Process alarm value setting?

In industrial process control systems, setting alarm values is a very important aspect; it enables operators to be alerted in a timely manner to potential problems or abnormalities, allowing them to take action to prevent accidents. It is not sufficient if a process parameter has an interlock value set for the Safety Instrumented System (SIS), but no alarm value has been set. An interlock system is used to take mandatory actions, such as shutting down the system or its components, when parameters exceed safe limits in order to prevent accidents, while alarms serve to alert operators before an interlock action is triggered, giving them the opportunity to intervene first and possibly avoid the activation of the interlock. Regarding the question of whether it is necessary to set alarm values, in industrial control systems, for critical process parameters, it is not only necessary to establish SIS interlock values but also one or more alarm values as a means of providing early warnings. Alarm levels may include low-level warnings, high-level warnings, and emergency alarms. The purpose of these alarm settings is to provide sufficient time for taking appropriate actions before the dangerous interlock values are actually reached. There are various industrial standards and best practices regarding the setting of alarm values; for example, ISA (International Society of Automation) provides several standards for alarm management, such as ISA-18.2 \"Industrial Automation and Integration – Alarm System Management\". In addition, APIs, IEC, and other organizations also have relevant standards, such as the IEC 61511 series of standards on Functional Safety – Safety Instrumented Systems, which also cover the management of alarm systems. In practice, the setting of alarm values should be determined based on specific production processes, operational experience, and historical data analysis; best practices from similar industries can also serve as a reference. It is recommended to work together with your company’s production technology department, suppliers of automation control and equipment, or professional engineering advisory teams to determine the alarm strategy that is most suitable for your process conditions. In summary, in addition to setting the interlock values for the SIS, it is necessary to establish relevant alarm values to improve the controllability and safety of the system. .

An alarm should be installed to give a warning first, triggering an SIS interlock shutdown

If there’s no alarm setpoint, with one less protection layer, wouldn’t the SIS level increase? Alarming is an operational requirement; interlocking is a safety measure.