Final answer:
The operating engineer is responsible for assuring refrigerant cylinders are within the hydrostatic test dates in a plant.
Step-by-step explanation:
The operating engineer is responsible for assuring that refrigerant cylinders are within the hydrostatic test dates in a plant. They are in charge of operating, maintaining, and monitoring the plant's systems, including the refrigeration system. It is their job to ensure that all equipment is functioning properly and meets safety standards.