[PSUBS-MAILIST] Speaking of MBT valve

hank pronk hanker_20032000 at yahoo.ca
Sat Nov 23 19:47:24 EST 2013 

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 _______________________________________________ Personal_Submersibles mailing list Personal_Submersibles at psubs.org http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles _______________________________________________ Personal_Submersibles mailing list Personal_Submersibles at psubs.org http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles _______________________________________________ Personal_Submersibles mailing list Personal_Submersibles at psubs.org http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles -----Inline Attachment Follows----- _______________________________________________ Personal_Submersibles mailing list Personal_Submersibles at psubs.org http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles 
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