Back Pressure Valve Question

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

barrmust

Contributor
Messages
159
Reaction score
4
Location
Baltimore, MD
I have a back Pressure valve on my compressor set up.

It looks like a 211 valve assembly but I don't think it is.

I have compared it to a current 211 valve and it is built different.

The adjustment set up on it is different though. It has a threaded plug that screws into the top to set the pressure. It does not have a spring inside, it has washers and you can see it probably never had a spring. I'm assuming it is an older style. My question is how do I adjust the pressure. If you adjust it for more pressure it never opens. If you set it for a lower pressure it will vent through the plug.
 
Without a photo always difficult to asses but purely from your description of these so called "washers" it sounds to me they may be "Bevelled Springs" also known as a "Belleville Washer"

If you have taken the BPV apart and thinking there simple flat washers you have most likely replaced them incorrectly.


Look carefully again at these "washers" are they slightly dome shaped? how many do you have? and are they an odd number? If so they need to be re arranged into pairs each pair making up a small raised disc.


This combination of discs makes up a very accurate control spring.


The remaining odd one left out is the lead disc this needs to go face down (large diameter first) and depending on seeing your photo will decide if its first in or last.

By way of example regulators we make for military diving applications that need a very accurate controlled rate flow and rapid pressure control use the same disc spring idea.

The spiral "bed" spring you see most often in scuba parts is by comparison a poor cheap alternative.

The enclosed website may be helpful in a fuller explanation.

http://en.wikipedia.org/wiki/Belleville_washer

Iain Middlebrook
 
After looking at it again you are correct.

It is a Belleville spring set up. # set of curved washers in it.

The problem I am having is it never opens and lets air through. I picked it up as a used part and after using it I realized it let air through all the time regardless of pressure. It had been adjusted by the previous person so it was open al the time. I am surprised that the last air quality check passed with great results. I have been playing around with the adjustment and amount of washers in it and cant seem to find a happy spot to set it at. It either opens to soon or just doesn't open.

Any suggestions?

Russ
 
After looking at it again you are correct.

It is a Belleville spring set up. # set of curved washers in it.

The problem I am having is it never opens and lets air through. I picked it up as a used part and after using it I realized it let air through all the time regardless of pressure. It had been adjusted by the previous person so it was open al the time. I am surprised that the last air quality check passed with great results. I have been playing around with the adjustment and amount of washers in it and cant seem to find a happy spot to set it at. It either opens to soon or just doesn't open.

Any suggestions?

Russ


I've got an AE 211 valve used for about 30 minutes I can sell you. Problem solved.
 
https://www.shearwater.com/products/perdix-ai/

Back
Top Bottom