Pneumatic slide valve

[Willyd5300]

Hi guys,

I am having trouble with a pneumatic valve i have designed. The operating pressure is 500psi and running dry air. Please see attached for the valve CAD snapshots. The scale is rather small, the smallest Oring is ID-4mm CS-1mm. The first iteration of the design i had the o-rings running over the ports and found the ports cut the orings. The second iteration shown in attachment has reliefs on the bores so that the oring no longer run over the ports. The issue now is when the valve is moved into the close position the back purging air from the small chamber pops the front (smallest) O-ring out of its groove.

I am hoping someone more experienced with this type of design can point me in the right direction.

Thanks, WIll

 

[hydtools]

Change valve design to use static seals in the bores instead of seals on the sliding spool. Or a mix of bore and spool seals.

Ted

 

[Willyd5300]

Hi Ted,

Thanks for the reply. Making at least the front seal static i think would be the way to go but i also think it would also make the oring hard to install. I could try a sleeved bore where oring could be pre-installed but i have very little wall thickness to play with and i think it would be hard to service the oring.

Do you think there is any chance of making design with the seals on the sliding spool work? One idea was to reduce flow around the front oring when the small chamber was back purging. Please see attached. I have added material behind the Oring in aim to reduce flow and reduce the chance of sucking the O-rings off. thoughts?

Any other ideas keeping with the seals on the sliding spool? Would tightening up the Oring groove width help at all? Any special type of seals?

Much appreciated,
Will

 

[hydtools]

Can you create a dovetail groove in the spool for the o-ring that washes out? Use a higher durometer o-ring. Use a smaller diameter o-ring so that residual stretch retains the o-ring.

Ted

 

[Willyd5300]

Thanks Again for the input Hydtools.

I got hold of some viton 85A Orings. This has stopped the Oring popping off but I am still seeing some damage to the Oring. Cutting and then eventually breaking after around four cycles of the valve.

I have asked around here locally for some advice on the matter. One person has told that it will be very hard/maybe impossible to get the valve working reliably in this configuration at this pressure etc.

I see a lot of cartridge spool valves where orings are passed over relived ports but haven't found a pneumatic example capable of over 500 PSI. Is what I am trying to do impossible or do i just need to be a bit more clever in the design.

Also I if anyone knows a off the shelf valve running a similar configuration Could you please point me in the right direction. My plan would be to buy and pull part to borrow aspect of the design to get mine working..

Thanks in Advance,
Will