I am an instrument technician at a chemical plant, and I would like to ask everyone for help regarding a problem with the Zhejiang Zhongkong control system.

Time relay: turns on for a seconds, then turns off for b seconds. The second valve is open for b seconds and closed for a seconds. Control in sequence one after another

For a control system, this requirement is not difficult.

Your program is somewhat similar to pulse valve control

A time relay is used to set the switching time for the first valve, thereby controlling that valve; by inverting this output signal, the second valve can be controlled

Two time relays and two relays that can achieve self-locking and interlocking – this is simple hardware control.

How to implement two valves: the first one opens for a seconds and then closes after that time; once the first valve closes, the second valve opens for b seconds, and after the second valve closes, the first valve starts opening again for a seconds, and this cycle repeats continuously. Set valve XV1, solenoid valve XSOV-1, closed position feedback XSC-1, open position feedback XSO-1 ； Set valve XV2, solenoid valve XSOV-2, closed position feedback XSC-2, open position feedback XSO-2 ； START → XSC-2 is in the closed position (condition) → XSOV-1 is powered on and the valve opens (action) → The XSO-1 valve remains fully open for a duration of t (condition) → XSOV-1 loses power and the valve closes (action) → XSC-1 is fully closed (condition) → XSOV-2 is powered on and the valve opens (action) → The XSO-2 valve remains fully open for a duration of t (condition) → XSOV-2 loses power and the valve closes (action) → XSC-2 is in the closed position (condition)………………

Set up a delay switch; you can learn more about function blocks. First, draw the logical sequence diagram, and then create the functional blocks