Mix gas and double hose regulators

[Ron Hearn]

Hi

Just a question regarding the use of mixed gas while diving double hose regulators. In past films such as the Cousteau flicks were sat diving was required for deep dive like on the Britannic, was there a special compound air hose and flapper valve used. I'm sure you know today we use 02 tolerant materials to reduce the possibility of flash and deterioration of components and I was Just wondering how they delt with this problem years ago.

Ron

[jrvancealt]

if they were doing deep dives they would not be useing high percentages of oxygen and it woud not matter

as to flapper and non return valves the pressure is not high enough for them to combust

[Ron Hearn]

Hi

Thanks for the reply, than why is it that we are very concerned about these possibilities today. Nitrox and trimix was used years ago by the military and scientific community in diving and only was introduced to the public maybe 15 years ago as a recreational breathing choice. I would think all gases today and of yesterday would of had the same effects or more on natural gum rubber products. I'm just curious if there was another rubber type used to accommodate and or protect diving regular components from higher levels of 02 lets say 30 years ago, or did they just changed the rubber parts more often.

Ron

[luis]

These are very good questions, which I have been thinking about, since I have done several dives using Nitrox with my Royal Aqua Master. The following are my thoughts about it, but let me point out that I am by no means an expert.

I would agree with jrvancealt, in that O2 exposure should not be an issue with trimix, since (as far as I know) trimix would always have equal or lower O2 percentage and therefore partial pressure as air.

With Nitrox, the accepted standard is that you can use any air regulator as long as the O2 percentage is 40% or lower. Well I had to think about that a little since I am not one to follow “accepted standard” blindly (especially since I am using a “non-standard regulator”). In my mind I concluded that it is ok to use higher O2 mixtures with double hose regulators for the following reason.

Higher O2 mixtures (as far as I know) are a concern with the high pressure and intermediate pressure components since those are the ones that will be exposed to high partial pressure. The ambient pressure components will never see a partial pressure higher than 1.6 atm under today’s standards (max 2 atm under old Navy standards). These will include the ambient pressure diaphragm, hoses, mouthpiece, mushroom valves, and duckbill. Since limiting the O2 exposure to the diver (both max partial pressure and time exposure to high PP) is the restricting factor, the regulators ambient pressure components would be protected. Using standard air at acceptable greater depths would expose them to the same partial pressures.

Since O2 partial pressure is the concern, the intermediate and specially high pressure parts of a regulator have to be O2 clean and compatible for service with O2 percentages higher than 40%. O2 clean means no petroleum lubricants and O2 compatible O-rings.

The interesting part is that the Aqua Masters have no O-rings (and the Mistrals have one that is basically at ambient pressure), so as long as they are serviced and cleaned properly, I tend to think they are O2 clean regulators by default. I don’t see a need to use any lubricant in a DA Aqua Master or Mistral and the rubber parts (HP diaphragm and LP seat) exposed to intermediate pressure in my DA are basically the same as in any modern regulator like the Conshelf, etc.

The Royal Aqua Master has one high pressure O-ring in the balancing chamber. This O-ring and its associated lubricant could easily be replaced with O2 compatible materials if I was using a mixture with an O2 percentage higher than 40%. The O-rings in my Royal Aqua Masters are from a modern Conshelf, which are suitable for Nitrox service (EAN40) without needing O2 cleaning.

For Nitrox service below EAN40 I am not concerned about combustion and even less about the O-ring deteriorating during the very short exposure time to high O2 partial pressures.

If I am missing something or there is a flaw in my logic please let me know. I just got Nitrox certified this Summer, but diving physics and physiology has always been an interesting subject to me.

[RMannix]

You might already have known this, but I'm sure some didn't.

From a CNN article when SpaceShipOne won the X Prize regarding its rocket engine:
"On Wednesday, SpaceShipOne streaked even higher to 337, 569 feet (64 miles). However, during its ascent, the private spacecraft began a series of rolls that Melvill brought under control only after ending the rocket burn 11 seconds early.

SpaceShipOne's thrust was provided by two innocuous substances that, when mixed together, are explosive: nitrous oxide and rubber.

A fuel tank about six feet in diameter at the center of the craft holds liquid nitrous oxide, also known as laughing gas. A hollow tube leading from the tank to the engine nozzle is filled with solid rubber. The combustive combination produces thousands of pounds of thrust, although exact amount remains secret."

the full article is here:

www.cnn.com/2004/TECH/space/10/04/spaceshipone.attempt.cnn/index.html

[Ron Hearn]

Hi

I'd have to guess that all is well than when using mix gas with double hose regulators that have been 02 cleaned and are used with a mixture under 40%, and I'm also betting no 02 cleaning ever took place years back due to lack of industry standards and regulations. I still do allot of deep air dive from time to time with my Nemrod snark III silver and deco with an 80 mix. I guess my reg of choice for the deco bottle should't be a twin hose. I'll stick with my posiedon and keep the air as air when using my double hose as a primary.

Ron

[luis]

Nitrous Oxide is not Nitrox. Nitrous Oxide (N2O, dinitrogen monoxide) is a molecule composed of two nitrogen atoms and an oxygen atom. Nitrox is just the name for nitrogen and oxygen gasses combined. Air is also known as Nitrox 21% (EAN21).



The accepted standard is that a regulator only needs to be oxygen clean for gas with more than 40% O2.
Any regulator can be used for a gas mixture with less than 40% O2.

As I mentioned above, IMHO a properly serviced Aqua Master should be, by definition, oxygen clean. There are no O-rings and no O-ring lubricants. I would not be concerned about using one of my Aqua Masters with 80% oxygen (32 feet max) or even 100% O2 (< 20ft). Since a diver has to limit his oxygen exposure, the hoses, mouthpiece, duckbill, etc. would be ok.

[RMannix]

I thought it was interesting that rubber was used for fuel.
Real rocket fins

[jrvancealt]

rubber is an excellent fuel for a hybrid type rocket engine because it makes a loot of smoke when burning, which powers the rocket, and burns for a very long time

[oldmossback]

jrvancealt,

A little correction there young man........rocket motors don't run on smoke, although they make a lot of it. They fly due to the fuels, mixed together, burning and creating a super heated GAS that has to pass thru a small opening, aka......the first stage nozzle upon which with all that back pressure pushing out the nozzle makes the vehicle rise............kinda like eating too many bean buritos for lunch......the back pressure is pretty great and makes great noise passing thru ones own first stage nozzle.......you put a flame to it......and voom!!! Fortunately, there isn't enough back pressure to launch one into space........although it may feel like it sometimes.

But your basic analogy is correct...........your pretty well read for one so young.........

[SeaRat]

By the way, I don't think that there is any natural rubber in a regulator today. Hoses are neoprene, and diaphragms are usually nylon-impregnated neoprene.

Luis made a very important point, in that there is no nitrous oxide (excluding the potential for air pollutants) in breathing air or nitrox mix.

John

[jrvancealt]

i know i wast just giving an example with rubber beacause as it burns it produces a lot of gas and the gas is the smoke

my anology was a little skew

i want to build a hybrid rocket motor

[nemrod]

Not sure where you live jrvancealt but you need to get with the Tripoli Rocketry Association. I am an early and still member but no longer active. My brother still launches however. When I lived in Houston and then worked for a major oil company one of the chemists was into rockets and had worked for the gubermeent. Anyways, we built several solid fuel rockets with mixed results. I will say it can be very dangerous. However, hybrid hobby rockets launched routinely at supervised Tripoli events are extremely impressive. Consider that while they may run for a few seconds or generally less than one second the larger motors can produce thousands of horsepower!!! My neighbor here in Kansaw was also an active member, an electrical engineer, he often tested the engines here in the backyard, we are out aways from the city, by digging a hole and then partially burying the motor. Warning, large hybrid engines so fired can damage hearing without good protection. He moved away to another state, job transfer, a few months ago. Good luck.
Nemrod

[mossback]

Yeah, I was into hobby rockets once myself, came mail order from Estes Rockets in Colorado, too many years ago, now you can buy them at hobby stores...launch pad was a 1 foot square plyboard and a straightened out coathanger wire......after several kits I built my first design that my dad offerd to use the battery in his 49 ford to ignite the motor with........rocket was top heavy and stabilzer fins too small,,,,,,,,rocket went up, came down and chased my father behind his truck.......had to find other battery launchers after that......even built a flying saucer once, using homemade fuel, right over my mothers stove I cooked it......darn thing flew too..........till it caught fire and fell into the 80 acre johnson grass field behind our house.....was a small fire, only one fire truck was sent...........was told I should find another interest...........so a few years later I learned to dive..............but no one I know to this day can make a flying saucer fly like I did.....

[jrvance]

i live in santa barbara , where you supposedly need a permit from mr fire marshall to launch rockets although i might just need to take a trip to arizona one of these day, but i find ways I have heard of Tripoli Organization

i am also interested in making my own fuels but i am trying not to get on the BATFE's bad list

about nitrous oxide, it is used in canned whipped cream, ummm cholestorol