4.1.2-11 Intelligibility of Processed Alarm Information

The alarm system should provide functions that enable users to evaluate the meaning or validity of the alarm messages resulting from alarm processing; for example, it should be possible to view the inputs to the alarm processing system.

Additional Information:
Complexity of the processing impacts the operator's ability, as the system supervisor, to understand the results of alarm processing and its constraints and limitations. Since the alarm system is the operator's first indication of process disturbances and operators will confirm the validity of alarm signals prior to taking action, it is essential that operators easily comprehend the meaning of alarm data, how they are processed, and the bounds and limitations of the system. An alarm system that combines multiple processing methods should not be so complex that it cannot be readily understood and interpreted by the operators who must rely on the system's outputs. If operators are unaware of the relationships among displayed alarms and how those relationships might depend on the processing being applied, they may draw incorrect conclusions about the state of the system or the reliability of the alarms. For example, operators may need to view sensor data and values that result from alarm system processing under certain circumstances, such as if the pattern of alarm messages appears to be contradictory, or if operators suspect that there is a problem with the processing system such that the results of alarm processing are incorrect.