Piston Ring Question

[kenrinc]

Believe I got mine from HydraPak but don't quote me on that. I'll go back and see where the invoice came from.

FWIW, I was astounded by the options for sizes ...

Ken-

[kenrinc]

Turns out it was Hercules Sealing Products, PS1600 series of hydraulic seals.

Ken-

[Dick_Morris]

Turns out it was Hercules Sealing Products, PS1600 series of hydraulic seals.

Thanks. I ordered a couple for my pistons.

Does anyone know if these will work for piston valves?

[NP317]

Dick:
If you are using superheated steam into the piston valves, I would recommend good old cast iron rings.
I machined the cast iron rings for my piston valve Mikado, following Bill Morewood's instructions in his Raritan book.
RussN

[Dick_Morris]

If you are using superheated steam into the piston valves

Saturated steam and bronze cylinder and valve cylinder liners.

[Bill Shields]

I would think very carefully about having PTFE rings moving across valve ports.

[Harold_V]

I would think very carefully about having PTFE rings moving across valve ports.

Oh, yeah! Even if the ports are well rounded.
PTFE is well known for the ability to creep. If a ring is allowed to sit in an open gap for a prolonged period of time (like through a long winter), it's entirely possible it will be shaved when moved. Even if it didn't get shaved, it likely will have been deformed.

Great O rings, though. I used one on the trunnion of a melting furnace, with the trunnion performing port duty as well. The O ring held up perfectly well under extended operational hours at high temperature.

H

[Dick_Morris]

Is there another type of non-ferrous ring/seal that is suitable for piston valves using with bronze valve bushings? I can make and fit cast iron if that's the best option, but I would prefer something that wouldn't rust.

[Bill Shields]

I would not worry about rust. Proper lubrication and purging of condensation will keep rust under control.

[10 Wheeler Rob]

I bought a partially completed locomotive and stayed with the x cross section o rings that were already done. After 2 1/2 seasons of limited use I think that they are having blow by. I hear it in the exhaust note at part throttle.

The cylinders are cast iron from Allen Models. When I looked for replacement x rings, all I found was Buna-N rubber. So I suspect they are not high temp rated material either. So either between the cast iron cylinders and/or the o ring material it was not the right choice.

Guess i will just make new pistons with the rings available from Allen Models this winter. I have an other engine with them and its been running 6 years with out any issues.

Rob

[rkcarguy]

I think the PTFE works great, but not in a piston or slide valve situation where it is sliding across a port. It "creeps" like Harold says, I tried using some as a spacer in a thrust bearing type application and it ate into the aluminum and then disappeared all together after an impact.
The X-rings are not well rated for linear motion, you can look the specs from most of the manufacturers and see the temp ranges, feet per minute of various directions of motion, expansion rate, etc.

These, or similar, are what I think would work the best:
http://www.boss-sealing.com/sale-130351 ... high-.html

[Bill Shields]

If you are going to go with soft rings..the suggested composites are about as good as you can get.

Just be sure to keep the ring gaps and associated ears away from a port.

Teflon bronze and glass is another combination with which I have personal industrial experience..given the correct application they work well.