Manifold failure - what should you do?

[Daniel Dilley]

Hi Everyone

Recently i was talking to another tec diver and we where discussing regulator and manifold problems.

We agreed about all procedures for free flowing regs but when we got onto manifold failure his idea is to initially close the isolator. work out where the problem is commng from and then just breathe the reg from that side no matter what.

I said that i agree to close the isolator, work out where the problem is coming from. But then is i would not breathe that reg i would also close that reg valve to save that gas. Maybe the problem could be with first stage and then i could reopen the isolator giving me access to all of my gas again. However, if there was a leak from a burst disk or the manifold bar then i agree to breathe that side down.

Can someone help me out if i am missing something? What would you do? Surely i have the correct precedure?

My Best Regards
Daniel Dilley

 

[PfcAJ]

You can often tell which side the leak is coming from. Why bother with shutting down the isolator when you KNOW its coming from the left (as an example)?

Proper manifold failures are vanishingly rare, especially in a catastrophic way. You might get a little bubbling, but that's it. Regulators have way more orings and moving parts and are far more likely to leak.

 

[Colliam7]

I said that i agree to close the isolator, work out where the problem is coming from. But then is i would not breathe that reg i would also close that reg valve to save that gas. Maybe the problem could be with first stage and then i could reopen the isolator giving me access to all of my gas again. However, if there was a leak from a burst disk or the manifold bar then i agree to breathe that side down.

I guess the answer is, as always, 'it depends'. And, 'it depends' in part because I am a bit confused by your description of the scenario. You specifically title the thread 'manifold failure', and you even preface the particular paragraph (above) with

but when we got onto manifold failure

However, you then go to raise the possibility of 'Maybe the problem could be with first stage'. That situation would not be a manifold failure, so what your buddy said about breathing gas from one side or another, although correct for a manifold failure, would not apply (to a first stage failure). In any event, I think you answer your own question later in your post.

However, if there was a leak from a burst disk or the manifold bar then i agree to breathe that side down.

If there is a leak, shut the isolator, to see if you can find the source of the leak, and to save gas. If the leak is truly a 'manifold failure', e.g. a leak at the point of connection to one valve or the other, and you can isolate that leak to one side or the other by closing the isolator, you may as well go ahead and breath down the remaining gas from the affected side because you are going to eventually lose it anyway. Closing the cylinder valve would do no good.

On the other hand, if the issue is - in contrast to the thread title - a first stage problem, you are right. Close the valve on the affected side, re-open the isolator and breath ALL of your gas through the regulator on the unaffected side.

 

[tbone1004]

what AJ said. It is highly likely that the failure was on one of the first stages, so my muscle memory says to listen or feel for which one blew, though it's pretty obvious. "I hear leaking, and can still breathe normally on my second stage" or "I hear leaking and my primary is not doing so well", and shut down accordingly. IF that doesn't stop the leak, then I close the isolator, however I have never encountered a real world failure requiring isolation.

If you think about it you have 2-3 static o-rings on each side of the manifold, all of which would have to fail in order to experience a leak *except the Sherwood and OMS designs, but those are captured and also pretty unlikely to fail*. You could also have a valve failure itself, however I have only ever seen those fail when you open them if the O-ring above the stem doesn't seat properly, but that shouldn't fail during use.

What Colliam said though is what I would do if the situation occurred. If the situation was truly the manifold, I'd breathe the affected side down until it was gone, then switch over. The gas is going away anyway, might as well use what you can out of it before it is all gone.

Or, if you're that worried, just remove the crossbar and dive independent doubles with appropriate gas planning

 

[dumpsterDiver]

Wouldn't you want to try to avoid allowing sea water into the tank? If it were not an emergency, wouldn't it be better to let it bubble away and hope that (by not using the gas) you can avoid flooding a first stage and or tank?

 

[tbone1004]

depends, if I'm in a cave? I'm breathing that gas. If I'm in the ocean, I will make an immediate ascent and yes, hope that it doesn't flood

 

[PfcAJ]

Breath it. Tanks and regs can be cleaned. Could you imagine how dumb you'd feel if you misjudged your remaining gas and ran out completely because you might have to plop a 1st stage in the ultrasonic and tumble your tanks?

 

[kensuf]

What AJ said about manifold failures is true. About a year and a half ago I had a set of 104's with the regs on them that took a tumble off a bench, landing manifold down. Everyone around that bench ducked for cover, but I just hoisted them back up. A reg was toast, but everything else was fine.

 

[The Chairman]

The chances of a manifold failure at depth are pretty minute but they exist. The chances of a regulator failure, including hoses, spg spool and so on are significantly higher. If you're on doubles, there's a good chance that you've been diving the rule of thirds. At the furthest penetration, you've consumed your one third, leaving a third in each tank. It's vitally important that you protect at least one third (now one half) of your air, so you can exit safely. Isolation is important.

But why not close down the offending reg first??? The short answer is that your senses can often lie, or least be deceived. Bubbles underwater are confusing at best. On top of that, they can travel a bit before they start to rise depending on the pressure, so a leaking reg on the right might seem to be a leak on the left and so forth. Hell, you're not even sure it's a reg at this point, so shutting down a perfectly good reg may not stop the leak. So, while you're figuring out that the leak is on the left side and not the right, or that it's not a reg after all, you've been losing air from both tanks. Lots of air. Do yourself a solid, and isolate at the first inkling of a problem. What? you can't reach that isolation knob? Buy an extender if you need to before your dive. If you didn't plan ahead like that, then loosen your harness and dip your head down so that the tanks can slide down a bit where you can reach them. Whatever it takes, get your hands on that isolater and crank it shut. Now, that you've got half of your remaining gas safe, you can try to identify your problem.

Now go with your intuition. Turn off the post you think is leaking. Be sure to breathe it down (you might have to switch regs) and listen. If the bubbles have stopped, then it was the regulator on that post. Open up the isolater and you now have access to all of your air. Clip off the dead reg and continue to exit ASAP. Don't forget safety stops and deco obligations if you have enough gas.

If the bubbles didn't stop, you've got more work to do. Open the post you just shut down and start to close the other post at the same time. The isolater should still be closed! Once you've closed the other post, the reg you're on should breathe down quickly. Switch to the breathing reg and listen. Are the bubbles gone? If yes, then clip off the dead reg open up the isolater and continue to exit with the same caveats as the other reg.

But what if the bubbles didn't go away? You've just discovered that you have a manifold leak. At this juncture, the isolater needs to stay in the closed position until you finish the dive. But you don't want to just waste the air? Make sure both posts are open and switch to breathing the right hand post, but look at your SPG. If like most divers, your SPG is off the left post. If it is decreasing, then that's your leak. Switch to breathing off of that post. If it's staying steady, then the leak must be on the right, so keep breathing on that reg. You're losing the air anyway, so why not use as much of that air as possible before it all escapes?

All of this should be done while you're exiting. Don't wait to figure out the leak before you start to exit. Hey, it's OK to be static while your instructor assesses your ability to do the drill, but in real life you're going to be exiting as soon as practical. Also, don't be afraid to let your buddy assist you. They can actually SEE where the air is leaking from. No need to be macho here and do it all on your own when help is near.

 

[LiteHedded]

aj has lost i believe two sets of doubles out of the back of his truck on the highway. i dont believe either set leaked