Plc Installation

I WORK FOR A SUGAR FACTORY THAT IS CRUSHING 120 TONS OF CANE PER HOUR
AND I HAVE A CONTROLLER (MATRA) THAT CONTROLLED THE THE MAIN CANE
CARRIER AND INTER CARRIER.
I WOULD LIKE TO INSTALL A PLC (TSX PREMIUM) IN PARALLEL
WITH THAT CONTROLLER,HOW DO I PROCEED WITH THE INSTALLATION.
THANKS.
ALBERTO

Well, I would start with a P&ID of your plant as it is now.
I would then make a second one showing what you want it to be like when you finished.
I would then get your production and maintenance people to check these to make sure this is what you want.

I would also make sure you know what is controlling which part of the plant.

I would also spend a bit of time writing out in detail what you want to do, why you want to do it, and what benifits you will get out of it.

Once you know this, you may find that the question you asked is easier to answer.

I'm assuming you want to get status into a PLC for connecting to a SCADA or HMI system, and leave the actual controls in place. When following the steps Doug outlined, you need to define which status signals are important to you. In general you can wire your PLC in parallel with the other controller's inputs without interfering with its operation. Watch your voltage levels, and make sure your PLC I/O common (- or neutral) is tied to the common for the existing controller.

For voltage analog signals you can also go in parallel without problems. For 4-20 mA analog inputs you can run the signal in series, but you should consider adding a signal isolator on each loop to avoid ground loops and excess load on the transmtters. I suggest using externally powered isolators, since the loop powered type usually create a higher load in the loop.

If you plan to put the PLC outputs in parallel and do actual control, the challenge gets much more significant. You will need switches or relays to determine which device is in charge, develop strategies for changing from one controller to the other, and get intimately familiar with the operation of the machine so you will provide equal or better control.

Interesting link on how sugar is processed: http://www.scgc.org/xsteps.html

I'm an ex-sugar man.....however it was beet sugar. Most people think sugar comes from "cane" in Hawaii....the truth is most of the world's sugar is beet sugar, from sugarbeets. Largely in Minnesota.

Greg