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Re: [PSUBS-MAILIST] MBT Vents
Hi Frank,
Yes, the K-boats have a separate line to release and add air to the
MBT's. Releasing air is through tubing from the top of the MBT on the
exterior, which runs horizontally on top of the hull and then bends
upward 90 degrees following the conning tower until it reaches the
release valve. Adding air is through tubing on the interior of the sub
which can be run anywhere convenient, and ends exiting into the MBT up
near the top of the tank head.
Check out the photos of Harold Maynards K-350 under the 2003 Convention
photos.
1) This photo shows the tubing that releases the air from the MBT. You
can see that it just comes off the highest top point of the MBT and runs
across the top of the hull, then bends up to join the valve. This is a
good shot of the valve on Harolds vessel as well. If you look inside
the conning tower, that valve on the extreme left, with handle pointing
left, is the inside of the same type valve that controls the aft MBT.
http://www.psubs.org/convention/2003/pics.cgi?pics/k350-3/PDR_0097.JPG
2) Another photo showing the MBT air release valves from the inside.
The left valve is aft MBT, the right valve is fore MBT. The valve
between the AFT MBT valve and the viewport is the "fresh air" access
valve which can be used when surfaced in conditions requiring the hatch
to be closed. Hook up a hose to it and you have an unlimited supply of
atmosphere air.
http://www.psubs.org/convention/2003/pics.cgi?pics/k350-1/PDR_0009.JPG
3) This photo shows the HP air supply tubing to the aft MBT. Its the
top-most penetrator on the tank head with copper tubing coming out of it.
http://www.psubs.org/convention/2003/pics.cgi?pics/k350-1/PDR_0022.JPG
4) This is a good view (albeit slightly out of focus) of the
air-release, and air-supply for the FORE MBT. The top-most hex adaptor
penetrating the fiberglass MBT is where the air escapes into the tubing
that leads to the valve in the conning tower. The tee fitting just
below it, but the top-most fitting attached to the tank head, is where
the HP air is added to the MBT from the piping within the interior of
the sub.
http://www.psubs.org/convention/2003/pics.cgi?pics/k350-4/PDR_0108.JPG
I believe Kittredge took the outside-hull approach to dispense as much
of the air in the MBT as possible. By tapping off through the tank head
you likely end up with a bit of a "bubble" left over inside the MBT just
because of the angles in involved, as can be seen by the last photo. I
can't say whether that bubble would be much of a nuisance or not. The
one criticism I have of George's design is that when the sub is in the
water with minimal freeboard, stepping on the MBT tubing is inevitable.
George used SS tubing on his K600, but you can see that Harold used soft
copper tubing. A big-boy like me can easily put enough weight on the
soft tubing to crush, dent, deform it. I suppose the upside is that
with flare fittings it is easy to replace. That problem could also be
subdued by covering the tubing with a protective cover of some kind, or
taking the approach that Don Palmer did and running the piping to the
side of the vessel.
The way you designed you piping sounds good to me Frank. You've built a
lot of redundancy into it which is a good approach that I am going to
follow.
Jon
ShellyDalg@aol.com wrote:
If the valve is on the outside with only the handle penetrating the
hull, how do you get the air into the ballast tank ? Is there a
separate thru-hull for the HP air line to blow ballast ? On the
maintenance as it relates to "exposure to problems" it seems with the
valve on the outside there is more chance for a problem with the
valve. Although the pressure inside versus outside of the valve is
less, the corrosion potential is greater as the valve is exposed to
water from the outside. Then there's the remote possibility that the
exterior valve could be impacted by something. Also, if only the
handle penetrates and there's a problem with the valve closing or
opening, you can't get at the valve while submerged to fix it.
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