Performance analysis of up/down counters in alarm design

Abstract

Alarm systems, as a layer of protection, play a critical role in process safety. Modern alarm systems, however, pose a challenge in the process industry due to alarm floods, missed alarms, and a large number of false, nuisance, and chattering alarms. In this paper, we propose up/down counter configurations as a technique to improve the quality of univariate alarm systems. Mathematical models are developed based on the Markov chain to study the performance of up/down counters and analytical expressions for performance indices (the false alarm rate, missed alarm rate, and expected detection delay) are derived. The results are confirmed using Monte Carlo simulation and the utility of the proposed technique is demonstrated through examples. This proposed up/down counter is specifically compared to delay-timers as a common and well-studied alarm configuration technique.