settle disagreement on din/yoke valve and max pressure

[pescador775]

Paintballers use urethane O rings for CO2 tank valves. These are 90 durometer and size -015. The SCUBA valve face ring is -014. Yes, it does appear that the "white" O ring, which formerly was widely available in dive shops, was urethane, 90 duro, similar to the paintball setup. Now, where to find some 014's cheap. I mean, the Ebayers sell CO2 rings at about $5/100.

 

[alemaozinho]

Yes, yes, I know that Din valves are superior. That is NOT the question.

The question is, which of the following is true:

1) Hp 3500 steel tanks should never have a yoke valve (pressure too high for yoke).

2) It is fine to use a yoke with an HP 3500 steel tank.

why would you wanna do that?Get your reg converted and that,s it................mmmhhhh

 

[Charlie99]

About NITROX: there are a lot of misconceptions. Viton, etc are only necessary when pure oxygen is used, ........

Does that include exposure to pure oxygen during partial pressure blending of nitrox, or do you expect the pure O2 exposure to be short enough duration that it doesn't matter?

Or to put the question another way .... do you use buna-n for partial pressure blended nitrox?

 

[pescador775]

The Air Force oxygen systems use nitrile ( neoprene) as permanent components of their oxygen plumbing. No problems that I'm aware of. Partial pressure filling is of short duration and is irrelevant. However, to Keep the folks happy use Viton for the tank neck ring. Incidentally, since the valve must be oxygen cleaned it is convenient and relatively inexpensive to use Viton rings internally if the valve has rings at all. The Sherwood 5000 use Teflon (R) seals which are oxygen proof. Other OEM valves made by Sherwood such as the OMS, may have an O ring. The ubiquitous Japanese valves (Thermo) use an O ring.

There is a lot of superstition promulated by "experts". The government is heavily involved making august pronouncements which amount to claptrap. The military bureaucracy loves to impose standards for breathing air and oxygen which can only be met by God. Rubber gloves, sterile this and that.Then, there is the kitchen science community. They like detergents for oxygen cleaning. My experience has been that Simple Green and Dawn might have their uses but the effort to make these soaps work is not worth the labor and difficulty. There is an oxygen safe solvent branded as "Ensolv". It replaces the banned trichloroethane. Expensive but it makes h*llish difficult tasks like valve cleaning a breeze. Dip the valve parts in this stuff and all the sticky stuff dissolves leaving a sparking clean collection of parts. Avoid dipping certain plastics like ABS.

 

[Rick Inman]

why would you wanna do that?Get your reg converted and that,s it................mmmhhhh

I did. My reg is din. It was during the conversion that this question came up between me, the shop owner and another diver.

 

[pescador775]

About neoprene (chloroprene, nitrile, Buna) O rings. These are cheap and widely available. Durometer 70 and 90 are most common. I would use 90 for the valve face but that's IMO. Personally, before I use nitrile rings in SCUBA I clean the ring by dipping in Ensolv and then lubricate with Christolube. I use oxygen or nitrox in just about everything and I don't like the idea of using an O ring which has been been lubed with some unknown substance, possibly silicone. I have no proof that the off the shelf O rings would rot or flameout in oxygen, not at all. Just say I'm sensitive to Murphy's law even though I've never heard of a problem.

 

[DA Aquamaster]

The Air Force oxygen systems use nitrile ( neoprene) as permanent components of their oxygen plumbing. No problems that I'm aware of.

Same thing in General Aviation O2 systems and again no reported problems. Viton is popular in scuba circles and they are probably fine for neck o-rings, but in my experience they do not wear well in dynamic applications. So you are trading relaibility and durability for a largely theoretical improvement in terms of decreased flammability. But when they do burn, Viton o-rings produce phosgene gas - one of the classic WWI era chemical warfare agents.

 

[mark99]

why would you wanna do that?Get your reg converted and that,s it................mmmhhhh

I recently purchased a PST, and have done a considerable amount of research about the valve/regulator attachment question, which I will share here.

ISO 12209 is a published standard that describes the issue you are discussing here.

• ISO 12209 (Gas cylinders - Outlet connections for gas cylinders valves for
compressed breathable air) was released in 2000, giving full dimensional details
and upper pressure limits for:
o In its Part 1, the yoke type connection almost universally used for SCUBA
applications, for use at up to 230 bar (23 MPa) cylinder filling pressure at
15°C
o In its Part 2, two threaded connections derived from the German DIN 477
Standard, one for use at up to 230 bar (23 MPa) cylinder filling pressure at
15°C and another for use at up to 300 bar (30 MPa) cylinder filling pressure
at 15°C
o In its Part 3, an Adaptor for 230 bar valves which allows a valve with the
threaded outlet of Part 2 to be connected to an application complying with
the yoke connection of Part 1.

As you can see, Part 1 is important to the reg manufacturers, because it defines the parameters of the high pressure yoke. Referencing page I-5 of the Scubapro MK25 regulator user instructions, "Scubapro first stage regulators are available with either of two different cylinder valve connections:
Threaded, this connector uses a knurled and threaded retaining wheel and complies with ISO 12209-2 (200 or 300 bar).
Yoke, this international connector consists of a yoke and knob type fixing screw for use in systems up to 230 bar and complies with ISO 12209-1."

So this is the answer to the first question, at least if you are using a Scubapro MK25 first stage, that you can use the yoke connector to connect to a HP tank up to 230 bar and be within manufacturer's specs for the reg. That is, as long as the tank and valve comply with Parts 2 and 3.

On to the issue of DIN valves, there are 2 types, labelled DIN 200 and DIN 300, but according to info at Diveriteexpress.com, a dealer for the PST company tanks,

"The endless confusion surround the terminology of that valve is
frustrating at times...it is commonly termed a '200-bar' valve in the US... but the proper term is DIN 477the valve itself (exclusive of the burst disk pressure) is engineered to handle pressures up to 6000 psi. The term 200-bar vs 300-bar simply
refers tothe number of threads in the opening 200-bar is DIN 477/13 and 300-bar is DIN477/50.... The terms 200-bar and 300-bar are "slang" used only in the US (which again has NOTHING to do with how strong the valve is... "

The 477/13 having 5 threads and the 477/50 having 7 threads.

(continued) "DIN regulator fitting is not long enough to mate properly with a female
7-thread DIN valve fitting, preventing the accidental connection of a high-pressure
cylinder to an older regulator not intended for high-pressure. However, a
regulator with a male 7-thread fitting will mate just fine with a female
5-thread DIN valve. Any first stage regulator DIN fitting can be attached to
a K-valve using an adapter that attaches to the regulator. The first stage
regulator yoke fitting can be attached to a 5-thread DIN valve using an adapter insert that screws into the valve. However, 7-thread DIN valves cannot be adapted to accept yoke fittings for diving, although there is a yoke adapter block used strictly for filling."

Here is a link for more info on the valves supplied with the PST co. tanks:

http://www.diveriteexpress.com/library/valves.shtml

Hope that helps.

Mark

 

[liberato]

So, if 230 bar @15C = 3442 psi @70F as mentioned earlier then using a modern yoke is fine with the likes of a tank, for example, in the PST E-series at that pressure with the standard DIN/Yoke convertable valve that it comes with. The older HP 3500 tanks aren't going to have a yoke valve on them anyway, right? And all bets are off if your yoke first stage is not modern or brand-name.

 

[mark99]

So, if 230 bar @15C = 3442 psi @70F as mentioned earlier then using a modern yoke is fine with the likes of a tank, for example, in the PST E-series at that pressure with the standard DIN/Yoke convertable valve that it comes with. The older HP 3500 tanks aren't going to have a yoke valve on them anyway, right? And all bets are off if your yoke first stage is not modern or brand-name.

Well I'd think that you should check out the manufacturer's recommendation for your particular yoke, even if it is modern. The older HP tanks would have the DIN477/50 7 thread valve, and you could not convert them using the yoke conversion insert that comes with the PST-E tanks, because that conversion is designed for the 5 thread DIN. As a matter of fact, Part 3 of the ISO spec only refers to a conversion for the 230 bar valves (5 thread DIN to yoke) and not for the 300 bar (7 thread) valves. I'm sure that is because (as mentioned in an earlier post) that the 7 thread valves are too thick (wide) to fit into the yoke, and (as mentioned earlier) the 5 thread adaptor would screw in too far into the 7 thread DIN. As you read the specs, you can see exactly why the PST-E tanks are the way they are.