The quick answer is yes, because it can help prevent accidents and loss in production. It ensures a maintained alarm system, which is more cost efficient than having larger alarm rationalisation projects at irregular intervals. For new projects and modifications, the alarm philosophy is the basis for the changes, so this should be in place in order to have an optimal alarm system.
The outcomes of a well-maintained alarm system are:
- Reduced chance of human mistakes
- Less risk of shutdown
- Cost savings
How do we reduce the likelihood of human mistakes?
According to alarm standards and guidelines, an operator must have enough time to detect an alarm, diagnose the situation, respond with corrective action(s), and monitor the condition, then verify that the abnormal condition has been corrected. The operator should be able to handle the announced alarms in this described way in a steady state of operation.
In order to have the ability to do this, the operator cannot handle more than 1-2 alarms during a 10-minute period.
Figure 1. EEMUA 191 Alarm analysis summary monthly report (S=Steady state, U=Upset state)
When the alarm load goes from robust to stable, the operator spends more time on alarms. When the alarm load reaches reactive or goes into overload, the operator loses track of the prioritisation of activities. If the plant is in overload condition the operator loses confidence in the alarm system and will be more likely to make mistakes. By using an alarm management system we can make sure that the alarm load is stable and at a rate that the operator can work with.
The content of maintenance
A successful maintenance procedure includes a description of the ownership of the alarm system. The main objective of the maintenance procedure is to ensure that the load to the operator with respect to alarms is at an acceptable level. The key to alarm maintenance is systematic monitoring with quick remediation of problems. The systematic monitoring of alarm performance is simplified by using an alarm management system. The report from the alarm management system will give you an overview of the alarm load of the operator and how much time it takes for the operator to get back to normal operation after an abnormal condition.
You can use the report from the alarm management system to get the top 10 alarms and to investigate why these alarms are in the top 10 list. Are the alarms activated due to...
- Field equipment failure...?
- Process disturbance...?
- Wrong alarm set points...?
- Not valid dead band and hysteresis on analogue inputs...?
Then you should take actions to solve the noise from these alarms.
The 10 most frequent alarms (bad actors) should be followed up weekly. Taking action based on these bad actors will be an advantage in getting the alarm load to a level where the system is usable for the operator.
Example of an alarm list for Pri. 1-3
The maintenance of the alarm system is an ongoing activity. There is no reason to take a break from the maintenance of the alarm system during alarm projects.
The savings of doing systematic maintenance of the alarm system is:
- No need for costly alarm projects after modifications
- No creeping changes
- Documentation and integrity is maintained
- Reduced chance of human mistakes
- Less risk of shutdowns
Consequences of not doing alarm system maintenance
Consequences of not maintaining the alarms with an alarm management system is that you will have too many alarms presented in the alarm system within a specified time period. The operator will be unable to respond to alarms in a structured and safe way during an alarm flood. This can in turn lead to mistakes, damage to people and assets and in worst case lead to shutdown of the facility, all of which are costly consequences.
To conclude: alarm maintenance is not only important, but also necessary in order to maintain an alarm system and make sure that the alarm management lifecycle is continuous. This includes a periodic review of key parameters against the alarm philosophy. All of these activities can be simplified by using an alarm management system.
Optimised alarms ensure optimised decisions!