# How do submarines fail?

1. Jun 4, 2006

### Pengwuino

You always see in movies tubes full of water coming apart with water spilling everywhere. Now, i know a submarine's structure can just fail at some point, but what exactly is going on when you have scenes like that where water is gushing in through pipes that were at too high of a pressure. Or is it all hollywood make-believe? I'm just trying to think where does the water interact with the outside water assuming you probably should have tried to close the water off from the outside at that point.

Then again maybe that last sentence is the problem. Do all those problems go away if you close whatever valve that is allowing water water in to submerge the ship? I have 0 knowledge of submarines so im

2. Jun 4, 2006

### Gokul43201

Staff Emeritus
Just watched Widowmaker, did you?

It is possible to stop a pressurized leak in a strained pipe-joint by valving off upstream of that joint, but this essentially prevents you from using that line anymore. You will have to find some alternative path for the water to get to the place that pipe was leading to...but that's just the details.

Also, nothing I've read about submarine design (which is bits and pieces of two books) tells me why cooling system pipes would be the first to give. I doubt that's true of any modern subs - it's relatively simple to design in flex into plumbing (in fact this is usually part of the noise reduction design). But lines carrying hot water (boiler lines perhaps, or coolant returns), however are most susceptible to stress-corrosion cracking.

3. Jun 4, 2006

### DaveC426913

Peng, what do you want to know? Do you want to know what they're showing in movies, or do you want to know what happens when submarines fail?

4. Jun 4, 2006

### Danger

There are a lot of reasons why internal pipes in a sub can fail, but it won't have anything to do with them being at ambient water pressure. Film makers will always put broken pipes in anything involving water, because it scares the hell out of the audience. Submarines are double-hulled, so you won't find an instance of a single penetration other than by a violent collision or attack by a weapon. If the external pressure hull is breached, the inter-hull space will be pressurized to ambient, and a new failure could occur in the inner hull. The likelyhood of it being a straight-line penetration is slim.
Most exposed piping in a sub will be involved with transporting drinking water, toilet plumbing, etc.. Others might be hydraulics or cooling water. It depends upon the model. Essentially the only systems that will be at or above ambient pressure should be the ballast tanks and any airlocks in flood mode.
I'm just going from memory here, though, so it might be incomplete. I'll have to get to my mother's place (where my library is) to find out for sure.

edit: And if you see anything about a sub at significant depth with a water jet coming through the hull, and someone tries to plug it with a towel or something, it's definitely BS. At that kind of pressure, a jet will cut steel.

Last edited: Jun 4, 2006
5. Jun 4, 2006

### LURCH

In the movies, when you see a sub go too deep, the whole thing collapses. This has probably never happened in real life. If it has, it is certainly rare.

When the hull of a sub fails, it normally fails ni one location, and water shoots in through that spot, relieving the stress on the rest of the structure. That's why all the wrecks you see in video from actual crash sites look so intact.

Of course, the inrush of water also has the effect of rapidly pressurizing the inside of the sub 'till it matches external pressure. This rapid compression of the air inside has the effect of drastically raising the temperature, so what the victems inside probably see is an explosion (big wall of flame rushing through the inside).

As for the pipes leaking, it appears to be a real danger for which submariners need to be prepared. Many of their training exercises fous on it.

http://www.navsource.org/archives/08/08454.htm

6. Jun 4, 2006

### Pengwuino

U-571

There was the usual submarine scene where they're going deep deep deep and then as they get down to the "dangerously deep levels", pipes start bursting on the inside. I'm just wondering if that is hollywood or reality.

7. Jun 4, 2006

### FredGarvin

The piping inside should have no direct link to the exterior of the ship. The only place that would make sense to happen is, of course, the ballast tanks. To my knowledge, the internal cooling, drinking and other water systems are closed systems that may be capable of being replenished at sea. That I am not quite sure.

The rupturing of pipes, etc...are most likely due, not to internal pressure, but to hull movement and the inability of the piping to flex enough to prevent a leak forming.

8. Jun 10, 2006

### Staff: Mentor

The Thresher was apparently a collapsed (imploded) hull.
http://www.nationalgeographic.com/k19/disasters_detail2.html#

http://www.csp.navy.mil/othboats/593.htm

http://en.wikipedia.org/wiki/USS_Thresher_(SSN-593)

The cause of Scorpion's failure is apparently unknown.
http://www.nationalgeographic.com/k19/disasters_detail1.html

http://www.nationalgeographic.com/k19/disasters_main.html
Map of Soviet/Russian and US submarine losses.

9. Jun 10, 2006

### Danger

I remember the Thresher incident (not clearly, though; unlike your aged self, I was a mere child at the time :tongue: ). Thanks for the links. I don't have time to read through them right now, but I certainly will later.

10. Jun 11, 2006

### Staff: Mentor

11. Jun 11, 2006

### Andrew Mason

Interesting point. Since compression is quick, it is adiabatic, $PV^\gamma = K$ applies. So if the pressure doubles, the volume of air reduces to .6 of its original volume the temperature will increase by a factor of 1.2 (eg from 300K to 360 K) which is pretty warm but not enough to ignite anything. When the wall of water has consumed 80% of the volume, the temperature is up to 570 K (300 C). So the sailors at the end of the sub watching the oncoming wall of water get fried before they drown.

AM

12. Dec 15, 2006

### danscope

Hi, Remember that you get 44 lbs per square inch for each 100 feet you decend
... It gets to be fun. By the way: there are All kinds of exposed pipes and valves in submarines. If you are ever in Providence, Rhode Island, you can visit aboard a Tango class Russian submarine. (My wife had to leave after about ten minutes.....:) ) .
Well,chief, the toilet is a straight shot through a 3 inch barrel valve into a
hard tank made of HY80 steel....1 inch thick. Then you have sea water flushing water to fill the bowl.
Then there is the low pressure blow piping, then you have 225 service air, and then you have 4500lb. air from the main air banks, and then there is ......
well, you get the idea that you have a lot of pipes and valves on a submarine.
The trim and drain system gets involved.
Anyway.....I used to make my living on these things.
The trick is to be nice to your boat, and respect the murdering sea.
Best regards, Dan

13. Dec 16, 2006

### Danger

Very nice. Can you supply more first hand knowledge? It's always fascinating and educational to hear from someone with first-hand experience rather than those who know in theory only.

14. Dec 16, 2006

### LURCH

For example; The pipes you spoke of in your previous post, are any of them directly exposed to external pressure?

Also; did you ever spend time in a "wet trainer"?

15. Dec 18, 2006

### danscope

Hi, Well, here's an example of how to almost lose a boat. Say you are going along at 240 feet, doing about 6 knts, when you suddenly lose the AC load on the motor generator. Not good. We make DC with the diesels on surface and snorkeling.Dc charges the batteries,one forward, one aft, the size of your living room. We then take DC and power a DC motor which turns an AC generator. This
is called an motor/generator, and delivers a synchonous AC power throughout the Boat. We use AC for all kinds of things,.....fans, the cook's mixer, the bug juice machine, the ice maker, and syncho/servo systems.....ah......synchro/servos. Interesting systems there. How do we indicate the position of "Things" remotely? Things like the forward and after diving planes? These are wings the size of a good sized car that control the attitude of the boat when submerged. "Take her down; make your depth 110
feet, 5° down bubble". The planes govern your descent angle. And the servo
system gives you a plane angle indication, in degrees. Well, when you lose AC, you lost that. There is also a servo system on the planes which electrically helps to control the whole system. When the AC system came back on, the
planes motorized, and locked the forward planes in ful dive, and the after planes in full rise. The boat went down at a 65° down angle. Through the heroic efforts of the crew, it stopped, wih the forward torpedo room well below anything it was designed for.....DEEP!!!!!!!!!!!!!!!!!!!!!!!!!!!
The Bow Bouyancy tank blew first, and she backed up to a reverse angle of 87°. That's about like a bad telephone pole. She finnaly surfaced and they bought new underware for everyone on board.
Life under water. This was a rare incident, but it illustrates what happens
while you sleep safe in your bed. Think of these brave men out there, while you enjoy your Christmas, and look towards the new year.
Best regards, Dan

16. Dec 18, 2006

### Danger

Scares me just reading about it. I'm not the least bit claustrophobic, but the thought of something like that waiting outside to squish you into jelly is a bit off-putting.

17. Dec 18, 2006

### danscope

Hi, To your question, Yes!!! There are many. The trim and drain system , and what we call "Negative tank" . Negative is a large "Hard Tank" dedicated to
controling neutral bouyancy. There are valves connecting to sea pressure.
Trim tanks are located for that purpose: Lighten one end,shift weight to the other. The best trim condition requires the least effort to control the boat.
You can "Pump water" and you can introduce air pressure to "Blow a tank"so that the water is directed to another position, tank , or jetisoned to sea.
Then you have your schnorkel system. Go to snorkel depth, raise snorkel,
drain down system to tank, observe valve condition,and notify engine room to prepare for snorkel. Little things mean a lot. learn every day.
Best regards, Dan

18. Dec 18, 2006

### danscope

Hi, To your question, Yes!!! There are many. The trim and drain system , and what we call "Negative tank" . Negative is a large "Hard Tank" dedicated to
controling neutral bouyancy. There are valves connecting to sea pressure.
Trim tanks are located for that purpose: Lighten one end,shift weight to the other. The best trim condition requires the least effort to control the boat.
You can "Pump water" and you can introduce air pressure to "Blow a tank"so that the water is directed to another position, tank , or jetisoned to sea.
Then you have your schnorkel system. Go to snorkel depth, raise snorkel,
drain down system to tank, observe valve condition,and notify engine room to prepare for snorkel. Little things mean a lot. learn every day.
Oh, I observed "wet Trainer". That is not easy. Hard to believe,Really.
A lot of water comes out of a small star rupture on a three inch pipe at 150 Lbs. pressure. You have to work fast, and as a team.
Best regards, Dan

19. Dec 18, 2006

### danscope

Hi Joe, Thresher was a terrible thing. On sea trials; at depth; had a leak iwhich splashed some electrical boards. They pulled the emergency blow system. The boat headed for the surface at a severe angle. Apparently, there was a severe angle detector switch that scramed the rector, shutting it down...QUICK!!! It takes too much time to bring the reactor back on line.
Turbines ran out of steam. No more propulsion. And.....The emergency blow valves which fed super high pressure air to the ballast tank nozzles succeeded in "Freezing" the valves(severe refrigeration effect) so they couldn't blow anymore. This boat was somewhat negative bouyant, and flew through the water. They made it to 150 feet,and stopped, and then slid back. That's all.
My brother had friends on that boat.
On Scorpion, They reasoned that an electric torpedo became "Live"
while she was headed for home(USA) . The fish goes so long and "arms itself"
so the work-around is to do a 180° which tells the fish it is trying to kill the
Boat. They did not succeed. Scorpion was found with hatches blown out.
A friend of mine was the last guy to get leave before she sailed. He painted my Picture in K West. It's a small world.
Anyway, The record is pretty darned good,considering the miles on patrol and the things they do, while we enjoy our lives.
Best regards, Dan

20. Dec 19, 2006

### FredGarvin

The valves freezing was what I remember being the number one cause for Thresher's accident.