What is the first action to take when isolating an electric motor driven pump?

Isolating an electric motor-driven pump begins with ensuring the electrical supply to the motor is safely disconnected. Opening the motor breaker is the correct first action as it cuts off electrical power, thus preventing any accidental startup while performing maintenance or isolating the pump. This step is critical for the safety of personnel working on or around the equipment.

While other actions may be taken subsequently, they do not prioritize electrical safety in the same way. For example, closing the inlet valve or releasing pressure from the system might be performed as part of the isolation process but should only occur after ensuring the motor is de-energized to avoid any unexpected operation. Turning off the power supply could also mean handling circuit breakers or switches that may still leave the equipment electrically live if not managed correctly. Therefore, initiating the isolation with the motor breaker allows for a systematic and safe approach.