Installation sequence of solenoid valve and positioner
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For a control valve with interlock, should the solenoid valve be installed in front of the positioner or behind it?
This post was last edited by budaoweng123 on 2017-4-25 at 16:57. The solenoid valve must be placed after the positioner.
The solenoid valve must be placed after the control valve??? Typo?
The solenoid valve must be placed behind the positioner
Why? Could you explain it?
The solenoid valve should be installed in the pneumatic pipeline that carries the output signal from the valve positioner to the diaphragm of the control valve.
After being placed in the positioner, under normal conditions the solenoid valve opens to send a signal to the diaphragm of the control valve, allowing the control valve to operate properly. During interlocking, the solenoid valve shuts off the signal from the positioner to the diaphragm actuator, draining the control air supply for the diaphragm actuator, thereby enabling the valve to go into FO or FC mode in emergency situations
The last edit to this post was made by rujimmy on 2017-4-26 at 09:35. In systems equipped with solenoid valves, the sequence is filter pressure regulator > positioner > solenoid valve, which serves to ensure the valve operates smoothly and in a timely manner
Why is everything here in front of the locator? Could you explain why?
In my personal opinion, it doesn’t matter whether it’s at the front or the back; as long as its normal sequential operation can be achieved, that’s sufficient. Generally, it is placed after the positioner, because this allows for rapid opening and closing of the valve. If it’s placed before the positioner, the gas flow and the parameters set for the positioner will result in slower opening and closing actions. There are also exhaust-type positioners, which are constantly releasing air; if such a positioner is placed before the valve, there will be no gas supply available after the sequential operation starts, which can have some impact on the positioner over time, but not significantly
Agree with what was said above; the main consideration is exhaust efficiency, and solenoid valves are clearly superior to positioners