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CLICK PLC - Alarm Bypass?

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  • CLICK PLC - Alarm Bypass?

    Hey everyone,

    So I am working on a project for monitoring tanks. There are 4 tanks, each hooked to a manual switch valve with product being supplied by a single pump. My click PLC is monitoring the tank levels and comparing them to a high set point and a low set point. What it currently does is if the level of any tank gets too high, it closes contacts Y1 and Y2, Y1 is the kill for the pump, and Y2 is an alarm. This prevents the tank from getting overfull. The problem is, now the pump isn't running, and the tank 1 is full. I need to change tanks, and start the pump again. I need to create a tank alarm bypass in my ladder logic so despite tank 1 now being full, i can start the pump again and fill tank 2. When tank 2 is full, i need to shut the pump off again. It almost seems like i need a shift register, but i am not sure how to implement that, as the tanks that will be full/filling will be completely random.

    Suggestions? Basically, all its doing is stopping the pump when ANY of the tanks get too full, then will proceed to pump into a new tank afterwards. This just prevents the operator from overflowing tanks. The pump doesn't know what tank is full, its just monitoring all 4 tanks.

  • #2
    One thing i might note, is the tanks may stay full two or three rounds into the filling scheme... such as tank one was full while filling tanks 2 and 3. So the bypass needs to check to see what all tanks are already full and take that into consiteration as well.


    • #3
      It sounds like you have shoehorned a PLC into the middle of a hardwired control scheme. It would be best if the PLC was in control of the valves and pumps. At the very least there needs to be a method to make the PLC aware of the valve positions so that it "knows" whether it is okay to allow the pump to run. I might be misunderstanding your description.

      What are your level sensors (analog? discrete floats?)
      Are all four sensors wired individually to the PLC?


      • #4
        You have to know where the product is going and a corresponding high limit for each tank. Bypass IMO, should only be used in a situation where you are physically there to know the tank is low and the sensor has malfunctioned. Bypasses we’ve used put the entire responsibility on the operator that authorized it.


        • #5
          Click image for larger version

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          A C-more micro could add considerably to this project, like your Bypass if you feel it is needed and/or replace all the pilot lights at considerable cost savings.


          • #6
            If you know the operator will never try to fill a full tank.

            Click image for larger version

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