Pos. check on Optima

Harvey Sisco · 30th January 2007, 00:07

Just wondering if any body els is having this problem. When I am doing a Positive check on my Optima laying on its back sid it dose not wont to hold preacher. When I set it up on end it will hold the positive preacher. I have check the dump valve both + and - makes no deference, all o rings in good shape. Last 2 dives it did this I went ahead and made the dive, had no leaks. just wondering if any body has had this problem?

Tecdiverfl · 30th January 2007, 00:11

Mine does the same thing. I gave up trying to figure out why.....

Downtime · 30th January 2007, 07:49

I find it sometimes difficult to get the pressure checks just right but with a little perseverance, I'm normally able to complete them.

One night it took me nearly 1.75 hours to get it to hold negative. In the end I won, and it held both pressure checks. On the other hand, my last dive I was able to get both checks to pass, the first time I tried after I put it all together

(I normally take it apart and Virkon it if it's going to be out of the water longer than 3 or 4 days).

Normally I get a slight leak in either end of the scrubber canister. Jiggle it and that's enough to seat the o-rings properly.

Good Luck,
Michael

Jordan · 30th January 2007, 14:34

As mentioned above, this has to do with the Extendair canister and its orings. Do your pos test with the unit upright...any Optima user knows the unit is extremely dry.

seafox · 30th January 2007, 18:50

A couple of suggestions:

1) The two "thin" o-ings on the CL connections to the breathing hose wear out quickly, if you remove the hoses often to clean and you should.
As they are very thin they don't take much abuse! Be gentle inserting the connection.
They will slowly leak eventually.
I change mine approx every 3months or 30 hours

2) If it's the cannister leaking, it's best to order the kit and replace the o-rings.
I would!

3) There exists a white plastic key used to lock the dump valve on the right CL.(Check with DR, not sure if it's still available)
It prevents leakage over longer periods of time, if tha'ts what you want to do.

Cornel

Harvey Sisco · 30th January 2007, 20:30

Thanks for the information I will do my Pos. and neg. checks with unit upright.

You'll have a good day!

***ScubaDadMiami*** · 30th January 2007, 22:33

I also went through this a year ago when I got my Optima. The canister o-rings will deform slightly when you lay the unit down, putting pressure on just one side of the canister, breaking the seal just enough to leak out the gas. Under even hydrostatic pressure (which you will get in the water), it is not a problem at all.

***ScubaDadMiami*** · 30th January 2007, 22:38

Quote: (Originally Posted by seafox)

. . . The two "thin" o-ings on the CL connections to the breathing hose wear out quickly, if you remove the hoses often to clean and you should.
As they are very thin they don't take much abuse! Be gentle inserting the connection.
They will slowly leak eventually.
I change mine approx every 3months or 30 hours

You are aware that they changed the o-rings on the inlets to a slightly larger (or thicker) size from the original design (which I think are now the same size as on the hoses), right? I have also noticed that the oxygen compatible lubricant can get dried and hardened after a while, causing small leaking at those connection points if forming at the o-rings. So, I have made sure to clean it out when it starts to get like this, and this has worked well.

n2diving · 30th January 2007, 22:51

Conventional wisdom is Optima's MUST be upright for positive and neg as discussed previously. IMO, the cause has to do with the position of the plastic buckle of the elastic retaining strap that threads through to hold the canister body in place in the case. The strap can be rotated easily, but if positioned such that the large plastic buckle is in contact between the canister body and the ground when the unit is on it's back, the 'high spot' on the canister wall it creates causes the thin wall of the canister body to flex enough to break the o-ring seal(s). When you tighten the strap, the buckle just naturally seems to want to end up at exactly position to cause the problem. If you are carefull to position the buckle so that its out of the way (which makes it damned hard to tighten), the unit will pass pos/neg on it's back.. at least it will for me. But it makes it such a hassle to tighten the strap I just stand it upright.

The O-ring problem mentioned by seafox should not be happening and could be that he is using 022 or perhaps even 023 Buna-n (nitrile) 70 durometer (Shore A) o-rings (the early units shipped with 023 Buna-n's that were later changed.) The correct Oring is 022 Viton 90 durometer.... mine have 200+ dives on them without replacement. FYI, I beleive scubadadmiami is incorrect on the original vs replacement sizes. The 023 diameter was too large and would not stay in the groove and was so soft it would wrinkle too easily. The 90 duro is important, a standard Viton is 75 duro and nearly all nitriles are 70 duro, but I did some testing and discovered the harder slightly smaller o-ring worked much better. The thickness (first digit = 0) did not change. The new O-ring spec was caught very early, but seafox did receive one of the very early units.

RE: I've also seen the canister failling positive/neg and having reseat the lids to correct. It's root cause in my personal experience is not lubricating the edge of the canister body (the long black cylinder) before each assembly. However, you don't have to smear the christo-lube all over until the black edges turn white... just apply enough so that the sealing surface is 'shiny black'. This issue is if the sealing surface on the canister body is dry/dirty... the very large silicone orings (the orange ones) that it seals with will 'wrinkle' as the end caps are pushed in and twisted causing enough of a seal failure that it won't hold a pressure test. For whatever reason, the problem seems more pronounced for me on the end with with the electronics. If it happens and I'm in a hurry (which is usually when it happens because I was too much in a hurry to take a moment to clean and lube the edges of the canister body) , rather than fuss with th lids I've found I can loosen the retaining strap, grap the canister body with both hands rotate it back to unlock it and then rotate it back to lock position... it will almost always pass after that.

In my observation O2ptima owners as a general rule are using WAAAAY TOOOOO MUUUUCCH lube.... on the various connections. When you lube, do so very sparingly and before you lube wipe the surfaces completely dry to remove all old pre-existing lube entirely.

-- Mark

Muzz · 30th January 2007, 23:37

Mark
You brought up a few good points. This might be a hijack.
First of all why is O2 lube used on Rebreather fitttings? Silicone works much better as a lube. Is it not safe to inhale or what? There isn't enough pressure for need of the O2 capability of the grease.
And second, your right about the over use of grease. If you can see it , it's too much. I rebuild regs for shops for a little extra cash in my spare time. You should see what happens when too much grease is used, it looks like glue.
Also I only use O2 grease if it needs it. silcone works better in most applications.

30th January 2007, 00:07	#1 (permalink)
Harvey Sisco New Member Current Rebreather/s: Optima Other Rebreather/s: Join Date: Jan 2006 Location: Farmersville TX. Posts: 20	Pos. check on Optima Just wondering if any body els is having this problem. When I am doing a Positive check on my Optima laying on its back sid it dose not wont to hold preacher. When I set it up on end it will hold the positive preacher. I have check the dump valve both + and - makes no deference, all o rings in good shape. Last 2 dives it did this I went ahead and made the dive, had no leaks. just wondering if any body has had this problem?
(Offline)

30th January 2007, 00:11	#2 (permalink)
Tecdiverfl New Member Current Rebreather/s: Optima Other Rebreather/s: Join Date: Oct 2005 Location: Delray Beach, FL Posts: 70	Re: Pos. check on Optima Mine does the same thing. I gave up trying to figure out why.....
(Offline)

30th January 2007, 07:49	#3 (permalink)
Downtime New Member Current Rebreather/s: Optima Other Rebreather/s: Join Date: Oct 2006 Location: Melbourne Posts: 39	Re: Pos. check on Optima I find it sometimes difficult to get the pressure checks just right but with a little perseverance, I'm normally able to complete them. One night it took me nearly 1.75 hours to get it to hold negative. In the end I won, and it held both pressure checks. On the other hand, my last dive I was able to get both checks to pass, the first time I tried after I put it all together (I normally take it apart and Virkon it if it's going to be out of the water longer than 3 or 4 days). Normally I get a slight leak in either end of the scrubber canister. Jiggle it and that's enough to seat the o-rings properly. Good Luck, Michael
(Offline)

30th January 2007, 14:34	#4 (permalink)
Jordan ebt called me stroppy! Current Rebreather/s: Optima Other Rebreather/s: Join Date: May 2005 Location: North Florida Posts: 225	Re: Pos. check on Optima As mentioned above, this has to do with the Extendair canister and its orings. Do your pos test with the unit upright...any Optima user knows the unit is extremely dry. __________________ Is it clear? No. Well, let's go anyways. "Those who would sacrifice a little freedom for a little order, will lose both, and deserve neither." Thomas Jefferson
(Offline)

30th January 2007, 18:50	#5 (permalink)
seafox 02ptima Instructor Current Rebreather/s: Inspiration Classic Optima Other Rebreather/s: Join Date: Mar 2005 Location: TORONTO, CANADA -Have "02ptima" will travel! Posts: 172	Re: Pos. check on Optima A couple of suggestions: 1) The two "thin" o-ings on the CL connections to the breathing hose wear out quickly, if you remove the hoses often to clean and you should. As they are very thin they don't take much abuse! Be gentle inserting the connection. They will slowly leak eventually. I change mine approx every 3months or 30 hours 2) If it's the cannister leaking, it's best to order the kit and replace the o-rings. I would! 3) There exists a white plastic key used to lock the dump valve on the right CL.(Check with DR, not sure if it's still available) It prevents leakage over longer periods of time, if tha'ts what you want to do. Cornel __________________ Protect the SHARKS! Excellence is never an accident; it is always the result of high intention, sincere effort, intelligent direction, skillful execution and the vision to see obstacles as opportunities. Experience is a hard teacher because she gives the test first, the lesson afterwards!
(Offline)

30th January 2007, 20:30	#6 (permalink)
Harvey Sisco New Member Current Rebreather/s: Optima Other Rebreather/s: Join Date: Jan 2006 Location: Farmersville TX. Posts: 20	Re: Pos. check on Optima Thanks for the information I will do my Pos. and neg. checks with unit upright. You'll have a good day!
(Offline)

30th January 2007, 22:33	#7 (permalink)
*ScubaDadMiami* Moderator Current Rebreather/s: Optima Other Rebreather/s: Join Date: Sep 2005 Location: Florida, USA Posts: 2,073	Re: Pos. check on Optima I also went through this a year ago when I got my Optima. The canister o-rings will deform slightly when you lay the unit down, putting pressure on just one side of the canister, breaking the seal just enough to leak out the gas. Under even hydrostatic pressure (which you will get in the water), it is not a problem at all. __________________ Howard Packer IANTD CCR Instructor Miami Beach, Florida CCRDiveTraining.com
(Offline)

30th January 2007, 22:38	#8 (permalink)
*ScubaDadMiami* Moderator Current Rebreather/s: Optima Other Rebreather/s: Join Date: Sep 2005 Location: Florida, USA Posts: 2,073	Re: Pos. check on Optima Quote: (Originally Posted by seafox) . . . The two "thin" o-ings on the CL connections to the breathing hose wear out quickly, if you remove the hoses often to clean and you should. As they are very thin they don't take much abuse! Be gentle inserting the connection. They will slowly leak eventually. I change mine approx every 3months or 30 hours You are aware that they changed the o-rings on the inlets to a slightly larger (or thicker) size from the original design (which I think are now the same size as on the hoses), right? I have also noticed that the oxygen compatible lubricant can get dried and hardened after a while, causing small leaking at those connection points if forming at the o-rings. So, I have made sure to clean it out when it starts to get like this, and this has worked well. __________________ Howard Packer IANTD CCR Instructor Miami Beach, Florida CCRDiveTraining.com
(Offline)

30th January 2007, 22:51	#9 (permalink)
n2diving Custom Title Allowed! Current Rebreather/s: Optima Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Feb 2005 Location: Florida, USA Posts: 271	Re: Pos. check on Optima Conventional wisdom is Optima's MUST be upright for positive and neg as discussed previously. IMO, the cause has to do with the position of the plastic buckle of the elastic retaining strap that threads through to hold the canister body in place in the case. The strap can be rotated easily, but if positioned such that the large plastic buckle is in contact between the canister body and the ground when the unit is on it's back, the 'high spot' on the canister wall it creates causes the thin wall of the canister body to flex enough to break the o-ring seal(s). When you tighten the strap, the buckle just naturally seems to want to end up at exactly position to cause the problem. If you are carefull to position the buckle so that its out of the way (which makes it damned hard to tighten), the unit will pass pos/neg on it's back.. at least it will for me. But it makes it such a hassle to tighten the strap I just stand it upright. The O-ring problem mentioned by seafox should not be happening and could be that he is using 022 or perhaps even 023 Buna-n (nitrile) 70 durometer (Shore A) o-rings (the early units shipped with 023 Buna-n's that were later changed.) The correct Oring is 022 Viton 90 durometer.... mine have 200+ dives on them without replacement. FYI, I beleive scubadadmiami is incorrect on the original vs replacement sizes. The 023 diameter was too large and would not stay in the groove and was so soft it would wrinkle too easily. The 90 duro is important, a standard Viton is 75 duro and nearly all nitriles are 70 duro, but I did some testing and discovered the harder slightly smaller o-ring worked much better. The thickness (first digit = 0) did not change. The new O-ring spec was caught very early, but seafox did receive one of the very early units. RE: I've also seen the canister failling positive/neg and having reseat the lids to correct. It's root cause in my personal experience is not lubricating the edge of the canister body (the long black cylinder) before each assembly. However, you don't have to smear the christo-lube all over until the black edges turn white... just apply enough so that the sealing surface is 'shiny black'. This issue is if the sealing surface on the canister body is dry/dirty... the very large silicone orings (the orange ones) that it seals with will 'wrinkle' as the end caps are pushed in and twisted causing enough of a seal failure that it won't hold a pressure test. For whatever reason, the problem seems more pronounced for me on the end with with the electronics. If it happens and I'm in a hurry (which is usually when it happens because I was too much in a hurry to take a moment to clean and lube the edges of the canister body) , rather than fuss with th lids I've found I can loosen the retaining strap, grap the canister body with both hands rotate it back to unlock it and then rotate it back to lock position... it will almost always pass after that. In my observation O2ptima owners as a general rule are using WAAAAY TOOOOO MUUUUCCH lube.... on the various connections. When you lube, do so very sparingly and before you lube wipe the surfaces completely dry to remove all old pre-existing lube entirely. -- Mark Last edited by n2diving : 30th January 2007 at 23:17.
(Offline)

30th January 2007, 23:37	#10 (permalink)
Muzz New Member Current Rebreather/s: Megalodon Optima Other Rebreather/s: Join Date: Mar 2005 Location: Pompano Beach FL Posts: 127	Re: Pos. check on Optima Mark You brought up a few good points. This might be a hijack. First of all why is O2 lube used on Rebreather fitttings? Silicone works much better as a lube. Is it not safe to inhale or what? There isn't enough pressure for need of the O2 capability of the grease. And second, your right about the over use of grease. If you can see it , it's too much. I rebuild regs for shops for a little extra cash in my spare time. You should see what happens when too much grease is used, it looks like glue. Also I only use O2 grease if it needs it. silcone works better in most applications.
(Offline)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode