[PSUBS-MAILIST] bilge pump

Sun Oct 5 17:46:33 EDT 2014

Hank,as I touched on integrating a variable ballast system, I thoughtI'd paste this post from Phil on how the DW variable ballast systemworks. He makes mention of pumping out with a manual hydraulic pump.
Re: Seat VBT: The system was one we (Nuytco) used in the earliest DeepWorker model subs – starting around ‘97. The seats were black, roto-cast plastic designed for use on/in snowmobiles, home-built race cars, dune buggies and the like – and they were hollow. We came up with the idea of using them as a VBT that could be very precisely trimmed immediately pre-dive and could be easily changed (made heavier or lighter) during the dive.  The seat was drilled and tapped for an inlet and outlet line. The water inlet line/hose had a needle valve on the inside of the hull at a convenient spot  for the pilot to reach. The outlet line/hose led to a simple, manually-operated hydraulic hand pump and from there to a  second on/off valve in front of a non-return valve plumbed through a hull penetrator. To use, the DW was trimmed to be buoyant with the seat empty. while the pilot was floating on the surface and the load line cast off, he opened the inlet valve to allow water into the seat until the dome went under and then the inlet valve was then shut off. This made the hull slightly negative and it would sink slowly, or faster with additional down thrusting. This, for pilots who like to dive a bit heavy. To lighten up, the outlet valve is opened and the water pumped out until the sub became buoyant – just a few strokes, usually. We did try using a heavy duty plastic bag full of fresh water attached to the inlet side to avoid the plankton and assorted little critters when diving in sea water – but we wound up just flushing the seat tank with fresh, soapy water after an ocean dive and that worked fine. All and all, a pretty neat systems except for a few downsides: Ambient water is pretty cold at depth and chills the butt and back – and, you have to studiously remember to shut the inlet valve, particularly at any appreciable depth, because even with a needle valve the water comes in fast. We had a hole in the top of the seat as an over-flow  and sometimes got sprayed by the overflow if something distracted you while allowing water in, and a few other minor things. At the time we had this system in place, we were training a bunch ( (40 – 50) scientists as DW pilots over a two year period – the experienced pilots had no problem with the seat VBT but we figured it was just too many things going on for new trainees, and so reverted to a conventional nylon box with holes in the bottom as the VBT, and that’s what we use today.  Speaking of which, we brought a couple of DW’s back from a series of science dives in California, a month or so ago – after a few days in the shop one the DWs developed an extreme case of ‘body odor’  - turned out to be a squid decomposing in the VBT! 
      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: personal_submersibles at psubs.org 
 Sent: Monday, October 6, 2014 6:54 AM
 Subject: [PSUBS-MAILIST] bilge pump

Are bilge pumps common or required by ABS, if so are they high pressure or low pressure for the surface only.
Hank
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