(under subclass 84.1) Reciprocating member seal wherein the flow prevention device is rotatable (via bearings) and is sensitive to excessive well bottom pressure.
SEE OR SEARCH CLASS
251, Valves and Valve Actuation,
1.1+, for blowout preventers of the type comprising plural relatively movable flow obstructing members controlling flow through the annular passage between an inner rod or pipe and a surrounding casing or tubing head and having characteristics which go beyond a mere packing means. Addition of a lateral port in a casing head structure for diverting flow from the well is enough to cause classification in Class 166, but Class 251 takes blowout preventers or other valves in appropriate subclasses even though the valve is operated by the well fluid pressure or even though there are plural valves and broad recitations of casing or casing head structure.
