Processing plant managers are increasingly approaching Mipac for help in addressing the status of their control system alarms and their effect on operator efficiency.
Operators are being overwhelmed with ever-increasing numbers of alarms — sometimes up to 600 an hour — and are unable to prioritise critical events to address.
Mipac’s process control engineers have an intimate knowledge of industry standards on alarm guidelines (including the ISA 18.2 and EEMUA 191*) and are highly experienced in designing and configuring control systems. This means they are adept at analysing and rectifying alarm issues.
For example, Mipac recently investigated a distributed control system with a heavily flooded alarm situation at a major Australian mine site.
Mipac discovered that the DCS was being flooded with alarms — more than 20,000 in just over 31 hours — reducing operators’ ability to recognise crucial alarms and apply mitigating measures. And these were just the initial alarms, part of almost 60,000 events during the 31-hour-plus assessment.
“The Abnormal Situation Management Consortium Guidelines for Effective Alarm Management practices state that an average alarm rate of six to 12 alarms an hour is manageable under normal conditions, or just 10 alarms in a 10-minute interval in the event of an abnormal situation, so how can operators react appropriately to more than 600 an hour?” Mipac Business Development Manager says.
“Mipac can reconfigure a plant to reduce problems and thereby reduce alarm frequency. Our engineers can also redesign alarm systems to enable operators to focus on critical plant events. The last thing you want to do is ignore a critical alarm and for it to lead to a production shutdown or safety issue, such as a fatality.”
Mipac’s assessment of the Australian mine site showed that many alarms (about one third) could be remedied through revised control strategies. Process alarms accounted for more than a third of the alarms and could be addressed through relaxed process constraints and operator set points. Instrument configuration, poor wiring connections, cable short circuits, valve limitations and maintenance issues also contributed to alarm generation.
After just a week on site analysing the DCS, Mipac was able to suggest cost-effective and timely solutions to instrument issues, loop tuning and control configuration settings which would reduce the alarm rate by about 70 per cent to about 200 alarms per hour.
To further reduce the alarm rate, Mipac also proposed successive stages concentrating on fixing set points, process issues, equipment issues, alarm masking, and resolving tight operating constraints, eventually reducing the alarm rate by more than 90 per cent and bringing alarms to manageable levels.
“We also recommend plants implement an alarm management philosophy championed by a dedicated alarm management team, as well as conduct regular alarm audits and maintenance,” Mipac says.
“Mipac can help clients develop alarm management philosophies and provide assistance with subsequent audits and enforcement, and to develop strategies to avoid ‘alarm creep’.
“These measures should be prioritised as relatively low-cost ways to improve operator responses, reduce process interruptions and downtimes to improve plant productivity.”