Better operator alarms can improve process profitability 31 October 2012

It is a mistake to believe that meeting the 'human-factors performance targets' of EEMUA 191 or SP 18.2 is sufficient to provide a 'good' operator alarm system.

That's the warning form Dr Robin Brooks of process plant systems specialist PPCL (Process Plant Computing).

"The fallacy arises, because there is no definition of what constitutes a good operator alarm system," insists Brooks.

"Guidance from EEMUA and others on setting operator alarm limits is to place them 'at the boundary of where the process normally operates'. But chemical engineering has never provided a method to identify such boundaries," he explains.

"Each operating envelope is the space within which the process can achieve the objectives you have chosen – and operator alarm limits should be boundary markers on some of the many variables," he continues.

"So you should be looking at alarm limits on many more than one variable at a time – which you can't do with today's methods."

Brooks suggests that, in fact, there are graphical methods that are quicker and easier than conventional alarm limit-setting or rationalisation methods.

"[These] let you quickly see and compare operating windows and operating envelopes for different objectives and, for the first time, correctly position operator alarm limits on the boundary," he says.

They then predict what the alarm performance will be so that plant owners and designers can make an informed choice of operating envelopes and operating objectives and see where improvement is needed.

Operating objectives, he explains, are based on the measurements available to control a process in real-time, as well as those not available until later – such as sample analyses.

Brooks says that, using the graphical method, everyone on a plant can understand why the operator alarm limits are positioned where they are – and also opportunities for process improvement that flow from better operator alarm limits.

Brooks is running a webinar on the subject. To attend, on 7 November 2012 at 8am or 4pm GMT, use the link below.

Brian Tinham

Related Companies
PPCL Ltd

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