Dual Solenoid Valve for Reliability?

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Be ready to explain in clearer terms than these.

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Good Luck, Old Salt

Hi, I'm not sure if this will help.

In my experience a 3/2 solenoid takes a single pneumatic input, and has 2 pneumatic outputs. It takes a single digital on/off signal.

When the solenoid is signaled to open it will direct air supply to one of the outputs (which can be used to move a single acting actuator on a valve). When the solenoid signal is removed, the solenoid internal spring forces the input closed, and the previously pressurised output is vented through the second output.

When pressure is removed from single acting actuator, the actuator spring pack moves the valve to its fail position. In case of either power failure or air failure, a single acting actuator will cause valve to fail to the set position based on spring pack within the actuator.

If you have double acting actuator (i.e. requires air to open & air to close), then you either need 2 x 3/2 solenoids or 1 x 5/2 solenoid.

A 5/2 solenoid will direct a single pneumatic input to one of two pneumatic outputs (one is directed to each side of the actuator, so when the solenoid is switched using a single digital signal, it will either open or close depending on how it is configured).

A double acting actuator (on electrical fault) will fail to the spring position in the solenoid. But on air failure will fail to last position.

Hope this helps.

Anthony

All the more reason for the OP to seek professional help instead of asking strangers on an anonymous forum for help to do his job.

<...There are two outputs from the same logic carrying same valve driving each of the solenoid valve....>

Therein lies the rub. Are those outputs logical OR with a spring return, logical AND with a spring return, or air-each-way? Valve suppliers' sales offices need to know...