Failure modes?

[AquaBob]

How do regulators fail?

I've read a ton of messages regarding the pros and cons of regulator service. There seems to be three camps....
-Those that do their own service
-Those that would like to do their own service
-Those that wouldn't dare do their own service because the consider the regulator their 'life-support equipment'.

I haven't bought a reg yet -- still using rentals -- but definitely fall into the middle category.

I have the skills to perform my own service, and with a little poking around, I've found the service manuals for several manufactures 1st and 2nd stages.

My real question is, if you do your own work -- how do you know it's done right?

It seems that it should be fairly obvious from the bench tests and the 'dunk' tests whether you have a leak or an IP problem. Further, if the cracking pressure is set and checked correctly, what are the unforseen problems that may arise?

It just doesn't seem like brain surgery to clean and replace some parts. I would suspect that any problems should show up either in the sink, or within the first shallow dive. Obviously, you would be foolish to jump into the water and plunge to 100' with a freshly serviced reg, but I would think that would go not only for one I've done, but one that came from the shop.

Am I missing something?


(btw, in the winter, a parka is also life-support equipment, but I'll still wash it and replace the old hood drawstring myself.)

 

[redacted]

So keep the availability of info, parts, and tools in mind when you shop around for your own rig. Reliable sources for parts is probably the biggest challange. Some manufacturers seem to have more leaks than others.

 

[DA Aquamaster]

It's almost unheard of for a reg to fail in a manner that it delivers no air. Virtually all failures result in either a slow leak or a freeflow.

You are on the money on what to check and what to look for after servicing a reg and obviously that requires a minimum number of tools (IP gauge etc).

The most serious concern would be mis-assembling something in the first stage which could have serious consquences when you first turn on the tank valve. You really need a manual deliniating the disasembly, assembly and adjustment procedures. You also need the correct tools, and some idea of what you are doing when you work on a first stage. It is not rocket science but some care and knowledge is required.

Second stages are safer to experiment with as the pressure involved is lower and the worst case scenario usually just involves a lot of noise when something is missing or misadjusted. Second stage maintainence and adjustment really could be taught in a specialty class without any serious liability issues and knowing how to adjust a second stagewould be nice for many divers to know.

 

[AquaBob]

That is about what I expected.

As a side note.... what do they mean by O2 cleaned?

Is it just replacing the o-rings and lubricant to something O2 compatible (viton??? cristolube(sp?))?

 

[scubahorse]

Dacor Viper, SCUBAPRO Ultra Light First Stage ,...
Maybe we need a poll for the worst reg.

 

[DA Aquamaster]

AquaBob once bubbled...
That is about what I expected.

As a side note.... what do they mean by O2 cleaned?

Is it just replacing the o-rings and lubricant to something O2 compatible (viton??? cristolube(sp?))?

O2 cleaning a reg is not required for Nitrox mixes of 40% O2 or less. For hotter mixes you need to use an O2 compatible lubricant and preferrably O2 compatible O-rings. Viton O-rings are O2 compatible but spendy and trade some wear resistance.

They are technically speaking not required as standard rubber o-rings work well and will not cause things to burst into flames but they do provide a fuel source once things start burning so the conservative approach is to replace them with another material.

In any event, when O2 cleaning a reg you need to replace the o-rings with new ones and insure they are lubed with an O2 compatible non petroleum based lubricant like christolube.

You also need to clean the interior surfaces of the reg to ensure that there is nothing in there that could react with the oxygen and cause a fire.

 

[AquaBob]

I don't plan on plan on sucking any really hot gas, just curious.

Thanks again.

 

[Genesis]

is that MOST O2 fires aren't caused by "contamination" per-se.

There is ALWAYS going to be something in there that will burn. Brass won't - up to 10,000 psi of O2, anyway. Your reg body is probably (unless you got one of those fancy titanium or junky "ultralight" regs) made of it. That's the good news.

The bad news is that the HP seat is made of some form of polymer. That WILL burn. The worse news is that what CAUSES ignition is the heating of gas when it is compressed - that is, low pressure gas comes rushing down a passageway and rams into a dead-end or is forced to make a sharp turn, creating localized high pressure spikes which, just as a freeflowing reg gets cold, get HOT. VERY hot.

Unfortunately the places where it is most likely to happen is right where you have combustable materials! Oh oh...

Viton will burn, by the way. If you don't believe me get a welding torch, take it OUTSIDE, light it, put the viton O-ring on something that won't burn up and is safe (like an asbestos pad), heat it a bit until it lights (it won't take much) and shut off the fuel - so only oxygen is flowing. It'll burn like hell. Just make damn sure not to inhale the fumes - it gives off some really nasty gasses when it burns. Now consider that this was in pure oxygen at NORMAL pressure. Then think about that same O2 at HIGH pressure.... oh oh...

Christolube will decompose too, and into some nasty stuff. It doesn't "burn" per-se, but you don't want the fumes it makes in your lungs. The only good news is that the temperature necessary to do this is in the 350F range - by which point you've got bigger problems. That, and the fact that its a really good lubricant, is why its used - silicone will ignite at a much lower temperature in the presence of pure O2. Don't believe me - go pull the MSDS! Its right there in nice black print.

So what does this all mean?

1. Cleaning a reg (and valve, and tank!) is a damn good idea if you're going to use >40% Nitrox. It might be a good idea for less, if for no other reason than you probably don't want to BREATHE the crap that could be in there if its not done once in a while. If you're going to clean a reg, you may as well O2-clean it - its really not any more work or difficulty to get it REALLY clean as opposed to just passably so.

2. If you slam open a tank valve with a high FO2 mix in it, you may manage to light up your kit irrespective of O2 cleaning. If you DO get it lit there's a lot to burn, including all the O-rings (irrespective of compound), the HP seat, and even your hoses! Don't do that. Good practice is to SLOWLY crack the valve to build the pressure SLOWLY, turn it OFF (if you got an ignition event you cut off the oxidizer doing this, which means that the damage will be limited to the reg and you won't have enough oxidizer to make a really BIG fire out of a small one!) and if all is ok after a few seconds, then go ahead and turn it back on for use.

3. If you're PP Mixing Nitrox, the tank and valve should be O2 cleaned and O2 service rated. That's easy for tanks, but not always for valves, as some valves simply don't have O2-service-rated seats available. In truth 99% of the time you'll get away without doing it as nearly ALL current production valves, including Genesis and Thermo (the two "big names") are assembled with Christolube nowdays, and you can put O2 on top of some really grody tanks and valves provided you do it VERY SLOWLY. Usually when accidents happen they occur because someone gets sloppy or in a rush and slams a PP O2 addition in - and finds out that there is junk in there. The real bad accidents happen when the "junk" is in the tank rather than the valve (nowhere for it to go) and there's a LOT of it, along with enough to get lit in the valve; the flame front flashes into the cylinder and ignites the junk in there, and the evolved combustion gasses can produce enough overpressure to explode the cylinder. But with that said its best to do it right, especially if someone ELSE is going to be filling that tank! If its YOUR tail, then you decide how much risk you are willing to PERSONALLY accept. (I personally DO NOT cut corners!)

 

[AquaBob]

Very informative. Thanks Genesis.

 

[Genesis]

BTW, one more thing. NEVER, NEVER, NEVER put any part of your body over any of the potential ejection sites on a reg or valve when you turn it on.

That is the HP seat cap on the regulator, and the stem of the valve. When you turn on a valve, grasp the handwheel AROUND the stem, NOT over the top of it. If it blows out, you will still have your fingers.

Likewise on the HP seat cap on the reg; if you get an ignition event in there, the most likely thing to go "bang" is the HP seat cap. If it happens you don't want the ejected piece(s) becoming the equivalent of projectile weapons impacting on your body.

Once the tank is "on", the risk is very low - its the turning on (excluding the filling process) that is when most problems happen.