About basics of Trip, Interlock, Permissive and Sequences which are regularly used in instrumentation control systems like ESD, DCS, PLC etc.

About basics of Trip, Interlock, Permissive and Sequences which are regularly used in instrumentation control systems like ESD, DCS, PLC etc.

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Interlock:

An Interlock is in essence a ‘self resetting’ Trip. Interlocks are not deemed safety related and can be used for on/off control.

Interlocks are normally initiated by the DCS or PLCs, however if an Interlock is deemed to be safety related it may, depending upon SIL rating, be implemented in the SIS or a Hardwired system.

An interlock will force a device or devices to a pre-determined state e.g. Close valve, stop motor, etc.

Once a device or devices have been forced to a pre-determined state by the action of an Interlock they will remain in that state until the initiating cause returns to a ‘healthy’ condition, the Interlock will then be automatically removed.

Under normal circumstances it shall be possible to ‘override’ Interlocks for operational reasons or ‘defeat’ them for maintenance or other reasons.

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‍Reference :https://lnkd.in/gZsPS97W