PLC Control System Failure – Top Five Problems

Phil Black - PII Editor 25/10/2016

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Systems integrator clarifies most common reasons PLC control systems fail

Systems integrator, Boulting Technology has released an infographic to help engineers mitigate problems with programmable logic controller (PLC) based control systems. The handy guide highlights the top five causes of failure and can be downloaded, free of charge, from the news page of Boulting Technology”s website

PLC-based control systems are invaluable to a manufacturing or processing business because they control and regulate critical production systems and processes. A failed control system can cause significant plant downtime and is likely to be extremely costly; it can also create a hazardous situation when the system is controlling a critical process. By following correct maintenance procedures, businesses can minimise the chances of system failure, which in turn increases productivity, minimises costs and helps to maintain a valuable business reputation.

Faults with PLC input/output (I/O) modules and field devices account for 80 per cent of system failures. Usually, fixing these types of issues is relatively straightforward; however diagnosing them requires a basic knowledge of the system and on occasion specialist test equipment such as a multimeter. In addition, more often than not some form of PLC software diagnosis can aid with identifying the root cause of the fault. Although diagnosing the fault can often be time-consuming and requires specialist knowledge and experience, rectifying it can be as simple as replacing an I/O module or reconfiguring a field device.

Other common causes of failure include environmental issues, the integrity of the system earth, power supplies, failure of battery back-up during a power outage, electromagnetic or radio frequency interference and network and communication problems.

“Understanding the main causes of PLC control system failure means engineers can do more to prevent them,” explained James Davey, service manager of Boulting Technology. “In most cases, the minute a control system fails a business starts to lose money through downtime and missed deadlines. At worst it can result in a hazardous situation that needs immediate attention. Simple steps, such as regular control system health-checks, backing up PLC software and planning for contingency in the event of a power outage helps keep production processes up and running.

“At Boulting Technology, we pride ourselves on our ability and experience to use planned maintenance to prevent problems before they occur. Similarly, our guide to PLC control system failure will help plant engineers look out for warning signs of a failing system and take action before the issue becomes severe.”