Non-destructive testing - Porosity

[Marbig]

Hi all,

We have a bearing pad at work that failed a porosity test and could not hold pressure (this was the pad itself and not the babbit surface).

I need to look into some NDT testing that will give us an idea about the porosity. I have googled and some sites say different things, from what I gather it will be penetrate testing, radiography or eddy current.

Basically I need a test that will allow me to say to someone that this pad needs to be repaired so that "XXX test" reveals that surface defects are less than "xxx (some sort of classification that corresponds to the test method)" so that it will past its porosity test.

This will be more specific than simply saying that the pad needs to be repaired so that the porosity test will be passed.

I would be interested in hearing your opinions. Thanks for all your help.

 

[Astronuc]

Penetrant testing only works for surface or open porosity, i.e. porosity connected to the surface.

Radiography might work depending on the type of porosity. Radiography usually looks for voids, but density (1 - porosity) would require calibration (with standards of know porosity/density).

Eddy-current may not work - it is usually used for surface flaws (voids) - and it also would require calibration.

Depending on the size, helium/gas pycnometry might work.

UT might also work.

Look here for some ideas.
http://www.ndt-ed.org/GeneralResources/MethodSummary/MethodSummary.htm