Alarms are used to trigger the operators', to attract their attention, and to inform about operational risks. If the operators are not aware of the new risks, they might not be able to prevent the failure . This chart demonstrates a way to identify hazards that might occur when starting the system. The chart demonstrates the following alarming features:

• A parameter used for hazard identification, based on measurements. For example, the temperature of an liquid in a container may be used to indicate of the potential incidence.
• Forbidden ranges are values of the  parameters which might result in an incidence. They are defined by the safety limits.
• The values of the parameter typical of normal initialization are defined by warning limits.
• The alerting point is a point where the measurements cross the warning limits.
• The grace time may be estimated by extrapolation of the measurements, between the warning limits and the safety limits.

 

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Updated on 19 Mar 2017.