Valve data sheet
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On the valve’s data sheet, the position in case of air supply failure is indicated as: Air Hold/Electric Off. What does this mean? Should the valve that prevents air leakage in case of power loss be closed or open?
Air retention = Loss of air maintains position: Instrument air is the ultimate power source; regardless of whether the solenoid valve (or actuator) is powered or not, the valve maintains its position in the case of a loss of air pressure. No air loss during power outage: Since there is no loss of air, follow the requirements for a power outage – close the valve.
Loss of air pressure is not necessarily the case; it depends on the configuration of the valve cylinder – whether it operates on air pressure to close, or on air pressure to open, or whether it uses a spring for position retention. In the case of double-acting cylinders, there are no springs and both sides are driven by air pressure.
If the data table requires a shut-off function in the event of air loss, no matter what type of actuator is used or what configuration is adopted, it is necessary to ensure this \"shut-off function\" is available, right? 1. There are springs; when the air is lost, the springs push the valve to a safe position. 2. It has no springs; after the air is lost, it relies on the air reservoir and pneumatic components to push the valve to a safe position. 3. To maintain position, use a lock valve to seal off the inlet/outlet of the actuator. The above actions have nothing to do with electrical signals.