(55bo) When Uninterrupted Power Supply (UPS) Was Interrupted, Safety Critical Elements Could Save the Plant

Safety critical elements (SCE) are components or equipment that are essential in safeguarding plant operation including normal, startup, shutdown, and abnormal situations. SCE are mainly extracted from bowtie analysis which are associated with major accident hazard. Some of the examples of SCE identified are safety valves, uninterrupted power supply (UPS), instrumented protective function (IPF), fire and gas detectors and etc.

In an unfortunate event, a power dip happened in 2023 caused damage to ageing UPS components and cut off power supply to Distributed Control System (DCS). Due to the same cause, plant trip was initiated and there is no way for panel man to monitor the status of plant during the shutting down period. During the blackout period, the only safeguarding system available are the safety valves and emergency shutdown system in plant which were activated during the event. Fortunately, electrical technician managed to normalize the UPS and restored the control at DCS which enable panel man to monitor all critical parameters for safe shutdown.

Arising from this incident, there is an awakening on importance of SCE during abnormal situations as final safeguard in prevention of process safety incidents. This can be done through inherent safe design and continuous review of Process Hazard Analysis (PHA). On top of that, it also prompts the team to look deeper into maintenance of SCE components in plant because failure of a single component can act as the escalation factors to defeat the function of SCE.

In summary, an unprecedented event managed to spark the continuous improvement effort in terms of SCE maintenance strategy and raise the awareness on healthy SCE importance. Besides, it also amplifies the importance of inherent safe design in petrochemical plant during abnormal operation.