tank failure

[lermontov]

thanks devon those pics are pretty dramatic and sobering

Tank failure.... or a general equipment failure that ceases effective gas supply to the diver?

Tanks don't "fail" often; but you do hear occasional reports of debris blocked valves, blown valve o-rings or, more commonly, leaks from the valve handle. These are all servicing and maintenance issues.

In respect to wider failures, there are many. It can be something as simple as a torn 2nd stage diaphragm, a mis-aligned mushroom valve, hose blockage, 1st stage IP drop, a yoke-valve getting forcibly jolted to misplace the o-ring... etc etc etc...

In more than 2 decades of diving, I've only had to deal (air-share donor) with one true out-of-gas emergency caused by an unanticipated equipment failure (double regulator hose failure... read the report HERE). Other than that, I've only had to donate gas in training exercises or as a pre-emptive action to prevent someone running low on gas.

 

[Dive Right In Scuba.]

4) Burst disk. Can fail as a result of a history of overfilling the tanks, or as a result of excessive assembly torque. I've seen one report.

This is the rational as to why most cave divers "double disc" their valves. [emoji41]

A lot of cave divers fill LP tanks very near the pressure at which the burst disk is supposed to blow. That's a reason for doubling. (Note that I am not advocating the practice--just noting that it is common.)

 

[CuzzA]

It seems rather silly to double the burst disk when you can simply use a higher rated burst disk to support a cave fill.

Am I missing something?

 

[drbill]

I've only had steel tanks fail... on VIP or hydro (never under water), but I have had gas supply cut off by a small piece of debris that entered the debris (or dip) tube when I did a head first descent. Ended up at about 80 ft with no air coming out of the valve and, like an idiot, I hadn't strapped my pony bottle onto the main tank. It happens although it is a rarity. They tell me regs usually fail open so air supply is rarely cut off, but I've never had that happen underwater.

 

[BRT]

I've watched one dip tube clog from a distance. Pressure just dropped from 1600 to 0 at 128 ft. Lady breathed with the divemaster to go up. I know one other guy who had a dip tube clog at over 140 in decompression. He still can't walk very well. Heard of some others. All in Mexico.

 

[Dive Right In Scuba.]

I've watched one dip tube clog from a distance. Pressure just dropped from 1600 to 0 at 128 ft. Lady breathed with the divemaster to go up. I know one other guy who had a dip tube clog at over 140 in decompression. He still can't walk very well. Heard of some others. All in Mexico.

It happened in Mexico to someone in a group with which a friend of mine was diving. They descended, then entered a swim through at about 100 feet, and it required them to go head down. As soon as it happened the guy went OOA. When they opened the tank on the surface, there was no dip tube at all, and there was about a liter of rusty water. The operator was then using a tank filling business for the care, maintenance, and filing of its tanks. Soon after that it went in-house. Wonder why.

 

[dumpsterDiver]

A failure can also occur from the dip tub falling off the valve... then there is very little to prevent clogging.

Also, it is not that unusual for tanks to end up with some appreciable amount of water in them. Without a dip tub, you would be sucking water when you invert.

Also it is not that unusual for a tank neck/valve O-ring to have a problem. If they are not tightened enough, then the valve can pop loose- especially when the pressure is down. I've seen many tanks with loose valves, but strangely - no emergencies arising from this situation. A tank o-ring will often start leaking (in a pretty obvious manner - underwater) before a failure would be expected.

The tank itself is pretty robust... hoses, o-rings, fittings in a regulator etc. are much more likely to cause an issue.

 

[lermontov]

thats great feedback thanks further to the TDI question its in the advanced wreck manual and suggest that the lighter breather (who had smaller tanks )could have carried bigger tanks to allow a greater margin of safety should the heavier breather have problems even though they had ⅓ reserve air, which is a good point but should the heavier breather be more responsible and carry extra bottle - is there a standard protocol in this case should each driver be ''independant' even when with a buddy

 

[Centrals]

There is such a thing as "turn pressure". This is really important if two divers have different SAC.

Is this question appropriate in Basic Scuba Discussions?

 

[KeithG]

Hi I'm new to scuba diving and reading about gas management and an example in the TDi manual asked for calculations to work out what two divers could do if one had a complete tank failure., but my real quest ion is how often does this really occur? I've tried to search on the internet about accidents re complete tank failure but can find any -so how common /rare is it/

Complete tank failure? Do you mean it explodes?

In this case, you are chum.

Thanks...