[PSUBS-MAILIST] Speaking of MBT valve

Sun Nov 24 13:26:31 EST 2013

That is also my understanding.

Rick

From: hank pronk 
Sent: Saturday, November 23, 2013 2:47 PM
To: Personal Submersibles General Discussion 
Subject: Re: [PSUBS-MAILIST] Speaking of MBT valve

Jon,
I think a first stage regulator is 140psi above ambient, if the regulator is in the water it will always be 140 over ambient.
Hank

On Saturday, November 23, 2013 5:31:23 PM, Jon Wallace <jonw at psubs.org> wrote:

A 600psi valve should be fine on the 350 as long as you keep any static pressure for the fill side a safety margin below, perhaps no higher than 350psi.  A first stage on your hp tank indicates a flowing pressure of 150psi or there abouts (the first stage standard).  The bigger issue you have to deal with using a typical first stage is that the air pressure is close to equalizing the pressure at 337 feet.  If you push the vessel to it's limit you could end up in a situation whereby you can't blow ballast because the outside pressure equals or is greater to that being put out by the first stage.  

On 11/23/2013 2:46 PM, Pete Niedermayr wrote:

I found these 3 way valves that have an off position. I want to go with the Vent/Off/Fill idea I mentions a few months back. I'll have a 1st stage reg on my HP tanks. the valves are rated 600 psi WOG is that high enough ? The K350 spec'ed one are 1000 psi. Any thoughts ?

On Sat, 11/23/13, Alec Smyth mailto:alecsmyth at gmail.com wrote:

 Subject: Re: [PSUBS-MAILIST] MBT valve
 To: "Personal Submersibles General Discussion" mailto:personal_submersibles at psubs.org
 Date: Saturday, November 23, 2013, 9:48 AM

 One more thing... I'm not
 sure how easy it would be to get a really accurate seal if
 you make the body from PVC. I always find plastics
 challenging when it comes to machining tolerances. For
 surfacing the sub a tiny valve leak is no problem, in fact
 you wouldn't even notice it. But a tiny leak is a
 nuisance, because the sub will have a tendency to dive
 herself in slow motion when you leave her at the dock for a
 few hours, when she's under tow, etc.  :)
 Alec   On Sat, Nov 23, 2013 at
 12:35 PM, hank pronk mailto:hanker_20032000 at yahoo.ca
 wrote:

 Jon,I have to agree with
 Alec.  I would not use an electric motor.  If it has to be
 electric, I would also go with solenoid valves.   I have
 personally used solenoid valves on my salvage rov  and in
 about a million dives we never had a single issue except for
 freezing when the rov surfaced in the winter.   Electric
 solenoids are also safe in your case because you have
 multiple mbt's and you should wire them separately.

 Hank 

     On Saturday, November 23, 2013 10:10:28 AM,
 Alec Smyth mailto:alecsmyth at gmail.com
 wrote:

     Hi
 Jon,
 Personally if I used a
 remotely operated valve I'd be much more comfortable
 with actuating it pneumatically than electrically, for
 reliability. This is after all the MBT valve, arguably the
 one thing on the sub that has to be the most reliable of
 all. If for some reason it just had to be electric, then
 I'd suggest using an electromagnet instead of a motor.
 The magnet would act against a spring so that the valve was
 of the normally closed type, and you could still surface if
 the electrons got wet.

 What I don't like about
 the K valves is the way George mounted them. But I'm a
 fan of the approach if you add a proper through-hull for the
 shaft, sealed with O rings instead of RTV like the original.
 If using a large bore valve, I'd add one more detail,
 which is to put round handles on them instead of straight
 ones. That's so that someone getting in or out of the
 sub won't dive it by snagging their clothes on the
 handles.  Best,
 Alec

 On Sat, Nov 23, 2013 at 11:51 AM, Jon
 Wallace mailto:jonw at psubs.org wrote:

 Looking for feedback on this MBT poppet design (see
 attachment).  It is very similar to the poppet Vance showed
 us in Islamorada but driven by an independent electric motor
 rather than pneumatic.  My goal is to move to an electric
 or pneumatic replacement for the Kittredge MBT ball valve
 thru-hull design for various reasons. First, I don't
 like the valve handles sticking in through the conning
 tower; second, I am adding saddle tanks for additional
 buoyancy which would mean adding at least one more valve;
 third, my saddle tanks are going to be big and I want a
 large diameter valve to provide quick venting.

 Illustration.

 The valve is made out of PVC plumbing material available at
 any good hardware store.  The square main body is a 4-inch
 PVC coupling.  A series of 1-inch holes drilled into the
 end allow venting when the "plunger" is retracted
 back to the motor side.  The "stop" on the closed
 side would have a gasket to provide an air-tight seal.

 The motor is a cheap electric screwdriver motor such as
 Black & Decker AS6NG.  It has plenty of torque,
 reversible, and is low power (2-3vdc).  When the body is
 removed the "guts" fit nicely into 1.5 inch PVC
 piping.  The rotating socket tip will be waterproofed using
 a home-made "Blue-Globe" type attachment.  Oil
 compensation will ensure the housing doesn't fracture at
 depth although theoretically 1.5 inch PVC is pressure safe
 to well beyond the depths I will be diving.

 The piston will be 1/4 inch thick (6mm) and can be aluminum
 or even 1/4 to 3/8 acrylic.  It is attached to the coupling
 nut by a 1/4-20 threaded rod.  The coupling nut is
 permanently attached to the rotating socket tip of the
 screwdriver by either epoxy or light welding.  As the motor
 and coupling nut turns, the threaded rod is drawn into the
 coupling nut pulling the piston toward the motor and
 allowing the MBT to vent.  Reverse the motor and the piston
 is forced back down to the closed position and seals the
 MBT.

 I have already prototyped the motor and it's PVC housing
 and they fit together very well.  Cost of battery operated
 screwdriver is about $10-20 (US).  PVC of course, is cheap.  I am looking at 4-inch material but this design could be
 easily scaled.

 I see lots of pros; looking for cons and potential issues
 with the design before I fully prototype it.  Any of you
 CAD'rs interested in creating a nice 3-D drawing for
 me?

 Jon

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