[PSUBS-MAILIST] Double Seal?

[Smyth, Alec]

Personally I think two O rings might make it harder to seal than one. The idea with this type of valve is to minimize the cracking power, which means using the weakest possible spring that will reliably achieve a seal. If you are squeezing two O rings instead of one, you probably have to squeeze harder. That's just a totally unverified, theoretical, and random thought.

Best,

Alec

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of James Frankland
Sent: Wednesday, July 24, 2013 11:51 AM
To: personal_submersibles at psubs.org
Subject: [PSUBS-MAILIST] Double Seal?


Hi All,



I have to re-machine the pop off top of my overpressure valve.  I threaded the hole by hand and now i have finally attepted to fit it with its O ring, i can see that the bolt is not straight, causing mis-seating of the valve top.   Im not over happy with having the bolt passing through anyway as it doesnt slide very easily.

So, im going to machine up a new smooth shaft which should be straight.  Thats easy enough.



BUT, at the same time, i am tempted to put in a second O ring groove and have 2 O rings on the pop off top.  There is enough room for one outside the existing.

I seem to remember there was discussion on double O rings a while ago.  Anyone have any thoughts on this idea?  Seems to me to be a good idea as its got 2 seals, but ?



Pic here as i was machining it.



Kind Regards

James



http:/<http://www.guernseysubmarine.com/publication2_files/Page20544.htm>/www.guernseysubmarine.com/publication2_files/Page20544.htm
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