10:39 Mar-19-2009 faran Engineering FFC Pakistan, Pakistan, Joined May 2005 17
SCC crack detection in SS
We have witnessed SCC in one of our columns, the cause of SCC is the Chroride presence in wet insulation. Now what NDT is usefull to detect the extent of attack quickly & effectively. PT we have done, MT is not applicable, How about Phased Array Eddy Current, is it sensitive enough to detect micro cracks, what about Omniscan. Do you think Metallography would help.
Detection of SCC for your application can be accomplished with OD Creeping Waves very effectively. OD Creeping Waves have been demonstrated to detect cracks on the scanning surface with a depth of 0.005 inches and less.
Phased Arrays are equally effective for detection and sizing of SCC. Even Phased Array using Creeping Waves would be effective.
Some questions are: what is the material type and what is the thickness.
Is detection your only concern. Do you need to size these Stress Corrosion Cracks.
What is your Critical Flaw Size?
To conclude this is a very easy application using Conventional OD Creeping Waves or using an OmniScan Phased Array System. The images you will get with the OmniScan will significantly help with detection and characterization.
You can use TOFD to detect, size and carcaterized the SCC probably your unique limitation could be the thickness, however I could detect this kind of cracks in low thickness (9mm Lab testings). The setttieng-up (probes, frequency,size) is the clue for this application