Arrrrrggghhh V4Tec BOV

Mark Chase · 29th September 2006, 19:08

OK so my new toy the V4tec BOV passes positive no problem but negative is an instantaneous failure. Having a look it is blindingly obvious that gas is escaping past the center spindle into the loop.

Neg test passes on everything except the BOV

This is pissing me off. What is it with BOVs and neg tests?

I striped the face plate and one of the feeeds enough to see the problem but is there anything specific I can do or is hopeing for a neg test on a BOV just a pipe dream

ATB

Mark Chase

colinicky · 29th September 2006, 19:49

I assume you have the feed to the oc reg side isolated with a flow stop or connected to a closed cylinder ?
try reading Mikes reply here post no 11
http://www.rebreatherworld.com/techn...up-test-2.html

decoweenie · 29th September 2006, 20:30

Mark,

You have to know your tool, M8.

The V4TEC will hold negative pressure if you put the mouthpiece in your mouth. There is no seal between the OC and CC sides.

Mark Chase · 30th September 2006, 08:57

Quote: (Originally Posted by decoweenie)

Mark,

You have to know your tool, M8.

The V4TEC will hold negative pressure if you put the mouthpiece in your mouth. There is no seal between the OC and CC sides.

Ooooooook

In that case it pases neg no problem at all.

So if you bail out off loop whilst on OC wont it let water in?

ATB

Mark Chase

Mark Chase · 30th September 2006, 09:08

Quote: (Originally Posted by colinicky)

I assume you have the feed to the oc reg side isolated with a flow stop or connected to a closed cylinder ?
try reading Mikes reply here post no 11
http://www.rebreatherworld.com/techn...up-test-2.html

Yes i have isolated the gas supply. Looking at it there apears to be no 0 ring on the barrel. Its just a tolerance seel. My one failes compleatly in under a second. It might as well be open

With the bov in my mouth the unit hold neg no problem so its definiatly sucking in through the mouth piece only.

ATB

Mark Chase

colinicky · 30th September 2006, 09:46

Mark
I think as Mike said if your that worried about water getting into the loop if you bailed of loop including the oc side & went to a stage reg .Then to prove it to yourself that the water is not going to get in then you need a big bucket or leybourne ! isolate & purge oc reg, put your head under water ,suck neg turn knob release mouth piece under water ,return head to air & breath

keep mouth piece under water untill you are either happy that it is holding neg in water or the neg fails .if it fails then open loop & see if it is flooded or if the gas leak is somewere else
hope that helps m8
see pm

jhaaja · 30th September 2006, 12:02

Quote: (Originally Posted by Mark Chase)

Yes i have isolated the gas supply. Looking at it there apears to be no 0 ring on the barrel. Its just a tolerance seel. My one failes compleatly in under a second. It might as well be open

With the bov in my mouth the unit hold neg no problem so its definiatly sucking in through the mouth piece only.

ATB

Mark Chase

Mine is just the same. I just set the unit up for diving and it holds neg when I keep it in my mouth.

If you bail it will not let any water in because you don`t have a neg. pressure in the loop. And water is tenser than gas so it needs a bigger hole to go through.

Skipbreather · 30th September 2006, 13:34

Quote: (Originally Posted by Mark Chase)

Neg test passes on everything except the BOV

This is pissing me off. What is it with BOVs and neg tests?

ATB

Mark Chase

Hi Mark-

I’ve built several BOVs with the rotating spool layout and I’ve learned a lot in the process. Here is what is most likely going on:

The EXTERNAL seal- to keep water out of the loop- is the O ring on the spool near whatever serves the function of a face plate/ spool retainer. The gas leaks that cause failure of the neg test occur within the loop- thru the mouthpiece as stated above. A BOV indeed CAN be built to allow a spool type design a decent neg test, but it ain’t easy. I found that the tolerance spool to body has to be in the 0.0005” range- yes 5 ten thousandths of an inch. The final seal is then achieved with lube in the spool to body interface. No O rings involved.

With this tight a clearance my BOV does good +/_ tests, but the spool is not an easy “flick” to twist ala Jetsam. The slight extra effort required to twist a spool vs how other more complex designs function is worth it to me because the internal bore is a LOT larger = lower WOB.

A spool design could be designed gas tight another way as well but would require some pretty exotic milling or molding gear that would allow O ring grooves to be produced on the face of a cylindrical shape. WAAAAAY beyond the capability of my stone age shop…………

Clear as mud, right?

Best,
Ken

***jradomski*** · 30th September 2006, 16:03

Quote: (Originally Posted by Skipbreather)

Hi Mark-

I’ve built several BOVs with the rotating spool layout and I’ve learned a lot in the process. Here is what is most likely going on:

The EXTERNAL seal- to keep water out of the loop- is the O ring on the spool near whatever serves the function of a face plate/ spool retainer. The gas leaks that cause failure of the neg test occur within the loop- thru the mouthpiece as stated above. A BOV indeed CAN be built to allow a spool type design a decent neg test, but it ain’t easy. I found that the tolerance spool to body has to be in the 0.0005” range- yes 5 ten thousandths of an inch. The final seal is then achieved with lube in the spool to body interface. No O rings involved.

With this tight a clearance my BOV does good +/_ tests, but the spool is not an easy “flick” to twist ala Jetsam. The slight extra effort required to twist a spool vs how other more complex designs function is worth it to me because the internal bore is a LOT larger = lower WOB.

A spool design could be designed gas tight another way as well but would require some pretty exotic milling or molding gear that would allow O ring grooves to be produced on the face of a cylindrical shape. WAAAAAY beyond the capability of my stone age shop…………

Clear as mud, right?

Best,
Ken

The BOV from Divematics, holds a reasonable negative test.. It wount hold overnight but no discernable gas loss after 30 minutes

pchanning · 30th September 2006, 16:26

Quote: (Originally Posted by jradomski)

The BOV from Divematics, holds a reasonable negative test.. It wount hold overnight but no discernable gas loss after 30 minutes

That'll be the o-rings then. [1]

Incidentally, the milling out done to seat the o-rings into the spinee central barrel on the DM is very difficult (as Skipbreather said), is well executed and is no doubt reflected in its price. Negative tests are quite precious to some CCR divers. Shame the V4tec BOV jeopordises that.

[1] now I understand what all the 'OC to CCR side is open when closed' stuff was all about a few months back.

BTW, Mark - sorry to hear that you have had this hassle, again. 1 second neg, thats rubbish.

Cheers
Paul

29th September 2006, 19:08	#1 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,697	Arrrrrggghhh V4Tec BOV OK so my new toy the V4tec BOV passes positive no problem but negative is an instantaneous failure. Having a look it is blindingly obvious that gas is escaping past the center spindle into the loop. Neg test passes on everything except the BOV This is pissing me off. What is it with BOVs and neg tests? I striped the face plate and one of the feeeds enough to see the problem but is there anything specific I can do or is hopeing for a neg test on a BOV just a pipe dream ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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29th September 2006, 19:49	#2 (permalink)
colinicky Custom Title Allowed! Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Mar 2005 Location: uk Posts: 667	Re: Arrrrrggghhh V4Tec BOV I assume you have the feed to the oc reg side isolated with a flow stop or connected to a closed cylinder ? try reading Mikes reply here post no 11 http://www.rebreatherworld.com/techn...up-test-2.html __________________ Colin I trust my rebreather completely , I just don't trust the user onwards & downwards
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29th September 2006, 20:30	#3 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,487	Re: Arrrrrggghhh V4Tec BOV Mark, You have to know your tool, M8. The V4TEC will hold negative pressure if you put the mouthpiece in your mouth. There is no seal between the OC and CC sides. __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
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30th September 2006, 08:57	#4 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,697	Re: Arrrrrggghhh V4Tec BOV Quote: (Originally Posted by decoweenie) Mark, You have to know your tool, M8. The V4TEC will hold negative pressure if you put the mouthpiece in your mouth. There is no seal between the OC and CC sides. Ooooooook In that case it pases neg no problem at all. So if you bail out off loop whilst on OC wont it let water in? ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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30th September 2006, 09:08	#5 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,697	Re: Arrrrrggghhh V4Tec BOV Quote: (Originally Posted by colinicky) I assume you have the feed to the oc reg side isolated with a flow stop or connected to a closed cylinder ? try reading Mikes reply here post no 11 http://www.rebreatherworld.com/techn...up-test-2.html Yes i have isolated the gas supply. Looking at it there apears to be no 0 ring on the barrel. Its just a tolerance seel. My one failes compleatly in under a second. It might as well be open With the bov in my mouth the unit hold neg no problem so its definiatly sucking in through the mouth piece only. ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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30th September 2006, 09:46	#6 (permalink)
colinicky Custom Title Allowed! Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Mar 2005 Location: uk Posts: 667	Re: Arrrrrggghhh V4Tec BOV Mark I think as Mike said if your that worried about water getting into the loop if you bailed of loop including the oc side & went to a stage reg .Then to prove it to yourself that the water is not going to get in then you need a big bucket or leybourne ! isolate & purge oc reg, put your head under water ,suck neg turn knob release mouth piece under water ,return head to air & breath keep mouth piece under water untill you are either happy that it is holding neg in water or the neg fails .if it fails then open loop & see if it is flooded or if the gas leak is somewere else hope that helps m8 see pm __________________ Colin I trust my rebreather completely , I just don't trust the user onwards & downwards
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30th September 2006, 12:02	#7 (permalink)
jhaaja Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Mar 2005 Location: Finland Posts: 884	Re: Arrrrrggghhh V4Tec BOV Quote: (Originally Posted by Mark Chase) Yes i have isolated the gas supply. Looking at it there apears to be no 0 ring on the barrel. Its just a tolerance seel. My one failes compleatly in under a second. It might as well be open With the bov in my mouth the unit hold neg no problem so its definiatly sucking in through the mouth piece only. ATB Mark Chase Mine is just the same. I just set the unit up for diving and it holds neg when I keep it in my mouth. If you bail it will not let any water in because you don`t have a neg. pressure in the loop. And water is tenser than gas so it needs a bigger hole to go through.
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30th September 2006, 13:34	#8 (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: 557	Re: Arrrrrggghhh V4Tec BOV Quote: (Originally Posted by Mark Chase) Neg test passes on everything except the BOV This is pissing me off. What is it with BOVs and neg tests? ATB Mark Chase Hi Mark- I’ve built several BOVs with the rotating spool layout and I’ve learned a lot in the process. Here is what is most likely going on: The EXTERNAL seal- to keep water out of the loop- is the O ring on the spool near whatever serves the function of a face plate/ spool retainer. The gas leaks that cause failure of the neg test occur within the loop- thru the mouthpiece as stated above. A BOV indeed CAN be built to allow a spool type design a decent neg test, but it ain’t easy. I found that the tolerance spool to body has to be in the 0.0005” range- yes 5 ten thousandths of an inch. The final seal is then achieved with lube in the spool to body interface. No O rings involved. With this tight a clearance my BOV does good +/_ tests, but the spool is not an easy “flick” to twist ala Jetsam. The slight extra effort required to twist a spool vs how other more complex designs function is worth it to me because the internal bore is a LOT larger = lower WOB. A spool design could be designed gas tight another way as well but would require some pretty exotic milling or molding gear that would allow O ring grooves to be produced on the face of a cylindrical shape. WAAAAAY beyond the capability of my stone age shop………… Clear as mud, right? Best, Ken
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30th September 2006, 16:03	#9 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,001	Re: Arrrrrggghhh V4Tec BOV Quote: (Originally Posted by Skipbreather) Hi Mark- I’ve built several BOVs with the rotating spool layout and I’ve learned a lot in the process. Here is what is most likely going on: The EXTERNAL seal- to keep water out of the loop- is the O ring on the spool near whatever serves the function of a face plate/ spool retainer. The gas leaks that cause failure of the neg test occur within the loop- thru the mouthpiece as stated above. A BOV indeed CAN be built to allow a spool type design a decent neg test, but it ain’t easy. I found that the tolerance spool to body has to be in the 0.0005” range- yes 5 ten thousandths of an inch. The final seal is then achieved with lube in the spool to body interface. No O rings involved. With this tight a clearance my BOV does good +/_ tests, but the spool is not an easy “flick” to twist ala Jetsam. The slight extra effort required to twist a spool vs how other more complex designs function is worth it to me because the internal bore is a LOT larger = lower WOB. A spool design could be designed gas tight another way as well but would require some pretty exotic milling or molding gear that would allow O ring grooves to be produced on the face of a cylindrical shape. WAAAAAY beyond the capability of my stone age shop………… Clear as mud, right? Best, Ken The BOV from Divematics, holds a reasonable negative test.. It wount hold overnight but no discernable gas loss after 30 minutes __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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30th September 2006, 16:26	#10 (permalink)
pchanning PFO free :) Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Feb 2005 Location: fixed! Posts: 454	Re: Arrrrrggghhh V4Tec BOV Quote: (Originally Posted by jradomski) The BOV from Divematics, holds a reasonable negative test.. It wount hold overnight but no discernable gas loss after 30 minutes That'll be the o-rings then. [1] Incidentally, the milling out done to seat the o-rings into the spinee central barrel on the DM is very difficult (as Skipbreather said), is well executed and is no doubt reflected in its price. Negative tests are quite precious to some CCR divers. Shame the V4tec BOV jeopordises that. [1] now I understand what all the 'OC to CCR side is open when closed' stuff was all about a few months back. BTW, Mark - sorry to hear that you have had this hassle, again. 1 second neg, thats rubbish. Cheers Paul __________________ Cheers Paul The key to enlightenment... is survival.
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