Ask questions regarding pneumatic valves
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As shown in the diagram, the position of the air supply fault shut-off valve is set to the FL fault hold position. Is there any connection between this and the solenoid valve shutting off when power is lost? I’m not quite sure about the relationship between the two; is it necessary for them to be in sync? I hope someone experienced can explain this clearly. Thank you
It depends on how your air circuit is designed. If the solenoid valve opens when there is no power supply, then it will allow the air circuit to stay open; in other words, there is no loss of air pressure even when there is no power supply.
The solenoid valve closes when power is lost, which indicates that the air path remains open even without power supply; the air source or the spring of the actuator can then close the cylinder. For maintaining the valve position in case of a gas supply failure, this can be achieved by adding a holding valve; both of these requirements can be met, depending on whether they are necessary according to the process design specifications.
The specifications are not very clear. You need to understand that the status of the two solenoids corresponds to the position of the main valve: A is powered on, and at the same time B is also powered on; A is powered on, while B is powered off; A is powered off, and at the same time B is powered on; A is powered off, and B is also powered off. As for FL, it can be achieved through a pneumatic lock, and it has nothing to do with the solenoids.
The above requirements can be met through the gas circuit along with a pressure holding valve, but it should be quite complex. There are two solenoid valves; according to the diagram, one solenoid valve controls the opening while the other controls the closing. It is also mentioned that there is long-term excitation (closing in the event of power loss), but it’s not clear which one will close in such a situation Generally, for such FL valves, two solenoids are used—one to control opening and the other to control closing—they operate the cylinder that controls the valve by pushing it back and forth; the cylinder does not have a spring. I’m not sure what the specific requirements are for the joining process of this valve?
FL safety valve: a solenoid valve enables fault retention; simultaneously, when the solenoid valve loses power, the valve closes. So, personally, I think there is a problem with this specification sheet