What is the purpose of an alarm and interlock system in process control?

• A. Detect unsafe conditions and automatically prevent or mitigate them
• B. Record data for maintenance logs
• C. Provide manual override
• D. Control device setpoints

Answer: (A)

Alarm and interlock systems are safety features in process control. Their purpose is to protect people, equipment, and the environment by detecting unsafe or out-of-spec conditions and then taking action to prevent harm or reduce risk. An alarm alerts operators when a process variable goes beyond safe limits, signaling that corrective action is needed. An interlock goes further by automatically enforcing a safe state—such as tripping a control loop, shutting a valve, or stopping a heater—without waiting for human intervention. This automatic mitigation is what stops hazardous conditions from developing or continuing. While data logging, manual override, or adjusting setpoints are parts of plant operation, they do not define the primary safety role of alarm and interlock systems.