Tracking down gas leaks

Posted Tue, 04/12/2011 - 21:04 by Ed

Guys....I'm stumped.   Replaced all the hose, added the hose "rivets" on the barbs over top the hose and still a 12 oz tank of CO2 is gone in a matter of 15 minutes and fired the cannons no more than 10 times per barrel.  I can't hear any fitting hissing!   The tank is cold as a result of the rapid gas loss.

Anyone have suggestions on where some gas germlins could be hiding?   I'm thinking about using a small air compressor with colored smoke to track down the leak(s). 

 

Ed

 

 

 

 

 

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Charles's picture

Re: Tracking down gas leaks

by Charles - 04/12/2011 - 21:09

Submersion. Put the whole assembly under water, under pressure, then follow the bubbles. They'll be there.

Brian's picture

Re: Tracking down gas leaks

by Brian - 04/13/2011 - 21:35

Submersion might be difficult for a ship this size... you might also try mixing up some soapy water and dab it on each of the joints. Slow leaks will often make bubbles.

However, there is one place you have not looked - inside the cannon. If the actuators are improperly adjusted they sometimes don't let the ball valve close all of the way. You might want to try loosening the MPA-7's a couple of turns on each cannon. They look like this:

 

If the 15/32-32 mount to the cannon (opening to right of above image) is screwed on to the point where the piston inside the actuator presses on the firing pin then gas will bleed from the accumulator into the cannon. I am not familiar with BDE terminator cannons. However, if they use MPA-7's then the MPA-7 probably presses on a brass plunger that opens the value. The following pictures shows one of Nassau's cannons with the MPA-7 installed and then removed


If your cannons use MPA-7's I recommend trying the following steps:

  • depressurize the boat and remove the bottle
  • carefully removing the MPA-7's from the cannons (careful they are easy to strip)
  • lubricating the little brass plunger for each cannon and make certain it moves freely. If the springs have rusted then can also contribute to the cannon not closing properly
  • pressurize the system (with the MPA-7's still removed)

If the gas leak disappears then either one of the plungers was sticking or one of the MPA-7's is not letting it close all the way.

 

Brian's picture

Re: Tracking down gas leaks

by Brian - 04/13/2011 - 21:40

The other great thing about internal leaks - is you can take the cannons out and submerge them individually. If bubbles seem to be coming from the body of the cannon then the ball valve is not closing properly.