Fast opening valve
Fast opening valve
(OP)
Hello everybody
Does anyone know what kind of air valve fits the following requirements and where it can be obtained?
-It should usually be closed
-It should open within less than 10ms and stay open as long as it is activated
-It should withstand air pressures up to 500psi
-Its smallest inside diameter should not be smaller than 0.2 inches
-If possible, it should operate mechanically (no solenoids)
Any hints would be greatly appriciated. Thanks.
Does anyone know what kind of air valve fits the following requirements and where it can be obtained?
-It should usually be closed
-It should open within less than 10ms and stay open as long as it is activated
-It should withstand air pressures up to 500psi
-Its smallest inside diameter should not be smaller than 0.2 inches
-If possible, it should operate mechanically (no solenoids)
Any hints would be greatly appriciated. Thanks.





RE: Fast opening valve
www.caleffi.com
RE: Fast opening valve
Selection of the actuator permits failing the valve open or closed. Your description sounds like you want it to normally be closed and fail open upon loss of signal.
-It should open within less than 10ms and stay open as long as it is activated
This is very fast and most achievable on very small valves.
-It should withstand air pressures up to 500psi
The valve body and pressure containing components are easily obtained suitable for 500 psi. A pneumatic actuator signal would be unusual.
-Its smallest inside diameter should not be smaller than 0.2 inches
This is quite small and might be specified to prevent plugging. What is the capacity that must be released and over what time? You need to determine the body size. A quarter-inch ball valve from Whitey (Swagelok) is looking like your solution.
-If possible, it should operate mechanically (no solenoids)
I selected a pneumatic actuator based upon you mechanical description. Clarify if you mean a lever, or some other mechanism.
John
RE: Fast opening valve
Air is stored in a reservoir at a pressure of 500 psi. When the valve is activated, the air should be released immediately. The capacity that must be released is about 0.3 cubic inches over not more than 50ms. However, it should open as quickly as possible so that the pressure increase is instantaneous (well, almost).
The valve should be actuated manually, via a button, lever or something of that kind. It mustn't be electrical because there is no power supply.
I understand that the requirements might be difficult to fulfill and I have also considered making a custom valve but I first wanted to know if there are any designs around which fit my requirements. Thanks again.
RE: Fast opening valve
David
RE: Fast opening valve
RE: Fast opening valve
writes
Air is stored in a reservoir at a pressure of 500 psi. When the valve is activated, the air should be released immediately. The capacity that must be released is about 0.3 cubic inches over not more than 50ms. However, it should open as quickly as possible so that the pressure increase is instantaneous
What pressure is instantaneous? The reservoir? If so, what pressure does it rise from (initial conditions)
I believe you are indicating that this is a transient problem.
RE: Fast opening valve
Can you give the resevoir volume too? Because the pressure in the resevoir is dropping during the discharge process therefore the air flow rate is not constand during the discharge.
How accurate you want the 0.3 cubic inch to be?
Air will be discharge during the valve opening process (the 10msec) too i.e. from the command to open until it is fully opened and then during the closing process (10 msec?) too.
The valve orifice should be very precise and specific if the 0.3 cubic inch required to be accurate?
Can you use the pressure in the reservoir to activate the valve?
RE: Fast opening valve
The 0.3 cubic inch needn't be accurate, it is an approximate volume. The air inside the reservoir is at room temperature. Let's say the narrowest cross section inside the valve must be as big as possible in order to maximize flow rate, but not exceed 1/4" in diameter. The most important thing is that the time it takes from the command to the full opening is as short as possible.
>>Air will be discharge during the valve opening process (the 10msec) too i.e. from the command to open until it is fully opened and then during the closing process (10 msec?) too.
Yes, and that's precisely why I want the opening and closure time to be as short as possible.
RE: Fast opening valve
>>Can you use the pressure in the reservoir to activate the valve?
Preferably not because the reservoir is not very large (approx. 150 cubic inches) and air should not be wasted in the process.
>>Can you give the resevoir volume too? Because the pressure in the resevoir is dropping during the discharge process therefore the air flow rate is not constand during the discharge.
Since the flow is restricted by other things that come after the valve in question, flow rate is not important, hence pressure drop is not a problem.
I hope that helps.
RE: Fast opening valve
Is there piping downsteam of the quick opening valve?
RE: Fast opening valve
The only important things are those that I mentioned in the original post:
The valve should stay closed unless the button is pushed so that air is stored in the reservoir. When the valve is actuated, air should flow out of the reservoir. The flow rate should reach its maximum as quickly as possible, hence the valve needs to open very fast. It should close as soon as the button is no longer being pushed. It should withstand pressures up to 500 psi because the air inside the reservoir is at that pressure and there mustn't be any leakage. It's narrowest spot shouldn't be smaller than 0.2 inches in diameter.
RE: Fast opening valve
Do I understand that you want this "valve" to be no smaller then .2 inches diameter,
"It's narrowest spot shouldn't be smaller than 0.2 inches in diameter"
and no larger then .25 inches diameter?
"The 0.3 cubic inch needn't be accurate, it is an approximate volume. The air inside the reservoir is at room temperature. Let's say the narrowest cross section inside the valve must be as big as possible in order to maximize flow rate, but not exceed 1/4" in diameter. "
Is that external or internal?
Can you make a valve to look something like a gun (revolver) with the rotating chambers sized for the .3 cubic inches? You can recharge one chamber when discharging another.
RE: Fast opening valve
Well, I've got a number wrong, it should be 3 cubic inches instead of .3. But still, the idea with the rotating chamber can not be done because the reservoir has a volume which is given, as I've stated in another post (150 cubic inches).
>>Is that external or internal?
The dimension requirements for the valve are internal. I'll put this in other words: The smallest cross sectional area of the tube within the valve should not be smaller than say 0.035 square inches (this corresponds to 0.2 diameter). However, it shouldn't exceed 0.25" in diameter because the reservoir outlet is 0.25" inside diameter, so flow rate is already optimal when the valve has that diameter as well.
I'm looking for the type of valve that can do the job. What kind of walve is usually used when fast opening and closure are required?
RE: Fast opening valve
I've persuaded size 23 stepping motors to move itty bitty plug valves (1/16" aperture) by 1/4 turn in 50 ms. The motion looked instantaneous, but of course it really wasn't.
You need a basic valve mechanism that 'produces' a relatively large open area in a small amount of time, which would ordinarily imply a poppet valve. But you also need a substantial stroke to meet your minimum particle size spec, so the moving parts have to be relatively massive.
That, in turn, means that you have to apply a substantial force to the moving parts to accelerate them rapidly, and that implies exhausting some of that 500psi air in a pilot- operated valve, or using some other stored energy source. Simplest thing that comes to mind is a poppet valve that's opened by a sturdy button that the operator depresses ... with a hammer.
You might take a look at the valves that are used in paintball guns.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Fast opening valve
I now thought about a design which consists of a hammer and a poppet with a reset spring. All this is contained in an angled 2/2 way valve body. The hammer is cocked beforehand and is held in this position by a pin. As soon as the pin is moved out of the way, the hammer strikes the rear of the poppet shaft. The poppet is accelerated and it opens towards the outlet. It is then set back by the spring. The opening time could be regulated by some screw which precompresses the spring, or simply by choosing a different spring.
My question is: Since the poppet is only held in the closed position by the spring, the pressure from the inlet will open it on its own, right? How can you prevent this from happening? Since the inlet static pressure is very high, it will amount to a large force. The spring mustn't be too stiff, though because this requires a bigger hammer. On the other hand, you could reduce the area on which the pressure acts by making the outlet smaller and decreasing flow rate. How is this problem usually solved?
RE: Fast opening valve
See 'force balanced' valves. See also trigger mechanisms for guns.
I was actually thinking of a poppet valve installed the other way, so the spring and the supply pressure both act to hold it closed, and the impact of the hammer forces it open.
;---
I think the first trick in camera shutters is that it's not necessarily the same element that occludes the light path at the beginning and end of the exposure. The second trick is that you don't need a big opening to pass a lot of photons.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Fast opening valve
1. The time to reach 63% of the final pressure (315psi) is 18 msec.
2. The time to reach 90% of the final pressure (450psi) is 28 msec.
2. The time to reach 100% of the final pressure (500psi) is 38 msec.
The calculations are based on an inlet orifice of 1/4" diameter with an orifice constant of 0.9. For orifice constant of 0.8 it will be 21 msec, 32 msec and 43 msec respectively.
I suspect that you may need even a faster valve than the 10 msec.
RE: Fast opening valve
Consider, though, an IC engine, with high spring rates on the exhaust valve return spring. Your 20 ms corresponds with the cam-and-spring arrangement operating at 3000 cycles per minute, which for a 4-stroke engine at 240 degrees or so of cam duration, seems to be 9000 RPM. Current motorcycle engines consider that mid-range....and 3 cubic inches is about 50 cc, and they would pass considerably more than that, and instantaneous pressures are at least of the same magnitude. Of course, the mechanism never starts from dead-stopped and is not dominant in the rotational acceleration equation...
COURSE, thats a 30 mm Diameter poppet, at about 5 mm of stroke.
If all that sounds like it could suit your need: the body still looks a lot like a high pressure SRV, but the mechanism to "fire" it still has some fun left in it...Something like a high torque spiral wound spring and a quick release sprag or brake might get there, but its a single shot weapon...And if thats what you need, so's a 12-ga.
RE: Fast opening valve
www.rupturepin.com