O-Ring Compression

AM · 18th June 2008, 08:04

I am looking for info regarding any "industry standard" for o-ring compression for rebreather applications.

Edit - to make my question clearer, I am trying to work out for a static o-ring seal in a CE specific depth-rated rebreather, is the depth of the groove machining the main factor used specifically to ensure proper compression/seal to their maximum depth rating. Within the CE criteria, is there any "industry standard" which decrees the level of o-ring compression? I know factors such as extremely cold temperatures also affect o-ring compression/shrinking but I'm not concerned with that right now.

Regards

AnneMarie

Wreck detective · 18th June 2008, 08:22

AM,

Not sure if that O-Ring compression is specific to Rebreather's themself's, but to the O-rings, material, Durometer (Hardness) and the groove tolarences they sit. In any application.

Not sure if this may help, but its a start.

AM · 18th June 2008, 08:24

Hi, I should frame that in the context of the depth/pressure rating on CE rated rebreathers.

Thanks for the link, I will take a look.

Regards
AnneMarie

Drmike · 18th June 2008, 09:38

Quote: (Originally Posted by am)

Hi, I should frame that in the context of the depth/pressure rating on CE rated rebreathers.

Thanks for the link, I will take a look.

Regards
AnneMarie

For high prerssure or static parts just go with 20-25% (it doesnt really matter a toss what the application pressure is)

but you can get away with much less on the loop o-rings as the differential is bugger all/zero as they are at ambient. For those o-rings the compression can be dictated by ease of assembly in most cases......

and the answer to your next question is yes

AM · 18th June 2008, 09:41

Hello Mike

Yeah ok if the app. pressure is irrelevant, if 25% compression is aimed for, what is the main factor used to ensure this compression level, is it primarily the groove machining? What about extrusion?

Rgds
AM

Drmike · 18th June 2008, 09:50

Quote: (Originally Posted by am)

Hello Mike

Yeah ok if the app. pressure is irrelevant, if 25% compression is aimed for, what is the main factor used to ensure this compression level, is it primarily the groove machining? What about extrusion?

Rgds
AM

25% is the most you will ever need (actually its quite a lot) for most applications you dont need so much (for eg the head o-ring) as you never see any real deltaP other than when you do neg test. for that application id select a smaller compression to make it easy enough to take head on/off

But to answer your question, in simple terms if you want a 25% compression and using a 4mm o-ring you can shove it in a 3mm deep groove (4mm wide) (1mm being 25% of 4mm) - face seal

If your making a barrel seal (eg head of unit) then you can if you wish take into account the gap between the body and the head - but either way so long as the final compression is over 10% or more it should be fine.

WD8CDH · 19th June 2008, 22:13

Here is another good design guide.:

http://www.parker.com/literature/O-R...g_Handbook.pdf

18th June 2008, 08:04	#1 (permalink)
AM Banned Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Earth. Posts: 964	O-Ring Compression I am looking for info regarding any "industry standard" for o-ring compression for rebreather applications. Edit - to make my question clearer, I am trying to work out for a static o-ring seal in a CE specific depth-rated rebreather, is the depth of the groove machining the main factor used specifically to ensure proper compression/seal to their maximum depth rating. Within the CE criteria, is there any "industry standard" which decrees the level of o-ring compression? I know factors such as extremely cold temperatures also affect o-ring compression/shrinking but I'm not concerned with that right now. Regards AnneMarie Last edited by AM : 18th June 2008 at 09:13.
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18th June 2008, 08:24	#3 (permalink)
AM Banned Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Earth. Posts: 964	Re: O-Ring Compression Hi, I should frame that in the context of the depth/pressure rating on CE rated rebreathers. Thanks for the link, I will take a look. Regards AnneMarie
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18th June 2008, 09:38	#4 (permalink)
Drmike RBW Member Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,378	Re: O-Ring Compression Quote: (Originally Posted by am) Hi, I should frame that in the context of the depth/pressure rating on CE rated rebreathers. Thanks for the link, I will take a look. Regards AnneMarie For high prerssure or static parts just go with 20-25% (it doesnt really matter a toss what the application pressure is) but you can get away with much less on the loop o-rings as the differential is bugger all/zero as they are at ambient. For those o-rings the compression can be dictated by ease of assembly in most cases...... and the answer to your next question is yes __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment Last edited by Drmike : 18th June 2008 at 11:24.
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18th June 2008, 09:41	#5 (permalink)
AM Banned Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Earth. Posts: 964	Re: O-Ring Compression Hello Mike Yeah ok if the app. pressure is irrelevant, if 25% compression is aimed for, what is the main factor used to ensure this compression level, is it primarily the groove machining? What about extrusion? Rgds AM
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18th June 2008, 09:50	#6 (permalink)
Drmike RBW Member Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,378	Re: O-Ring Compression Quote: (Originally Posted by am) Hello Mike Yeah ok if the app. pressure is irrelevant, if 25% compression is aimed for, what is the main factor used to ensure this compression level, is it primarily the groove machining? What about extrusion? Rgds AM 25% is the most you will ever need (actually its quite a lot) for most applications you dont need so much (for eg the head o-ring) as you never see any real deltaP other than when you do neg test. for that application id select a smaller compression to make it easy enough to take head on/off But to answer your question, in simple terms if you want a 25% compression and using a 4mm o-ring you can shove it in a 3mm deep groove (4mm wide) (1mm being 25% of 4mm) - face seal If your making a barrel seal (eg head of unit) then you can if you wish take into account the gap between the body and the head - but either way so long as the final compression is over 10% or more it should be fine. __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment Last edited by Drmike : 18th June 2008 at 09:57.
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19th June 2008, 22:13	#7 (permalink)
WD8CDH New Member Current Rebreather/s: MK 15.X Other CCR Other SCR Home Build Other Rebreather/s: Not Bought Yet Other CCR Other SCR Home Build Join Date: Dec 2007 Location: NY Posts: 69	Re: O-Ring Compression Here is another good design guide.: http://www.parker.com/literature/O-R...g_Handbook.pdf __________________ Ron Schroeder Former Commercial Diver, now Lazy Diver
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