First Stage Regulator Failure Rates

[AfterDark]

No data for you except personal experience. Been diving the same brand/type piston regulators (I have 4) for 50+ years and 2090 dives to date, no failures. I did borrow a regulator 48 years ago to do a dive, THAT regulator had a major failure, a rare no air condition. It was not however the regulator but the clown the rebuilt it and assembled wrong that caused the failure.

EDIT: This darn thread!!! I went diving today, mounted my reg on the tank turned on the air and presto air coming out the over pressure valve on the 1st stage, FAILURE!!. It's been 3 years since service and I was going to service all 4 this winter, looks like I had it about right. I'll use Mrs.AD's regulator until then. She's nursing a broken arm so she doesn't need it. I was able to dive because I never travel with less than 2 regulators.

 

[Angelo Farina]

The conclusion for me is the following: with the failure rate I experienced of 1 failure every 1000 reg-dives (with yoke mount) I find "not safe enough" to use just one first stage, and in fact I usually employ two. The chances that both fail simultaneusly is absolutely negligible...
However I had some rare cases when double-post tanks were not available, so I was forced to use just a single first stage.
In such cases I find "safe enough" diving with just one first stage (and 2 second stages, of course) only if:
1) it is DIN mounted
2) it is a balanced piston (I consider diaphragms slightly less reliable)
3) it is environmentally protected (SPEC or the like).

 

[cerich]

Any DATA will be much appreciated. Not just anecdotes, but real DATA—graphs, charts, annotated lists, etc.

Thanks,

Joe

If you service your regs annually, the likelihood of you seeing a failure is so near 0 it's simply not worth worrying about. Doesn't matter what kind of regulator it is.

No, the O-ring failures were due to the scratched surface on the part of the reg which mates with the O-ring in the valve. So IT IS a regulator failure, which was fixed replacing the part affected.
And it was not the dip tube which was clogged, it was actually the conical filter in syntherised metal inside the reg which was clogged.
Finally the piston O-rings causing small bubbles needed to be replaced earlier than the standard 2-years interval recommended for these regs: this happened only on the two older MK5, those without SPEC, and is due, in my opinion, to sand or silt entering the first stage. Or perhaps to salt crystals, being very difficult to rinse properly the interiors of the first stage. The other two more recent MK5, with their silicon-packed first stage, never suffered of the same problem.

umm.. NOPE, a regulator failure would be if failed from any damage it occurred in operation thru it's mechanics leading to a failure. A scratched surface is user failure. A clogged filter is also NOT a regulator failure, it's either lack of service, bad gas, bad maintence or poor user habits. A filter that clogs is performing as designed.

The body o ring around piston.. could be considered a failure but while I have seen them bubble past, the regulator normally continues to function and the only risk is the user ignores until there is a total failure.

 

[Angelo Farina]

umm.. NOPE, a regulator failure would be if failed from any damage it occurred in operation thru it's mechanics leading to a failure. A scratched surface is user failure. A clogged filter is also NOT a regulator failure, it's either lack of service, bad gas, bad maintence or poor user habits. A filter that clogs is performing as designed.

The body o ring around piston.. could be considered a failure but while I have seen them bubble past, the regulator normally continues to function and the only risk is the user ignores until there is a total failure.

In fact none of the failures I had was a catastrophic failure, and I continued the dive.
Only in the case of the clogged filter I needed to abort the dive (and complete the work free diving).
However I think my own data are relevant. The yoke O-ring failure is a common issue, which deserves to be prevented with additional inspections and maintainance, or converting the reg to DIN, as I finally did.
The clogged filter is a design fault which was affecting the old SP regs. Later models had a wider air entrance and a filter with triple surface.
After the failure I drilled the brass part to the same diameter as the latest MK5, and installed the new concave filter.
Also the leakage from the piston O-ring was a known problem of earlier MK5, which was solved in the more recent version. It is true that the reg continues working while bubbling, but it is indeed a failure.
I was happy to see that in just 5 years (1975 to 1980) all three of these problems have been recognized, addressed and fully solved by the manufacturer.
A 1980 MK5, with the new yoke attachment (ensuring better protection of the O-ring surface, a stiffer joke allowing for less clearance between the mating surfaces), the new concave air filter and the SPEC is an almost perfect 1st stage which substantially can never fail if maintained properly.
Add the DIN kit and I consider it the safest you can get, even today.
More modern regs are more complex, hence with more possible failure points.
Probably the best in SP evolution was the MK10: it has a very nice rubber boot on its SPEC chamber, ensuring to not disperse the silicon grease and no water entering the chamber.
It is still as simple as the MK5, very easy to service. And it was matched with the G250, the more reliable second stage ever built.

 

[Joris Vd]

I've had a catastrophic ds4 failure. The hp seat got dislodged somehow. It was thé second dive I ever had on it and I bought it new from a reputable dealer.
So for me the apeks ds4 is a no go. Which is ridiculous seen how good it's track record is.

What I'm trying to say is: all evidence concerning reg failures is anecdotal. As long as there is no significant data it's just a matter of opinion and sometimes getting (un)lucky.

Die example the mk5 has a proven track record but both the mk5 and similarly later the mk20 have had turret issues were overtorquing causing catastrophic reg failures. I'd say turret firsts are more Fragile when improperly serviced. But then again, as soon as SP changed thé brass turret bolts to SS, there have been no major reported issues.

It's all anecdotal, for example if you look at rebreather deaths, the Ap inspiration is a death machine. But not looking at all the other factors makes the data unnecessary and useless for anything other than Determening a stat.

 

[tursiops]

if you look at rebreather deaths, the Ap inspiration is a death machine

Apparently this is due to it being an early RB, and also there are many many of them, so simply more problems occurred. The probably is always how to normalize the data....what do you divide by?

 

[Luis H]

This is what I have found.

During 2006 to 2015 there were an estimated 306 million recreational dives made by US residents and 563 recreational diving deaths from this population. The fatality rate was 1.8 per million recreational dives.

From: Buzzacott, P; Schiller, D; Crain, J; Denoble, PJ (February 2018). "Epidemiology of morbidity and mortality in US and Canadian recreational scuba diving". Public Health. 155: 62–68.

In 14% of deaths there was a regulator fault reported, and in 1% the regulator was misused. Subsequent testing of the regulators showed that most of the problems were caused by leaks resulting in inhalation of salt water (this is a second stage issue, not first stage), but in some cases there was excessive breathing resistance following a mechanical dysfunction (the first stage can contribute to this issue, but it is still more likely a second stage issue). In a few cases the regulator failed catastrophically (this could be either, more information needed), or the hose burst (a first stage IP increase, due to leak, could cause this, but only if the second stage or an OPV did not relief the pressure). The difficulty of breathing from the regulator was often aggravated by other factors such as panic, exhaustion or badly adjusted buoyancy.

From: Edmonds, Carl; Thomas, Bob; McKenzie, Bart; Pennefather, John (2015). "Why divers die", Diving Medicine for Scuba Divers. pp. Chapter 34.

Using that data, I calculated that 0.25 deaths per million rec dives were caused by reg problems. However, they don’t discuss what the reg types were. Hence, my question.

I have not read the entire thread to see where it is going, but based on the post above, I am not sure why you would be focusing on a first stage. Most of the issues you quoted are second stage issues, not first stage.

Most regulator failures (both first and second stages) are simple minor leaks that are just an inconvenience, unless the diver freaks-out.

1. "problems were caused by leaks resulting in inhalation of salt water": (this is a second stage issue, not first stage)
2. "excessive breathing resistance following a mechanical dysfunction" (the first stage can contribute to this issue, but it is still more likely a second stage issue)
3. "few cases the regulator failed catastrophically" (this could be either, more information needed)
4. "hose burst" (a first stage IP increase, due to leak, could cause this, but only if the second stage or an OPV did not relief the pressure) This could just be a bad or worn-out hose.

 

[johndiver999]

The incidence of properly cared for and properly serviced regulator first stages failing is pretty low. A first stage diaphragm failure would be an example of a catastrophic failure that has occurred.

Extruded o-rings, clogged dip tubes or filters should probably not be considered first stage failures. I have had valve face o-rings extrude and even had a first stage that would not seal correctly because the tank took a tumble and landed on the first stage and bent the yoke cage to such a degree that is was no longer sitting square on the valve (I’ve personally seen this happen at least twice).

When the thing stops giving you air, the exact cause might really not be that important to the diver - at the moment it occurs.

So if you get the reg serviced properly (with respect to parts, labor and frequency) and you are reasonably observant about the occurrence of tell tale leaks and also IP problems and you don’t use contaminated tanks and you don’t let saltwater get into the first stage, then the incidence will be very low.

However, if this discussion is anything other than theoretical, from a practical point of view, scuba delivery systems do fail from time to time. I am MUCH more concerned about a LP hose blowing, or a crappy o-ring extruding from a yoke tank valve compared to the chance that a well functioning first stage is just going to explode or stop delivering air.

So the relevant idea is that there ARE failures – are you prepared to deal with it?

 

[Angelo Farina]

Die example the mk5 has a proven track record but both the mk5 and similarly later the mk20 have had turret issues were overtorquing causing catastrophic reg failures. I'd say turret firsts are more Fragile when improperly serviced. But then again, as soon as SP changed thé brass turret bolts to SS, there have been no major reported issues.

I did forget to mention this because rupture of the brass bolt keeping the turret never occorred to me. But I had reports of this problem, so I changed the bolts of all my MK5....
This reg was born with a number of issues, which required to be fixed with modifications, generally retrofittable to older units.
In the end the final version is one of the most reliable and safe reg ever built. But this was possible only after learning from failures...
The seventies were still years when new inventions were appearing on the market every day. 10 years later all this was finished, and in 1990 most equipment was already substantially the same as today. Which means that buying a new reg now one expects that the chances of failures are substantially zero. I had a number of failures, but all of them occured to my two older MK5 models. The two newest ones were already the final model, and they gave me zero problems.

 

[Luis H]

If you service your regs annually, the likelihood of you seeing a failure is so near 0 it's simply not worth worrying about. Doesn't matter what kind of regulator it is.

I don't want to derail this tread or give you a hard time, but this statement really bothers me, depending on what you mean by it.

If you mean by service annually as in inspect and do a detail check of the regulator, make sure there is no detrimental corrosion and everything is working correctly, the IP is solid, etc., then I am OK with that statement. But if it is the industry recommendation of a complete tear down, a complete rebuilt, adding new unproven parts that may need to be broken in to play well with the existing equipment, then this goes against one of the most basic engineering principles:
If it ain't broke, don't fix it!

It is well documented that most failures occur just after a rebuilt (or new equipment). It is called "infant mortality". And it happens for a number of reasons (examples: introducing new unproven parts, introducing new parts that could be out of tolerance, and most important the potential for human error, etc.).

In engineering we have a failure rate versus time curve we call the "bathtub curve distribution". It is a well know pattern of failure rates. The highest number of failure occur due to "infant mortality" at the left of the curve and then far to the right you have end of life, due to wear, etc.

You restart the clock on infant mortality every time you tear down a regulator, introduce new parts, and allowing any human hands mess with the piece of machinery.

This is the reason we buy stuff with a warranty. Not because it is not going to fail, but because it will hopefully be replaced before the infant mortality period.

Extremely good quality control can mitigate infant mortality to a large degree, but it is always something that we need to deal with.


You can Google "Bathtub curve" and you will find lots of information.

The Bathtub Curve and Product Failure Behavior
Part One - The Bathtub Curve, Infant Mortality and Burn-in

Bathtub curve - Wikipedia

Bathtub Curve Reliability and How Repairs Affect It