Which component closes the main valve of the 302AF refueling/defueling valve in case of excess flow at the hydrant outlet?

The component responsible for closing the main valve of the 302AF refueling/defueling valve in the event of excess flow at the hydrant outlet is the pressure-differential shutoff (CDHS-3). This device is designed to enhance safety by ensuring that if the flow rate exceeds a predetermined level, the system will automatically shut off to prevent potential hazards such as fuel spills, damage to equipment, or over-pressurization within the system.

The pressure-differential shutoff functions by monitoring the difference between the inlet and outlet pressures; when it detects an abnormal condition indicating excess flow, it actuates the closure of the main valve. This mechanism is crucial in maintaining safe operating conditions during refueling operations and helps protect both the equipment and personnel involved in the process.

The other components, while important in their specific roles, do not perform the same function as the pressure-differential shutoff. The pressure-reducing control is mainly for regulating downstream pressure, the loading pressure-relief control serves to relieve pressure during loading, and the control valve flow control manages flow rate but does not specifically address emergency shutoff scenarios due to excess flow. Thus, the selection of the pressure-differential shutoff highlights its critical role