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RE: [PSUBS-MAILIST] Compressable ballast tanks
Title: Message
In our
system the regulator keeps the vbt pretty much qt 15 psi above ambient. As you
descend it automatically. On ascent we use the buoyancy of the VBT to begin the
ascent. During that time we apen the vbt vent valve to release the pressure
from the tank as you ascend. If you forget to do this, you will be reminded by
the hissing noise of the pressure relief valve.At about 600 ft we open both
flood and vent valves to use the vbt as a brake, in order to maintain control of
ascending rate.
Hugo
That's
interesting, keeping the VBT close to ambient. The VBT principle I'm familiar
with isolates the tank, so it is possible to end up with quite a large
pressure differential and I've had email exchanges along the lines of whether it
is best to pressurize with air prior to opening the flood valve at depth. Can
you elaborate on this setup Hugo?
thanks,
Alec
The
JSL submersibles use only HP air to adjust the Variable Ballast Tanks, it also
has an externally maounted regulator, which keeps the pressure inside the tank
close to the ambient pressure. The system is bulletproof and in almost 10
years of working with it I have yet to see it fail.
Hugo