| CPC F16K 1/465 (2013.01) [F16K 1/14 (2013.01); F16K 1/2263 (2013.01); F16K 1/54 (2013.01); F16K 27/0245 (2013.01)] | 16 Claims |

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1. A valve assembly comprising:
a valve body;
a control shaft coupled to said valve body for rotational movement relative to said valve body;
a valve element coupled to said control shaft for movement in conjunction with said control shaft relative to said valve body through a range of positions between and including a closed position and an open position, said valve element having an outer valve surface defining an outer radial diameter; and
a valve seat disposed in said valve body and comprising:
a cylindrical body portion having an inner seat surface and an opposing outer seat surface, said inner seat surface defining an inner radial diameter, and
at least one seal disposed around said opposing outer seat surface sealingly coupling said valve seat to said valve body,
wherein said cylindrical body portion is formed from a polymeric material which maintains dimensional stability at temperatures ranging from −40° C. to 66° C. and which is configured to self-adjust said inner radial diameter to correspond to said outer radial diameter of said valve element to maintain a portion of said inner seat surface in contact with said outer valve surface of said valve element through said range of positions.
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