Re: [PSUBS-MAILIST] MBT Vents

["Jens Laland" <laland@artematrix.org>]

Guys

I think it would be far more educational for us all if discussions like
this were backed up by P&ID drawings (read: 'quick sketches') or Process
Flow Diagrams (still read: 'quick sketches').

The thing is: It can sometimes become quite an intellectual challenge
trying to visualize (read: 'understand') all these piping systems when
they are presented in writing only.

Best regards,
Jens Laland

**
** In a message dated 3/4/2010 7:45:11 A.M. Pacific Standard Time,
** jonw@psubs.org writes:
**
** you end
** up with two penetrations instead of one.  You also end up with more
** exposure to problems with valve failure (possibly) since the entire
** valve is inside, whereas with the valve on the outside you only have to
** worry about stem failure.
**
**
** Hi Jon. Now you got me thinking......not a good idea this early in the
** morning.
** 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.
** For instance......let's say you're down 100 feet and the valve gets banged
** or just plain fails. If it's open and you can't close it, you can't fill
** that  ballast tank with air. Your only option to surface would be to drop
** your
**  emergency weight, and when you reach the surface you wouldn't be able to
** blow  the other ballast tank or the sub would likely tilt and be unstable.
** On the other hand, with the valve(s) on the inside, you can pump the air
** into the pipe leading to the ballast tank, so no separate HP thru-hull for
** air is required, and if either valve malfunctions you can get a wrench on
** it
** from inside the sub. Again, you're down 100 feet, and one of the valves
** screws  up. By closing either valve the vent pipe to the outside is
** blocked.
** Shoot  air into the pipe and the ballast tank fills with air.
** I made my sub like that. A 1" nipple enters the sub from the ballast tank
** and has a "T" on the nipple. The branch has a small valve and air line
** attached.  The main line has the 1" ball valve and goes up the wall inside
** the
** sub where it  connects to another ball valve and penetrating nipple to the
** outside. This is  all "hard piped" except for a short HP hose with
** compression
** fittings used as a  "union" so the parts can be threaded. If any component
** fails along this line, I  can isolate the pipe from the outside pressure,
** dis-assemble it, make the  repair, and I'm back in business. The HP air
** line
** has a valve at the "T" and  another at the HP Air manifold. Both valves
** are
** normally closed until I need to  blow ballast. If I need to, I can take it
** apart while submerged, and even  re-configure the set-up like if one of
** the
** thru-hull nipples gets  banged/crushed. Re-pipe the vent to the other vent
** nipple, change where the air  goes in, or any number of routes to get rid
** of the
** water in the ballast  tank.
** It sounds a little more complicated but really isn't. Two thru-hulls per
** ballast tank, both are 1", with a valve on every connection.The "spares"
** box
** will have a variety of extra valves, short nipples, HP hoses and  other
** replacement parts, etc.
** I know Jay said we won't be doing repairs while submerged, but hey, maybe
** we'll need to.
** The same thoughts are incorporated in my electrical system. Four separate
** 36 volt circuits for the motors, each with it's own battery bank, fuses,
** switches, thru-hull, controllers, etc. If one system fails for some
** reason,  I
** can shut it down and re-wire what's still good to another circuit. ( The
** 12
**  volt lights/controls circuit is another separate circuit, with a back-up
** battery. )
**  Switching from one battery bank to another will most likely mean  moving
** some battery leads because I don't have any switches connecting one bank
** to
** another. They are TOTALLY separate. Again, a little more complicated, but
** the  ability to isolate a potential problem is the goal here.
** Frank D.
**
**


-- 
In asserting which technologies are likely to be of crucial importance we
must also take due note of some spectacular errors that have been made in
the past:

"There is no likelihood that man can ever tap the power of the atom",
Robert Millikan, Nobel Laureate, 1923

"Heavier than air flying machines are impossible", Lord Kelvin, President
of the Royal Society, 1885





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