Part of the barrier to achieving better quality weld repairs is the problem of how to determine whether a welder is competent to carry out the required crack repair.
Traditional “Welder Qualification” testing is typically carried out using a generic welder qualification process as per AS2980 or ISO9606. Via these standards, the qualification is based on butt weld and fillet welds made in plate sections with perfect weld preparations. This purpose of these standards is fundamentally to determine whether a welder has the required skill to manipulate the welding torch/electrode to achieve a satisfactory weld when following a Welding Procedure Specification (WPS), with the assumption that the welder should then also be able to do any “easier” welds.
The problem with this “qualification” method is that it does not simulate a repair, which requires crack removal via carbon arc gouging and then achieving a suitable weld preparation prior to welding. Furthermore, crack repairs are typically highly variable in geometry and are very different from fabrication using machined weld preparations. Crack removal via gouging and then achieving a good weld preparation are crucial skills for crack repairs. Another issue is that Welder Qualifications are usually performed using a backing strip for the overhead butt weld. The use of backing strip in crack repairs is highly undesirable due to the poor fatigue properties. It is therefore preferred if full thickness single sided crack repairs (such as in hollow structures like a Boom or Chassis) are carried out using a good quality open root weld.
Lastly, there is the issue of the level of welder knowledge required. Most structures are fabricated to be compliant to a design standard, with the welding carried out to comply with AS1554, using qualified WPS’s with a Welding Supervisor present. The welder is required to follow and use the parameters specified in the WPS for each joint type. In comparison, most repairs of equipment on mine sites are carried out with no welding procedures. Therefore, the welder must be able to select the appropriate/optimum welding parameters without reference to a WPS. The welder must also be able to identify the material type, know the best repair methodology, understand about fatigue cracking and residual stresses, and be able to apply this knowledge to achieve an effective repair.
That’s why we have developed Mining Welder Competency. The Mining Welder Competency consists of a combination of theory training to increase a welder’s knowledge, and practical assessment whereby the welder must demonstrate their proficiency and safety in using the welding processes, and apply their knowledge and repair welding skills via a test coupon. The test coupon simulates a range of difficulty in actual repair requirements. Welders will be classed from Level 1 to Level 3. We provide access to an online Portal for the Welder Competency records. This means that the right welder can be assigned to the job to ensure that the repair is done right.
Click on the button below to go to the main Mining Welder Competency website. www.miningweldercompetency.com