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Re: [PSUBS-MAILIST] Main ballast.

Chris,
 
Your right in what you say about the piping not having to all be above the tank if it's full of air.  But, if your piping is routed to a point below the top of your MBT and you get water in the pipe, which is sure to happen when filly blowing the tank, the water held in the pipe will be heavier then the air that is trying to be forced out. 
 
I'm not doing a good job with this explanation! Sorry
 
Think of what happens if you siphon with a hose.  If part of the hose has air in it you can't get the siphon going.  In this case, if the lower part of the piping has water in it, it till take more pressure in the MBT to blow the low lying water out and allow the air to pass through.  Since the only pressure is the head of water, it can't lift a trapped column of water higher then it self.
 
Agree?????
 
Hope I made enough sense for you to follow my thinking. 
Dan H.
----- Original Message -----
From: Chris Nugent
To: personal_submersibles@psubs.org
Sent: Thursday, May 22, 2003 8:40 PM
Subject: Re: [PSUBS-MAILIST] Main ballast.

    "The vents for the fore and aft soft MBT have to be mounted at the top of the tanks in order to release the air above the water.  Since the MBT's top is the same height as the top of the hull, the piping and valves had to be located at the height of the conning tower. "
 
 
     Ok, so if the sub is sitting on the water on the surface, the air in the MBT's should be under some pressure since the weight of the sub is forcing it down, and thus forcing water into the bottom of the MBT's, and thereby displacing the air in them and compressing it until it achieves equilibrium and the sub floats, right?  I understand why the valve has to be at the top of the MBT, but your piping doesn't have to be at the same level as the valve, right?  If I reckon right, the somewhat pressurized air in the MBT's, once the valve is opened, should rush right out no matter where your piping is, as long as the MBT is able to flood completely, right? 
    At the depths I'm aiming for (ummm....50 feet?)   I hadn't thought that my valve configuration would pose a problem as far as withstanding the pressures involved.  I may re-do it anyway though.
 
Chris

"Dan H." <JMachine@adelphia.net> wrote:
Chris,
 
First I have to say, I didn't design it but from what I see in the over all design, and knowing the designer, I think the valving was done this way for safety and simplicity.  All other valves except these vent valves are located within the hull.
 
Since each of these vent valves run from an external tank to outside the hull, each valve would have two through hulls for the piping.  Better three, quarter turn through hulls, then six pipe through hulls, more fittings and a still three valve stem seals inside the hull. 
 
The vents for the fore and aft soft MBT have to be mounted at the top of the tanks in order to release the air above the water.  Since the MBT's top is the same height as the top of the hull, the piping and valves had to be located at the height of the conning tower.  It would be cluttered to have these valves and their piping inside the conning tower.  On both K subs, the MBT vent valves are taken apart and altered with long stems that screw right on to a special threaded replacement for the packing nut that is welded in through the conning tower wall.  It makes a clean package and has double O-ring seals for added safety.  Even if the valves get sheared off, the stems have shoulders that prevent then from blowing through to the inside.
 
The less holes in the hull the better. 
----- Original Message -----
From: Chris Nugent
To: personal_submersibles@psubs.org
Sent: Wednesday, May 21, 2003 10:33 PM
Subject: Re: [PSUBS-MAILIST] Main ballast.

   Hey Dan,
 
     Just wondering, what is the reason for mounting the valves external to the hull on the K-350?  Is it because it's easier to put the actuating shafts in a thru-hull and run that through the hull to the valve, rather than mount the valves inside the hull with the air lines and air supply and run the air lines through the hull to the MBT's?  Or something else I missed?
 
              Thanks,
 
                     Chris Nugent

"Dan H." <JMachine@adelphia.net> wrote:
Pierre,

On the K-350 the "hard ballast tank" is located under the hull. There is a
shaft that runs through the hull with a flex coupling on it that is directly
above a quarter turn valve on the sea water opening of the hard ballast
tank. A quarter turn of this threw hull shaft turns the ball valve
directly.

The "soft ballast tanks" are of fiberglass and are located fore and aft.
They are opened to sea water all the time. The vent air is controlled with
quarter turn ball valves located on the conning tower. The valves are also
located external but are altered with special long stems so they are
controlled from inside the conning tower. The valves are connected to the
top of the tanks with tubing. The valves are mounted high in the tower and
vent from the tops of the tanks.

Hope this is what your looking for.
Dan H.
----- Original Messa! ! ge -----
From: "pierre&marie"
To:
Sent: Wednesday, May 21, 2003 6:31 PM
Subject: [PSUBS-MAILIST] Main ballast.


> Hi People!
>
> How do you "plug" the main ballast tank to adjust buyoncy (man, that word
is
> killing me...)
>
> I'm trying to figure a way to use a 5/3 pneumatic valve. It would be easy
to
> use to adjust bouyancy. But, I can't have the plumbing right at the
moment.
>
>
> Any advise? Somebody know how it's done in a K-350?
>
> Thanks!
>
> Pierre Poulin
> "At last the sun is here!"
>
>
>

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