Abstract: An automatic vacuum-relief apparatus for liquid suction systems includes a vessel defining a chamber filled with liquid in communication with a liquid flow line, a rotary shaft extending through the chamber to support a valve device adjacent to the liquid flow line and to move the valve device to open a relief-air flow channel to relieve increased suction caused by inlet blockage, and a piston on the rotary shaft responsive to suction increases within the liquid flow line and chamber to actuate shaft rotation. The valve device, chamber and relief-air flow channel are configured and arranged to cause a spurt of liquid from the chamber into the inlet while the valve device is moving from its isolating position toward its opening position upon inlet blockage, whereby the spurt of liquid pushes the blockage away from the inlet and the relief air reduces the suction.

Abstract: An automatic vacuum-relief apparatus for liquid suction systems includes a vessel defining a chamber filled with liquid in communication with a liquid flow line, a rotary shaft extending through the chamber to support a valve device adjacent to the liquid flow line and to move the valve device to open a relief-air flow channel to relieve increased suction caused by inlet blockage, and a piston on the rotary shaft responsive to suction increases within the liquid flow line and chamber to actuate shaft rotation. The valve device, chamber and relief-air flow channel are configured and arranged to cause a spurt of liquid from the chamber into the inlet while the valve device is moving from its isolating position toward its opening position upon inlet blockage, whereby the spurt of liquid pushes the blockage away from the inlet and the relief air reduces the suction.

Abstract: A rotary-plug shut-off valve (10) of the type having a valve chamber (20) with multiple inlets includes: an actuator chamber (26); a base member (36) forming (a) an end of the actuator chamber (26) and (b) a guide (44); a vacuum-reactive member (48) movable with respect to the base member (36); a spring (54) in axial compression and rotational tension between the base member (36) and the vacuum-reactive member (48) and compressible by vacuum force on the vacuum-reactive member (48); and a piston (60) affixed to the vacuum-reactive member (48) and slidable 1) with respect to the rotary plug (22) and 2) with respect to the base member guide (44), to achieve automatic shut-off when vacuum pressures in protected line are too intense.