A vacuum valve includes a main flow channel that connects the first port and the second port, a main valve seat that surrounds the main flow channel, a main valve disc that opens and closes the main flow channel by contacting and separating from the main valve seat, a sub-flow channel that is formed inside the main valve disc, a sub-valve seat that is formed on an outer surface of the main valve disc, a sub-valve disc that opens and closes the sub-flow channel by contacting and separating from the sub-valve seat at a position outside the main valve disc, and a rod that causes the main valve disc and the sub-valve disc to open and close. The sub-valve disc opens and closes the sub-flow channel by being operated directly by the rod, and the main valve disc opens and closes the main flow channel by being operated via the sub-valve disc by the rod.

A vacuum valve includes a main flow channel that connects the first port and the second port, a main valve seat that surrounds the main flow channel, a main valve disc that opens and closes the main flow channel by contacting and separating from the main valve seat, a sub-flow channel that is formed inside the main valve disc, a sub-valve seat that is formed on an outer surface of the main valve disc, a sub-valve disc that opens and closes the sub-flow channel by contacting and separating from the sub-valve seat at a position outside the main valve disc, and a rod that causes the main valve disc and the sub-valve disc to open and close. The sub-valve disc opens and closes the sub-flow channel by being operated directly by the rod, and the main valve disc opens and closes the main flow channel by being operated via the sub-valve disc by the rod.

A fluid transfer system includes a transfer device coupled to a dry break coupler. The transfer device includes a valve assembly moveable between an open and a closed position. The valve assembly includes a main valve and a pilot valve. An actuator controls both the main valve and the pilot valve. A cam plate interconnects the actuator and the valve assembly. The cam plate provides a quick acting shutoff to quickly move the valve assembly to the closed position. A pivotal and rotatable connector couples the transfer device to the dry break coupler. A lock is integrated with the actuator to lock the valve assembly in the closed position.