A backflow prevention device includes a main pipe body extending along a first center longitudinal axis, at least one check valve disposed within the main pipe body, an inlet pipe connected to an inlet side of the main pipe body, and an outlet pipe connected to an outlet side of the main pipe body. The inlet pipe and the outlet pipe extend along a second center longitudinal axis. The first center longitudinal axis is offset with respect to the second center longitudinal axis in a direction perpendicular to the first and second center longitudinal axes. A center of the valve seat of the at least one check valve is offset with respect to the second center longitudinal axis in the direction perpendicular to the first and second longitudinal axes.

A backflow prevention assembly includes a body forming two buckets, wherein flow passes through the body from an inlet to an outlet along an axis and consecutively through each of the buckets. A single zone test cover encloses a first of the buckets to form a single zone chamber. A dual zone test cover encloses a second of the buckets with a dual zone cartridge assembly therein. The dual zone test cover has two test cocks. The dual zone cartridge assembly includes a frame having a valve seat, wherein the frame includes a lumen providing fluid communication from a dual zone chamber upstream of the valve seat to a first of the two test cocks of the dual zone test cover, and wherein the second of the two test cocks of the dual zone test cover is in fluid communication with the dual zone chamber downstream of the valve seat.

A check valve for a backflow prevention assembly includes a linkage with a platform having a proximal end and a distal end and a first coupling member supported by the platform for engaging a bias assembly. A stop protrudes from the proximal end of the platform to engage a frame of the check valve for limiting travel of the platform. A branch depends from the proximal end of the platform, the branch having a hinge pin configured to nest in a slot defined by check valve. A second coupling member depends from the distal end of the platform for engaging a valve member.

A backflow blocking apparatus for axial fans may be provided. The apparatus may comprise a sheet. The sheet may comprise a first section and a second section. The first section may comprise a plurality of flaps cut out of and retained by the first section of the sheet. The second section may comprise a guard structure. The apparatus may further comprise a fold about which the first section and the second section are folded on one another. The guard structure may inhibit the movement of the plurality of flaps in a direction toward the guard structure when the first section and the second section are folded on one another.

Disclosed is an air mix valve including: a wall having at least three openings; and at least one airflow-regulating device. The airflow-regulating device includes: at least two shutters placed in the internal volume of the valve, at least one aerodynamic shutter of which is arranged with respect to one of the openings so as to be able to receive an airflow passing through this opening, and a linking mechanism between at least two shutters. Each of the shutters is arranged and guided so as to be able to be caused to move with respect to the wall. At least one airflow-regulating device, named aero-controlled regulation device, is mounted to be freely movable under the effect of aerodynamic energy from airflows passing through the openings.

An apparatus to allow or stop an air flow into an enclosed environment or piping system comprises (a) a housing, (b) a first valve seat, (c) a first sealing member, (d) a second valve seat, (e) a second sealing member, (f) at least one locking mechanism configured to limit a movement of the first sealing member and/or the second sealing member; wherein the first sealing member moves away from the first valve seat when the second pressure is greater than the first pressure in a predetermined pressure difference; wherein the second sealing member moves away from the first valve seat when the third pressure is greater than the second pressure in a predetermined pressure difference; wherein the first pressure communicates with a system pressure in the piping system; and wherein the third pressure communicates with an ambient air pressure.

A valve assembly with a spring retention assembly including an elongated cylinder portion having an open threaded end and a closed end and an elongated piston portion having a free end and a threaded tab end configured to thread through the open threaded end and, thereby, be slideably captured in the cylinder portion. A spring couples to the body portion and the piston portion to provide a force to urge the body portion and the piston away from one another, wherein the closed end and the free end are similarly shaped so that the spring retention assembly can be reversibly mounted to a valve member that can also be reversibly mounted.

A butterfly valve includes a valve body and valve clack in the valve body. The valve body is installed with at least one sprinkler connected to an inlet valve outside the valve body for purging the inner surface of butterfly valve in the middle of the valve clack is a horizontal drainage tray, one end of which is closed and the other is water outlet, and the valve clack is equipped with at least one drain hole connected to the drainage tray; the sprinkler is above the drainage tray. This invention can be filled with corresponding media for online cleaning, sterilization and drying of non-sterile areas of a butterfly valve group after conveying the powder to realize repeated butt-joints.

A variable valve may include a housing having hinge support portions protruding from a first side thereof, and an opening at a second side thereof, a first gate rotatably coupled to the hinge support portions so as to open and close a part of the opening, a first spring mounted on the housing to apply elastic force in a direction in which the first gate is closed, a second gate rotatably coupled to the hinge support portions so as to open and close a remaining part of the opening, and a second spring mounted on the housing to apply elastic force in a direction in which the second gate is closed, in which the first spring and the second spring may have different spring constants.

A gate valve for positioning in the open upper end of a grain bin below the lid thereof which closes the open upper end of the grain bin. The gate valve permits grain to pass downwardly therethrough but which prevents warm moist air from the grain bin from passing upwardly therethrough into a grain spout or deadhead box.