A welding quality control system starts with clearly defined and quality standards. These standards should be clearly communicated to the welders with providing appropriate training and equipment to meet those quality standards.
Welding is used to join two or more metal parts. Since these joints encounter loads and fatigue during their lifetime, there is a risk that they may fail if not welded to the proper specification. Quality control of the welding is an essential part of the steel fabrication quality control.
Weld quality control is the use of different methods and actions;
- To test or ensure the quality of welds,
- To confirm the presence, location and coverage of welds.
2. Acceptance Criteria
An acceptable weld should be defined as a first step in developing welding procedures. It should be determined to what level an allowance for discontinuities like porosity, undercut, reinforcement and overlap should be allowed. The acceptance criteria should set the minimum level of quality required for the weld.
Figure 1: Weld Quality Control
3. Procedure Qualification Records (PQRs)
After setting the Acceptance criteria welding procedures can be prepared. Procedure Qualification Record (PQR) is the record of the welding test parameters used. It is the fundamental document as far as welding procedures are concerned and is used to produce welding procedure specification sheets (WPS) for production welds. It is company dependent and never expires.
4. Welding Procedure Specification (WPS)
A Welding Procedure Specification, or WPS, is a guideline document for the effective creation of a weld that meets all applicable code requirements and fabrication standards. It is a recipe for welders which contains details that are necessary to create the desired weld. WPS includes information such as base metal grade, filler metal type, amperage range, shielding gas composition, and pre-heat temperatures. When a team of welders follow all the details on a WPS, they should each be able to produce welds with similar mechanical properties.
5. Welder Performance Qualification Records (WPQRs)
Once the procedure is approved it is necessary to demonstrate that all your welders working to it have the required knowledge and skill to make a satisfactory weld. If the welder has completed the procedure test then he will be considered approved but each additional welder must be approved by completing an approval test to an appropriate standard.
Regardless of having PQRs, WPSs, and WPQRs there might be situations where welding defects occur. An adequate inspection procedure is necessary to identify non confirming welds. This inspection should be starting with the welder since they were the first one who can inspect and identify in the early phases. Other personnel must also be involved which include welding supervisors, welding inspectors, quality personnel and others.