What’s Lurking in Your Enclosures?
Let me know if this sounds familiar to you: somewhere in the plant there’s an enclosure that houses your controls hardware. It’s seen some changes over time – some components may have been replaced or may no longer be needed, but no one seems to know if there’s been any documentation of the changes: the old napkin on which someone drew a schematic disappeared long ago. And there may not be any documentation at all for the wiring connections to your field or internal devices.
Actually, there are some pretty simple steps you can take to keep your enclosures from resembling a rat’s nest of wires, old drawings, or schematics with a bunch of redlines. Here are a few suggestions:
* Place all of your wires into the panel’s wire-way, wire tying them to the back of the wire-way to make them tight. Of course, this only works if your wire-way is not already 110% full.
* Do a “panel audit” to go through your existing schematics and PLC programs and examine which devices are used and which aren’t. Then remove your old and unused devices. You might be surprised to find out how frequently we open a panel and find that no one has taken this simple step.
* Make sure you update schematics by creating a drawing of devices that you’re no longer using, and remove all wiring associated with the device. This will make it much easier for both your own people and contractors who come in to work on the enclosure.
* After you’ve cut wire ties off the wiring, replace them with new ones. Don’t leave the wires drooping – you might again be surprised at how often we encounter that.
* Upgrade to smaller components that do not take up much room in the enclosure.
* Upgrade the existing PLC if it was manufactured in the 1990’s. Most of the time manufacturers are trying to provide smaller component footprints, and new software tools to make it a lot easier and efficient to program.
* If you have Allen-Bradley hardware, change the terminal blocks to either point i/o, flex i/o or IFM modules. Do the equivalent for Schneider, Siemens, or other manufacturer’s hardware. This allows field termination directly for any of the devices. They would either be connected back to the PLC via Ethernet or by pre-wired cables. This approach takes up less space in the panel enclosure.
* Place your covers back on the wire-ways after troubleshooting or running new wire – or put covers on in the first place; it’s a simple step that just makes everything look neater.
One more point: it’s pretty obvious, but it’s still worth repeating, as I’ve run into situations where it hasn’t been followed: remember to keep things easy for the next guy working in the panels– practice good housekeeping, keep the panels free from clutter, and document your changes. That’ll be much appreciated, especially if the next guy is you.
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