What Are the Best Tips for PLC Maintenance?
Given that PLCs (programmable logic controllers) are integral to many industrial operations, including predictive maintenance, it’s important to keep them well-maintained. The way PLC maintenance looks in any given facility depends on the working environment and the number/types of PLCs in use.
What Types of Maintenance Are Common for PLC Systems?
While the exact maintenance strategy you use for your PLC systems will be unique to your facility, there are a number of tasks that are commonly required. These tasks are best done as part of a preventive maintenance plan.
First of all is dust removal. PLCs are computers, and as such, they need to be kept clean in order to function optimally. The various components, including its input/output (I/O) modules and CPU, aren’t dustproof, and a buildup of dust could cause the system to overheat. Thus, the area should be cleaned of dust on a regular basis.
Any ventilation filters used in the PLC’s enclosure should also be cleaned or replaced on a regular basis. Doing so helps prevent dust buildup and makes your system more reliable. The frequency with which you replace ventilation filters depends on how much dust and debris is generated in your facility, so it’s a good idea to do some routine checks to determine how quickly filters clog up before committing to an exact frequency.
Along with changing the filters on a regular basis, other objects such as manuals, papers, tools, and so forth should be kept clear of the unit, particularly the CPU rack. Leaving items on top of the unit can block airflow and cause the system to overheat or otherwise malfunction.
Connections such as sockets, plugs, and terminal strips should be routinely checked to make sure they are secure. Loose connections could cause reliability issues, particularly in areas with high levels of vibration. As such, this check should be performed more frequently in areas with rotating equipment or other vibrating machines.
In addition to I/O connections, check to make sure the system itself is securely installed, particularly in high-vibration applications. If any screws, bolts, or sockets are loose, tighten them down to keep the system from rattling.
Installing a vibration meter can act as a preventive measure. By connecting it to the PLC, you can track vibration in the area.
Replace I/O Modules
Sometimes I/O modules will need to be replaced. Typically, this should be done only as needed, not on a scheduled basis. When replacing these parts, it may be necessary to disconnect the power, though some systems do allow I/O module replacement while still online.
If modules need to be replaced too frequently, it may be a sign that there are other issues present, such as power spikes or shorts in the system.
Every so often, the PLC’s programing should be backed up. If something goes wrong that causes the system to go offline, there’s a risk that current programming could be lost, costing thousands of dollars in lost production time as the system is reprogrammed. By backing up these systems every six months or so, you’ll ensure continuity in the event of an outage.
How Frequently Should I Maintain My PLC System?
The frequency of PLC maintenance depends on the task being performed and the nature of your working environment. The harsher the environment, the more frequently some tasks will need to be performed.
Some tasks, such as dusting or cleaning, are often best performed daily in order to keep the system in top working condition. Often, simple cleaning tasks can be given to operators as part of a total productive maintenance (TPM) strategy.
Other tasks are more or less independent of working conditions. For instance, it’s recommended that maintenance teams back up their PLC’s programming on a semiannual basis.
Additional PLC Maintenance Tips
With a basic idea of how to maintain your PLC systems, it helps to be aware of some best practices when it comes to executing your maintenance plan. Some general tips for PLC maintenance include the following.
Keep Up on PLC Data
If you haven’t inventoried your PLCs, do so. It’s common for organizations to be unaware of how many PLCs they actually have in operation, so take some time to check around to find them all. When you do, record their information, such as the machines they control, their brand, their programming, when they were last backed up, etc.
At least one person per shift should be trained in using, troubleshooting, and maintaining your PLCs. Make sure your training focuses on using the products you have in your facility (or plan to have in the future) in a safe, reliable way.
Stick to One Brand
This tip comes more from the angle of system design than preventive maintenance, but it can help streamline your maintenance processes. When installing PLCs and ordering spare parts, make sure you stick to one brand. Doing so will help standardize your processes and improve reliability.
Another design tip is to include measures that can protect your PLCs from harm, such as placing them in enclosures with dust filters or installing power line filters. These safeguards can reduce the need for parts replacements and routine repairs by minimizing wear.
Keep Enough Spares On-Hand
Keeping a good stock of original equipment manufacturer spares on-hand is essential to any preventive maintenance plan, including PLC maintenance. Make sure you have enough to handle your existing maintenance needs, but not too many since that can result in waste.
Like any other asset, PLCs can be maintained with a well-planned preventive maintenance program. The most effective program will be firmly grounded in the systems you’re using and the general context of your work environment.