Should a BOV screw up a -/+ test ?

colinicky · 25th May 2006, 21:03

As it says in the title my original opinion of a BOV was that when you turned the BOV to bailout mode then the loop was TOTALLY sealed .Having read various threads it would seem that some of your BOVs do not do this ?
Therefore you cannot hold a negative or positive test with out shutting flow stops etc or even clingfilm over the mouth piece

.
So the questions are
Do you think they should seal the loop totally ?
If you own one ,which one & does it seal the loop or not ?

& Decoweenie isn't eligible as he's already said he has/has had them all & he's jinxed because they all leaked

decoweenie · 25th May 2006, 21:45

Quote: (Originally Posted by colinicky)

& Decoweenie isn't eligible as he's already said he has/has had them all & he's jinxed because they all leaked

OK, but I will have 2 brand new BOV designs to test as soon as I get home in 2 weeks...

Padowan · 25th May 2006, 21:48

My Divematics can hold positive and negative perfectly - as long and hard(!) as it used to with the std mouthpiece (my unit can hold a pos or a neg for about week if I want). With the negative test there's no difference to the normal mouthpiece, suck, crush and twist the level. But for the positive test it's less easy to get a really hard test by mouth as when you turn the level there's a short period of time that the loop vents through the 2nd stage so you lose a bit of pressure, but it's only a little if you blow hard and twist quickly! If I really want a hard +ve test then I can use the manual injector to pump up the loop when the BOV is shut.

pchanning · 25th May 2006, 22:42

Quote: (Originally Posted by Padowan)

My Divematics can hold positive and negative perfectly - as long and hard(!) as it used to with the std mouthpiece...

Yep, same as that. I cant say that I follow recent threads and that maybe to an extent mouthpiece dependant. The kiss is very differnent to the divemetics. Mine works a treat (divematics) - no problems.

Andy M · 25th May 2006, 23:48

Quote: (Originally Posted by colinicky)

As it says in the title my original opinion of a BOV was that when you turned the BOV to bailout mode then the loop was TOTALLY sealed .Having read various threads it would seem that some of your BOVs do not do this ?
If you own one ,which one & does it seal the loop or not ?

KISS, never had a problem with sealing the loop at all. The key is to keep it lubricated. and when the Rebreather is in storage i keep it partially open (45 degs) to take the strain off the o-rings. Still opens and closes with a satisfying click

***diverklondike*** · 26th May 2006, 02:05

I will try it on my Golem bov tomorrow.

M

Skipbreather · 26th May 2006, 02:27

Not if it is correctly built. The key- in the basic turning drum/ cylinder type design- is VERY close tolerances. We are talking +/- less than 1/2 of one 1/1000 th of an inch. My homebuilt BOV (4th iteration) does and does. I learned it the hard way.

Other types must, by nature, rely on added seals of some kind. There you pays yer money & you takes yer chances.......

Best of luck!

Ken

Drmike · 26th May 2006, 03:36

Does the inner barrel have o-rings that close off (seal) the inlet/outlet when valve is closed? if not then it might not pass a neg test, especially if the 2nd stage has no shut off valve or is not connected.

colinicky · 26th May 2006, 06:35

Quote: (Originally Posted by Drmike)

Does the inner barrel have o-rings that close off (seal) the inlet/outlet when valve is closed? if not then it might not pass a neg test, especially if the 2nd stage has no shut off valve or is not connected.

Mike
That is my exact point though ,I would have thought there should NOT be any way for air to migrate from the CC side to the OC side or vice versa .

Quote from Geordiediver about the V4tec :-
" On fitting the BOV, it was impossible to get my Inspiration to hold a negative pressure test (or indeed a +ve test) - the air appeared to be getting in through the mouthpiece - I am not sure how, but when I streched some clingfilm over the mouthpiece, it was definately being sucked in."

This is one of the comments that started me thinking .If you think about it in relation to a standard inspo DSV it would be like saying " oh I closed the mouthpiece but it leaked water in through the little slot at the bottom which filled the loop !"
I know its a little more technical than that but basically (very) take an inspo DSV & slap a reg underneath & you have a BOV !
Or is this were manufacturers have gone wrong ? In trying to get away from the "Twist mouthpiece" to close the loop they have moved away from the most effective way of sealing ?
Further ponderings to come

abowie · 26th May 2006, 07:52

Maybe I'm missing the point here, but what's the point of a BOV that DOESN'T seal the loop when you're on OC?

My KISS one does.

25th May 2006, 21:03	#1 (permalink)
colinicky Custom Title Allowed! Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Mar 2005 Location: uk Posts: 668	Should a BOV screw up a -/+ test ? As it says in the title my original opinion of a BOV was that when you turned the BOV to bailout mode then the loop was TOTALLY sealed .Having read various threads it would seem that some of your BOVs do not do this ? Therefore you cannot hold a negative or positive test with out shutting flow stops etc or even clingfilm over the mouth piece . So the questions are Do you think they should seal the loop totally ? If you own one ,which one & does it seal the loop or not ? & Decoweenie isn't eligible as he's already said he has/has had them all & he's jinxed because they all leaked __________________ Colin I trust my rebreather completely , I just don't trust the user onwards & downwards
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25th May 2006, 21:45	#2 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,510	Re: Should a BOV screw up a -/+ test ? Quote: (Originally Posted by colinicky) & Decoweenie isn't eligible as he's already said he has/has had them all & he's jinxed because they all leaked OK, but I will have 2 brand new BOV designs to test as soon as I get home in 2 weeks...
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25th May 2006, 21:48	#3 (permalink)
Padowan Proper Boffin Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Feb 2005 Location: Kent, UK. Posts: 518	Re: Should a BOV screw up a -/+ test ? My Divematics can hold positive and negative perfectly - as long and hard(!) as it used to with the std mouthpiece (my unit can hold a pos or a neg for about week if I want). With the negative test there's no difference to the normal mouthpiece, suck, crush and twist the level. But for the positive test it's less easy to get a really hard test by mouth as when you turn the level there's a short period of time that the loop vents through the 2nd stage so you lose a bit of pressure, but it's only a little if you blow hard and twist quickly! If I really want a hard +ve test then I can use the manual injector to pump up the loop when the BOV is shut. __________________ Padowan The future's bright, the future's Yellow .....for now padowan.net - Latest Video: Scapa Flow Rebreather Diving
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25th May 2006, 22:42	#4 (permalink)
pchanning PFO free :) Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Feb 2005 Location: fixed! Posts: 454	Re: Should a BOV screw up a -/+ test ? Quote: (Originally Posted by Padowan) My Divematics can hold positive and negative perfectly - as long and hard(!) as it used to with the std mouthpiece... Yep, same as that. I cant say that I follow recent threads and that maybe to an extent mouthpiece dependant. The kiss is very differnent to the divemetics. Mine works a treat (divematics) - no problems. __________________ Cheers Paul The key to enlightenment... is survival.
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25th May 2006, 23:48	#5 (permalink)
Andy M Dude Current Rebreather/s: Home Build Other Rebreather/s: Sport Kiss Home Build Join Date: Mar 2005 Location: Cambridge, UK Posts: 415	Re: Should a BOV screw up a -/+ test ? Quote: (Originally Posted by colinicky) As it says in the title my original opinion of a BOV was that when you turned the BOV to bailout mode then the loop was TOTALLY sealed .Having read various threads it would seem that some of your BOVs do not do this ? If you own one ,which one & does it seal the loop or not ? KISS, never had a problem with sealing the loop at all. The key is to keep it lubricated. and when the Rebreather is in storage i keep it partially open (45 degs) to take the strain off the o-rings. Still opens and closes with a satisfying click __________________ Know your PO2 at all times
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26th May 2006, 02:05	#6 (permalink)
*diverklondike* Moderator Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Oct 2005 Location: Delaware, USA Posts: 1,556	Re: Should a BOV screw up a -/+ test ? I will try it on my Golem bov tomorrow. M
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26th May 2006, 02:27	#7 (permalink)
Skipbreather Reads the fine print Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet MK 15.X Home Build Join Date: Mar 2005 Location: Chicago, Illinois, USA Posts: 543	Re: Should a BOV screw up a -/+ test ? Not if it is correctly built. The key- in the basic turning drum/ cylinder type design- is VERY close tolerances. We are talking +/- less than 1/2 of one 1/1000 th of an inch. My homebuilt BOV (4th iteration) does and does. I learned it the hard way. Other types must, by nature, rely on added seals of some kind. There you pays yer money & you takes yer chances....... Best of luck! Ken
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26th May 2006, 03:36	#8 (permalink)
Drmike Custom Title Allowed! 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: 3,157	Re: Should a BOV screw up a -/+ test ? Does the inner barrel have o-rings that close off (seal) the inlet/outlet when valve is closed? if not then it might not pass a neg test, especially if the 2nd stage has no shut off valve or is not connected. __________________ 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
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26th May 2006, 06:35	#9 (permalink)
colinicky Custom Title Allowed! Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Mar 2005 Location: uk Posts: 668	Re: Should a BOV screw up a -/+ test ? Quote: (Originally Posted by Drmike) Does the inner barrel have o-rings that close off (seal) the inlet/outlet when valve is closed? if not then it might not pass a neg test, especially if the 2nd stage has no shut off valve or is not connected. Mike That is my exact point though ,I would have thought there should NOT be any way for air to migrate from the CC side to the OC side or vice versa . Quote from Geordiediver about the V4tec :- " On fitting the BOV, it was impossible to get my Inspiration to hold a negative pressure test (or indeed a +ve test) - the air appeared to be getting in through the mouthpiece - I am not sure how, but when I streched some clingfilm over the mouthpiece, it was definately being sucked in." This is one of the comments that started me thinking .If you think about it in relation to a standard inspo DSV it would be like saying " oh I closed the mouthpiece but it leaked water in through the little slot at the bottom which filled the loop !" I know its a little more technical than that but basically (very) take an inspo DSV & slap a reg underneath & you have a BOV ! Or is this were manufacturers have gone wrong ? In trying to get away from the "Twist mouthpiece" to close the loop they have moved away from the most effective way of sealing ? Further ponderings to come __________________ Colin I trust my rebreather completely , I just don't trust the user onwards & downwards
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26th May 2006, 07:52	#10 (permalink)
abowie Fighting Girl Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: May 2005 Location: Land of Oz Posts: 573	Re: Should a BOV screw up a -/+ test ? Maybe I'm missing the point here, but what's the point of a BOV that DOESN'T seal the loop when you're on OC? My KISS one does. __________________ Andrew Bowie Rebreather-friendly Buddy
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