Safety Instrumented Systems / Alarm Management

An Alarming Disconnect?

The Values of Alarm Limits Are the Biggest Single Factor Governing Alarm Performance

By Robin Brooks

[The following is an observation in the discussion about alarm management on the Controlling Interests blog. See "Alarming Déjà Vu."]

The values of alarm limits are the biggest single factor governing alarm performance, but there was never any science relating the values of alarm limits to how the process actually operated. The missing link is an "operating envelope" of the process. But an operating envelope used to be a very difficult thing to work with, so advice such as, "Position the alarm limits around the boundary of where you normally operate," was impractical to use. We have made it much easier with our interrogative visualization of operating envelopes, allowing limit values for many variables to be found in far less time than in the past. And because the alarms are consistent with one operating envelope, there are far fewer false alarms. The new method is being used by Phillips 66 and several other companies already.

- Robin Brooks