The Operating Envelope Method for Alarm Limits

The alarm system is key communicating operation status to the operator. Setting alarm limits without considering the process operating envelope doesn’t make sense but is normal in alarm management. Why? Lack of tools (no way to see the envelope), belief that the current way is easiest (despite rationalization having to be revisited and repeated), and organizational inertia are common. This webinar dispels the first two, and gives some support for overcoming the third. We will show you how, with novel multivariate visualization, alarm rationalization and maintenance produce better alarm limits, respecting the actual process operating envelope, while saving manpower in the process. We’ll share some examples of demonstrated successes and discuss how to maintain your alarm system, retaining the benefits gained.

Alarm and operating limits, process capability, and operating objectives are linked by the multidimensional operating envelope. While it’s normally difficult to visualize, it appears implicitly in the historic operating data of your plant, and CVE, our powerful multi-dimensional visualization tool, can bring this together with operating objectives and alarms to provide a holistic view. This makes it clear how to position alarm limits at the edge of the envelope, giving your operators the best opportunity for reacting and controlling your process.

Geometric Process Control (GPC) considers alarm limits as a set, linked to each other, the process capability, and the objectives through the operating envelope. As the process and operation change, reflected in changes to objectives and capability, the alarm limits need to change as well. This is recognized in maintenance steps of alarm management, but changing alarms outside this framework leads to inconsistencies. Continuing to use CVE to recognize the changing operating envelope and inform alarm changes keeps consistency and the good alarm performance achieved.