Regulator failure - theories?

[resnick]

I had a full-out regulator failure on a dive a few weeks ago. So far, neither the divemasters on the boat, my local shop, nor Aqualung have any particular theories, so I'm curious if anyone here has some reasonable educated guesses. Here's the story, with as much info as I've got (some of it irrelevant I'm sure):

The scene: First day of diving on O'ahu. The first dive of the day was to 102 feet for 30 minutes. Tank went from 2930psi to 569psi. No
The Reg: Aqualung Legend LX ACD yoke first stage and matching second stage (2007), Airsource 3 Octopus/Inflator (2010), Suunto D9 transmitter (2006). I'm pretty good about maintenance: I bring it in yearly, and after diving, I soak it in the bathtub in warm water. Basic tune-up service/test 1 week before the dive; shop says everything is fine. I have a DIN kit that I switch out with the yoke when I need it, but I had the yoke on at the time.

The scene: First day of diving on O'ahu. The first dive of the day was to 102 feet for 30 minutes. Tank went from 2930psi to 569psi. No problems. Ready for dive 2.

The Tank: Aluminum 80 with a changeable DIN/yoke valve in it, with the plug is so that I could use the yoke. Starting pressure 2975psi.

The Dive: Second dive of the day, to a max depth of 47 feet. At 33 minutes, my D9 shows 1150psi in the tank, but other divers are at 1000psi, so the DM signals us to start heading to the mooring line to ascend. At 35.5 minutes, I'm at 25 feet, tank showing 1055psi. At 36 minutes, just as I hit 22 feet, I suck and nothing comes out of my primary. I try my Airsource; nothing. Look at my D9 and it's flashing "0psi/FAIL". Divemaster is right there with a very friendly looking octo. I do the safety stop and complete the dive on her alternate.

Back on the boat: Check the tank knob; it's open. My reg still has no air coming out of it. Turn off the tank. Take my reg off and grab a spare reg to try. It shows 1000psi. Now it gets weird: I put my reg on a full tank with just a plain old yoke valve. Shows 3000psi on my D9 and works fine. Switch my reg back to my original tank; zero. Repeat that 2 times (spare reg/full tank/interchange all) to see if I'm nuts; same results. So I'm going to try a little test (and this may be completely irrelevant): I take out my DIN kit and tools, and switch the reg to a DIN. I pull the plug out of tank (and right now I can't remember if it was a fresh tank or the one I just dove with) and attach my reg with the DIN. When I turn on the tank, it leaks air out of the first stage like crazy. (That's happened before when I haven't tightened down the DIN properly.) I try tightening everything down, but I can't stop the thing from leaking. Screw it: I switch back to the yoke. Put it on a fresh tank. Everything seems to be working fine. After lunch, I put my reg on a fresh tank and go on a dive (glued to the DM ). Dive to 80 feet for 38 minutes, tanks starts at 2970psi, ends at 770psi, no problems, and no problems for another 11 dives that week.

Back home: Bring the reg into the shop. He calls Aqualung. They've got no idea what would have caused it. My guy decides to tear the whole first stage down. (It's been a while since I've had that done.) He tells me it's full of salt and corrosion. Yuck. He replaces all the innards, tries it in both yoke and DIN configuration; everything is working like a champ.

So, any theories why, at 20 feet at 1000psi, my reg decided that I was not to have any more air?

 

[dumpsterDiver]

Ummmm.. Salt and Corrosion?

 

[Nemrod]

Tank dip tube missing and FOD. Tank/valve contamination. N

 

[JohnN]

How many dives since last service?

Do you blow your regulator dry with tank air after a dive?

 

[Stoo]

It takes a surprisingly small bit of caca in just the wrong place to mess up a reg. I bit of salt crystal is especially insidious as it can dissolve away without a trace.

Regs aren't especially complex, so problems always boil down to a bit of guck, a nick in an oring, or a groove in a seat. If your reg has been rebuilt (as it should be annually if it's in the salt all the time) then you should be golden...

A messed up reg is exciting isn't it? ;-)

I'm glad it all worked out!

 

[redacted]

Your troubleshooting procedure makes little sense. Did you check to see if gas came out of the tank with no regulator attached?

Sounds like a tank problem rather than a regulator problem. But you may never know.

 

[scubafanatic]

Sounds like, whatever other variables may have been involved, your 1st stage was in pretty rough shape (internally) so that's most likely the culprit. Failures can start out as sporadic, then progress to ongoing as internal 1st-stage conditions continue to deteriorate with deferred maintainance, although with the ACD feature I'm surprised the innards got so filthy. I'd agree with the tank dip tube being blocked, and/or water in the tank which will cut off your air if you dive 'inverted' so any water in the tank pools and floods out the reg. It could be you flooded your reg by diving inverted with a water filled tank and no dip tube or even the dip tube won't save you if you have a lot of water in the tank, it will swamp the dip tube too. Perhaps the filthy reg was caused during your trip after you flooded it with sea water with a wet tank, then that started the corrosion spotted by the dive shop during the post trip rebuild.

 

[resnick]

Some answers to your comments so far. Thanks; some good ideas here:

Ummmm.. Salt and Corrosion?

Yeah, especially given the ACD, as scubafanatic mentions below. I like the theory that when the tank went to 0psi on the dive in question, the ACD was obviously open and some water leaked in at that time, causing the salt and corrosion.

Tank dip tube missing and FOD. Tank/valve contamination. N

So something with the dip tube was the first thing that my dive shop guy thought of, but that didn't explain the other reg working on the tank and my reg continuing not to.

How many dives since last service?

Do you blow your regulator dry with tank air after a dive?

40 or so dives since previous service.

No, I don't blow my regulator dry. My instructor taught be better than that! That doesn't mean some "helpful" divemaster didn't do so when switching my gear from one tank to another, but again, remember this is an ACD regulator. That ability to blow crap into the first stage is greatly reduced.

It takes a surprisingly small bit of caca in just the wrong place to mess up a reg. I bit of salt crystal is especially insidious as it can dissolve away without a trace.

Regs aren't especially complex, so problems always boil down to a bit of guck, a nick in an oring, or a groove in a seat. If your reg has been rebuilt (as it should be annually if it's in the salt all the time) then you should be golden...

A messed up reg is exciting isn't it? ;-)

I'm glad it all worked out!

Yeah, me too. I'm pretty confident the tear-down should solve the problem.

Your troubleshooting procedure makes little sense. Did you check to see if gas came out of the tank with no regulator attached?

Sounds like a tank problem rather than a regulator problem. But you may never know.

Yes, air came out of the tank with no reg attached (in addition to coming out of the tank with a reg other than mine attached). That's why I suspected my reg was somehow involved.

Sounds like, whatever other variables may have been involved, your 1st stage was in pretty rough shape (internally) so that's most likely the culprit. Failures can start out as sporadic, then progress to ongoing as internal 1st-stage conditions continue to deteriorate with deferred maintainance, although with the ACD feature I'm surprised the innards got so filthy. I'd agree with the tank dip tube being blocked, and/or water in the tank which will cut off your air if you dive 'inverted' so any water in the tank pools and floods out the reg. It could be you flooded your reg by diving inverted with a water filled tank and no dip tube or even the dip tube won't save you if you have a lot of water in the tank, it will swamp the dip tube too. Perhaps the filthy reg was caused during your trip after you flooded it with sea water with a wet tank, then that started the corrosion spotted by the dive shop during the post trip rebuild.

But that doesn't quite explain why another reg worked on the tank while on the boat and my reg *continued* not to work while on the boat, switching them back and forth. And it doesn't explain why my reg worked fine throughout the rest of the diving (a few days) on other tanks without a hitch. (Yeah, I know: "He must be nuts." )

It's this set of facts that I can't square:

1. My reg worked fine on other tanks
2. My reg continued to fail on the tank from the dive in question
3. Another reg worked on the tank from the dive in question

 

[Jim Lapenta]

Here's a tip, treat the ACD feature as if it does not exist at all. Oceanic regs started using their DVT feature and I was an Oceanic tech working for an Oceanic shop at the time. Those "features" are good for the accidental quick drop in a few inches of water. The springs are so light that more than a foot deep will create enough pressure to open the ACD/DVT. That is just general advice.

Why your reg did what it did is hard to say without looking at it. That other regs worked on the same tank could be telling. Did those other regs have auto closures on them? When you switched to DIN it leaked. Your tech opened it up and it was full of salt and corrosion.

Seems the ACD failed in some way. I had two Oceanic regs that came with the DVT. First thing I did was get rid of that "feature".

 

[resnick]

Why your reg did what it did is hard to say without looking at it. That other regs worked on the same tank could be telling. Did those other regs have auto closures on them? When you switched to DIN it leaked. Your tech opened it up and it was full of salt and corrosion.

Seems the ACD failed in some way.

Ooooo….this sounds like the beginning of a good theory. The other regulator did not have an ACD. The tank that failed had the DIN/yoke plug. I like the theory that the ACD failed closed in combination with this particular tank valve and whatever else might have been going on with the reg.

Still, it's not clear to me how the ACD gets closed while attached to this tank valve even though it worked for most of the dive when the pressure was >1000psi.

(And FWIW: I'm not expecting that we'll get "the one true answer" here. I'm just hoping for interesting theories.)