Oxygen regulators, medical type

The short answer is, yes, the pressure will most probably build to a point that the hoses and/or connections will fail with the system blocked downstream of a simple flow restricting orifice.

Most regulators for aviation use (i.e. Mountain High E & S) have an internal diaphragm that shuts off flow when the downstream pressure equals the upstream pressure. I highly recommend regulators with this feature, for obvious reasons.

At the same time, I can also recognize the (cheaper) alternatives IF YOU DO NOT SHUT OFF THE FLOW COMPLETELY. The pressure will not increase to the point that mechanical components (tubes and connectors) are likely to fail. However, don't forget to turn the flow rate up when you salvage your flight with a low save and are feeling like a superhero for getting back above 12,000. I have heard more than one badly performed bit of karaoke on the radio when somebody forgot to adjust the O2 flow at altitude.

Pressure in the cylinder is often at 2,200 psi or more (using Aviators Breathing Oxygen from a reputable supplier) but nominal pressure is generally from 1,800 to 2,000 psi on a full tank. Most regulators (orifice type) only reduce the pressure to 15-100 psi, and do not shut the flow off when this pressure is reached, allowing the downstream pressure to eventually try to match the much higher cylinder pressure, resulting in failure of the downstream components. Don't worry, your head won't explode, but you might freak out at the sudden pop and hissing noise when it happens. And then the cylinder empties at an enthusiastic rate.

Please extinguish your cigarettes when this happens, or your whole airplane might explode. or at least turn into a merry little fireball.

Regulators with a diaphragm will regulate the pressure to the optimum level needed to operate the delivery mechanism, whether it is an electronic demand system (MH EDS) or a simple flow meter. Medical regulators are not capable of doing anything but reducing pressure to a manageable rate suitable for a constant flow rate with no change in altitude (and therefore increased O2 requirement).

In a nutshell- buy the best stuff for the application (aviation). If you get cheap crap because you are, well, cheap, don't shut off the flow entirely..

It is just your life, so go as cheap as you think it is worth. Remember that Oxygen refills are generally pretty cheap, and unless you have an extremely small cylinder, saving O2 by shutting the flow down doesn't save much in the way of time vs. altitude. Especially when you have to constantly remind yourself to turn it up at altitude or turn it down when the "houses get bigger." The automatic demand systems (M H E&S) take that out of the equation, so you can just concentrate on flying as best you can.

(I have been giving this lecture to hang glider and sailplane pilots since 1988, when I started selling 02 systems. I am also a dealer for M H E&S. In 2014, I got 147 hours of airtime. I was on 02 for 136 of them.)

Have fun, but don't be stupid. Just because you do not use 02 very often does not mean that you should go cheap. Oxygen is fuel for your brain.

Thanks for the advice, Mark. I'd love an EDS system. But here in the East we rarely go high enough to need oxygen, it seems that spending $1000 on a system is overkill for use once a year or so. Also, we have very few convenient places around here to refill, other than at "wave camp".

Do those medical regulators not have a diaphragm? You'd think that's necessary, in order to shut off (at least mostly) the flow coming from the high pressure cylinder? I was guessing they have a diaphragm-based pressure reduction followed by an orifice to set the flow rate, but I may be wrong. And perhaps even the diaphragm system would have some leakage through the high pressure side valve even when it's supposedly shut because the diaphragm senses that the output pressure is high. Then again, these regulators have an "off" position, on the same knob as the non-zero flow rates. If that is simply a zero-size orifice, wouldn't the pressure then build up dangerously in the low-pressure side of that device?

On Thursday, November 5, 2015 at 6:51:25 PM UTC-8, wrote:
Thanks for the advice, Mark. I'd love an EDS system. But here in the East we rarely go high enough to need oxygen, it seems that spending $1000 on a system is overkill for use once a year or so. Also, we have very few convenient places around here to refill, other than at "wave camp".

Do those medical regulators not have a diaphragm? You'd think that's necessary, in order to shut off (at least mostly) the flow coming from the high pressure cylinder? I was guessing they have a diaphragm-based pressure reduction followed by an orifice to set the flow rate, but I may be wrong. And perhaps even the diaphragm system would have some leakage through the high pressure side valve even when it's supposedly shut because the diaphragm senses that the output pressure is high. Then again, these regulators have an "off" position, on the same knob as the non-zero flow rates. If that is simply a zero-size orifice, wouldn't the pressure then build up dangerously in the low-pressure side of that device?

Agree with others... It's life support.
As evidenced in another thread, it's easy enough to get yourself into trouble on the "occasional 18,000' flight". 100% brain power when that happens is fairly important.
Jim

An Aerox system is cheaper than an EDS, maybe half the price. This is life support, as in LIFE, this epitomizes "pound foolish". If you really wanted to save the money on an O2 system, the much smarter choice is to stay at lower altitudes where you do not need it. This is not something to jury rig or kluge together on a budget with parts not designed for this use. Honestly!!!!

On Thursday, November 5, 2015 at 6:51:25 PM UTC-8, wrote:
Thanks for the advice, Mark. I'd love an EDS system. But here in the East we rarely go high enough to need oxygen, it seems that spending $1000 on a system is overkill for use once a year or so. Also, we have very few convenient places around here to refill, other than at "wave camp".

On Thursday, November 5, 2015 at 6:51:25 PM UTC-8, wrote:
Thanks for the advice, Mark. I'd love an EDS system. But here in the East we rarely go high enough to need oxygen, it seems that spending $1000 on a system is overkill for use once a year or so. Also, we have very few convenient places around here to refill, other than at "wave camp".

Do those medical regulators not have a diaphragm? You'd think that's necessary, in order to shut off (at least mostly) the flow coming from the high pressure cylinder? I was guessing they have a diaphragm-based pressure reduction followed by an orifice to set the flow rate, but I may be wrong. And perhaps even the diaphragm system would have some leakage through the high pressure side valve even when it's supposedly shut because the diaphragm senses that the output pressure is high. Then again, these regulators have an "off" position, on the same knob as the non-zero flow rates. If that is simply a zero-size orifice, wouldn't the pressure then build up dangerously in the low-pressure side of that device?

I also agree that you should not cobble an Oxygen System. Please read this article about Hypoxia

http://www.craggyaero.com/hypoxia.htm

Mountain High has the constant flow systems including a cylinder price range from $500 to $600.

http://www.craggyaero.com/xcr_systems1.htm

EDS system with a small bottle about $849

http://www.craggyaero.com/edssystem1.htm

Call to get exact prices and cylinder sizes.

Richard
www.craggyaero.com

What's the difference, if any, in the principle of operation of the regulators in these constant-flow systems vs. the medical ones? (Other then them not having a flow restrictor built in.) In both cases, if the output is blocked (flow valve closed), does the regulator ensure the high input (cylinder) pressure does not bleed into the output?