Reg lockup

[NancyLynn]

I wouldn't take it apart yourself unless you have the proper tools and knowledge. Since this is your primary reg, you're just asking for more trouble. Practice on an old reg to learn.

After I posted that, I was thinking I should see if I could find a cheap one on e-Bay to play with.

You didn't mention anything about cold so I'm guessing it couldn't have been blocked by ice. And I'll assume you know for sure the air was actually on and the hose wasn't kinked.

78 degrees water temperature, so ice is not likely. Air was on - that was my first thought. If I hadn't been able to replicate the problem the next morning, after removing, rinsing, and reinstalling it on a different tank, a hose kink could have been the problem, since I didn't check specifically for that at the time of the incident.

It could have been debris in the first stage blocking the port.

Probably not likely - the replacement reg worked for 2-3 dives immediately following the morning replication of the problem and the swap out of reg only - not the LP line. I would think if it was debris, it would have locked up the replacement second stage since there wasn't any significant movement that would have dislodged it before I tested the replacement reg.

I'm still leaning towards improper parts or assembly during the original service. I don't know anything about your LDS but I can see where an LDS would not want to admit they seriously botched a service job that could have had catastrophic consequences if they could quietly fix things and ensure it doesn't happen again.

I think I want to see if I can figure out what might have caused the sound/feel of the incident before I go down that route - if the innards are as straightforward as the explanation I posted earlier, I'm having a hard time figuring out what I heard/felt.

 

[redacted]

I can't think of anything a tech could do that would allow a 2nd to operate OK for a while, and then deliver no usable gas, and then be OK again. A blockage in the LP hose perhaps or something inside the 2nd stage that blocked the operation of the lever.

 

[NancyLynn]

I appreciate all of the pointers as to what might have gone wrong in this specific incidence.

I posted the question here (rather than in the reg specific section) because the sequence of events made me realize that what I thought was a safe solution for what appeared to be a second stage failure may not have been - and there may be others who have had similar experiences (not necessarily a lockup - but a failure that appeared to be isolated to the second stage).

So - generally - I have a problem that appears to be isolated to my second stage. Later, after diving on a replacement second stage, it is suggested to me that it is the first stage that is the source of the problem (although after the discussion above, I am inclined to believe the identified problem wasn't the real problem - but if the first stage was the problem for any reason it would have made those last few dives with a replacement second stage potentially deadly).

Are there field tests to reliably isolate the source of the problem (first stage/second stage/LP hose)?

Do I just rent a replacement first/second stage until I can get the entire set back to the shop?

I guess it goes without saying that if there is a problem anywhere, the entire setup needs to go back to the shop for full analysis - but if I'm on a week-long dive trip, what do I need to do in order to be safe until I can get back to my LDS?

 

[redacted]

Nothing guarantees a dive trip free of lost dives due to regulator problems like a spare regulator. One spare setup covers both my wife and I (and sometimes others on the boat who have problems).

The fact that your octo worked while your primary didn't is a strong indication that the problem was in your primary system. Manual purging should have made it obvious whether the 2nd stage lever was operating correctly. Hose stiffness (or lack thereof) should make it apparent if the hose is carrying IP. It is too bad more thorough troubleshooting was not done sooner to try to isolate the problem.

 

[ReefHound]

A few more things...

I've learned over the years whether it's a reg or car or software program, the symptoms can be seemingly unconnected to the true source of the problem. While it appears to be a second stage problem since you replaced the second stage and the reg seemed to work fine, I wouldn't conclude that with absolute certainty. It would have been interesting to install the "faulty" second stage on another first stage right at the time to see if the problem continued with the second stage. If so, that would have fingered the second stage for me. If not then we have a real mystery.

While I suspect the previous service I'm not saying to go make such allegations. Whether true or not it would just lead to hard feelings with no resolution. Something was physically blocking the air supply. Either it was one of the regs own parts or a foreign object. I can't think how any object strong enough to create a blockage could get inside while diving.

We may never know the cause of the problem. In the end, you may have to accept that it was a fluke that cannot be foreseen or analyzed. All mechanical devices will suffer failures at some point. You are best served by being trained and experienced enough to deal with them. A reg lockup at 120' is best avoided but should be something you can deal with if you are near your buddy and you have managed your gas properly. But kudos to you for calling the dive. Sounds like a no brainer but some divers might have been more concerned with "saving the dive" and just used their octo, which of course is how accident chains get started.

 

[SteveAD]

The Mk 16 is a pretty finicky reg to work on and does require some special tools to make sure you don't damage its internals. With the mk17 upgrade in it, it does get better, but it still requires special tools to do the job right.

 

[dave4868]

I can't think of anything a tech could do that would allow a 2nd to operate OK for a while, and then deliver no usable gas, and then be OK again. A blockage in the LP hose perhaps or something inside the 2nd stage that blocked the operation of the lever.

Nothing guarantees a dive trip free of lost dives due to regulator problems like a spare regulator. One spare setup covers both my wife and I (and sometimes others on the boat who have problems).

The fact that your octo worked while your primary didn't is a strong indication that the problem was in your primary system. Manual purging should have made it obvious whether the 2nd stage lever was operating correctly. Hose stiffness (or lack thereof) should make it apparent if the hose is carrying IP. It is too bad more thorough troubleshooting was not done sooner to try to isolate the problem.

All great advice!

The intermittent nature of this problem makes it an intriguing mystery.

Yep, simply pressing the purge button during the failure would have been revealing.

After the incident, I suppose one could take a look inside that LP hose now and see something that might cause intermittent obstruction.

This is one of those challenging problems one would love to work on! At least when it's someone else's gear....

Dave C

 

[dave4868]

The Mk 16 is a pretty finicky reg to work on and does require some special tools to make sure you don't damage its internals. With the mk17 upgrade in it, it does get better, but it still requires special tools to do the job right.

Did you have some particular damage in mind that might have caused this intermittent failure?

Dave C

 

[bleeb]

Here's a wild idea for the equipment experts to comment on: Was this a (poorly maintained) rental tank? Would the symptoms be explained by large debris in the tank and maybe a missing dip tube, or the dip tube falling rattling around and plugging the outlet?

 

[ReefHound]

Explain how the octo breathed OK if it was a tank orifice blocked?