Cleanliness Test

Q. The application I have is a cleanliness requirement for a metal washer. The specification on the print is as follows:

Maximum contaminants mass per piece permitted is 0.011mg. 99% of particles to be smaller than 150 microns (excluding particles smaller than 15 microns)

The cleanliness test procedure states: (Gravimetric cleanliness of components)

1. A method for washing the part so as to transfer particulate contamination from the part to the washing fluid.
2. A method for filtering the washing fluid so as to transfer the contaminant to an analytical membrane filter of defined size.
3. A method for weighing the change in filter mass so as to determine the contaminant mass.
4. A method for reporting results.

 

Please let me know if you know of a test kit available to perform this type of analysis. F.C.

 

A. I am not aware of a single kit available for purchase to perform this testing. This sort of cleanliness requirement is not uncommon, though, and can be put together with components you can purchase from any scientific supply company. It is specified to capture and characterize metallic contamination that is left behind from a manufacturing process (such as saw chips, metal turning, etc.). As the print reads, it is not meant to measure cleanliness regarding oil or grease removal.

I am not sure of the parts you need to test, but essentially you need to wash/rinse them with a clean test fluid. Assuming the parts are relatively clean (since it looks like they will be exiting a parts washer), I would suggest using a solvent (something like mineral spirits) to rinse down the parts. You need to capture the solvent and any particulate that may become dislodged from the surface in a clean container such as a beaker of clean stainless steel pan. That liquid is then filtered through a flat filter membrane, typically about 5 microns. This is usually done with a suction filter apparatus available from several companies, one supplier is Millipore. The solvent is collected and can be used again, assuming the parts do not contain much oil. The filter is then dried and weighed to determine weight gain (note that it is essential to determine a clean, dry filter weight initially). Additionally, particulate can be sized using a binocular microscope that has been fitted with a measuring scale. If high volume measurement is required, there is automated digital imaging equipment that will capture an image of the surface and size particulate based on contrast with the filter background.