There has been some discussion with my group on using check valves (MCV-1) as noted in the Jeff Burns article ""Safe, Effective CO2 Delivery" on the NTXBG knowledge base ntxbg.org/tikiwiki/tiki-featured_link.php --article 15. Does the MAR-1 act as a check valve on the low pressure side of the system when switching the SMTV-3 to "Safe"? One school of thought says that the safeing of the system on the high pressure side will also vent the accumulators as when the pressure on the "IN" side of the MAR-1 drops below the "OUT" side, any air in the cannon accumulator will purge ou the exhause side on the SMTV-3. The other school of thought says "well the article states pretty clearly that it is an intergral part of running a safe CO2 system." Could any biggunners perhaps explain better?
If you have a MAR-1 and a pressure gauge, you should be able to test the idea pretty easily. If you still see pressure in the accumulator after flipping the safety toggle, you've got a problem.
None of the MAR-1 valves I have used acted as check valves. I have no idea why the NTXBG website says they act like one. But if they say so, then there may be some variants that do act like one, so you'd better test yours and find out. If they do act like check valves, then you need additional plumbing in order to safely use them. Whenever you safe your air system, the entire system must be drained. It's dangerous to have one part of the system that doesn't vent: imagine trying to disassemble your cannons thinking they're safe when there's really 120PSI of air in them.
When the system is safed, low pressure gas from the accumulator should go "backwards" through the MAR-1 to the exhaust unless there is some function of the part that prevents that from happening Unfortunately, i do not have a pressure guage. I guess the meat of the question is the necessity of the check valves (MCV-1) at all. One of the ACTIVE big gun groups has documentation on their website that says EVERY SINGLE indiana cannon must have an MCV-1 on a the low pressure side of each MAR-1 with a flow direction to the High pressure loop to safely vent the accumulator when the system is safed. However, one of the INACTIVE clubs BANNED the MCV-1 from boats on the water because it was unsafe (probably because it was directly between the MAR-1 and accumulator, if i were to guess)
I have only seen the MCV-1 used on a stern gun, to prevent bleed-down of the rear accumulator every time the forward cannons were fired. The ship had a seperate MTV for venting the rear accumulator postioned beside the main MTV.
