Performance comparison of various delay timers on alarm system design

Abstract

Alarm systems are critically important for safety and efficiency of industrial plants. Not designed properly or not receiving the attention they deserve, alarm systems suffer from poor performances. Alarms notify the operator of the abnormality on the plant. Unfortunately, most of these alarms are false and nuisance, they can be a real distraction to the operator and may additionally mask vital alarms. Deadbands, filters and delay timers are industrial techniques proposed by the industrial community to reduce false and nuisance alarms. In this paper, we investigate the use of three different delay timers; conventional delay timer, generalized delay timer and multi-setpoint delay timer; in the process and compared their effects on accuracy and detection delay. False alarm rate (FAR), Missed alarm rate (MAR) and average alarm delay (AAD) are the three performance indices used to design optimal alarm system. Simulation results show that alarm performances can be improved and even optimized via delay-timer with proper choice of the delay timer order