Test Media Systems

Classification of test media
The classification of test media s for magnetic particle testing is done according to the disposition of contrast creation. The following types can be distinguished:

I. Fluorescent (visible under UV-light)
II. Non-fluorescent (visible in daylight)
III. Daylight and fluorescent.

Fluorescent testing fluids will preferably be used for stationary series testing. If testing takes place outside and/or at permanently differing locations, daylight visible penetrants offer advantages. Hereby the different sensitivity of the testing media must be considered.

Suspensions or dry powder

There are two types of application: dry powder and suspensions. Due to the high requirements concerning indication sensitivity, today usually suspensions are used. The rough graining of the magnetisable particle of dry testing process (approx. 20 µm - 300µm) restricts the application field, in addition to the difficult handling. The detection sensitivity with suspensions is considerably higher, due to the grain size up to 1µm. In addition additives e.g. for corrosion protection can be already part of the product and do not have to be added by users.

Carrier

Water and oil are used as carrier medium for the inspection means:

As the use of water causes no disposal costs and the handling is less problematic (smell, skin reactions), oil is only used, if the testing regulations require it, e.g. if the materials used are especially susceptible to corrosion or parts with very oily surface need to be examined.

Delivery form
Suspensions are usually offered as concentrate. It contains already all wetting and corrosion protection agents next to the ferromagnetic particles and has to be diluted according to the instructions of the producer. Thus errors due to wrong mixture of the single components can widely be reduced. If needed the user can adopt the indicator sensibility through variation of the basic concentrate optimally.