BOV and extra 2nd stage

**Dave Sutton** · 21st September 2007, 01:33

(quote=silent running;138197]"QUESTION: What are the sources of ignition in oxygen systems?

ANSWER:

Adiabatic (isentropic) compression of the oxygen. When oxygen is rapidly compressed, it gets hot. The temperature of oxygen can rise to 1688 degrees F if it is quickly compressed to 2000 psi, hot enough to ignite seals or contaminants within the device. This is why it is recommended that cylinder valves be opened slowly.
A particle larger than 100 microns moving at high speed within a pressurized oxygen system may ignite upon impact and could cause the material, which it strikes to start burning.
Heat generated by the friction of materials rubbing against each other - rare.
Acoustic resonance - rare."

So here is a reference to friction of materials rubbing against each other, although rare. Also, isn't the heat generated by compressing gas coming from the friction of gas molecules as they are forced closer together? Sorry if I'm a PITA, I'm just trying to figure out how I came to think O2 fires had anything to do with friction.

[quote]

Friction would be mechanical friction... file a a piece of iron in an oxygen filled hyperbaric chamber and you'll have that one pegged. Have a resonant vibration between two pieces of metal in a high pressure 02 system and you have the same thing. It's NOT caused by the gas itself "rubbing across" anything, but by "materials" *within the 02 environment* rubbing against *each other*.

Adiabatic heating is something you can look up on Wikipedia. That's the Diesel engine analogy.

Adiabatic process - Wikipedia, the free encyclopedia

Back to the basics... we breathe 02 from regulators all the time.... why worry about that regulator being a wings-inflator also?

Dave

silent running · 21st September 2007, 04:38

[quote=Dave Sutton;138431](quote=silent running;138197]"QUESTION: What are the sources of ignition in oxygen systems?

ANSWER:

Adiabatic (isentropic) compression of the oxygen. When oxygen is rapidly compressed, it gets hot. The temperature of oxygen can rise to 1688 degrees F if it is quickly compressed to 2000 psi, hot enough to ignite seals or contaminants within the device. This is why it is recommended that cylinder valves be opened slowly.
A particle larger than 100 microns moving at high speed within a pressurized oxygen system may ignite upon impact and could cause the material, which it strikes to start burning.
Heat generated by the friction of materials rubbing against each other - rare.
Acoustic resonance - rare."

So here is a reference to friction of materials rubbing against each other, although rare. Also, isn't the heat generated by compressing gas coming from the friction of gas molecules as they are forced closer together? Sorry if I'm a PITA, I'm just trying to figure out how I came to think O2 fires had anything to do with friction.

Quote:

Friction would be mechanical friction... file a a piece of iron in an oxygen filled hyperbaric chamber and you'll have that one pegged. Have a resonant vibration between two pieces of metal in a high pressure 02 system and you have the same thing. It's NOT caused by the gas itself "rubbing across" anything, but by "materials" *within the 02 environment* rubbing against *each other*.

Adiabatic heating is something you can look up on Wikipedia. That's the Diesel engine analogy.

Adiabatic process - Wikipedia, the free encyclopedia

Back to the basics... we breathe 02 from regulators all the time.... why worry about that regulator being a wings-inflator also?

Dave

Well, I had thought that maybe moving metal parts of the inflator mechanism spring/button assembly-might be a source of friction in the path of the O2. But now that I understand more, I won't worry about it. Thanks for all the info Dave, -Andy

Gilles · 21st September 2007, 09:52

Quote: (Originally Posted by Stephane)

Hello hello,

For those who have their BOV connected to an off-board bailout tank, do you also have an extra 2nd stage (to give to a buddy) or is the BOV the only way to breathe OC on the stage?

And last question: do you have a shut-off valve on the BOV gas line? Why?

Merci beaucoup.

Stephane;

The extra 2nd stage is needed for a buddy, but can also be for yourself.

Last weekend while hanging on to a line in a current, I was looking downstream when the current suddenly pulled the BOV off of the mouthpeice. Faffed about trying to get the BOV back in the mouthpeice, but after a few seconds, opted for the left hand grab of the 2nd stage.

I'm using a shut-off valve mainly because I had it spare, but I think it adds value for reasons to discuss later if wanted.

Stephane · 21st September 2007, 10:39

Thank you all for your comments.
I'm going to leave the second stage and will add a nice shut-off valve from TDL (as it's very cheap, I will put one onto the BOV and one my other bailout reg).

21st September 2007, 01:33	#21 (permalink)
Dave Sutton Diveshop of Horrors Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Classic Kiss rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,671	Re: BOV and extra 2nd stage (quote=silent running;138197]"QUESTION: What are the sources of ignition in oxygen systems? ANSWER: Adiabatic (isentropic) compression of the oxygen. When oxygen is rapidly compressed, it gets hot. The temperature of oxygen can rise to 1688 degrees F if it is quickly compressed to 2000 psi, hot enough to ignite seals or contaminants within the device. This is why it is recommended that cylinder valves be opened slowly. A particle larger than 100 microns moving at high speed within a pressurized oxygen system may ignite upon impact and could cause the material, which it strikes to start burning. Heat generated by the friction of materials rubbing against each other - rare. Acoustic resonance - rare." So here is a reference to friction of materials rubbing against each other, although rare. Also, isn't the heat generated by compressing gas coming from the friction of gas molecules as they are forced closer together? Sorry if I'm a PITA, I'm just trying to figure out how I came to think O2 fires had anything to do with friction. [quote] Friction would be mechanical friction... file a a piece of iron in an oxygen filled hyperbaric chamber and you'll have that one pegged. Have a resonant vibration between two pieces of metal in a high pressure 02 system and you have the same thing. It's NOT caused by the gas itself "rubbing across" anything, but by "materials" within the 02 environment rubbing against each other. Adiabatic heating is something you can look up on Wikipedia. That's the Diesel engine analogy. Adiabatic process - Wikipedia, the free encyclopedia Back to the basics... we breathe 02 from regulators all the time.... why worry about that regulator being a wings-inflator also? Dave __________________ "Changes in Lattitudes, Changes in Attitudes, Nothing remains quite the same".... www.nobubblediving.com Last edited by Dave Sutton : 21st September 2007 at 01:45.
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21st September 2007, 04:38	#22 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,832	Re: BOV and extra 2nd stage [quote=Dave Sutton;138431](quote=silent running;138197]"QUESTION: What are the sources of ignition in oxygen systems? ANSWER: Adiabatic (isentropic) compression of the oxygen. When oxygen is rapidly compressed, it gets hot. The temperature of oxygen can rise to 1688 degrees F if it is quickly compressed to 2000 psi, hot enough to ignite seals or contaminants within the device. This is why it is recommended that cylinder valves be opened slowly. A particle larger than 100 microns moving at high speed within a pressurized oxygen system may ignite upon impact and could cause the material, which it strikes to start burning. Heat generated by the friction of materials rubbing against each other - rare. Acoustic resonance - rare." So here is a reference to friction of materials rubbing against each other, although rare. Also, isn't the heat generated by compressing gas coming from the friction of gas molecules as they are forced closer together? Sorry if I'm a PITA, I'm just trying to figure out how I came to think O2 fires had anything to do with friction. Quote: Friction would be mechanical friction... file a a piece of iron in an oxygen filled hyperbaric chamber and you'll have that one pegged. Have a resonant vibration between two pieces of metal in a high pressure 02 system and you have the same thing. It's NOT caused by the gas itself "rubbing across" anything, but by "materials" within the 02 environment rubbing against each other. Adiabatic heating is something you can look up on Wikipedia. That's the Diesel engine analogy. Adiabatic process - Wikipedia, the free encyclopedia Back to the basics... we breathe 02 from regulators all the time.... why worry about that regulator being a wings-inflator also? Dave Well, I had thought that maybe moving metal parts of the inflator mechanism spring/button assembly-might be a source of friction in the path of the O2. But now that I understand more, I won't worry about it. Thanks for all the info Dave, -Andy
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21st September 2007, 09:52	#23 (permalink)
Gilles Worship the feminine Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2005 Location: Den Haag (Netherlands) Posts: 762	Re: BOV and extra 2nd stage Quote: (Originally Posted by Stephane) Hello hello, For those who have their BOV connected to an off-board bailout tank, do you also have an extra 2nd stage (to give to a buddy) or is the BOV the only way to breathe OC on the stage? And last question: do you have a shut-off valve on the BOV gas line? Why? Merci beaucoup. Stephane; The extra 2nd stage is needed for a buddy, but can also be for yourself. Last weekend while hanging on to a line in a current, I was looking downstream when the current suddenly pulled the BOV off of the mouthpeice. Faffed about trying to get the BOV back in the mouthpeice, but after a few seconds, opted for the left hand grab of the 2nd stage. I'm using a shut-off valve mainly because I had it spare, but I think it adds value for reasons to discuss later if wanted. __________________ Gilles http://www.dirrebreather.com
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21st September 2007, 10:39	#24 (permalink)
Stephane Stéphane Acounis Current Rebreather/s: rEvo Other Rebreather/s: rEvo Join Date: Nov 2005 Location: Nantes - France Posts: 769	Re: BOV and extra 2nd stage Thank you all for your comments. I'm going to leave the second stage and will add a nice shut-off valve from TDL (as it's very cheap, I will put one onto the BOV and one my other bailout reg). __________________ Stéphane
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