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Just a comment on that Frank is that I understand that for ABS,
Lloyds or whatever you have to have another valve for each penetration.
So if you have an operating valve for venting then you are supposed to have
another shutoff valve right against the hull penetration for emergency use.
Don’t know if that makes any difference. Chs Hugh From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of ShellyDalg@aol.com A few thoughts on externally operated valves..... I remember seeing a red sub owned by Gary in Michigan that
had remotely operated valves on the stainless saddle tanks. Over all the
sub looked well made, but it always had some small problem so never saw it
dive. My thought here is that adding complexity to a basic system like
filling/dumping ballast tanks is not needed and along with the complexity....unreliability
is also added. If the vent valves are outside the sub, and something happens to
stop it's operation, you can't fill the tanks and float up. Now, I would expect a vent valve to fail in the closed position
with a spring loaded mechanism of some type, but there's still the chance that
something can get into the valve and prevent it from fully closing even if the
pneumatic system is fully functional. With a remote valve, you need thru-hulls to operate it, so why not
just control the water in/out from inside the sub? The thru-hulls need to be
larger for carrying water, but all you need for each ballast tank is "one
in-one out" with an air line attached to blow the tank. With the valves, air supply, connections, plumbing, and stuff
inside the sub, the chance of it plugging up are minimized, and if needed, the
systems can be blown out by switching valves and sending the high pressure
air up, down, or around, to blow out any small debris that might have entered
the tanks and found it's way to the valves. It just seems to me that the added complexity of a remote valve,
along with the inability to get at it while submerged, makes less sense. The only plus I can see is that a vent valve outside the sub can
be very large which makes dumping the air quick. My sub will be using 1 inch
valves to dump the air, and the ballast tanks should be able to fill with water
in about two or three minutes. OK, that sounds like a long time, but if
anything funky starts happening with the valves or venting system, I can fix it
from inside the sub. The other issue is maintenance. If the vent valve is outside,
exposed to the elements be it sea water or sunshine, it seems like it might
require regular inspections and maintenance more often than a simple set of
ball valves inside the sub. With just the two ball valves inside, ( with a
"T" connection for injecting HP air ) the maintenance and inspection should be fairly easy, and
replacement of any valve will be simple and inexpensive. Just pull out the
valve and put in a new one. Replacement can't be done while
submerged, but a ball valve is a pretty reliable device, and inexpensive enough
to carry spares. A remotely operated vent valve, with it's air control valves, and
related thru-hulls and plumbing seems like an overly complex way to
accomplish a simple task like dumping air or water from an ambient tank. Frank D.
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