Alarm and Display System Analysis Overview

The widespread use and advances in distributed control systems have focused attention on the design of the operator-process interface. Numerous events have occurred at refineries that were either caused or made worse by the alarm and/or display system design. The propagation and proliferation of process alarms has become a major burden and problem for DCS operators. In man-machine system design, not only are more alarms/displays not better, they are often the cause of "operator error".

Proper configuration of the interface eliminates problems with alarm flooding/avalanche, excessive display paging, and wasted CRTs. Unfortunately, most DCS configurations are not developed with adequate forethought or care, potentially resulting in a multitude of problems. Too often the thought behind DCS configuration is to give the operators some blank paper to draw displays and P&IDs to mark what they would like to have alarmed. The fear of not alerting the operator to an off-normal event frequently results in the creation of so many alarms that the operator can’t properly diagnose the event when it does occur.

Proper alarm and display system design is a two step process: (1) determining the content (what to display/alarm) and (2) determining the form (how it should look). Selection of alarms and the content of the displays is critical to the success of the system. Presentation of the information becomes extremely difficult if the "right" information has not been chosen and/or properly organized.

A flowchart of display system development is shown below.

Flowchart of Display System Development
Click image for full-sized version