Submarines and DCS

[USMC Diver]

I was sitting here watching the tonight show and for some strange reason I started thinking about sub-mariners. My question to the DECO world is, WHY DON'T SUBMARINERS GET THE BENDS OR OTHER DIVING (AIR PHYSICS) RELATED INJURIES?

I mean, a sub is basically a giant scuba tank right? Does the air compress as it dives? If so then that would suggest some of the same properties of SCUBA, maybe?? Is there some sort of pressurization answer for this? I know subs have a crush depth due to pressure differences. When a sub comes up does it do DECO stops? If a sailor held his breath when a sub was 200m below and then the sub did an emergancy surface manuver would he blow up like a balloon or what?

Not that I am going to worry my self to death over this issue but I was just curious...I figured either someone here would know the answer, make up an answer, or at least give me a DIR related answer. You can always get a DIR answer, they have answers for everything.

 

[ajparr]

subs keep a constant pressure of about 1 atm. that is why they have crush depths.

 

[SCUBAMedicBill]

I'm no expert, but this is the way I understand it. The air in your SCUBA tank, when brought depth, is not really effected by the pressure becourse of its metal construction. The air isn't compressed, as stated in Boyle's Law. The actual compression affect occurs when the air leaves the tanks and enters into the regulators. This is so the air pressure will better equal the ambient pressure, making breathing easier.

A sub, is a big tank, so the pressure inside is not all that effected by the ambient pressure. The pressure in the sub can also be adjusted so that if the pressure went up, it could be vented and brought down and visa versa. It similar to being in a diving bell or recompression chamber.

So therefore, as long as the subs eviromental controls are working, there should be no need to worry about DCS.

Stay well and dive safe.

Bill

 

[Soggy]

A sub is a solid chamber. It doesn't compress under the pressure of the sea, and thus the air breathed inside is at ~1ATM.

If it were a submarine balloon, people would get bent (and crushed).

 

[diverbrian]

I can say that Soggy is correct. The pressure stops at the pressure hull. That is precisely why the sub has a crush depth. There is a slight increase of air pressure, but nothing like when diving. Ear equalization is a slight issue when descending and when they open the snorkel valve to ventilate the sub at periscope depth (trust me on this, it was painful a couple of times when I had a cold).

Another place that this comes into play is that submariners are told to blow out all the way up if they are forced to leave a sub from depth. They essentially take a breath of pressurized air from inside of a flooded escape hatch in this situation. This would obviously be an air embolism risk if they didn't blow out while ascending.

 

[Diver0001]

USMC Diver once bubbled...
I was sitting here watching the tonight show and for some strange reason I started thinking about sub-mariners. My question to the DECO world is, WHY DON'T SUBMARINERS GET THE BENDS OR OTHER DIVING (AIR PHYSICS) RELATED INJURIES?

I mean, a sub is basically a giant scuba tank right? Does the air compress as it dives? If so then that would suggest some of the same properties of SCUBA, maybe?? Is there some sort of pressurization answer for this? I know subs have a crush depth due to pressure differences. When a sub comes up does it do DECO stops? If a sailor held his breath when a sub was 200m below and then the sub did an emergancy surface manuver would he blow up like a balloon or what?

Not that I am going to worry my self to death over this issue but I was just curious...I figured either someone here would know the answer, make up an answer, or at least give me a DIR related answer. You can always get a DIR answer, they have answers for everything.

It's the difference between a rigid and a flexible container.

Subs maintain a more or less constant pressure inside as ajparr said. That's possible because it's a rigid design and the walls of the sub don't get compressed as it descends. Your scuba tank is like that too. It's a rigid structure, which is why the pressure in your tank doesn't increase as you descend.

Having said that, the idea of compressing a sub to reach deeper depths was probably not overlooked by the Navy and I would be surprised if they didn't do some experimenting with it.

BTW there are some rigid diving suits too. Called 1ATA or 1BAR suits. You've probably seen them in movies. They allow divers to go to extreme depths and surface without decompressing, just like a tiny form-fitting submarine.

R..

 

[Scubaroo]

There were two threads on this topic, they have been merged.

 

[Don Burke]

Diver0001 once bubbled... Having said that, the idea of compressing a sub to reach deeper depths was probably not overlooked by the Navy and I would be surprised if they didn't do some experimenting with it.

It would be quite ineffective since you only gain the amount you've pressurized to. Putting over one hundred people in saturation at 100 feet would only gain you 100 feet of depth capability and would really screw you if you had to come up and ventilate or snorkel since it would take about two days for deco.

Ponder what happens if you have the boat pressurized to 100 feet and have a fire.

Dealing with long diver lockouts with the Dry Deck Shelter system was bad enough.

The ships I was on stayed between about 720 and 800 Torr, which translates to about .95 to 1.05 ATM. Even that much variation makes dealing with oxygen and CO2 levels interesting. Most of the time about a third of the crew is trying to sleep.

 

[USMC Diver]

Interesting. Thanks for the info.