need help problem with Allen-Bradley PLC5/40 & Flex IO

[amilasri]

Currently we have 2 nos hevy fuel oil engine driven generators with a capacity of 2MW each to be used along with Steam Turbine Generators for the electricity requirement of the Refinery. The maker of the Engine/Generator is Ssanyong-Korea and the control and protection system of the generators are implemented with Allen-Bradley PLC5/40 controller with Flex IO. A diagram which shows the PLC configuration is attached herewith for your reference.
[FONT=&quot] Sometime back we have experienced that some of the analog inputs and thermocouple inputs get freeze without any fault indications. When we recycle the power the system becomes normal. Earlier this was rarely happened may be only once or twice in 6 month’s period, but recently we observed that it gets more and more frequent. In addition recently we encountered another problem, i.e some of the digital outputs which have been turned on depending on the present conditions get turned on and off repeatedly. Last time we observed this on the remote flex IO rack no 6 (refer attachment) and in the same time we observed that the local fault indication on the remote adapter of the flex IO rack no 5 was blinking. We managed to get this rectify by power recycling of the whole system but after sometime the same scenario starts again. Can anyone help me us in this regard since this it is very essential for us to have a stable power generation system for the smooth operation of the Refinery. Due to this problem the two generators are kept as backup generators and are not in continuous operation.

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[Lancie1]

Signal noise, perhaps unshielded cables, or shields too far from terminal ends?
Poor system grounding, perhaps.
Loose connections on the Flex I/O communications cable to the PLC/5, maybe.

 

[yam785]

I'm assuming that you ....

tightened and checked all the communication connections. When ever I've had weird stuff happened, I'd say 90% of the time, it was a connection problem. Or look for something in common, to the signals you are losing.

I used to work at a factory, where we melted glass with an electric foreharth. I remember every time I had a call about a bunch of readings going crazy, I would go up and look for welding rods, peices of wire, etc., going from building ground, to the foreharth, which needed to be isolated. Any ground, and all kind of readouts went haywire.

Not sure if this is aplicable in your situation. Just my two cents, for what it is worth.

 

[Lancie1]

In addition recently we encountered another problem, i.e some of the digital outputs which have been turned on depending on the present conditions get turned on and off repeatedly. Last time we observed this on the remote flex IO rack no 6 (refer attachment) and in the same time we observed that the local fault indication on the remote adapter of the flex IO rack no 5 was blinking.

Check the power supply to your Flex I/O Racks No. 5 & 6. The loss of Remote I/O power could cause some of the symptoms that you describe. You might need to add a UPS on this rack (if it does not already have one).