A nozzle check valve comprises a valve body (10) and a nozzle (20) centrally arranged within the upstream end of valve body (10), a fluid channel (90) is defined by the outer face of the nozzle (20) and the inner face of the valve body (10). A guide bush (60) is mounted on a nozzle axial extension (26) and an annular disc (30) comprising a disc sealing ring (31) connected to a central barrel (32,33) by a plurality of webs (34) is mounted on the guide bush (60) for axial movement of the annular disc (30) relative to the valve body to open and close the fluid channel (90). A spacer (80) is arranged on the nozzle axial extension (26) downstream of the guide bush (60) and a diffuser (40) is arranged on the downstream side of the spacer (80). A spring (50) between the annular disc (30) and the diffuser (40) urges the disc towards the valve closed position. The stroke of the valve, the maximum movement of the annular disc (30) from the valve closed position to the valve open position where the annular disc (30) is in contact with the upstream face of the diffuser (40), is determined by the axial length of the spacer (80). The centre of mass of the annular disc (30) is located along the central axis of the disc (30) at an axial position where the barrel (32) is in sliding contact with the guide bush (60).

A nozzle check valve comprises a valve body (10) and a nozzle (20) centrally arranged within the upstream end of valve body (10), a fluid channel (90) is defined by the outer face of the nozzle (20) and the inner face of the valve body (10). A guide bush (60) is mounted on a nozzle axial extension (26) and an annular disc (30) comprising a disc sealing ring (31) connected to a central barrel (32,33) by a plurality of webs (34) is mounted on the guide bush (60) for axial movement of the annular disc (30) relative to the valve body to open and close the fluid channel (90). A spacer (80) is arranged on the nozzle axial extension (26) downstream of the guide bush (60) and a diffuser (40) is arranged on the downstream side of the spacer (80). A spring (50) between the annular disc (30) and the diffuser (40) urges the disc towards the valve closed position. The stroke of the valve, the maximum movement of the annular disc (30) from the valve closed position to the valve open position where the annular disc (30) is in contact with the upstream face of the diffuser (40), is determined by the axial length of the spacer (80). The centre of mass of the annular disc (30) is located along the central axis of the disc (30) at an axial position where the barrel (32) is in sliding contact with the guide bush (60).

An embodiment wall hydrant includes a reservoir, conduits containing an operating rod assembly and a service rod assembly, and a fluid outlet with a hose connector. The service rod assembly allows water supply to the hydrant to be shut-off from the front of the hydrant which allows servicing of the hydrant without requiring water shut-off to all or a portion of the water supply to the building. Embodiments include a vacuum relief dual check valve assembly at the fluid outlet which prevents backflow of water into the hydrant. Embodiments include a box which protects the hydrant controls.

An embodiment wall hydrant includes a reservoir, conduits containing an operating rod assembly and a service rod assembly, and a fluid outlet with a hose connector. The service rod assembly allows water supply to the hydrant to be shut-off from the front of the hydrant which allows servicing of the hydrant without requiring water shut-off to all or a portion of the water supply to the building. Embodiments include a vacuum relief dual check valve assembly at the fluid outlet which prevents backflow of water into the hydrant. Embodiments include a box which protects the hydrant controls.

An apparatus for allowing the repetitive oscillation of pressure in a container or vessel having a finite volume. The apparatus comprises a valve having first opening, a valve enclosure having a second opening, and a first tension device. In some embodiments the apparatus can have a chamber capable of oscillating in volume. The oscillation of the chamber volume causes a decrease in the pressure of the container. As the pressure of the space or container decreases, two openings of the apparatus become more proximate. Eventually the openings partially overlap, allowing a gas, or fluid, to enter the container, increasing pressure of the space or container. As a result of the pressure increase, the first opening and second opening become less proximate by a force of the first tension device. The apparatus can allow the container to approach substantially perfect vacuum and rise toward atmospheric pressure.

An apparatus for allowing the repetitive oscillation of pressure in a container or vessel having a finite volume. The apparatus comprises a valve having first opening, a valve enclosure having a second opening, and a first tension device. In some embodiments the apparatus can have a chamber capable of oscillating in volume. The oscillation of the chamber volume causes a decrease in the pressure of the container. As the pressure of the space or container decreases, two openings of the apparatus become more proximate. Eventually the openings partially overlap, allowing a gas, or fluid, to enter the container, increasing pressure of the space or container. As a result of the pressure increase, the first opening and second opening become less proximate by a force of the first tension device. The apparatus can allow the container to approach substantially perfect vacuum and rise toward atmospheric pressure.

Disclosed is a differential pressure valve comprising: a valve body, the valve body having at least one flow inlet and one flow outlet: at least one shutter, the shutter being movable between an open position and a closed position under a differential pressure across the valve; at least one flow passage from the flow inlet to the flow outlet; at least one biasing member configured to bias the shutter towards a closed position so as to block the flow passage through the flow inlet. The biasing member is a non-linear biasing member.

Disclosed is a differential pressure valve comprising: a valve body, the valve body having at least one flow inlet and one flow outlet: at least one shutter, the shutter being movable between an open position and a closed position under a differential pressure across the valve; at least one flow passage from the flow inlet to the flow outlet; at least one biasing member configured to bias the shutter towards a closed position so as to block the flow passage through the flow inlet. The biasing member is a non-linear biasing member.