With our thanks to Hennie de Wet.

Memo to Techs – No. 3

Good day everybody.

Penetrant testing is a relatively simple method and the practical application is basic, but it is the one method that is easily ruined.

Recently the client was not happy with the following statement on the report:

“Limited sensitivity due to the surface being corroded before the inspection.”

The client argued that the test surface was wire brushed before the PT inspection. True, but any cracks open to the surface would have been filled with corrosion. No amount of wire brushing will remove corrosion from a crack.

This is only accomplished with proper chemical etching. A time consuming, dangerous and expensive exercise.

The only way to get reliable results is to perform the Penetrant Inspection soon after the weld is completed and before corrosion sets in.

A lack of control in the manufacturer’s workshop will inevitably lead to you being requested to test a corroded part with PT.

RECOMMENDATION

Ask the client if you can do MPI on the welds instead of PT. MPI has no problem finding cracks filled with corrosion or paint, and it is faster. Explain to the client why you would like to deviate from the procedure.

You may have to go through the whole exercise of getting a procedure drawn-up and the rest. But the end result is a test that will find all possible defects and you can sign off the report with confidence.

Thanks guys.

Keep up the good work.

Hennie de Wet