tank failure

[lermontov]

no i mean complete gas fail

Complete tank failure? Do you mean it explodes?

In this case, you are chum.

Thanks...

 

[DevonDiver]

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

Principle of Gas Matching - team members must have sufficient volume of gas (differs from pressure) to enable gas donation egress with any other team member (varying SAC/RMV rates).

That principle applies even though wreck divers will adhere to (at least) Rule of Thirds gas management (1/3 in, 1/3 out, 1/3 reserve).

Both of those principles still apply even though the Principle of Redundancy (life support & gas) is always applied.

Thus, even if one regulator / tank fails, the diver should have sufficient remaining gas to exit. But for the worst case scenario, even assuming higher gas consumption than the donor, the donor should gave enough gas to share and assure survival for both.

 

[Peter69_56]

Minor leaks at the attachment point between the valve and cylinder are common but are not sudden or catastrophic. They can be identified early in the dive. Otherwise, here are some of the actual reports I've seen of failures in the water:

1) O-ring failure at the sealing surface between the tank valve and the regulator. Not uncommon. This is a problem particular to yoke valves, never heard of it happening with DIN. Usually happens at the very beginning of a dive, but DumpsterDiver reported an incident of this type at depth. [ETA: crossposted, this is the incident DumpsterDiver reports upthread]

2) Clogged dip tube. I've only seen one report of this. It was unclear to me how the tank accumulated enough particulate contaminants to pose a problem.

3) O-ring failure between the tank valve and cylinder neck. Cause unclear in the reports I've seen although I have trouble imagining how it could happen without the wrong parts or insufficient assembly torque.

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.

5) Valve stem seal failure. Not uncommon on older valves. Some shops replace all the valve O-rings at the annual tank inspection, which I think is prudent.

1, As stated common enough, but usually shows signs of leaking prior to failure, however if the valve/reg is hit hard it can instantaneously fail.

2, This can happen where aluminium tanks are not regularly inspected and cleaned, in particular where the dive shop is located at the sea and thus fill air containing salt. It causes contaminants to build in the tank, often you can shake the tank and hear them (little balls of corrosion), or as others have stated, water contamination in the tank. This usually blocks the cinter filter in the reg before the actual dip tube but has the same effect.

3, Tank neck O ring failure can happen when tanks are never checked or washed (Thailand is good for this). This can cause the neck shoulder to corrode which can allow the O ring to extrude past the corrosion point and catastrophically fail (although again usually there are signs of leakage prior to failure). Seen lots of this damage. Also O rings tend to soften with age and exposure to high O2 levels and lose their shape and consistency and tend to become more mushy and thus are more able to squeeze out any minute openings.

4, As stated, continual over pressurisation, and perhaps contamination of the tank causing corrosion. Usually also associated with not inspecting and servicing tanks/valves regularly.

5, Valve stem O rings usually show signs of leakage long before any potential catastrophic failure.

 

[tstormdiver]

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

Actually it is turn pressures for divers with dissimilar cylinders & SAC/ RMV.

 

[Dive Right In Scuba.]

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

As stated earlier, this is a case of technical diving, and you are asking the question as a new diver doing non-technical dives. Advanced wreck divers have to plan for emergencies in which the surface is not available to them, so they both need to have redundant air supplies and be able to share air for extended periods of time. The diving you will be doing for a while will be different.

If you do want help with this specific issue, I suggest you ask your question in the technical diving forum instead of the Basic Diving forum.

 

[IBjones]

What are you calling "tank failure"??

If you are talking about a tank exploding, that's very rare. There was an issue quite awhile back with some exploding aluminium tanks that were recalled due to defect.

I've seen pressure valves pop due to over-filling, and that's less rare, and usually happens when they're being filled.

I've also been on the U352 and a O-ring blow on the first stage. The chick was freaking out at first. It's a pretty suck feeling be be at 100 feet and see all the air leaving your tank really fast. As I understand it those are less rare and happen every once in a while. She handled it well and used the spare octo from her dive buddy and surfaced safely and calmly.

I have a little keychain thing that looks like a miniature scuba tank. The lid screws off and you store extra O rings inside. I will usually replace an O ring if there's and or grit in there that would cause it to fail. O rings are dirt cheap. But a dive can be ruined if you blow one and don't have a spare. I assume the dive boat would have a spare, but I don't depend on others to keep my gear serviceable if it's user-level maintenance.