Dry Suit Death?

[mello-yellow]

The type of accident you heard about, where someone is crushed into the helmet can only happen when there is a direct air passage to the surface.

Basically, what happens is that the air pressure at the surface is 1 ATA and if you were at 33 feet the ambient pressure around you is 2 ATA. If the compressor stopped and there was no check valve to hold the pressure in the hose, then the air would flow back out of the hose until it was at 1ATA (air pressure at sea level). Then the bottom end of that hose inside your helmet would have only half of the ambient pressure outside the helmet. Then the effect is the same as shooting out a plane window, greater ambient pressure at depth creates suction in the hose that is greater than any vacuum cleaner and just sucks everything in until the hose is full up to sea level. Unfortunately, the first thing to get sucked in is the helmet diver.

Are you sure this is not a myth? Your explanation makes sense, but only if the hose remains open. As the pressure in the lower portions of the hose drops, wouldn't the water pressure squeeze it into a flat ribbon, preventing anything (including the helmet diver) from being sucked upward?

 

[theskull]

I've seen several of each. In fact when I had the shop we had a bunch of zeagle bc's for rental. We eventually tossed all the zeagle inflator valves because they would gum up and stick. You could clean them and they'd be ok for a while but it seemed we were always messing with them. They used a bent washer spring and it just wasn't enough.

I was teaching an AOW deep dive when my zeagle inflator stuck. I disconnected it without a problem but I could still hear air...with the valve still open it was then letting air out of the wing. I stopped the class so I could look things over and one of my students noticed my inflator was disconnected and while I was looking at something else the nice lady connected it for me, starting things all over again.. LOL another class with real lessons for students.

I had one stick on an OW student and I got to him and got it disconnected.

I was teaching an advanced nitrox class and we were doing shallow skills part of which was shooting a bag and ascending while doing timed stops on the way. One student had his inflator stick nearly full open and what a sight it was. It happened as soon as he hit his 20 ft stop and if he had owed real deco time he would have been in trouble. Tou guessed it, another zeagle inflator.

Use an inflator with a reasonable amount of button travel and a good spring to return it...none of that silly crap that uses a schrader and a bent washer for a sring.

We were at Gilboa once teaching an OW class when an ambulance came for a guy that was shot to the surface by a stuck inflator. He had no idea how to deal with it from the sounds of it. If I remember right he wasn't injured but the ambulance was called anyway as soon as he hit the surface screaming. It was a great wakeup call for my students. I don't know what kind of inflator he had or what the condition of it was.

I've had more trouble with dry suit inflators letting water in than I have air but somewhere I have a video of me on an early dry suit dive using a rental suit where the inflator stuck wide open. I was descending in shallow water and the valve stuck wide open on the first tap. In that shallow water I was almost back on the surface before I even knew what was happening.

Several times I've had dry suit deflators jam and not vent, usually after crawling through small sandy caves. Having to vent through a neck or wrist seal can make for some cold deco even in 70 degree water after a longish dive.

Runaway inflation is something that a diver had better be prepared to deal with.

Do you have a lot of monkeys flying out of your butt?

As diverbob was so nice to point out, I don't have to worry about the monkeys during a dive since I don't have a "monkey valve" installed on the suit.

Your incidents are an interesting addition as usual, Mike, and make me wonder whether this Gilboa place has bad karma. . . I must go there some day to dive with the Polaris missiles and Raining divers.

theskull

 

[H2Andy]

Are you sure this is not a myth?

oh yes, this is documented. this happened enough times that they had to
invent a valve that would prevent it.

 

[pt40fathoms]

I just uploaded a video to my Members Photo Gallery. It's the video of a commercial robotic pipe cutter, cutting a pipe at a depth that I don't know, but am sure is quite deep. The crab gets close and is sucked into a 1/8 inch slit. If a diver were to venture too close, I would hate to think of what would happen.

 

[JasonH20]

I just uploaded a video to my Members Photo Gallery. It's the video of a commercial robotic pipe cutter, cutting a pipe at a depth that I don't know, but am sure is quite deep. The crab gets close and is sucked into a 1/8 inch slit. If a diver were to venture too close, I would hate to think of what would happen.

That video is incredible! So what exactly is that pipe, and why was there so much suction? It wouldn't matter how deep it was if filled with a liquid. I guess it must have been "empty", but then why would there be an empty pipe so deep, and why would someone be cutting it open! :11:

 

[Daryl Morse]

For those people saying drysuit squeeze is not such an issue, I would hazard a guess your experience is limited to a neoprene drysuit. Trilam drysuit squeeze, uh, "sucks".

I've dived in both neoprene and shell suits. (I currently use a shell suit.) They both squeeze if you don't use the inflator. Squeeze is a bit more uncomfortable in a shell suit, but I still don't see how it could "kill" you. It just doesn't sneek up on you that quickly.

 

[Daryl Morse]

Are you sure this is not a myth? Your explanation makes sense, but only if the hose remains open. As the pressure in the lower portions of the hose drops, wouldn't the water pressure squeeze it into a flat ribbon, preventing anything (including the helmet diver) from being sucked upward?

I read about Mark Ellyat's 300m record deep dive. Apparently when he was doing a deco stop at 20 fsw, he was breathing O2 through a hose from the surface. (The stop took several hours.) When they changed the tank, his tongue sucked into the reg due to the pressure drop.

 

[dilligaf368]

In the old OLD days before the MK-5 there were NO check valves in the hose system. When the compressor stopped the air would be forced back up the hose, the diver would be squeezed up into the Hat like toothpaste. The Brass (really Copper) hat would be rigid and the Diver made up of 90% water....
Other times the hose would have ruptured by cut or failure by cutting..same thing happened. Check valves allowed the air to flow one direction. Of Course, the diver would cut, pull the sleaves open to allow the water to fill the suit, as the Master Diver said " Cut like hell and rip the dress off and swim away.." Right!

 

[TwoTanks]

Are you sure this is not a myth? Your explanation makes sense, but only if the hose remains open. As the pressure in the lower portions of the hose drops, wouldn't the water pressure squeeze it into a flat ribbon, preventing anything (including the helmet diver) from being sucked upward?

If the hose were to compress flat and cut of the air flow then, you are correct, there wouldn't be any pressure difference in the helmet, but I have read in several different books, texts and novels, about this happening. I also think that since the helmets have check valves, that someone considers this a real danger.

I can't point out a case where it happened, but the physics is sound and there are a lot of stories about it having happened.

TT

 

[seakdivers]

I wear a shell suit - a DUI trilam... I like the "hug". It makes me feel loved... lol