Hazard Asia Pacific 2017
Alarms are an audible and visual means of alerting an operator about an abnormal condition or a system out of normal operating range. They provide early indication of a potential hazard or production upset. Due to the introduction of advanced control system, the uses of alarms have increased since they are easy to configure and carry no additional cost. This resulted in an increased number of alarm generation.
In many instances, safety related alarms or critical alarms such as pre-trip alarms are displayed along with other non-critical alarms. Moreover, all alarms sound alike which may result in operator being unable to respond to critical alarms within the process safety time. Such scenarios may lead to unnecessary plant trip or lead to a major process upset or cause a safety hazard. Alarm Management System (AMS) involves the application of human factors to the alarm system design to increase its usability. AMS enables alarm system to effectively perform its primary function by providing relevant and actionable information. Alarm systems help in directing operator’s attention to important problems requiring immediate action, using a priority matrix to indicate the degree of importance. Also various priority alarms can be displayed in different colour/ sound to attract operator response. Such prioritisation is based on consequence of delayed action and the available response time.
AMS also employs methodologies like static and dynamic alarm suppression. Static suppression is usually employed to screen out alarms from equipment such as compressor/ pump, fired heater or sections of plant which are shutdown for maintenance or on standby. Similarly dynamic suppression is employed after a trip of a section of plant or process upset, to prevent alarm flood.
In this paper, the author has provided an overview of various standards for AMS and has proposed a simple, user friendly methodology (including suppression techniques) for prioritisation of alarms combining urgency for operator response and the consequence of delayed action. A case study based on past projects along with lessons learnt are presented to highlight the benefits of such alarm management techniques in improving operator response and thereby improving operability and process safety.