Take into account that 2-posture, solitary solenoid valves have a spring return. So by having an energized valve, In the event the double-performing cylinder it’s linked to is extending, that cylinder will retract if electrical energy is shed (for example when an emergency prevent is pressed) but air stays on. https://expertsolarenergysystemde63062.oblogation.com/26950028/little-known-facts-about-types-of-pneumatic-valve