welded and welding process, among numerous other factors. Because of huge number of variables involved, the knowledge of the welding engineer and the skill of the welder need to be validated by a series of tests.
This information is documented Section IX of the ASME Boiler and Pressure Vessel Code (BPVC), on:
- Welding Procedure Specification (WPS)
- Welding Procedure Qualification Record (WPQR)
- Welding Performance Qualification (WPQ)
Welding Procedure Specification
The Welding Procedure Specification is a required document for all code welding. Your customer either directly or indirectly specifies to what code your company must qualify. The WPS outlines all of the parameters required to perform your welding operation.
In short the WPS is the recipe for your welding operation. It describes the welding process or processes used, the base materials used, the joint design and geometry, gases and flow rates, welding position and includes all of the process conditions and variables. Each code has a recommended format.
Welding Procedure Qualification Record
The Welding Procedure Qualification Record is the document that qualifies the Welding Procedure Specification. In order to qualify your WPS, a procedure qualification plate is welded the code requirements. The actual test parameters are recorded at the time of welding to ensure the WPS was being followed. Generally any supporting documentation, such as material specifications, electrode specifications and shielding gas specifications, are included as part of the WPQR. All required testing, both non-destructive and destructive, is recorded as well. These tests typically include X-Ray examinations, ultrasonic examinations, tensile testing, bend testing and when required impact testing.
The WPQR combines all of the information of the WPS and adds the test results to provide a complete document that certifies the welding specification. This document is also required by all codes unless you are qualifying under American Welding Society (AWS) specifications. Under certain conditions the WPS may be considered prequalified in which the WPQR is not required.
Welder Performance Qualification
This document is required by all codes for all welders. It details and summarizes the following information: Indicates the WPS referenced during the qualification test Identifies the welder by name and/or clock number Lists what the essential parameters were during this test Reports the results of the required qualification tests Specifies qualified limits for welder For most codes there is a time limit associated with the welder qualification test.
However, the American Welding Society provides an unlimited qualification period if certain conditions are met. As with the WPS and WPQR, each code has a recommended format.