Re: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT) knowledge)

["Dan H." <jmachine@adelphia.net>]

Brian,

The VBT has two connections attached to it.  One is a one inch pipe that
water moves through and the other is a half inch pipe that air moves
through.

The water port is located at the rear of the tank (not important) and has an
internal elbow and pipe that goes to the bottom of the tank, so when
reducing ballast, it drains clear to the bottom.  The smaller line in
located at the top of the tank so when reducing pressure, it vents out air.

The water port has a one inch ball valve attached to it after it exits the
tank.  This is controlled from the pilots seat through linkages that pass
through a thruhull fitting.

The air port is plumbed directly into the sub and then to two valves near
the pilot seat.  One of these valves allows you to blow air into the ballast
tank to pressurize it.  The other valve is a vent valve that connect to a
vent thruhull in the top of the hull. This valve allows you to bleed off
pressurizes air from the MBT to allow water to enter the water port.  To
allow water to fill the MBT properly, this venting system must be located
above the top of the MBT.  My vent is located just forward of the conning
tower in the hull.  An added advantage is that you can see the air venting
through a viewport.

To decrease buoyancy:  (go down)
Open the vent valve.
Open the water valve.
When neutral buoyancy is reached close off both valves and power down with
the thrusters.  ( Of course if you go to negative buoyant, you can just sink
downward.)

To increase buoyancy:  (come up)
Open the air pressure valve to charge the VBT above ambient pressure.
Open the water valve.
When you hear air blowing out the water port, the tank is empty and you can
close all valves.  (If making a miner adjustment to the positive, pressurize
and then just crack the water valve a bit until you reach the desired
buoyancy.)

I hope this helps!

Pierre,  Your hatch seal really isn't a difficult problem.  There is no need
to reinvent the wheel!  O-rings exist and they are perfect for your needs.
A standard Buna O-ring, with a cross section of around .200 inch or more, in
a groove within two flat matting surfaces is all you need.  Your "hatch hold
downs" will apply all the force you need to compress the O-ring if your
mating surfaces are flat.  A 24 inch Buna O-ring is about $10.  Cheep, off
the shelf and easy to replace anywhere if needed.

Keep It Simple, Dan H.

----- Original Message -----
From: "Pierre Poulin" <pipo305@hotmail.com>
To: <personal_submersibles@psubs.org>
Sent: Tuesday, May 04, 2004 9:49 PM
Subject: [PSUBS-MAILIST] To Dan H. (or anybody with VBT (MBT) knowledge)


> Hi Dan!
>
> I know that there is a Variable Ballast Tank in a K-350. And I imagine
that
> yours have one too.
>
> Could you please tell me how this VBT is connected? Valves, vents,
drains...
> I was planning to have a pneumatic cylinder and a piston to adjust
buoyancy
> using readyly availible ambient pressure but maybe a VBT is easyer to
built
> and could do the same job.
>
> I was thinking that we could use some pneumatic push button valves for
ease
> operation...
>
> Thank you very much!
>
> Pierre Poulin
>
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