The alarms should be presented in an obvious manner, distinguishable from other alarms, have the highest priority, and remain on view at all times when it is active.The operator should have a clear written alarm response procedure for each alarm which his simple, obvious and invariant, and in which he is trained.The alarm system should be independent from the process control system and other alarms unless it has also been designated safety related.The alarm system should be designed in accordance with IEC 61508 to SIL 1 or 2, with the designated reliability.It provides the following guidance in regard to safety related alarm systems: However, where a risk reduction of better than 10 -1 failures on demand is claimed then the alarm system, including the operator, is a safety related system which requires a suitable safety integrity level (SIL 1 or SIL 2 as defined by IEC61508). Alarm Management SystemĪlarm systems alert operators to plant conditions, such as deviation from normal operating limits and to abnormal events, which require timely action or assessment.Īlarm systems are not normally safety related, but do have a role in enabling operators to reduce the demand on the safety related systems, thus improving overall plant safety. More complex plants had more complex panel boards, and therefore often more human operators or controllers. To do this they employed behavioural psychology practices which revealed how much information a human being could collect in a quick glance. Instrumentation companies put a lot of effort into the design and individual layout of the instruments they manufactured. This was due to both the design of the instruments and the implementation of the alarms associated with the instruments.
It was a simple matter to look at the entire panel board, and discern whether any section of the plant was running poorly. So instrumentation indicating operating units with the plant was grouped together for recognition sake and ease of problem solution. (For instance, green lights meant OK, Yellow meant not OK, and Red meant BAD.) Panel boards were usually laid out in a manner that replicated the process flow in the plant. Additionally, Emergency Shut Down (ESD) systems were employed to halt a process that was in danger of exceeding either safety, environmental or monetarily acceptable process limits.Īlarm were indicated to the operator by annunciator horns, and lights of different colours.
They include situations that have a necessary or possible operator response to ensure:Īlarms were added to alert the operator to a condition that was about to exceed a design limit, or had already exceeded a design limit. The purpose of alarm management system is to alert the operator to relevant abnormal operating situations.
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