In what situation does a person man NET 53 at the turning gear?

The correct choice pertains to the specific actions involved when locking and unlocking the shaft. In this situation, manning NET 53 at the turning gear is critical to ensure safety and proper operation during the process of engaging or disengaging the shaft. The turning gear is a mechanism that allows the shafts within the machinery to rotate at low speeds and is utilized for various operational tasks, including preparing the machinery for start-up or maintenance.

When locking and unlocking the shaft, personnel must be present at NET 53 to monitor the gear operation closely, prevent accidents, and respond to any issues that may arise during this critical phase. This ensures that all safety protocols are followed and that the operation does not pose any hazards to the crew or equipment.

In contrast, the other scenarios such as performing routine checks, conducting emergency drills, or situations with no personnel available at NET 83 do not specifically pertain to the immediate need for presence at the turning gear to manage shaft locking and unlocking processes effectively. Therefore, the focus on operational safety during this crucial mechanical function solidifies why the correct choice involves the locking and unlocking of the shaft at NET 53.