Check valve assembly with removable seat

A check valve of the type wherein a clapper is pivotably mounted to be movable between an open position wherein the clapper is spaced from a valve seat disposed in an inlet port to provide flow communication between the inlet port and a valve chamber, and a closed position wherein the clapper abuts the valve seat to block flow communication between the inlet port and the valve chamber, and wherein the clapper and the valve seat are removably mounted so as to be capable of being withdrawn from the valve chamber via an access port having a removable bonnet, an improved apparatus for retaining the valve seat comprising:

• a cylindrical seat retaining section defined at a downstream end of said inlet port and having a first diameter larger than upstream portions of said inlet port, wherein an annular downstream-facing shoulder demarks a transition between said seat retaining section and said upstream portions of said inlet port;
• an annular flange projecting radially from said valve seat and having an outer diameter constituting the largest diameter portion of said valve seat, said outer diameter being larger than said upstream portions of said inlet port but smaller than said first diameter, wherein said flange has an upstream surface disposed adjacent said shoulder and a downstream surface facing said valve chamber;
• wherein said valve seat includes a downstream section extending downstream from said flange and having an outer diameter smaller than said first diameter;
• an interior body portion of said valve having a hanger surface that is both visible and accessible through said access port when said bonnet is removed, said body portion having at least a first retainer bore defined entirely therethrough from said hanger surface and opening into said seat retaining section at a first location just downstream of the upstream surface of said valve seat flange;
• at least a first retainer pin slidably disposed in said first retainer bore and having a length greater than the length of said bore such that one end of the pin abuts said valve seat downstream section while a portion of the pin retains said flange between said pin and said annular shoulder, and such that a second end of said pin extends beyond said hanger surface;
• and
• stop means disposed on said bonnet for projecting into said access opening adjacent the second end of said pin to trap said pin between said stop means and said downstream section of said valve seat and thereby prevent substantial inadvertent longitudinal movement of said pin so as to continuously retain said flange between said pin and said shoulder.

The method of retaining a removable valve seat in place in a valve body comprising the steps of:

• disposing one surface of a radially projecting flange of the valve seat against an annular shoulder in a flow passage of the valve;
• defining first and second retainer bores through an interior body portion of said valve such that one end of each bore opens into said flow passage adjacent a second surface of said flange facing opposite from said one surface, and such that a second end of each bore opens at a hanger surface disposed in proximity to an access port of said valve to render the bores both visible and accessible via said access port;
• slidably disposing first and second retainer pins in said first and second retainer bores, respectively, such that each pin abuts the valve seat periphery at one end and extends beyond said hanger surface at a second end, whereby a portion of each pin is positioned adjacent the second surface of the flange to axially retain the flange between said shoulder and said pin;
• and
• preventing inadvertent lengthwise retraction of said pins into said second end of said bores and out of adjacency with said flange by projecting a stop member from a cover of said access port into adjacent relation with the second ends of said pins.