Varnish problem in air valve 1

[prakash20305]

The oil particles in compressed air from truck decomposed and forms varnish inside the solenoid valve assembly after certain period of operation of valve. Due to this pluger gets sticked to sleeve which fails the operation of valve. It would be highly appreciated if you could help me on following,
a) How varnish created in air valves?
b) How to test our valve design for varnish ?
c) How to measure oil in compressed air from a truck?

Prakash

 

[gerhardl]

Air solenoid valves are common on cars, trucks, buses etc. running on air from vhicle air compressors, and they normally run without problems.

Any solenoid for air will get the problem you describes if oil-mixed air with oil that might harden at normal temperature, or harden after a longer time exposed to air, or harden mixed with dust or air and/or water.

I do not think any producer has overcome this problem, the only thing you can do is to put an antisticking disc or coating on top of your plunger, and this is more to avoid electrical/magnetic sticking.

The real solution is to be sure that the air entering is filtrated, clean, without dust and water, and that your valve is eqipped with dampers and filters at exhaust ports, not admitting particels and exhast this way.

 

[prakash20305]

Thank you so much for your comments on the varnish issue. It would be so grateful if you could provide more details on antisticking disc or coating for the valve to avoid this issue.

I agree with your solution to this problem is by providing clean air to valves. But this varnish problem arised even after air filter and dryer installed were installed in the truck which removes the dust particles to certain microns and filters oil from air.

So I would be intrested to know about the test methods to detect varnish at worst case oil level in compressed air.

 

[gerhardl]

Sorry, my expertise ends here, but a brief comment anyway: Non sticking devices on top of plunger is normally a very thin disc of non-sticking plastic material.

I cannot advice you on material type, but what about covering the whole plunger in a microthin smooth layer of a suitable plastic (delrin, nylon, teflon....???). Purpose: to get a different surface from metal, and to cover microscopic pores in metal, and get a slipping surface.

How do producers of frying pans solve this problem?