Curvaceous & Six Sigma

Alarm Management

Alarm Management has always been a difficult topic because of false alarms, standing alarms, high annunciation rates, multiple operating Modes and Alarm Floods. Traditional methods have concentrated on Management of Change of Alarm Limits, Statistical Analysis of Alarm Logs and Alarm Rationalisation projects every few years to provide a fresh start.

The root cause of all these problems is actually that there has never been a method to find the values at which to set alarm limits other than isolated examples such as the use of metallurgical properties to find extreme limits for furnace tube temperatures. These are usually so far from where the plant operates that they are better considered as safety limits than operating limits.

Curvaceous Visual Explorer changed that by giving the first method to set High/Low Alarm Limits that were consistent with each other so removing bad actors and most false alarms, hence much lower annunciation rates, at a stroke. HiLo Limits were in consequence ‘tighter’ so giving the operator more time to react and improving process safety. Visual Explorer will let you do this quickly and easily for many hundreds of variables at a time and can give you multiple sets of limits for multi-Mode processes (sometimes called 'State-based Alarming') just as easily.

All this starts not from Alarm Logs but from Process History and requires much less time and effort than traditional Rationalisation Projects.

Visual Explorer (CVE) is the only program that lets you see hundreds of process variables and their alarm limits in a single graph. You can actually see, for the first time, where the process has operated in the past and where its current alarm limits are too wide or too tight. Create new alarm limits at the boundaries of where the plant has actually operated and use these as the starting point for the Alarm Review. Add, remove and change limit values to create new sets of alarm limits and CVE will immediately calculate and show you their Annunciation Rates and Standing Alarm Counts. The Alarm Review Meeting will move away from being opinion-based and towards being fact-based. It will be at least 20% shorter and create better alarm limits.

Working with many variables you will soon see how the alarm limit values interact with each other and why making them Consistent makes them so much better. Consistency also means the limits should be managed as a Set across many variables instead of individually by variable as you do today. This substantially reduces the on-going administrative burden of Change Management for the Unit Process Engineer and others.

And this is just the beginning. Discover the Modes of operation in your process and create Alarm Limits for each Mode. With little additional effort you can implement Public Alerts to keep your process always inside the fixed Alarm Limits by giving intrinsically safe corrective advice for the process operator.

Operator Alerts are generated and displayed to the operator by Curvaceous Process Modeller using the envelope formed by the fixed HiLo Alarm Limits and with all variable interactions taken into account. This reduces the likelihood of the HiLo Limits being challenged and hence reduces the Probability of Failure on Demand (PFOD). Alert Limits change continuously, which is why they were so difficult to manage previously, but Process Modeller is able to recalculate their values in real-time and shows them to the operator pictorially. And because the whole method is based on sound-science, Process Modeller also calculates intrinsically safe operating Advice for the operator to help him clear alarms and alerts. Adhering to the Alerts will further minimise the number of HiLo Limit alarms so reducing the Probability of Failure on Demand and increasing process safety. Your operators may already be using Alerts provided by some DCS systems. These are simple fixed markers that the operator can change at will outside of the chenge control system. They are very useful to operators so GPC just renames them 'private alerts' and our new ones 'public Alerts' and both can happily co-exist.

And it is all done visually by geometry and without maths so is easy and natural for anyone to use. After all, your brain doesn’t formulate and solve the equations of motion when you put out your hand to catch a ball, does it?

This method won the European Process Safety Centre (EPSC) Award for the biggest single contribution to increasing process safety.

If Alarms are of interest to you please call us for a webinar. We’ll show and explain how all of this fits together mathematically and tell you how Alarm Floods are being tamed too.