Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Pneumatic slide valve

Pneumatic slide valve

Pneumatic slide valve

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

RE: Pneumatic slide valve

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.


RE: Pneumatic slide valve

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,

RE: Pneumatic slide valve

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.


RE: Pneumatic slide valve

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,

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close