plastic/steel waer resistance 1

[magusinp]

I am testing a PD meter with a reciprocating valve design. The fluid being measured must switch from the inlet to the outlet strokes. In order to switch the meter a plastic valve seal rubs across a metal seat. The parts are all immersed in SAE 30 oil. The valve works like this: The oil travels through a port in the metal body, it then is switched to an adjacent port through the plastic valve body, then back again. Very slowly (a stroke a minute) and at low pressure (from 3 psi).
My prototype used aluminum against acetal but the acetal started to leak and I noticed wear on the aluminum plate and fine abrasion on the acetal.
My research inclines me to try a stainless steel seat with a 16 microinch finish with acetal+20% PTFE fill.
What do you all think about this?

 

[rnd2]

You are correct to consider stainless. Also a re-enforced novalac/phenolic resin will make an excellent dimensionally stable complimentary sliding surface. There are a host of brand names and many different versions of this material. Because you are running in clean? oil just buy one the regular versions that is free of special lubricants. As they bed-in, the complimentary sliding surfaces inter-polish. For an application requiring slow lightly loaded travel in oil, a far better choice than acetal aluminium.

 

[magusinp]

Thanks for your tip. Can you possibly tell me a brand name for a common novalac/phenolic so I can contact my local plastics supplier?

 

[rnd2]

A brand name I am familiar with and available in North America is Micarta. This website contains a good range of that product. When you scan down the list of phenolic laminates you will find more information about the one I selected and pasted below. Micarta is a good brand but by no means the only one.

http://www.sdplastics.com/phenolic.html

MEDIUM WEAVE COTTON CLOTH PHENOLIC Mechanical grade, marine bearings, piston and packing rings, pump valve, doctor blades, marine Phenolic Low moisture absorption, dimensional stability Natural