How do manifold isolators (barrel style) seal?

[guruboy]

How do manifold isolators (barrel style) seal? Specifically, what are the sealing surfaces?

Is it a compression seal that squeezes the o-ring between the isolator shaft and valve inlet tube wall?
This would be a two surface seal, "top" and "bottom"

Or does the o-ring also need to push against the o-ring channel wall?
This would be a three surface seal, "top", "bottom", and "side"

 

[2airishuman]

It would be a three surface seal insofar as what you call the "isolator shaft" has square-cut grooves in it. The o-ring sits in the groove, and pushes against the bottom of it, the outside of it, and the inner wall of the modular valve body.

 

[guruboy]

But does the groove "side wall" on the shaft actually seal or just stop the o-ring from moving?

 

[MaxBottomtime]

 

[guruboy]

That is the manifold style in question

 

[Caveeagle]

Great picture. I have been told that the isolator valve only really fully protects tank pressure in one side but did not understand the valving before seeing that pic..

Point is if outer seal blows on the isolator valve, closing the valve will only save gas on one side.

 

[Scared Silly]

There are only two sealing surfaces, the surface that is part of the grove that the o-ring sits in on the isolator (the ID) and the surface of valve (OD). As the pressure builds up the o-ring is deformed into a D-shape which then puts the o-ring into greater contact with the sealing surfaces. The greater the pressure the greater the contact. Here is what the o-ring looks like under pressure from the right.

|D|

The side walls of the grove are not meant for sealing but for providing the wall for the o-ring to deform against.

 

[cool_hardware52]

How do manifold isolators (barrel style) seal? Specifically, what are the sealing surfaces?

Is it a compression seal that squeezes the o-ring between the isolator shaft and valve inlet tube wall?
This would be a two surface seal, "top" and "bottom"

Or does the o-ring also need to push against the o-ring channel wall?
This would be a three surface seal, "top", "bottom", and "side"

All you ever wanted to know about orings, the applications they are used in and theory of operation. A genuinely great resource.

http://www.parker.com/literature/O-Ring Division Literature/ORD 5700.pdf
http://www.parker.com/literature/O-Ring Division Literature/ORD 5700.pdf
Tobin