With our thanks to Hennie de Wet.
Good day everybody.
MPI tips, again.
We know the theory behind the 90 degree criss-cross technique. Clients look at this; they want to see you swing the yoke 90 degrees while testing. They want to see this because we Level III’s tell them that this is what good MPI technicians do.
Tip number two is something I am sure most of you know already, when working vertical, start testing from the bottom and work your way up. This ensures that the inspection area is clean and not covered in left-over ink.
I was embarrassed recently when a QA inspector told me that our technicians do not blow onto the weld when they perform MPI. I had to explain to him that we only blow when we need to clear excess ink from the weld or when we need to give the ink some extra mobility. When working vertical the ink runs off the weld anyway and there is no need to clear excess ink. He seemed convinced.
Tip number three. People, the QA inspectors know that a good blow comes with MPI. Give it to them. Seriously though, you are being watched. And when you get a bit light headed from all that blowing, take a short breather.
Tip number four is coverage. Recently an inspector asked me what the maximum side-way distance is that the yoke can test at a time. We call it the inscribed circle. Let’s say the inside distance between the poles of the yoke is 150mm, then the sideways area of inspection is also 150mm, like a circle.
When you move the yoke along the weld, swinging sweetly, remember to place the yoke so that you get proper coverage. A small area of overlap is recommended. Placing the yoke close to the previous inspection area means a bigger overlap, which is good, but it also means a slower inspection – not necessary.
Lastly. And this one will get your certification revoked immediately. Dragging an energised yoke down the length of a weld, while spraying ink. This is even worse than cowboy style. We call it idiot style. I will personally kick you off site.
Thanks guys.
Keep up the good work.
Hennie de Wet
