【2025.1.1】3. What is the difference between alarm masking and alarm suppression functions?

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【I&C Garden】3. What is the difference between alarm masking and alarm suppression functions? 【Answer】 The purpose of alarm suppression is to disable the alarm function, while the purpose of alarm inhibition is to prevent alarms from requiring operators to be notified or to respond to them. According to ISA18.2, alarm suppression is one of the three methods for alarm inhibition (the other two being design inhibition and alarm cancellation). (1) Alarm Shelved: This is a feature available to operators in the control room to disable the real-time management of alarms (with the option to re-enable these functions later), in order to meet temporary or short-term needs (for example, when alarms become a source of disturbance due to abnormal operating conditions). The use of this tool must be subject to formal change control, and the time, date, and reason for disabling a particular alarm should be recorded accordingly. (2) Alarm Suppressed: During operational and maintenance shutdowns, alarm suppression can be considered to reduce the alarm load. Alarm suppression can be performed manually by personnel in the control room, and it can result in the suppression of alarms from several alarm groups or units. An automatic alarm suppression method (design-based suppression such as state-based alarms) can be used, but approval must be obtained prior to implementation.