November 2017

24 | Plant &Works Engineering | November 2017 Process, Controls & Plant Focus on: Drives, Motors & Controls T here are several reasons for replacing an MCC, but the most common ones include obsolescence, incompatibility with new legislation or the condition of the MCC deteriorating. Technological advancements that allow the design of intelligent, more efficient MCCs are another reason why companies sometimes opt for an upgrade. Many engineers will wait until an MCC breaks down completely before commissioning a replacement, but best practice dictates that through proactive maintenance and regular checks, plant managers and maintenance engineers can identify the early warning signs of a failure and better plan for the upgrade. The potential defects discussed below are what maintenance engineers should look for when performing regular MCC checks. These audits should take place at least twice a year and log faults so that the information can be used retrospectively to better understand the condition of an MCC and predict potential risks. Mechanical defects A motor control centre has several electro mechanical components that are particularly susceptible to failure. These include the filters and fans, which need to be cleaned and checked regularly because they provide adequate air ventilation within the MCC. Poor ventilation can easily lead to overheating and the failure of critical components. Visual checks should also cover whether the relevant warning labels are in place before performing maintenance on an MCC, so that maintenance engineers are not put in any danger during these audits. Electrical faults Maintenance engineers can employ several methods to check electrical equipment. These vary from simple visual checks that identify discoloured or burned out components, to more complex investigations using an infrared camera to analyse electrical equipment or bus bars and to highlight hot spots. Engineers should also pay particular attention to the cables and connectors of the MCC, as these tend to degrade relatively quickly. Checks should also cover the running currents and shielding of the MCC, to ensure employees cannot access live components. Health and safety MCCs, particularly ones that have been in operation for a long time, can become health and safety hazards. Engineers were not as safety conscious back in the 80s or 90s as they are today, so there is a good chance that any MCC that is a couple of A motor control centre (MCC) sits at the heart of an industrial plant. If well maintained, an MCC can last for decades, but despite their sturdiness, even the most reliable MCCs have to be retired at some point. Pat McLaughlin, operations director of Boulting Group, explains the early warning signs that an MCC needs replacing. Time to say goodbye?