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E-Zine October 2015Years ago, when you wanted a pump station control panel, you bought a pump station controller. You can still do that, but many engineers are now designing their own, using a PLC and assorted sensors and other inputs, instead of buying one preconfigured and pre-programmed. This “do-it-yourself” method of pump station control can have both its good features and its flaws. On the positive side of the balance, you have exactly the type of control you need and want, and you aren’t forced to buy something that almost fits, and work to make the pump station fit the control system you bought. On the negative side, though, there are the number of things you have to remember to include in the PLC programming. Al Pawlowski and Paul Dackermann answered a question about how to do water pump control with a PLC on the control.com automation list. They made some very good points, some of which are captured here. In the “bad old days,” the pump station controller you bought was analog, but it was “smart.” By that I mean it knew what it was supposed to do, and it came all ready to do its job. You bought a controller that would control “n” pumps, and you installed it, wired it and it ran. The controller knew, for example, to wait several seconds and/or for a signal from a current meter, before signaling pump failure. It knew how to sequence pumps on, and how to put one in standby. There are a number of design considerations for you to keep in mind when writing the pump sequencer for your PLC.
Click here to read “Pump Control with a PLC (Part 2)” From Flow Control (April 2002) ISSN 1538-5280 |
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