[PSUBS-MAILIST] O2 fittings

[Sean T. Stevenson via Personal_Submersibles]

CGA 540:

This connection is on your industrial oxygen bottles, and will be made via either wrench tightened or handwheel tightened fittings. The CGA 540 is a metal to metal seal which requires preload to deform the mating surfaces within the connection. When you buy oxygen in large bottles, this is the connection you get.

CGA 850:

This is your standard SCUBA yoke connection which mates to a yoke style SCUBA regulator. The connection is sealed by an o-ring, and tightened by a yoke screw on the regulator against the rear side of the valve.

CGA 870:

This is also known as a "pin-indexed" yoke, and is the valve / connection used on medical / therapeutic oxygen bottles and regulators. Your D, jumbo D and E size medical cylinders will have this style of valve. This connection is sealed by means of a brass washer with an elastomer insert (reusable), or by a teflon washer (single / limited use). Medical oxygen regulators, which typically not only regulate pressure but also incorporate flow control devices, mate to the CGA 870 with a yoke screw similar to the CGA 850 arrangement. Oxygen regulators incorporate pins which mate with aligned holes in the cylinder valve, to prohibit using an oxygen regulator on a non-oxygen valve.

DIN 477:

This is the "technical" SCUBA cylinder / regulator threaded connection, which is manufactured in 200, 232 and 300 bar working pressure versions. The only difference between these is the depth of thread, with the 300 bar DIN being the most secure connection, but prohibiting the use of adapters which can screw in to the female valve thread and permit their use with CGA 850 regulators with a yoke screw in the shorter 200 bar version of the valve. The DIN 477 connection seals with an o-ring (threads are straight and non-sealing), but the o-ring groove exists on the regulator side, rather than on the valve stem as with the CGA 850. DIN 477 is viewed as superior to CGA 850 both because of it's mechanical robustness when assembled, and because of the reduced chance of entanglement in diving applications owing to the lack of a yoke screw.

Permanently installed vessels which are filled via manifold may do away with cylinder valves entirely and be plumbed in via fittings in the cylinder neck threads, with appropriate overpressure relief mechanisms and flow control devices incorporated elsewhere.

Sean
-------- Original Message --------
On Jan 11, 2018, 15:58, Brian Cox via Personal_Submersibles wrote:

>   All,
>                  I'm still a bit perplexed about which fittings I should get for my small inside O2 bottle.  At my local dive shop they have a rebreather bottle that is commonly used ( I believe 17 cu ft.) but it has a female fitting on it.  The fittings I see at EMT  http://www.emtmedicalco.com/OXYGEN-AIR-FLOWMETERS-FITTINGS_c85.htm   have a different type of fitting .   The rebreather bottle seems like a good size for inside bottle.  Apparently Poseidon Rebreathers has an office close to me just south of LA,  the guys at the dive shop are helping me sort out the right fittings and are inquiring through Poseidon,.  They deal with Poseidon and know the people over there.
>
> On those regulators, is there just a single stage and it is then just cracked slightly above your flow rate?
>
> Brian
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