Operator Alarms – The Operating Envelope Approach

Operating Envelope Process History Data
Most of the operator alarm problems today arise from incorrect alarm limit values. Plants assume that they are independent of each other - which they aren't.

In our GPC Technology we position the alarm limits around the boundary of the operating envelope that corresponds to the operating objectives. This results in much better alarms which operators soon understand are reliable indicators of the process operating point moving out of the operating window (the hypercube enclosing the operating envelope) so one gets better operation and the measurable economic benefits that come from that. That means that the ‘capability’ (the ability to meet the operating objectives) of the envelope has improved so there is actually a three-way inter-dependence between the Operating Envelope, Alarm Limits and Operating Objectives in that if one is changed the other two are likely to need changing too.

If you use the ‘bad actor’ method of alarm management in your plants than stop now because it can’t work and consumes man-hours per week in reviewing the bad actors and results in moving one or two alarm limits inevitably outward until the bad actor alarm stops being a ‘bad actor’ – which simply lets other alarms come forward as next months bad actors.

Diligently repeating this month-after-month eventually leads to alarms so far outside the envelope of normal operation that they rarely sound and the resulting inconsistent operating envelope that they now define has little or no relationship to the operating objectives so you’ve given away the protection you were expecting from the now-silenced alarms and won’t get the economic benefits of a consistent envelope either.

Defining and seeing an Operating Envelope for the first time will point out the fastest way to improve in general and sometimes will give you unexpected insights into your process which can lead to improvements too. And the Operating Envelope is a uniquely simple way of ‘remembering’ a particular mode of operation and quickly re-establishing it after a stoppage.

All this is done with the offline CVE product.

The real-time CPM product takes all of this further including Predictive Alarming implemented through Alerts, Event Prediction and Mitigation where Events can be imminent process events such as column flooding or compressor surge or equipment faults such as sticking or stuck dampers or changing behaviour of a pump motor in plenty of time to allow the operator to switch to a standby pump and avoid unknowingly running the primary to total seizure.

If you’d like to find out more about then click here to view one of our previously recorded webinars on Alarms.

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