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Measuring pitting

Measuring pitting

Measuring pitting

I have erossion pitting in an inch and a half diameter tube.  I need an easy method for measuring extend of pitting, to put a measurement value on failure/nonfailure of the part.  What kinds of easy, cheap measurement methods are available?

RE: Measuring pitting

You might want to try I.R.I.S inspection. I have used it to get an idea of the extent of oxygen pitting in boiler / economizer tubes. Contact your local NDE company to see if they offer the service. It is a form of nondestructive testing that is usually available for a fairly reasonable price.

Richard Schram
Mechanical Integrity Specialist
Pharmacia Global Supply Arecibo-P. Rico

RE: Measuring pitting

The cheapest method is to have a wrap-on repair kit available and wait until the pipe useful life in the affected areas is complete because it leaks.  Some facilities use an external, blind-drilled hole in the most erosion-susceptible location - leakage from the hole shows that the pipe thickness has decreased to that selected thickness equal to the hole depth.

More sophisticated techniques range from the semi-automated UT thickness testing from inside the tube already suggested, to IR inspection, to discrete manual thickness testing with UT instrumentation, to laser internal inspection (similar in concept to IRIS, but using a laser to measure the ID) and radiography.   

RE: Measuring pitting

Is the tube easy to get at, at low temperature and is the erosion localized? If so, I recommend radiography. Direct measurements from shadow shots are easy to do, are quite accurate, and you have a 'hard copy' to show everyone. Talk to your local NDE company and ask for their rec's based on your situation.

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