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Crack detection process

Non-destructive crack detection by use of the liquid penetrant method 

This process - based on the physical law of capillary action - is universally applicable and can be adopted regardless of the raw material at use. The consecutive process steps are as follows:

The raw materials start undergoing the testing process in their initial state. 

It needs to be ensured that the surface of the raw materials - including any possible cracks - is completely clean and dry. Therefore the raw materials have to undergo a preliminary treatment process if needed.

In a next step the penetrant is applied by dipping or spraying and has to stay on the surface long enough to allow for an adequate residence time.

Next, the penetrant is partially removed during the following intermediate cleaning. While it is taken off the surface of the tested parts it still remains in the cracks. In case the emulsifying process is put to use at this time the emulsifier is first applied to and then carefully removed from the surface. Here again, residues of the penetrant remain solely in the cracks.

After the subsequent drying process a developer is applied onto the testing surface. This developer extracts the remaining penetrant from the cracks, just like blotting paper. Depending on the utilized penetrant at this point the cracks are finally made visible either without extraneous cause or with the use of UV light.


Please note that in order to apply the liquid penetrant method the cracks in the raw material have to open up towards the testing surface – if necessary, the required preconditions for  successful crack detection by use of this method can be created by adequate preparation such as grinding or various other suitable techniques.

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