Compact hybrid triple seal for reversible gate valve and method

A gate valve assembly comprising:

• a valve body defining a throughbore;
• a gate movable within said valve body between an open position and a closed position;
• and an upstream seat and a downstream seat, each seat positioned between said gate and said valve body, wherein each seat comprises:
• a metal seat body, a first outwardly extending flange and a second outwardly extending flange;
• a single unidirectional seal positioned between said first outwardly extending flange and a pocket end of said seat, said unidirectional seal having an opening oriented away from said gate;
• a single bidirectional seal positioned between said first outwardly extending flange and said second outwardly extending flange;
• and
• wherein, when said gate is in said closed position, said unidirectional seal on said upstream seat provides a primary seal against an upstream fluid pressure, said bidirectional seal on said upstream seat provides a secondary seal against said upstream fluid pressure if said primary seal leaks, and said bidirectional seal on said downstream seat provides a tertiary seal against said upstream fluid pressure if said primary seal and secondary seal leak.

A gate valve seat assembly for a bidirectional gate valve having a throughbore and a gate movable between an open and a closed position, said gate valve seat assembly comprising:

• a metal seat body having a metal-to-metal gate seal end and a pocket end;
• a first outwardly extending flange and a second outwardly extending flange radially extending from said metal seat body;
• a single unidirectional seal positioned between said first outwardly extending flange and said pocket end, wherein an opening of said unidirectional seal is oriented towards said pocket end;
• a single bidirectional seal positioned between said first outwardly extending flange and said second outwardly extending flange;
• and
• wherein the combination of said unidirectional seal and said bidirectional seal on said seat forms a hybrid seal arrangement configured to provide a triple seal against fluid pressure when combined with a complementary seat assembly in a gate valve, regardless of the gate valve's installation orientation.