A check valve includes a housing defining a pair of valve openings, a pair of flappers pivotably mounted to a pin and such that they are configured to rotate relative to the housing between an open position in which they permit fluid flow through the valve openings and a closed position in which they prevent fluid flow through the valve openings, and an element configured to stop and hold the flappers in the open position. A cavity is formed between the pair of flappers and stop element when the flappers are in the open position. Each of the flappers comprise one or more contact surfaces configured to contact the stop element when in the open position. The stop element has stop surfaces with stationary contact areas configured to oppose and abut the flapper contact surfaces when the flappers are in the open position.

A block forged swing check valve body includes a fully encapsulated seat ring. The swing check valve body includes a through hole and a chamber having a shelf portion defined by a D-shaped passageway. The shelf portion overlies an annular shoulder that encapsulates the valve seat. Methods for the manufacturing and use thereof are also provided.

A block forged swing check valve body includes a fully encapsulated seat ring. The swing check valve body includes a through hole and a chamber having a shelf portion defined by a D-shaped passageway. The shelf portion overlies an annular shoulder that encapsulates the valve seat. Methods for the manufacturing and use thereof are also provided.

A check valve includes a valve body defining a valve bore extending from a first axial end to a second axial end, the valve body including an annular body and a cross member secured to and extending across the valve bore from the annular body on one side of the valve body to the annular body on an opposite side of the valve body, the valve bore at the cross member divided into more than one portion by the cross member; a position block extending from the cross member; a valve member positioned within the valve body and configured to rotate between an open position and a closed position; and a pivot pin extending from the valve member, engaged with the position block, and fixed with respect to the valve member; the valve member and the pivot pin configured to rotate together between the open position and the closed position.

A subsurface safety valve assembly that includes a valve housing comprising a valve seat with a circumference and a seat seal surface. The valve assembly also includes a flapper rotatably connected to the valve housing and comprising a flapper seal surface. The flapper is rotatable into sealing engagement with the seat seal surface in a closed position to form a circumferential surface-to-surface seal. The valve assembly also includes a dovetail groove cut into the seat seal surface or the flapper seal surface and a seal ring held within the dovetail groove and positioned to form a seal against the seal ring when the flapper is in the closed position. The seat seal surface, the flapper seal surface, the dovetail groove, and the seal ring are shaped such that the load on the seal ring is uniform around the seal ring when the flapper is in the closed position.

A subsurface safety valve assembly that includes a valve housing comprising a valve seat with a circumference and a seat seal surface. The valve assembly also includes a flapper rotatably connected to the valve housing and comprising a flapper seal surface. The flapper is rotatable into sealing engagement with the seat seal surface in a closed position to form a circumferential surface-to-surface seal. The valve assembly also includes a dovetail groove cut into the seat seal surface or the flapper seal surface and a seal ring held within the dovetail groove and positioned to form a seal against the seal ring when the flapper is in the closed position. The seat seal surface, the flapper seal surface, the dovetail groove, and the seal ring are shaped such that the load on the seal ring is uniform around the seal ring when the flapper is in the closed position.

The present invention relates to a variable-flow-path air valve for water hammer prevention and a design method. The variable-flow-path air valve includes a valve body with a top provided with an air intake-exhaust port. A ball valve seat and a floating ball are arranged below the air intake-exhaust port. The valve body is provided with at least one swing check valve configured to be opened inward. The swing check valve includes: a swing valve disc connected to a valve body hinge, a variable-flow-path air inlet controlled by the swing valve disc to open and close, a device for limiting the opening degree of the swing valve disc, and a sealing device. In the present invention, the air valve takes in air through the air intake-exhaust port and the variable flow path, and discharges air only through the air intake-exhaust port.

A pressure control valve includes an upper body, a lower body affixed to the upper body, a supply passage in the upper body, a delivery passage in the upper body, an exhaust passage in the lower body and a pivotable member positioned between the supply passage and the delivery passage. The pivotable member has a generally curved body, a first leg, a second leg and a third leg extending from the body. The pivotable member pivots on the second leg and the third leg in response to air pressure in the supply passage being less than the air pressure in the delivery passage. The positioning of the pivotable member restricts air from flowing from the delivery passage to the supply passage, thereby opening a path for the air to pass to the exhaust passage.

A pressure control valve includes an upper body, a lower body affixed to the upper body, a supply passage in the upper body, a delivery passage in the upper body, an exhaust passage in the lower body and a pivotable member positioned between the supply passage and the delivery passage. The pivotable member has a generally curved body, a first leg, a second leg and a third leg extending from the body. The pivotable member pivots on the second leg and the third leg in response to air pressure in the supply passage being less than the air pressure in the delivery passage. The positioning of the pivotable member restricts air from flowing from the delivery passage to the supply passage, thereby opening a path for the air to pass to the exhaust passage.

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.