Help In Identifying Necessary Valve Type - High Speed 2

[wallybygolly]

Folks,
First things first: I am not a valve guy, period. I do not profess to know anything about valves other than the ones in the kitchen and bathroom. I am a test pilot and flight test engineer, I know airplanes, and that I just got transplanted to a Systems Engineering role for a leading defense contractor. I realize that there are bunch of bright folks that work here, but none in pheumatics, and out there are more bright folks, hence I am pleading for help to make this project a success. Enough said there.

Problem: Build a 100 meter tube 4 inch I.D. to launch projectiles at speeds approaching 1100fps using compressed air (up to 150psi upstream and moderate vaccum downstream) as the source to help an 8 pound projectile along its merry way.

Stuff: I have the tube, I have the compressor to fill the air reservoirs, I have the air reservoirs (141 cu ft upstream and downstream)with 6 inch outlets, transitioning to a 4 inch feeder tube, breech tubing to load the projectile with end caps to keep the air in, scavenge tubing at the far end to collect the air in the tube in front of the projectile and I have the brake at the far end. What I don't have or have not identified is "the valve" to make this thing work. I have 5000 opinions but no solutions.

Requirement: I need help in identifying a high speed valve manufacturer and valve that will open in 5 - 30 milliseconds and is electroniclly/electrically/pneumatically operated or something else that anyone of you can offer. I know something exists but do not know the terminology necessary to ask for the object in question. If I have to specially build this valve I can do that also.

Thanks in advance to all that respond,

Wally by Golly
Chief Rocket Scientist
and Jack of All Trades

 

[JimCasey]

Wally,
It's hard to get a 4-inch valve to open that fast.
I would look at a rupture disc.
You would get essentially full opening in 5msec or faster. The disc pops like a balloon.
One vendor I have been pleased with in the past is Continental Disc, and they have a reverse-buckling (and possibly significant: Nonfragmenting) disc called the ULTRX. I think they even have a quick-change holder you can crank in so you can do repetitive tests every minute or so. Expensive, but not as expensive and a space-age super-doo valve.

 

[Compositepro]

1100 fps is about the speed of sound. You need to design the piping very carefully as well as the valve. I'm not even sure what to suggest.

 

[stanier]

Perhaps an explosive device such as used in modern car seat belts could be used to fire the device that opened the valve or to break the rupture disc.

In fact it would be easier to use a fuel such as LPG that was ignited with a spark plug to provide the energy to move such a mass.

I doubt if expanding air would provide the acceleration you have specified. If it did the military would have used it instead of cordite.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[wallybygolly]

JimCasey and Stanier,

Good input from the both of you, thanks. I went surfing a little more and found a quick sliding gate valve in the ~15-20 milliseconds manufactured by ATEX Explosion that could be modified to bang open at the same speeds. Stanier thoughts drove me down that path and the manufacturer informed of the other option. So hats off to the both of you!!!! Thanks Again!!!!!

 

[wallybygolly]

JimCasey,

We thought about using the rupture disks as you had presented. I called a company that made no fragmenting disks and they wanted $175 per disk...hmm. We shoout the present 3 inch tube about 20 times per day 5 days a week and have been doing so for the last 16 years. The expense seemed a tad bit huge. Thanks again for the input!

Wally

 

[JimCasey]

Wally,
Congrats on finding the gate valve.
I gave a little thought to that, but it becomes exponentially more difficult as you make the opening faster.
Remember that the moving parts are accelerating all the way thru opening. Likely the entire trim/actuation stack will crash into a stop at something like 50 miles per hour as it reaches fully open.
Keep a bag of spares handy.
I heard of a user who tried to quick-cycle a large butterfly valve with a rack and pinion actuator. He got it going fast but it turned out the valve needed travel stops as well as the travel stops in the actuator. He crashed the entire moving mass into the actuator travel stops and broke both racks in the actuator.

On the brighter side there is a company called Kaye and MacDonald (division of Cashco) who have modified their pressure reducing valves to be very snappy. THey sell them to the guys who make fountains that shoot cleanly cut slugs of water thru the air. The fountain at Epcot uses those valves.

 

[wallybygolly]

Jim,
Again, many thanks. I will go surf to the company website and keep the thread posted as to the progress. Nothing better than shooting the world's largest potato gun or punkin chunkin device so to speak.
Wally