Re: Pressure testing, THOOMP or BANG that is the question!

[EdwMullin@aol.com]

In a message dated 2/22/99 8:08:29 PM Eastern Standard Time,
shawl@torchlake.com writes:

> > Just a note on the use of "Bang" in describing hull failure.  The failure 
> of a flourescent light bulb (tube) is the same as a "crush" failure and it 
> sounds more like a "THOOMP" than a "Bang".
>  
>  My spell checker said it is more like a "THUMP".Your are right I just
couldn'
> t find the right word, I stand corrected. ..er... uha...maybe?
>  Let me think again, if you were on the inside wouldn't it be a bang, 
> followed by silence & darkness?
>  We better think about that one some more. I hope no one has to find out 
> which is right.
>  Another way to pressure test a hull to about 30' before you put it in the 
> water at all, is to use a vacuum pump to suck down the hull to -1 atm or 
> about = to 30' depth, My first sub didn't make past 15" Vac or about = to
15'.
>  I was lucky enough to be on the outside of my first hull when it went
THOOMP!
>  I was tapping on the hull with my knuckles to see what it sounded like and 
> that's all it took to trigger it, the back end went flat in a split second. 
> That is what happens to thin, unreinforced, and flat sections, at a 
> relatively shallow depth.
>  Again just be careful.
>  
>  Jon Shawl


Bang is a good description, I work with vacuum systems and I've had a small
steel vessel implode.  Sudden, surprising and definitely not good for the
stuff inside!!!   

I think the vaccum/sub test is a good idea!   I wonder, I've notice that
fittings on the outside of vacuum vessels/pumps etc, can loosen when we pull a
vacuum, due to the outside pressure compressing the o-rings/seals.  I would be
curious to know if a similar action occurs on subs at depth?