ALARM MANAGEMENT
BENEFITS OF AN ALARM MANAGEMENT PHILOSOPHY
Giving operators on the manufacturing floor a simple and clear-cut philosophy for alarm management with a simple and clear-cut system can help reduce downtime and improve overall automation and efficiency, says Martyn Hilbers.
A
larm acknowledgement is a widely accepted industry practice, but the reason why we apply it is a question that is not often asked. During a recent meeting for a project, with the purpose of developing an alarm management philosophy and implementing an alarm rationalisation, the question “why do we need alarm acknowledgement?” finally arose. The essence of an alarm is to notify operators about whether a process is going out of bounds, or whether it is out of bounds and requires intervention, because the automation system is incapable of changing the situation. Alarm acknowledgement is used to help the operator manage the active alarms. It allows the operator to distinguish which alarms have been addressed and which have not, providing a clear to-do list. From an alarm acknowledgement standpoint, this leads to an assumption it has been accepted that the control system can generate multiple concurrent alarms that affect the process. It also assumes that the automation is not able to deal with many situations and/or the automation is generating too many alarms.
Fewer alarms are more effective Can we avoid too many alarms? Consider the following: a valve limit switch has malfunctioned and opening the valve results in a ‘failed to open’ alarm. The valve is part of an equipment module and this too needs to provide an alarm of this event. The equipment module is part of a phase and the phase might be part of an operation and part of a procedure. Control Engineering Europe
In order to put the phase on hold and possibly the operation and perhaps even a procedure, an alarm condition must be propagated from the valve up through the hierarchy. It is important to provide the operator with a notification that explains the reason for the hold of the phase (and possibly the operation and procedure), but it is important that the operator is not overwhelmed with alarms.
management are not immediately noticeable nor impactful. The effects compound over time and this can lead to significant production inefficiencies. Circling back to why we need alarm acknowledgement, the answer to that question says something about the alarm efficiency and the level of automated operation, versus manual operation of the automation.
Alarm rationalisation
When sitting down to discuss and design a new automation system, ask whether the question ‘Should alarm acknowledgement be in the top 10 of our requirement list when selecting and/ or developing an automation system?’ If this question is at the top of the list and the answer is ‘No,’ the implication is that the system will be expected to perform at a higher automated level, that it will be applying alarm rationalisation and it will require less operator interaction. plus-circle
This makes it necessary to identify possible situations involving multiple pieces of equipment and implementing alarm masking schemes for these situations to give the operator one message conveying the reason for the hold. For large processes, this is where an alarm management philosophy and the implementation of an alarm rationalisation becomes important. It will require an ongoing effort to keep the alarm rationalisation and alarm-masking schemes up to date in order to provide the operator with effective alarms. However, for many organisations this often falls by the wayside. The effects of neglecting alarm
www.controlengeurope.com
Raising the bar
Martyn Hilbers is principal engineer at PLC-Easy. This article originally appeared on www.controleng.com March 2021
11
