Developing an AM system is a team-based activity that requires technical know-how as well as diplomacy in dealing with diverse groups of stakeholders. For new systems, follow the guidelines and requirements given by ISA-18.2, IEC 62682 or EEMUA-161:
Alarm philosophy. This is the umbrella document that specifies the processes to be used for each lifecycle stage (discussed below). The focus is to ensure operational or working definitions exist for, e.g., alarm priorities, settings, performance metrics (such as frequencies), design of alarm displays (human/machine interface (HMI)) and MOC. A companion document called the alarm system requirement specification goes into greater detail on specifications.
Identification. Determine the alarms needed for safety, regulatory compliance and smooth plant operation. Some alarms also could be dictated by other activities such as hazard and operability studies, and process and instrumentation drawing reviews. The key questions to think about are: “Do I really need this alarm? What do I lose if this alarm is not there?”
Rationalization. Review each alarm and develop supporting documentation such as the basis for the alarm set point, corrective action necessary, consequence of inaction, alarm priority and alarm organization. Rationalization likely will enable elimination of many unnecessary or nuisance alarms. You possibly may find a need to add some other alarms. Results of rationalization typically are captured in a document called the master alarm database.
Detailed design. Broadly put, you must address three major areas in this stage: specifics of alarms (set point, deadband, associated control systems, etc.); particulars of the HMI; and advanced alarming, the need for which will depend upon your process.
Implementation. It’s not uncommon to find that many alarms don’t perform as designed because of poor installation. This stage of the AM lifecycle involves logical and physical installation — including location of the alarm as well as its testing and commissioning. Operator training also takes place during this step; it should focus on what the operator must know about the alarm and how to respond properly.
Operation. This is the stage in which the alarm system is functioning. You may consider refresher training for the stakeholders.
Maintenance. Periodic repairs and testing are part of the maintenance stage of the lifecycle. Lack of appropriate procedures could lead to alarms that end up shutting down the plant. The key is communication among the parties involved.
Monitoring and assessment. You regularly must check the performance of each alarm and the whole AM system, and compare performance metrics with the ISA-18.2 (IEC 62682; EEMUA 191) guidelines. Periodic reviews of the results will help you initiate appropriate troubleshooting.
Management of change. From time to time, you may need to add or remove alarms, modify their set points, deadbands or other parameters, or alter displays. Unless these changes are properly controlled and documented, the AM system will deteriorate. You must review a proposed change from the standpoint of each of the lifecycle stages.
Audits. Their purposes include, for instance, identifying deficiencies in the AM system against the alarm philosophy and potential areas of improvement. Audits are more comprehensive than periodic monitoring and assessment. Audits involve, e.g., management commitment, AM practices, comparison of performance indicators against the standards, MOC, operator’s ability to respond to alarms, and training and documentation.
AM is a tool to enhance safety, productivity and regulatory compliance in a quantifiable manner. It is a multi-discipline activity. Teamwork and vigilance are the key to its success.
GC SHAH is a senior advisor at Wood Group, Houston. E-mail him at email@example.com.