This probably isn't the right site to ask about something this specific, but it is for an arduino controlled project.
Looking for tiny valves that can isolate 125psig hydrogen gas, Specifically I want to find something that can fit onto 1/8" or 1/4" NPT thread. I'd like them to be able to be remote actuated, similar to the sort of "Air-Operated Valve" (AOV) operation of valves in the chemical, oil and gas industries. Should ideally "fail-closed" in the event of power loss.
It's for a hobby-sized project, but needs to conform to reasonable standards of safety.
Obviously it's hard to find something like this, so I'm asking around.
For controlling hydrogen flow on a small vehicle maybe 16"Wx24"Lx10"H
Update: The following companies could not recommend any of their products currently:
Gems Sensors
Parker
Kip-Norgren
The consideration was usually that they don't have experience with Hydrogen gas, it's a small molecule that can permeate some materials.
ASCO suggested U8256A002V with a Buna-N or Viton seal. I'm not a valve expert but Buna-N and Viton are pretty common, and the aforementioned companies carry very similar valves. The valve can be purchased for $35-45.
Our distributor, who looked at many company's valves for us, gave a price for that Asco valve but was unwilling to recommend it, primarily because we haven't fully established our specification. The representative wanted to know what our media temperature was, and we only knew that the tank can get below freezing when the hydrogen is being used heavily (some frost forms on the tank, but not on the fittings downstream). Until I get back to school we won't be able to measure the gas temperature at the valve position.
I'm actually pretty sure that each of these companies make valves that would be appropriate for this use (DIY hobby-scale PEM fuel cell "vehicle" - R/C car like). However, trying to hold myself to the standard of safety present in industrial applications makes the selection difficult.
Out of interest, what "standard of safety" are you interested in :
a) reliability of closure
b) reliability of opening
c) tightness of closure
d) suitability for use in an explosive atmosphere (now that's a stumbling block)
e) prevention of leakage from valve body
Important aspect to consider are :
is the device to be used within enclosed spaces
is the device to be used in the presence of members of the public
are you adverse to taking risk
If any of the above 3 are "yes" then I'd suggest another project. Hydrogen gas and insurance litigation are mutually exclusive subjects
Making something "safe" is a long way from making something that works with minimal risk.
The proprietor, Trevor Langfield is quite a character. He's worked with controlling liquid / gaseous nitrous oxide and fuels for years. I know that he's made custom one offs for customers in the past specifically in terms of making solenoid valves with custom seat materials. Might be worth a shot.
Our car as-is is considered safe enough for the competition, and actually won a "Best Application of Safety Practices" award at an earlier competition. We just think hydrogen is dangerous (duh) and want to build on our no-compromises approach this year. We've already put a lot of work into making sure the car was safer than any other hydrogen-powered vehicle.
I'm building a hydrogen leak detection system with MQ-8 sensors from Hanwei Electronics. If hydrogen is detected, an arduino should cut power to a normally-closed solenoid.
The system's purpose is to impress judges (we're optimizing the engineering for a competition, after all), provide me and other students with experience designing and implementing control systems, and give me an excuse to write programs for the arduino.
We're also going to be designing/building our future cells from scratch, so a properly controlled isolation valve like this could be used to protect our investment.
Thus, the real safety considerations are: reliability of closure, tightness of closure, and compatibility with hydrogen gas.
If we could find one rated for at least "Class 1, Div 2, Group B" service, that would be great. If we could find one that's explosion-proof, that would be great. However, it has to fit in a small vehicle and be powered by a relatively low voltage DC source (maybe could go up to 24V, but would prefer <=12V DC). So far I haven't found anything at any price.
We're also going to be designing/building our future cells from scratch, so a properly controlled isolation valve like this could be used to protect our investment.
Thus, the real safety considerations are: reliability of closure, tightness of closure, and compatibility with hydrogen gas.
If we could find one rated for at least "Class 1, Div 2, Group B" service, that would be great. If we could find one that's explosion-proof, that would be great. However, it has to fit in a small vehicle and be powered by a relatively low voltage DC source (maybe could go up to 24V, but would prefer <=12V DC). So far I haven't found anything at any price.
I don't believe you have stated the flow capacity needed for the valve (Cv) but you might consider small (1/4" or even smaller) quarter turn ball valves actuated by a servo. Such ball values are avalible for nearly any service requirements and might give you a better selection choices then intergated solenoid valves.
Taking Lefty's idea a stage further, have the ball valve lever pulled closed by a strong spring. The lever itself could be held in the open position by a trigger/latch mechanism operated either by a small solenoid or an RC servo motor.
Nice to see you understand the techniques of Ex systems - at least you are not shooting in the dark.
Flow capacity should be minimum 0.5L/min, which is not hard to find.
I really like the idea of using a spring-loaded ball valve. Perhaps a linear action solenoid bolt could block the valve handle so that if it loses power, the pin/bolt is pulled back into the solenoid, releasing the handle. Might need a little lubrication so friction doesn't make the bolt stick. I like that.
Will look super hacky of course...but it would be the most effective for its real purpose.