Accuracy of ultrasonic thickness measurement.

[robot6]

Do you get a more accurate result measuring the thickness of the metal of an elbow, when the process is running or when it is shut down? I'm concerned about interference from other sources.

I think it may not matter, because the frequencies of ultrasound are not within the spectrum of the regular frequencies of vibration at a plant, but I don't have any real experience in this area.

Thanks for the reply.

 

[EdStainless]

It shouldn't matter.
The surface condition, size and style of transducer, and curvature of the surface will have more impact.

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P.E. Metallurgy, Plymouth Tube

 

[robot6]

Thanks!!!

 

The nut behind the wheel is the biggest variable.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[brimmer]

It doesn't matter. If your process flow introduces temperature (i.e. very hot) this could affect readings and you need to stay within confines of equipment.

 

[cap1a79]

The most reliable & powerful way (although it would take some time) is to consult with inspector. Referring to API 570 clause 5.7.1, it is as below.
(API 570 - Piping Inspection Code: Piping Inspection Code: In-service Inspection, Rating, Repair, and Alteration of Piping Systems)

"When ultrasonic measurements are taken above 150 °F (65 °C), instruments, couplants, and procedures should be
used that will result in accurate measurements at the higher temperatures. If the procedure does not compensate for
higher temperatures, measurements should be adjusted by the appropriate temperature correction factor. Inspectors should be aware of possible sources of measurement inaccuracies and make every effort to eliminate their occurrence. As a general rule, each of the NDE techniques will have practical limits with respect to accuracy."




Lee SiHyoung,
Material & Corrosion Engineer,
WorleyParsons Oman Engineering,
cap1a79@gmail.com