Oil lubricated air in an oil-free pneumatic system.

[tralala]

Hello Everyone!

We have a Gripper system (working on compressed air) for the handling of silicon products, which is supposed to be runed only with oil-free compressed air. Our customer is complaining that our system is leaving marks in their products. he sent us pictures of the marking and they look very similar to oil stains.

Is there a way to prove if lubricated compressed air was used in the system?

How can we test if a metal surface (Aluminium) is contaminated with oil or grease?

Is there some simple test which I can just use?

Cheers!
Tra

 

[rmw]

Do you have a low spot in the air piping that you can tap into to see if you get oil out?

What kind of compressors do you have that produce your "oil-less" air? Some "oil free" compressors aren't as oil free as they are said to be. If you have an oil lubricated compressor that is filtered in some way, filters aren't 100% efficient, so even small amounts of oil that get by can accumulate in the piping over time and sow up on your product.

Have you ever had a oil lubricated compressor on the piping system? If so, you may have previous leakage still in the piping.

If you read some of my other posts on the subject you will find that I have often said "clean dry instrument air is an oxymoron."

rmw

 

[btrueblood]

Simple ways to detect oil:

1. Wipe a piece of clean, new, brown paper ("kraft paper")across the surface (wear clean dry rubber gloves when doing this). If the paper becomes translucent, there is oil on the surface.

2. Many lubricating oils will fluoresce under black light; inspect the surface in a dark room under black light. If the surface glows, it probably has been contaminated with oil.

3. There are more expensive detection systems used to detect oil and other contaminants on surfaces before they are admitted to clean rooms (e.g. in semiconductor foundries, optical assembly areas, etc.). One such method is "OPTICALLY STIMULATED ELECTRON EMISSION", try googling that as a search term, also see:

http://www.photoemission.com/downloads/allen2000.pdf

or just the parent website under the "surface quality" section.

 

[tralala]

Hello!
Thank you very much for the help.

@rmw:
We'll have to definetly checkt the compressor. The probability that the contamination comes from there ist very high.

@ btrueblood:
the "OPTICALLY STIMULATED ELECTRON EMISSION" method is going a little to far away for our problem. The other systems sounds ok. Probably we'll find something with them. Is not, wel'll just send the part to a lab.

Thanks again!
Trala

 

[kenvlach]

tralala, don't you have spray painters to bi_ch when the CA is less than perfect??

The most common method of checking CA for contamination is to direct the flow onto white paper or cloth (upon a flat clean backing plate). There is even an ASTM standard, D4285,

http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/D4285.htm?L+mystore+rniz4167

but about the only necessary details are that the paper or cloth be within 24" of the CA nozzle & that the flow is at least 1 minute.

Another simple method is to direct the CA upon a pre-cleaned metal sheet, then immerse in or mist with DI water and see if it forms a water break-free surface. I.e., if clean, the water forms a continuous film w/o breaks or beading.

A more sophisticated method is to direct the CA upon a pre-cleaned metal sheet (316 SS is usual), extract any contaminants off the metal surface using a 20% isopropyl alcohol (spectroscopy grade) – DI water solution, then run a sample of the extract through a GC (gas chromatograph) to identify the contaminating molecules.

 

[tralala]

Thanks Kenvlach for your reply.
The sheet mehtod sound also quite simple and effective. Thanks!
Just a question. We can get isopropyl alcohol 70%. Could we use that one instead of the 20%?
cheers!
trala