Valve NDT Test - UT/RT/PT? 1

[CKchi]

Hi,
I am new in valve industry, i have a lot confusion on the NDT test (UT/RT/PT). In what situation shall we carry out the correct NDT method?
I understand my company that:
1. We dont carry RT on forging valves.
2. We dont carry UT on Casting vavles.

Can anyone give your opinions? what are the limitations of each NDT test?

 

[gerhardl]

The limitation is given by the market you want to sell to. Market research requierd. What do competitors do, what does endusers require, what is common? (A valve is not a valve).

 

[reverman]

PT and MT (liquid penetrate and Magnetic particle testing) are surface examinations. Either one can be used to find surface defects on the part being tested. MT must be used on a part that is magnetic so it won't work on most stainless and most corrosion resistant alloys.

RT and UT are volume examinations. While you can use either method ASME B16.34 has the primary method of examination for castings as RT and Forgings as UT.

 

[CKchi]

Hi Gerhardl/ Rverman,

Thank you. the information is very helpful. BS16.34 does define the applications of surface examination, i will go back and read through it.

 

[mbelly84]

also please note that UT requires a regular shapes and smooth surfaces to be correctly read by the operator, that is why UT is not performed on castings.

 

[PeterIgg]

Further to 19081984's response, doing the UT/RT on the raw forging/casting (or at least with minimal machining) is preferable as there are fewer shadows cast by machined bores / holes &c &c. Therefore the results are easier to interpret. Conversely MPI/DPI should generally be done when the part has been fully machined - there may be 'acceptable' defects that were below the surface that become 'unacceptable' when disclosed by machining. There are exceptions, of course, one cannot reliably perform MPI/DPI on UN form threads, for instance, so you have to be practical about when, within the manufacturing sequence, MPI/DPI is done.