Oxygen - equipment, getting refills, refill hoses, safety, etc

This came up before here

The outlet pressure of the MH first stage reg is about 20psi, and to maintain that it obviously needs more than 20psi input. How much more, isn’t really stated anywhere clearly. But it is definitely much less than 500psi because that would be 1/4 of the cylinder which would be unusable as a result. I have run them much lower than that.

In practice you refill whenever convenient – a bit like the fuel tanks except oxygen is a lot more scarce unless you have your own cylinder

Thanks Peter

Peter wrote:

The outlet pressure of the MH first stage reg is about 20psi

I’m not sure about that – it should be around 120 psi (I’m talking from scuba experience).

Definitely about 20.

Scuba is different because it has to be able to match the water pressure :)

@Emir

I don’t think so : for scuba diving the first stage give 8 to 10 bars (about 120 psi) and you cannot breath it directly : it’s the purpose of the second stage which will give you air at ambiant pressure.

With oxygen bottle there is only one regulator : the output pressure is breathable directly, at about 20 psi / 2 bars

Sure, but it would be a challenge to design a 2nd stage regulator which takes 3000psi in. Hence the scuba 1st stage needs to just exceed the deepest water pressure.

120 psi is about 80m water.

You’re right – I was under impression that the design is similar (2 stages) but now I checked the schematics for my aviation oxygen

Referring to this testing contact, I am looking at getting my two composite cylinders tested.

AIUI, the testing of these composite cylinders involves checking for the % expansion and that dimension has to be within limits. OTOH, all-metal cylinders are simply tested at a certain pressure and they must not blow up.

Does anyone have any details? I have read that unless this information can be found, the cylinder cannot be tested.

I have contacted T.P.F. Parachute Services, as posted above, and they say the test pressure is simply on the cylinder.

They charge £40, plus £20 return shipping. That’s actually very reasonable. Some quotes are well into 3 figures, and normal scuba cylinders cost a lot more than this here in the UK (I have seen cases where it would be cheaper to buy a new cylinder than have the existing one tested).

I am looking into buying my first oxygen system and am keen for any feedback on the below set-up from experienced users. I’ve skimmed through the 400+ posts in this thread and it appears that Mountain High oxygen is a favorite among users.

• MH Cylinder AL-647 (22.8 cu.ft) / CFFC-048 (48.2 cu.ft) – depending on how much you’re willing to spend ($200 vs $1k). Using the DIN477 fitting. Appears this is easier to fill within Europe?

• XCP-FPR-G-DIN477 4-place gauged regulator – thinking here is that this allows one to attach two additional (cheaper) constant flow systems if ever travelling with 3-4 vs. 2.

• MH O2D2-2G Kit (incl. 2 cannulas / 2 face masks etc.)

• 2x MH3 Flowmeter (for infrequent usage – rear passengers)

• 2x MH Oxymizer cannula (for use with MH3 Flowmeter)

• MH Full Pack

• Pulse Oximeter

Am I missing anything? Is the DIN477 norm more compatible with filling stations in Europe?

In regards to refilling – many scuba shops mention they can fill O2 tanks to appropriately certified divers and those with an “oxygen administration certificate”. Does anyone have any experience with completing a course like this one here. A 2hr £25 online course which appears to give you 3yrs of oxygen administration privileges? May be worth it if it gives hassle free access to the wide network of scuba filling stations.

Thanks!