x ring vs o ring

[Candiru]

Im sure Im not the first person to notice the selection of x rings at Mc Master Carr. Would this work in a regulator? I would be willing to try it if seemed reasonable.

 

[herman]

I would think they would work but why bother? Standard orings work fine and are proven in scuba service so why change? At 4 times the cost (still pennies each I know) and no clear problem with standard orings to solve, I just don't see a good reason to change. I am a firm believer in "if it ain't broke, don't fix it" and this would fall into that catagory.

 

[Candiru]

Thanks for pointing out the cost Herman. I didn't take a look at that factor. Just so I understand, you do think that they would work in the hp piston position?

 

[Zung]

I wouldn't even think of trying.


Edit
Do as herman says, buy a baggy of 010VT90 for 10 bucks and you're good for the next 100 years or two.

 

[herman]

Interesting question, at first thought, you have a smaller surface area on each leg of the X the handle the delta P (differential pressure) so it sounds like a bad idea but on second thought, the delta P is spread between 2 surfaces, effectively reducing the load across each leg to 1/2 the total delta P. The area between the legs would create a good space for lube to be captured, keeping the piston better lubricated. On the other hand, my gut feeling is they would also be a lot more sensitive and prone to failure if not adequately lubricated. I would also think the failure mode would be worse with the Xring. With the smaller area of each leg, once it started to fail I would think it would tend the extrude worse than a standard oring. All that said, they are not new and if there was a major advantage, you would think someone with a lot of engineering resources (Scubapro/Atomic and the like) would have started using them. I go back to "if it ain't broke, don't fix it". No reason not to experiment if you are just curious, I often do so just to see what happens but obviously I would be cautious of any req with them installed until I had a lot of experience with them. Any reg I modified like that would spend a lot of time in the pool and shallow at the quarry before I trusted it for more serious diving. Self servicing is one thing, modifying the internal parts of a regulator takes you into a totally different realm, one that should not be entered into carelessly.

 

[Akimbo]

My experience with various lip-seal or knife-edge seals is they perform better on surfaces that can’t be made as flat and smooth as an O-ring requires, but do not handle higher pressures as reliably. Naturally there are lots of variables.

Parker has an excellent O-Ring design handbook:
http://www.parker.com/literature/ORD 5700 Parker_O-Ring_Handbook.pdf

Here is an image from this manual that shows how O-rings work and fail.



At the risk of stating the obvious, the higher pressure side is on the left for Figures 1-5 through 1-7.

 

[lucca brassi]

X ring is normaly used for lubricating/colecting oil on hydraulic pistons

 

[Tigerman]

Heres atleast some "sales pitch" information about them.. X-Ring Seals, Quad® Ring Seals & Low Friction Seals | Precision Associates Inc
Personally Im also of the "if it aint broke dont fix it" state of mind though..

 

[Afishianado]

I use these type of seals at work. We refer to them as Quad rings. They are generally not used in static situations like hose ends or valve body seals etc...We use them where a shaft is moving through the seal and there is a pressure differential across the seal. They are not mounted to the moving part, they are mounted to a case per se and the shaft moves through the stationary seal. The case is milled differently that it would have been if an O-ring had been used so I don't think you could just change the seal from an O to and X and it would work the same.

That being said... I would try it...out of curiosity...like Herman said though I would work through it slowly. Big picture though I agree with the thought process of why change it, the Orings work just fine.

~Chris

 

[JBRES1]

Years ago I worked for a valve manufacturer , and we used the viton quad rings as static seals on high pressure ball valves.
The quad rings had a higher failure rate than the standard 90 duro viton o-rings , so we went back to the standard o-ring.
The valves were seeing pressure in the range of 3,000 to 4,500 psig.
So , if it were me, I would just stick with the standard o-ring.

Jim Breslin