I'm looking for a 3 way SST diaphragm solenoid valve. I want it to be direct acting with a 24 VDC coil. I'd also like it to have positive position feedback that a PLC could interpret. I want to use this valve to shut off the upstream hydrogen fuel supply and vent the downstream pressure caused by the supply of resident hydrogen gas.
Hydrogen embrittles stainless, I believe. Diaphragms use supply pressure and "controlled leaks" to operate the valve. Diaphragm valves fail in horrible ways, ways that you would not want to occur in a fuel cell system, for example.
Direct acting *diaphragm* solenoid valves do not exist. You might get a motorized cam to close a diaphragm with still a very high Cv.
Motorized ball valve, 2-way, and let the engine bleed off and oxidize the last of the fuel, rather than sending that shot to space. If you have to, use a 3 way and vent it to a catalytic converter. Ball valves have stems that are easy to monitor for position. Do not get one with all ports in a plane perpendicular to the actuation axis. Get one with the common port in line with the axis of acutation. That way you have a hope of sealing the hydrogen gas.