By Harry W. Ebert
Most Codes, such as ASME Section IX and AWS D1.1, permit the testing of weldors without imposing any space or access limitations. As indicated by Sketch “A”, weldors can perform their tests in the middle of an empty dance floor. That qualifies them to perform typical field welds in refineries, chemical plants and power plants such as the ones illustrated by Sketch “B”. Weldors confronted with such space and access limitations will encounter a high rejection rate unless they are trained and tested under realistic conditions.
Recognizing this inconsistency and the resulting quality problems, some organizations have added the following type of statement to their QA documents:
“Additional procedure and performance qualifications shall be performed whenever the accessibility or the working conditions of the Code qualifications fail to simulate the production conditions.”
In other words, the employment of mock-up test conditions is demanded.
While there are many designs for such mock-up test samples, Supplement
F to AWS QC7-93, “Standard for AWS Certification of Weldors,” represents
one option. It represents typical field welds on piperacks and in tight
spaces. When one field location implemented Supplement F, it took more
time to qualify their field weldors, but the rejection rate of pipe butt
joints dropped from about 25% to about 7 1/2%.