Max Pressures for Regulators

[adza]

Hi,

I know this may sound like a stupid question, but I'm after a 'real life' answer, and not the 'official we don't want a liability issue' answer.

When I get tank fills, the tanks are normally filled between 200-230bar. (Tanks rated for 300bar).

The reg's that I'm using however - are rated to either 220bar, or 200bar. (In this case, Dacor and scubapro regs).

The question: How strict are the 'limits' on the stage 1 regs that you attach to the tank? If I have a 220 bar reg, is it OK to attach to a tank with 230 bar? If I have a 200 bar reg, same question? Is this normal practise for dive hire shops (as seems to be the case from what I've seen todate).

And - For anyone more technically informed: What happens if a stage 1 reg exceeds it's limits to failure point? (ie, if someone attached a 200bar reg to a tank with 300bar). Don't worry - I'm not going to do it.

I'm just curious. Does it put too much pressure down the stage 2 and reck your gear (or your lungs), or does it 'blow it's top', etc? (I'm not overly familiar with how reg's work and what the potential dangers are if one grossly overlimits their reg).

Thanks

Adza

 

[Luis H]

Conversions for my benefit (and maybe some others):
200bar = 2900psi
220bar = 3190psi
230bar = 3336psi
300bar = 4351psi

I can’t think of any modern (two stage, single hose) regulator that will have any problems with pressures up to 3500psi (240bars). Maybe an unbalanced piston first stage like the Scubapro Mk2 may develop a slightly higher than normal intermediate pressure, but I dough that it would be a real issue.

The limiting factor for most regulators could be the yoke, if it has an old style thin yoke. Most modern style heavy yokes (and DIN connections) will handle 3500psi without any problems. And, I am willing to bet that most modern yokes can easily handle 4500psi, but they are not rated or advertised as such. Even an old thin yoke will tend to deform and allow the O-ring to extrude (reliving the pressure), not a catastrophic structural failure (that being said, I wouldn't push it with a thin yoke).


If your regulator has a balanced first stage, the mechanism in general is not affected by the tank pressure. However, in a balanced first stage, there will normally be at least one dynamic O-ring (whether it is a piston or diaphragm mechanism) that will be operating at the higher pressures. At higher pressures (above 3500psi for any modern regulator), this O-ring could experience excessive wear or even some minor extrusion, causing it to fail and leak.


The first stage on my wife’s regulator is a 35 year old Scubapro Mk5 with an old heavy yoke and she uses it on 3442 psi tanks all the time. It is not a problem.


Note: No failure should ever hurt your lungs. Even a free flow will vent out the exhaust valves.

 

[m3830431]

Check with the company to be certain. Typically thay would be rated to 232 bar or the approximate psi of a high pressure tank (3364.8).

 

[evil_xander]

Hi,

When I get tank fills, the tanks are normally filled between 200-230bar. (Tanks rated for 300bar).

Just a small digression, it would be impossible to fit a 200/232 bar DIN reg into 300 bar DIN valve, as the 200 bar version has 5 threads and is shorter on the regulator side then 300 bar one, which has 7 threads (note: number of threads may vary from the real count, but you get the point). The 300 bar DIN valve on the tank is also deeper accordingly.

Hence, your reg wouldn't fit properly to the tank and air would flow all over the place when turned on. On the other hand, a 300 bar DIN reg would fit a 200 bar DIN valve without problems, it would only stick out a little.

 

[Diver0001]

Hi,

I know this may sound like a stupid question, but I'm after a 'real life' answer, and not the 'official we don't want a liability issue' answer.

When I get tank fills, the tanks are normally filled between 200-230bar. (Tanks rated for 300bar).

The reg's that I'm using however - are rated to either 220bar, or 200bar. (In this case, Dacor and scubapro regs).

How they're rated will probably have something to do with local laws but I wouldn't personally be troubled by putting a modern 200 bar reg on a 232 bar tank. Older regs used thinner metal on the A-clamp and I've hear stories of some of those cracking.... The question is how reliable the stories were, what other abuse the regs took prior to cracking and if it was possible that they were isolated incidents as opposed to design issues....

And - For anyone more technically informed: What happens if a stage 1 reg exceeds it's limits to failure point? (ie, if someone attached a 200bar reg to a tank with 300bar). Don't worry - I'm not going to do it.

I'm just curious. Does it put too much pressure down the stage 2 and reck your gear (or your lungs), or does it 'blow it's top', etc? (I'm not overly familiar with how reg's work and what the potential dangers are if one grossly overlimits their reg).

Thanks

Adza

The attachments for 232 and 300 bar tanks are very different so you wouldn't be able to do it. Internally the reg can take the pressure. In fact, the only difference between a 232 bar and a 300 bar first stage is typically the attachment. In fact, you can remove the A-clamp from most of them and screw a DIN clamp in to convert it to 300 bar.

R..

 

[adza]

Hi All, and thanks for replying. The tanks I have been using have k-type valves on them, and not DIN's - not sure if this makes a difference. (I guess the tank could be rated to 300bar, and the valve attached to the top rated to 232?) Either that, or I've misunderstood the tanks in general.

Either way - I think I've got a handle on it thanks to you guys! I have 2 identical regs here which I've just checked, (Dacor viper Tec) - one rated at 232, and the other 200 bar. My understanding is one was retailed locally, and the other sourced from overseas. That would probably fit with what Diver0001 said about local laws. (Same reg - different law on max pressure I guess). Not much to worry about.

Can't double-check the scubapro's at present, as I don't have them on me. I'm guessing they'd be the same though.

Appreciate all your feedback! Thanks heaps!

 

[jeraldjcook]

Conversions for my benefit (and maybe some others):
200bar = 2900psi
220bar = 3190psi
230bar = 3336psi
300bar = 4351psi

The first stage on my wife’s regulator is a 35 year old Scubapro Mk5 with an old heavy yoke and she uses it on 3442 psi tanks all the time. It is not a problem.

Does your wife Mk5 have a max pressure on it? I have a 15 year old Mk10 that reads 200 bar max on the yoke. I've been tempted to buy a 3442psi tank but wasn't sure if it was good idea.

 

[DA Aquamaster]

Scubapro has had a a few differnet yokes over the years. The original thin ones were rated for 2250 psi tanks. The slightly later and slightly thicker yokes were rated and stamped 3000 psi. However these had a tendency to stretch at that pressure so the latest yokes have had much thicker construction and much heavier yoke screws.

This pretty much paralleled yoke development in the entire industry.

If you have a heavy yoke and alrge diameter yoke screw, pressures up to 3500 psi should not be an issue. If you have an older Mk 5 with a thin yoke, you can upgrade and use the current SP yoke on it.

The potential issue with a piston reg at high pressure is pinching of the high pressure o-ring. This becomes an issue at pressures over 3300-3500 psi. if the regulator has looser than normal tolerances either due to manufacturing tolerances or due to wear over time. That was the reason SP went with repalceable bushings in the Mk 15, 20 and 25 and it allows pressures up to 4350 psi (300 bar) that would be potentially problematic with an earlier Mk 5 or Mk 10.

 

[pescador775]

As I understand it, Scubapro approached the extrusion (pinch?) problem by using an O ring made of harder material (hyperthane). I can understand production variables resulting in dimensional differences with the O ring groove but am unsure of how "wear" could cause an O ring groove to loosen up or wop out. More likely, the technicians cause it during service procedures.

 

[DA Aquamaster]

A technician can damage an o-ring groove by scratching it with an o-ring pick,but they don't cause any wear. And that scratch will result in a very msall leak, not HP o0ring pinch.

I think the "wear" overtime has much to do with corrosion, etc. given the environment that regulators get used in. But don't under estimate the cumulative effects of 2-3 decades of use on a regulator either.

For example, I do about 100-150 dives per year averaging 45-60 minutes in lenght with maybe 6-7 breaths per minute. If I figure 100 dives per year at 45 minutes each and 6 breaths per minute, that is 27,000 cycles per year, not counting BC power inflator and dry suit inflator use.

Ten years of that kind of use equates to 270,000 cycles and it all gets done in a salty, sandy, gritty corrosive environment and believe it or not, not everyone gets their reg cleaned and serviced each year, so you have the potential for a lot more abrasive action going on than you would think at first.

If I caluclate using 150 60 minute dives at 7 breaths per minute, its 63,000 cycles per year, 630,000 per decade, and well over a million cycles since I bought my last new Mk 10 in 1985. Add a little resonance here and there that causes some piston vibration and the number of cycles goes through the roof even on a little used reg.

Sounds like a recipe for wear to me.