BCD Failure

[Zef]

A small handful of years ago a member of one the dive clubs I was apart of passed out underwater due to a panic attack while struggling to ascend. One of the dump valves on her bcd had unscrewed to the point it would not seal and she could not establish enough bouyancy to get off the bottom. I would not doubt she was over-weighted as well as she was a relatively new diver. A rescue was effected and she was taken to a local hospital for evaluation. In the end she survived the incident without injury.

About a year and half ago I was recounting the story while standing on a pool deck to an instructor in another club and suggested that he include teaching students to check their dump valves are secured properly as part of their buddy check and stated that I dont think people check them often/often enough...he began to dismiss the idea argumentatively and while doing so I reached out and checked his valve fittings and to his surprise, all of them were loose. He apologized and agreed it is something that should be taught.

Murphy's Law: What can go wrong, will go wrong.

-Z

 

[Pressurehead]

check their dump valves are secured properly as part of their buddy check and stated that I dont think people check them often/often enough

Good point this ^^.
Solo diving tomorrow so me, myself and I just did a check [ all good ], must admit I don't do enough checking of dump valves.

 

[John C. Ratliff]

I have heard here that many times BCD attachments for the power inflator or the ORV have failed underwater, because they “unscrewed.” Well, believe it or not, this is a design failure. I seem to remember that some of the old valves had a set screw that was screwed into the valve when it was tight, at the factory. This precluded the fitting from unscrewing until the set screw was removed. Apparently, this has been left off on current designs.

It really isn’t

It’s a failure to carry out the most basic Pre use checks and then Pre dive checks

I remove my inflator hose and dumps regularly to clean my BCD’s and wings. There’s a fair amount of built in resistance on the threads. I’ve never found one loose Pre dive, and I only tighten them finger tight

obv the shop should have put them together properly but even so, if you’re going to jump into water too deep to stand in, best check your gear before hand

Actually, as a former product safety engineer, it is a design failure. For each life safety product, a "Failure Modes and Effects Analysis" needs to be done. For a BCD, that includes what would happen both upstream of the design and downstream of the design if the inflator hose or ORV accidentally unscrewed. The "upstream" means the step or part before that part, and the downstream means the step or part downstream of that part. In this case, it means that the BCD (buoyancy control device) will not or cannot inflate as designed, which is a single-point catastrophic failure. As Nemrod so poignantly pointed out above, an easy "fix" for this design failure is that small screw that can be tightened to preclude the unscrewing of the part.

Now, concerning the equipment check that divers should always do prior to diving, this is considered an "administrative control” under the Hierarchy of Controls in the ANSI/AIHA Z10-2012(R2017) American National Standard for Occupational Health and Safety Management Systems, this is less effective than an engineering control (like a small set screw to ensure that the part cannot unscrew).

SeaRat
John C. Ratliff, CSP(Retired), CIH(2006-2017),* MSPH
*CSP = Certified Safety Professional; CIH = Certified Industrial Hygienist

 

[Diving Dubai]

it is a design failure.

I was a design engineer in Aerospace and conducted lots of risk mitigation. You're blowing the problem out of all proportion

The plastic threads are designed to have locking friction, teh rubber seal also provided a locking force, proven by the fact that on a properly installed inflator hose you can waggle it around from side to side all you like and it won't become loose. Thus your set screw isn't required. If you want belt and braces then all your hose connections should be wirelocktd to prevent them being unscrewed in adventantly same principle

Go inspect abused rental jackets for proof - none of their inflators are coming loose unless its been removed and not assembled correctly, thus human not equipment error

 

[Diving Dubai]

The simplest solution is almost always the best. Dumping lead was his safest option to stay at the surface and get on the boat. A couple of minutes dicking around with a DSMB may have put him out of reach of the the boat, making the situation worse not better.

Exactly this.

 

[John C. Ratliff]

I was a design engineer in Aerospace and conducted lots of risk mitigation. You're blowing the problem out of all proportion

The plastic threads are designed to have locking friction, teh rubber seal also provided a locking force, proven by the fact that on a properly installed inflator hose you can waggle it around from side to side all you like and it won't become loose. Thus your set screw isn't required. If you want belt and braces then all your hose connections should be wirelocktd to prevent them being unscrewed in adventantly same principle

Go inspect abused rental jackets for proof - none of their inflators are coming loose unless its been removed and not assembled correctly, thus human not equipment error

You are ignoring the Hierarchy of Controls. The fact that this happened negates your argument.

 

[Subcooled]

the rear shoulder dump on his Mares BCD came completely unscrewed [...] how does one prevent it from happening?

Pre-dive equipment check.

It's a fear of death thing... to double check buoyancy/breathing aids.

Make sure that all things are screwed tight, or else you'll be screwed yourself.
Right, yeah, open that cylinder valve

__________
And, oh, make sure that the regulators too are screwed tight and will not drop off the hose. That happened to me once. And please do a BCD over pressure test to avoid the fate of Yuri Lipski. A negative pressure test on the reg (inhale before opening the valve) is advised too. It sucks if you have to breathe from a flooded regulator. I've done it. It's too wet.

 

[Subcooled]

You do understand that water in a bcd is neutral, right?

An interesting point.

Water displaces air though, air that may exist even in an "empty" BCD (you do not suck it into vacuum, do you?).

 

[James79]

An interesting point.

Water displaces air though, air that may exist even in an "empty" BCD (you do not suck it into vacuum, do you?).

If you are emptying it correctly, pressure differential will drive it to a near vacuum. Put something (like a small bolt//screw) into a plastic baggie, the leave the top open and lower it into a pot of water. Even that one inch or so of water column is enough to shrink wrap the bolt. If you are holding the inflator up, you are giving it even more pressure differential.

Respectfully,

James

 

[Subcooled]

Correct.

I was thinking about gear on the surface, on dry land (where there is no differential pressure).
But yeah, in the water things change.

Anyway, back to the topic. Sinking after a BCD failure on the surface after a dive looks very much like overweighting.