Are scuba regulators life-support equipment?

[KD8NPB]

Discriminating divers prefer to breathe from a $719.00 reg with more features than bling while not having their money needlessly sucked out of their wallet.

Is that a balanced 2nd stage?

For the price, I'd rather have an Apeks XTX200. Pneumatically balanced 2nd stage, overbalanced diaphragm type 1st stage, replaceable HP nozzle, and environmentally sealed for $755.

Then again, I'm not a huge fan of piston regulators. Once silt gets in to the ambient pressure ports, those dynamic o-rings are goners.

 

[rhwestfall]

Once silt gets in to the ambient pressure ports, those dynamic o-rings are goners.

so much for being life support....

 

[KD8NPB]

so much for being life support....

I just saw an interesting failure with a piston stem o-ring, near the HP seat in a Scubapro knockoff regulator.

The o-ring actually "unrolled"...imagine a spiral. The o-ring looked normal sitting down, but it had a slit in it. If you pushed it with your finger, you could unroll the o-ring making a little flat strip of rubber.

Definitely a "lack of lube" scenario! This was a factory fresh regulator with 1 year / ~60 dives on it.

It caused high pressure air to flow down the piston stem and out the ambient pressure ports... a HUGE air leak.

Luckily, the diver was just starting a dive when the failure happened.

 

[redacted]

Is that a balanced 2nd stage?

For the price, I'd rather have an Apeks XTX200. Pneumatically balanced 2nd stage, overbalanced diaphragm type 1st stage, replaceable HP nozzle, and environmentally sealed for $755.

Then again, I'm not a huge fan of piston regulators. Once silt gets in to the ambient pressure ports, those dynamic o-rings are goners.

Yes, dynamic o-rings that seal a piston action can be vulnerable to abrasion damage in silty/sand conditions. A sealed diaphragm 1st is one way to combat this problem but brings with it the slight penalty of added complexity. A piston 1st can be protected by packing the ambient chamber which is messy and costly. Or you can add wiper rings to protect the sealing ring like Scubapro does with the piston head o-ring on the Mk20/25. Even the HP piston o-ring on that 1st gets similar protection from the washer between the o-ring and the ambient chamber. It looks like Scubapro recognized that potential silt problem and also added protection to the piston like balance chamber in the 2nd stage of their pneumatically balanced 2nds. When do you think Apex and others will follow suit?

It is also worth recognizing that what you call "goners" are really the annoying failure mode of a small, inconvenient leak. I am beginning to think that when we talk about regulator failures (problems) e should include the performance effect incurred by such a failure. For example, it is interesting to realize that those potential failures that may be averted by periodic service tend to have a pretty minor effect on performance. The competenyt inspection is probably more important that the service in averting real problems. Changing an O-ring before it "fails" is usually just preventing a small leak, at best. HP seat "failures" usually results in some increase in creep which is readily detectable my checking IP often. (I don't replace my HP seats until I see more creep than I am willing to accept.) LP seat "failures" usually mean a leak and/or a loss of performance that can not be corrected with an adjustment. Even filters in the 1st stage are usually changed unnecessary. When a filter does get clogged enough to degrade performance, that is usually a problem with one dirty tank and can just as well occur with the tank right after a service as the tank just before. I rarely change any of my filters but do inspect them often.

When you look at what can cause a regulator to just stop delivering gas, assuming gas in the tank, there are just not many failures that could cause that. And it is probably more likely that such failures are caused by service errors rather than prevented by servicing a fully functional regulator.

---------- Post added February 6th, 2014 at 01:49 PM ----------

I just saw an interesting failure with a piston stem o-ring, near the HP seat in a Scubapro knockoff regulator.

The o-ring actually "unrolled"...imagine a spiral. The o-ring looked normal sitting down, but it had a slit in it. If you pushed it with your finger, you could unroll the o-ring making a little flat strip of rubber.

Definitely a "lack of lube" scenario! This was a factory fresh regulator with 1 year / ~60 dives on it.

It caused high pressure air to flow down the piston stem and out the ambient pressure ports... a HUGE air leak.

Luckily, the diver was just starting a dive when the failure happened.

I suspect that is more likely a tolerance and o-ring hardness problem (extrusion) rather than just a lack of lube. While such a failure produces lots of bubbles, the loss of gas is not that quick and a normal ascent can easily be accomplished by an OW diver.

 

[halocline]

Then again, I'm not a huge fan of piston regulators. Once silt gets in to the ambient pressure ports, those dynamic o-rings are goners.

Really? Then how do you explain the fact that the MK5 (and it's descendants) is one of the two most long-lived, imitated, and proven 1st stage designs in history? Literally millions of dives have been performed in all kinds of conditions, over several decades, world-wide, with piston regulators. I realize that the ambient chambers of piston regs, unless packed, are open to environmental conditions, including silt. But to say something like 'once silt gets in....goners" is absolute nonsense. If it were true, NOBODY WOULD EVER USE ONE, and the design would be considered a miserable failure.

But, mis-statements about regulators are par for the course in the dive community.

 

[KD8NPB]

Really? Then how do you explain the fact that the MK5 (and it's descendants) is one of the two most long-lived, imitated, and proven 1st stage designs in history?

It's cheap and easy to reproduce with minimal fine machined parts. If the regulator is used in clear water conditions, you can also go a very long time between rebuilds because of the hardness of the HP seat.

Then again, we aren't blessed with sandy bottoms here in Michigan. Everything is muck & marl bottom. 10 ft of viz with heavy floating particulate is common.

But to say something like 'once silt gets in....goners" is absolute nonsense. If it were true, NOBODY WOULD EVER USE ONE, and the design would be considered a miserable failure.

But, mis-statements about regulators are par for the course in the dive community.

Almost every regulator failure I've seen with a piston regulator has been due to wear on the dynamic o-rings. They usually show tiny little cuts, fraying, and/or extrusion. I have to scrub the crap out of them to get all of the built up residue out.

For the record, I'm not a huge fan of open diaphragm regulators either. But then again, the commercial guys bring me Conshelf XIV 1st stages packed with mud, missing almost all the chrome, and showing scorch marks due to thermic lance use...and they still work great with no failures.

But, the piston vs diaphragm debate is the SCUBA world's Glock vs 1911 or AK vs AR15 debate...there are no winners, only people deadset in their systems.

I have a Scubapro Mk10 that has never been rebuilt to my knowledge. Works great as a shop regulator...helps when it never sees water/mud/salt/debris. I don't think a diaphragm regulator would last that long before the diaphragm tears out or extrudes heavily.

I'll see myself out.

 

[captain]

You all still at it. To quote a famous American "what difference does it make".

 

[redacted]

You all still at it. To quote a famous American "what difference does it make".

You are right, it really should not make much difference. At least until some folks use the answer to scam divers into spending much more $$$ than they need to or; worse yet, make divers believe that they should accept their inevitable death if their regulator should fail.

divers need to realize that it is not some kind of miracle when a diver "survives" a regulator (breathing system component) failure. It is simply the result of proper equipment, training, planning, and practice.

 

[Nemrod]

I have hundreds of dives on piston regulators. Often in really poor, turbid water. I do not find all this wear and tear. The MkV is probably the most dependable first stage ever made only rivaled by the USD/AL diaphragm first, this one here, munch on this;

Regulator Rubbish: Dive Gear Makers Should Get Back to Basics | Halstead

Quote:

I stripped the regulator, an original US Divers Conshelf XIV – but I already had a good idea what had gone wrong. The first stage of these regulators has an upstream valve opened by a thin stainless steel pin with a cylindrical knob at one end. If the knob sheered off, the pin could not open the valve and, suddenly, it could not supply air to the second stage. Mostly the problem with these first stages was that the high pressure seat would fail – but if this happened the regulator would provide too much pressure and the second stage would free flow – not nearly as serious a problem.
I did not care for regulators that were not “fail safe”, that is, no matter how they failed you should still be able to breathe. In my dive shop, the Diver’s Den in Port Moresby, I did not sell “diaphragm” first stages as they all in theory (and some in practice) could fail catastrophically. Over the years the pin design has been changed and I have not heard of any diaphragm first stage failing due to a failed pin in many years (let me know if you have).

End Quote:


Hmmm, balanced flow through pistons fail open and balanced diaphragms fail closed, hmmmmm.

N