INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!

*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.

Jobs

Valve Seal design - Issues with holding pressure

Valve Seal design - Issues with holding pressure

(OP)
Hi Guys,

I am working with a prototype in which we designed a valve seating against an Oring. Please see below


To seat the valve there is a spring force and a pressure force as indicated by the arrows. The valve works well for our pressure range 0-600 Psi. The problem is when a colleague tried to scale up the design 2x the diameter and the pressure in the scaled version will not hold above 350 PSI. Scaled up version below.


My gut feel would have said this new scaled design should work also. We could not scale the seating spring proportionally but in theory it will be the air pressure that mainly acts to set the valve. Spring seating force around 7 Kg. Air pressure seating force at 500 PSI is around 30kg for the scaled version and 18kg for the non-scaled version. We used a ratio of the circumference lengths to scale up the seating pressure force.

I have heard i should aim for a pressure between the two faces sealing faces of 2x the pressure i am trying to seal against. I this correct? It is a little hard to calculate as is it sealing on an Oring and the exact deformation on the sealing area is unknown. The other issue could be with air escaping around the back of the Oring. The Oring in the scaled version was not given as much squash in the cross-section. Around .3mm for a 5.33mm CS Oring. The working design has a 0.5mm squash in a 5mm CS.

Would be very interested to hear any thoughts. Am i missing anything obvious as to why the scaled version is not working?

Many Thanks,

RE: Valve Seal design - Issues with holding pressure

It is not customary to put same post on more than one forum.

RE: Valve Seal design - Issues with holding pressure

The O-ring compression is key for a 5.33 CS you should have between 0.55 to 0.66mm (depending on manufacturer/material grade it might vary)

You have 5.6% o-ring compression and you need at least 10%. I would think this lack of compression easily explains why you aren't getting above 350psi.

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!


Resources


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