When to Inspect Welding?

Inspection is a critical part of all welding operations. Knowing when to do the inspection and what to look for as well as what the acceptable criteria of the particular specification or code. These are some of the things we need to concern ourselves with when we do welding inspection. Welding inspection should be done before, during and after welding operations.

Before we start to weld there are number of things that we should check. We should check that the preparation of the material for welding is done correctly and in accordance with the drawings. If there is a welding procedure specification, we should also check that to make sure that the joint configuration and materials prep is compliant with respect to that document. We should check the material and make sure that it is clean and free of rust, grease, paint, oil or any other residue or surface contaminants that may affect weld quality. We should also check and make sure that we have the right welding rod according to the welding procedure specification. We should check and make sure that the base material matches the requirements and the bill of materials on the drawing. We should also check and make sure the proper shielding gas and any other welding variables that affect quality are correct, and do not start unless everything has been checked and properly approved. We should check and make sure the welder has been properly qualified too.

There are a number of features and things that we should check during the welding process also. We should check and make sure the weld is free of discontinuities. We should make sure that the proper cleaning is being performed between individual passes. We should make sure that the proper inter-pass temperatures are not exceeded. We should check and make sure that no cracks are present as well. Sometimes we have to do additional inspection other than visual inspection in the process of making weld. For example, sometimes we have to do magnetic particle inspection or die penetrant inspection following the initial root pass of some joint configurations.

After we get done welding we should take one last critical look at the weld and make sure that it meets or exceeds all the requirements of the drawing and welding procedure specification. We should make sure the weld metal is well bonded to the base material. We should make sure that the porosity does not exceed the acceptable criteria. Any size requirements should be checked using the proper gage or tool. If there is any post weld heat treatment the weld should be checked after that as well. If there is any nondestructive testing requirements we should also perform those as well in accordance with the specifications. For example if the drawing says RT in the tail of the welding symbol that means radiographic testing or an x-ray of the weld must be performed. If we see the symbol PT in the tail of the weld a penetrant test must be performed. If MT appears in the tail of the symbol magnetic particle testing must be performed. If the drawing invokes the requirements of a CWI, a certified welding inspector must inspect the part in accordance to the respective code requirements.

It's always important to do welding inspection before during and after welding. It is important for the welder to understand the inspection requirements because the fact the welder when they raise their hood or take off their goggles are the first person to inspect the weld and they should be our first line of defense in quality control issues.



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