Re: Pressure Testing

[Phil Nuytten <72020.572@compuserve.com>]

Hi, John:
        At Nuytco, we use a high pressure pump to get our chamber up to
test pressures - test pressure on the DeepWorker , for example, is  2k x
1.4 = 2800 ft. -  the pump is the sort used on HP water blaster systems,
capable of 2 to 3 thousand psi. The sub chamber is 7' X 9' and the entire
end opens by hydraulic ram and is secured by an interupted, castellated,
ring . .turned by a second hydraulic ram. The sub chamber is 2" thick. Our
deep pot is 20,000 foot capable and is pressurized by a low-volume, high
pressure water pump  with a pressure capacity of 15,000 psi. We use the
deep pot several times weekly to test electrical penetrators and connectors
- (as I posted to Axel's enquiry, we find the failure rate in 'certified
connectors' to average between 10 and 20% ) 
        In theory, you could use an 'O' ring sealed, threaded bolt to
pressure a fully closed, completely de-aerated system to enormous
pressures. In practise, however, there is entrained air (seemly)
everywhere!! The hull compression, for example, is quite a large volume
factor in pressure drop, and so on.  
        Finally, you may be interested to know that all certifying agencies
require a manned, full depth test. After the unmanned test depth runs, we
dive a technician to full depth, where he tests all external and internal
systems at full pressure while being observed by the certifying agency
surveyor via internal and external video. This is after the strain guage
runs to test depth. Average cost of the  certification process for each sub
is about $30 -35,000 prior to sea trials. If you have to rent chamber time,
figure cost about double, incuding modest sea trials. And people wonder why
little subs are so expensive!! (G)

Regards
Phil Nuytten