7.3.4-1 Use of Interlocks, Lockouts, and Lockins

Interlocks, lockouts, and lockins should be provided to restrict personnel actions that may affect plant safety.

Additional Information:
An interlock is a feature that requires user actions to proceed in a specific sequence. A lockout prevents personnel from providing input that may generate a negative effect. Statically defined lockouts may restrict inputs to a specific, predefined range or set of values. Context- sensitive lockouts may restrict input values based on the current situation. A lockin keeps an ongoing operation active by preventing personnel from terminating it prematurely. Personnel actions that may affect plant safety include control actions and manipulating stored data important to safe plant operation.