2" Valves

[MikeVDS]

I want to be able to control a fire cannon remotely. Ideally I'd use a 2", 12 volt, 120psi control valve which opens fully in less than 1 second, and closes under loss of power. A solenoid valve seems ideal. McMaster-Carr has a 24 volt one for about $200. I was wondering if anyone knows where I can perhaps get something cheaper. Maybe something I can scrap a similar valve off of.

[mdmf007]

Mike -
many control valves on our firetrucks use an air solenoid to open and close a ball valve. We have to use nipples so they do not open and close too fast to prevent water hammering plumbing. without the control orifice they are incredibly fast as compressed air has a great reactive impulse.

You can adapt just about any handle to accept a control arm and solenoid.
plumbing is easy - air in, air out, and a vent.
air solenoids are cheap as low as 30 bucks for a 1" bore and 4 inch stroke.

hope this helps as an alternative.
later all

[MikeVDS]

I was hoping to run off of a car battery or other small 12VDC source. Do you use tanks of compressed air? That might be a good replacement for a battery. I use a lot of air control valves at work but it didn't occur to me to use a tank of compressed air until now. I was always thinking compressor -> 120VDC and noisy.

[mdmf007]

A storage tank for air would be necessary toprevent an air compressor from cycling on and off all the time. if it is going to be engine mounted, you can buy an air compressor for a tuck with pressure activated clutch from a junkyard for 50 bucks. it would be fan driven and would require a pressure sending unit to be inlin in the plumbing that would start and stop the compressor as the tank is drawn down.

a solenoid would not need much air to cycle. at 1" x 4" your around 3 inches cubed. at pressure thats around 15ci at 120 PSi (this is all of the cuff I dont have my calculator) so a 20 gallon tank (60 bucks at target) would cycle a valve a hundred times before it was empty.

A little electric compressor could probably keep up with it.
A scuba tank is typically charged to 3000 or more pounds, and you can get bottles into the 220 foot range of air at 3000# from a welding supplier - and a regulator to adjust it to whatever you want.

[MikeVDS]

Yeah, I'd probably get a 3000psi tank and the valves I work with should work just fine and operate between 5 and 15psi. Regulate down, and if you use 3ci of air for each actuation, you would drain 3/200ci from the tank (assuming it acts like an ideal gas). A 20 gallon tank has 4600 cubic inches. If we say we actually use 1/50 cu of 3000# air per actuation then it's about 200,000 actuations from that tank of compressed air. I don't think we'd need a compressor, I think we'll run out of propane.

[StevenGoodman]

For air at 3,000psi just use an 80cf aluminum scuba tank. Pretty cheap and easy to find used ones.

[MikeVDS]

Thanks for the tip