BOV and extra 2nd stage

silent running

Hi Dave, when using your inflator, do you ever worry about the high flow of O2 through it starting a fire? Is the bore on the Zeagle QC as big as the Scubapro Air2? I like your idea, I just worry about any potential friction/turbulence in the inflator mechanism sparking the O2...

Hanssing

Hi Dave,

About the freeflow - I get that, since the reg can be detuned for use only near the surface, and the fixed IP means its even less likely to when descending.
Still I'm vary due to stories about Inspo-inflators freeflowing and loosing all dil at depth. Though its a different piece of gear and IP is balanced, in their case. The reg-combo is simple since it does away with the T-piece and OPV, so like everything else in these setups its a matter of cost-benefit (cost as in possible failures - NOT monetary).

The reason for sticking with the normal inflator is that if I ever need access to the onboard O2, I attach the O2 hose to the the male offboard connector or directly to the BOV, wich I would have time to do, since I'm in the shallows then. Granted its easier to just grab the inflator and put in your mouth, again its a tradeoff, where I don't have enough experience to decide. I know I want one of the two solutions, so I could test both and decide.

The checkvalve is offcourse needed af the male offboard connection.
But I dont see why a high cracking-pressure is really needed?
If no offboard is attaced, the DIL-ip will give the valve a back-pressure of 8-10bars. If offboard is connected it will be sealed by the orings, and pressure.
The only issue would be splashing with dil turned of.
Or perhaps you're thinking off water-ingress when rinsing?

As long as its just cracking pressure, but in check-valves that would normally be added to the total pressure-drop over the valve (i think, since no venturi-assist etc exists), causing reduced IP at the BOV

Hmm, you will have a hard time getting Rasmus to use it
So by process of elimination the only remaining Danish rEvo-diver would be little ol' me

Granted my signature still stays in effect.

Regards
Nicolai

__________________
Woohooo - I can change my rEvo!
Its going to be bitchin' tricked out piece of gear

Dave Sutton

Uhh...... no, because I studied basic physics: A gas going from a high pressure state to a low pressure state gets colder... and a regulator is a regulator, dig? Who cares if it also can be directed to add gas to a set of wings in addition to a mouth?

I'm really very discouraged in the level of peoples 02 awareness, which is a result not of the divers, but of poor initial training (IE: blame your instructor for not teaching you): You get fire when you have FUEL, OXYGEN, and *HEAT*. When you OPEN a valve with HP 02 and pressurize an area with HIGH PRESSURE GAS you make heat. Once it's pressurized, you will not have a fire *ever* unless conditions that are virtually impossible to set up in diving apparatus occur. There is *zero* potential for a fire in low pressure areas, and certainly not while pressure is being reduced.


Zeagle (Apeks) inflators use CEJN fittings, which is why I use them: They are standard to all of my other QD's. They breathe remarkably well too.... don't compare them to the Buddy POS "whatever it is". The Apeks is a good regulator, and was sold for a number of years, sans the BC part, as a normal diving regulator (that looked remarkably like a plastic Poseidon Cyklon).



Dave

Dave Sutton

Yup on the first (showing high marks for intellectual understanding of the system, well done), and "don't compare shit to shinola" on the second. (there's an American English slang phrase to contemplate for a while! ).

(OK, here it is: "Shinola" was a 1930's shoe polish, advertised on radio "only 5 cents for the best shine...". It looked like, well..... you know. So the expression is "You don't know shit from shinola". Don't compare the Buddy POS to the Apreks regulator. The latter is top-quality. And if it freeflows.... disconnect the damned thing.


I took the liberty of making up a manifold for you, so when you have your dives logged, let me know.


Dave

Hanssing

Sorry cant talk now, gone diving

I'm just a little bit curious as to when the piece was made?
BTW exactly how do you route the drysuit hose?

Best Regards
Nicolai

__________________
Woohooo - I can change my rEvo!
Its going to be bitchin' tricked out piece of gear

silent running

Dave, thanks for the explanation. Yes, I'm aware that high to low pressure=temp drop, just didn't know that it was enough to cancel out any friction. I suppose I got the idea that friction was the main culprit after learning that most O2 fires start in the tank valve and being trained to open the valve slowly.

Dave Sutton

Friction has zero to do with anything here... the reason you are taught to open the valve slowly is to reduce the adiabatic compression.... IE: The heat of gas being *compressed* in the downstream area. The rate of compression controls the temperature of the gas being compressed. Think of a Diesel engine... that's how they ignite the fuel/air mix. Note the trio: FUEL, AIR, and HEAT...that's a Diesel. Take a piece of tubing, add a fuel to it's interior, ensure there is adequate oxygen there, and then *raise the system to the ignitioin point of the fuel*. Then you'll have a fire. Use the *heat of compression* as the heat source and you have a Diesel engine. Do the *exact same thing* in a regulator and you have an 02 fire. You need a LOT of heat to raise the fuel to ignition. What's the fuel? oil, grease, neoprene O-Rings, and metal (yes, it can burn). How hot? 1000 degrees F? Bloody hell.... friction? Try rubbing two sticks together one day... even in pure 02. No heat? No fire. No fuel? No fire. We keep fuels out by cleaning. We keep the temperature down by *slowly* opening *high pressure 02 sources* On the LP sde? Forget it.

Yes, you can also produce heat with a shock wave forming behind a piece of debris (a metal burr, for example) in the gas stream. In that case it's the gas VELOCITY that is the culprit... it needs to be at near sonic speeds for this to occur. Once again... open HP valves slowly.



Not picking on you here, I promise: I'm picking on your instructor, who failed to teach you what you need to know:

*What in the world are instructors actually teaching students about this stuff?*. Do any of them actually know what the heck they are talking about?


Dave

MarcLaukien

The Diesel engine analogy is a great one! You should talk to the training agencies to put this into their literature...

silent running

Hi Dave, thanks for the further explanation. No, I didn't think you were picking on me, I try not to assume the worst when reading posts. The diesel engine example is helpful, I have a diesel and I'm familiar with compression ignition and the need for 2 powerful batteries to power that big starter which has to have enough power to move the pistons forcefully enough to compress the fuel and start an adiabatic reaction.

But here's this explanation from an O2 regulator company web site called Flotech:

"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.

And to be fair to my instructor, I can't remember very much of what he said to me about O2 fires other than not to turn the valve too fast and that the particular valves on our cylinders were sourced for their slow turning mechanism. My Mod 1 class was over 5 years ago...

Rickoz

At first my idea was just have QD on the first stage (all can connect to a manifold) then my MDV keep failing & could get no gas at all so thought this aint gonna work.
So YES i have a 2nd stage as well, BOV on the KISS.
No shut off Valves at all on my setup.
Rickoz

__________________
Rickoz
KISS Rebreather Pilot 109