Maintaining Control Systems
Mechanical systems typical come to mind when preventative and predictive maintenance is discussed. It is for good reason, as mechanical systems like gear boxes, chain/belt drives, conveyors, etc. require planned maintenance activities in order to minimize downtime. While the maintenance activities for control systems are more subtle, they are no less important. The following topics should provide ‘food for thought’ for your control system maintenance planning. After all, the genius is in keeping equipment running, not in repairing it after it fails.
Enclosure Environment: Newer electronic controllers are more robust, but enclosure heating and cooling systems are still often required to maintain proper operating temperature. In the spring, check the A/C systems, chillers, fans, and filters. Also clean out and check for proper routing of the condensate drains. In the fall check the heating systems.
IR Scan: Once per year, perform an IR scan (also called Thermal Imaging) of electrical enclosures. Equipment must be operating when the scan is performed, but corrective action is performed when the equipment is down. This tool identifies loose connections through the elevated temperatures that result. Loose connections result in ‘arcing’.
Arcing causes burnt-off wires resulting in downtime. There are many firms that perform IR scanning at reasonable costs. Ask for samples of IR scan reports. The report should provide a regular picture of trouble spots for ease of locating during corrective action.
Battery Backed Up Devices: Many control systems are equipped with Uninterruptable Power Supplies (UPS) to ride out minor power ‘blips’ caused by thunderstorms or other power grid disturbances. Check the manufacturer’s recommendation for testing and replacement of UPS batteries. Also, many older controllers have Ni-Cad batteries to maintain the memory while power is turned off or goes off unexpectedly. These batteries need replaced regularly with fresh batteries (not a battery that has been on the shelf for years). Most controllers provide a warning light when the installed battery requires replacement.
Check these lights regularly and follow manufacturer’s recommendations to replace batteries. Finally, make sure a current program/configuration for installed controllers is stored on another media in the event that there is a memory loss event or a CPU failure.
The combination of a dead back-up battery, a thun- derstorm, and no program back-up has led to many lengthy downtime incidents.
Visual Inspection: Visual inspections can identify excessive moisture, improperly secured components, broken/separated conduits, and improperly sealed enclosure doors/covers.
E-stop Checks: A regular operational check of the e-stop buttons and devices is a good idea to maintain confi- dence that equipment will stop as required.
Vibration analysis: While not a preventative tool, vibration analysis can predict when a critical motor is about to fail either electrically or mechanically. The prediction can allow for advanced planning of the motor replace- ment verses the typical unplanned replacement when it is least tolerable. This is another service you may want to farm-out to an experienced firm.
Quotable Quotes – By Industrialist Henry Ford
On the Competition: “The competitor to be feared is one who never bothers about you at all, but goes on making his own business better all the time.”
On Innovation: “If I’d asked people what they wanted, they would have asked for a better horse.”
On Productivity: “If you need a machine and don’t buy it, you will ultimately find that you have paid for it and don’t have it.”