Well that works :D

I’m curious on what type of safety devices you guys use on these pneumatic launchers?

... When it's pressurized It'll shoot.

When it's not.... It wont.

So its okay to have a vessel pressurized above 14.9 psig without a safety device to protect against human error?

Mortars are only pressurized right before they're going to be shot.

and most of them are shot from a stationary position... so no one's going to be running around with a 5 foot piece of pressurized pipe.

Whether it is stationary or mobile, pressurized for a few seconds or hours, human error or system error can still occur. I have seen what pressure can do to piping with no form of blow off and it’s not pretty

That's why you use pressure rated pipe, fittings and connectors... Most of the mortars in Manitoba are using pipe that are rated to 120 PSI, and most of the mortars are shot at about a 60 PSI max.

What type of piping do you use?....is it rated for air, water, steam. Using the correct type of fitting and piping is great. But if you look at it, what wrong with putting on a safety blow off, just in case.

Like Amos said, our mortars our only ever charged before firing, and they always have a pressure gage on them.
Our launchers on the other hand are charged well before firing, they have pressure gages too but they also had safety valves rated to 100PSI.
The last safety measure on the rocket launchers is coincidental; we recommend 40PSI max since your shooting it towards people and not straight in the air. Well if it's shot above 60PSI the rubber on the valve gets destroyed lol

Furthermore, theres always leaks no matter how hard we try to stop them they always appear somewhere. Up to 60PSI its not noticeable. But try pumping a mortar with a tiny leak past 90PSI, it's a LOT of work for one guy to get past 90 PSI

How much volume are you putting in these tubes?

Well after some very basic quickly done math, the volume of the air tank is approx. 300 cubic inches of 60PSI air, being fed into a 2" barrel (125 cubic inch inside) via a HIGH flow valve. Although since the valve was custom built there's no telling how many gallons per minute it is, but it's a huge step forward from the 1" sprinkler valve we were using before lol
The second valve we use (the firing mechanism) was a 1" sprinkler valve, but we changed it to a 1" plastic ball valve for reliability, safe decompression of the mortar, and no longer having to depend on batteries or worrying about wiring faults or rain.

i was shopping for my young niece and found bags of 100 ball pit balls for $3 at the local superstore. i got her a couple bags for her playpen
i was thinking they could be launched from a pneumatic device and since they are very light air filled soft plastic balls they probably wouldnt hurt at all if hit
and they are extremely cheap bright coloured and easy to see

If you made a huge multi-tube launching system that could actually be really neat to simulate cluster munitions or multiple strikes. I'd back that. You won't get much range but this is Airsoft, you don't need range. Having your arty support closer to the front lines forces teamwork, as the combatives have to assist and protect the supporters.