A vent valve includes an outer frame, a ventilation box movable in the outer frame, a sealing cover, a buoyant box and elongate sliding members. The ventilation box has an interior space. The sealing cover has a cover opening, and closes/opens a surrounding space defined by the ventilation box and the outer frame. The buoyant box is disposed within the interior space. When the buoyant box abuts the sealing cover and closes the cover opening, the cover opening is disconnected from the interior space. When the buoyant box moves away from the sealing cover, the interior space communicates the cover opening. The sliding members slidingly contact the outer frame and ventilation box to guide sliding movements.

An automatic aeration device includes a first floating roof, a second floating roof and a movable valve. The first floating roof has a through hole and a first enclosure. The second floating roof is disposed in the through hole and has a second enclosure. The movable valve is disposed above the first floating roof and the second floating roof and has a plate which has an outer wall and an inner wall. The outer wall is mounted in the first enclosure and has a plurality of first vent holes. The inner wall is mounted in the second enclosure and has a plurality of second vent holes. The automatic aeration device further includes a plurality of balls mounted between the first enclosure and the outer wall, and mounted between the second enclosure and the inner wall.

An example valve includes a seat element; an outer piston configured to be seated against the seat element at when the valve is in a closed position to block fluid flow from a first port of the valve to a second port of the valve; an inner piston disposed partially within the outer piston and configured to be seated against the outer piston when the valve is in the closed position to block fluid flow from the second port to the first port; and a setting spring applying a biasing force on the inner piston in a distal direction. The valve can operate in: (i) a first mode of operation wherein fluid is received at the first port and relieved to the second port, and (ii) a second mode of operation, wherein fluid is received at the second port and relieved to the first port.

An expansion tank includes a tank body mounted inside a housing forming a sump, and defining an internal expansion volume. A fluid inlet opening in the tank body is in communication with the sump and the expansion volume. A combination valve may be disposed on a lower end of the tank to control fluid flow between the sump and the expansion volume. The valve may be a combination duckbill valve and umbrella valve. Fluid enters the expansion volume through the umbrella valve when sump pressure exceeds expansion volume pressure by a first predetermined amount, and fluid exits the expansion volume through the duckbill valve to the sump when expansion volume pressure exceeds sump pressure by a second predetermined amount. The tank body may include a cover on which an inlet tube is formed.

A vent valve includes an outer frame, a ventilation box movable in the outer frame, a sealing cover, a buoyant box and elongate sliding members. The ventilation box has an interior space. The sealing cover has a cover opening, and closes/opens a surrounding space defined by the ventilation box and the outer frame. The buoyant box is disposed within the interior space. When the buoyant box abuts the sealing cover and closes the cover opening, the cover opening is disconnected from the interior space. When the buoyant box moves away from the sealing cover, the interior space communicates the cover opening. The sliding members slidingly contact the outer frame and ventilation box to guide sliding movements.

An expansion tank includes a tank body mounted inside a housing forming a sump, where the tank body defines an internal expansion volume. A fluid inlet tube on the tank body has an upper end open to the sump and a lower end open to the internal expansion volume. A single 2-way check valve is located at the lower end of the tube, and fluid enters the expansion volume when the pressure in the sump exceeds the pressure in the expansion volume by a first predetermined amount, and fluid exits the expansion volume to the sump when the pressure in the expansion volume exceeds the pressure in the sump by a second predetermined amount. The check valve may be a combination duckbill valve and umbrella valve. The tank body may include a cover on which the inlet tube is formed.

A hydraulic fluid expansion tank is located inside a housing of a drive device and includes an upper check valve and a lower check valve in communication with a sump located within the drive device and an internal volume of the expansion tank. The tank may also include a vent opening in communication with a vent of the drive device that is in communication with atmospheric pressure.

A flow control valve including a passage, and first and second valve devices disposed in the passage and comprising first and second valve members, valve seats, and seal members, respectively. Each valve member is movable for opening and closing the passage. Each seal member may seal between the corresponding valve member and seat. The first valve member moves in a first direction toward a closing position of the first valve device. The second valve member moves in a second direction, opposite the first closing direction, toward a closing position of the second valve device. The first or the second seal member may include a base portion attached to one of the corresponding valve member and the corresponding valve seat, a lip extending from the base portion, and a turning-up inhibiting device configured to inhibit the lip from turning up when the corresponding valve member is in the closing position.

One embodiment relates to a valve device. The valve device includes: a valve case; a valve element slidably disposed within a valve chamber defined in the valve case; and a positive pressure spring configured to urge the valve element toward a valve seat in the valve case. The valve element includes an outer circumferential portion having a predetermined length extending along an inner circumference of the valve chamber. The outer circumferential portion includes plural opening portions. And, ribs project from the inner circumference of the valve chamber to enter into the opening portions, thereby limiting movement of the positive pressure spring in a radial direction.

An in-line serviceable cutoff valve with excess flow capability includes a valve body and a separable cover. Internal valve components are accessible for service or replacement when the separable cover is removed from the valve body. The internal valve components may optionally be attached to the separable cover so that the separable cover and the internal valve components may be removed as a single assembly.