Plug valves

Claim 1

A PLUG VALVE FOR CORROSIVE FLUIDS AND THE LIKE COMPRISING A METALLIC BODY HAVING A TAPERED BORE EXTENDING TRANSVERSELY THEREOF AND PORTS OPENING INTO SAID BORE IN ANGULARLY SPACED RELATION, A METALLIC TAPERED VALVE PLUG ROTATABLY RECEIVED IN SAID BORE AND HAVING A PORT THERETHROUGH FOR ALIGNMENT WITH SAID BODY PORT, SAID PLUG BEING OF SUFFICIENTLY SMALLER RADIAL DIMENSIONS THAN SAID BORE TO ESTABLISH AN ANNULAR CLEARANCE BETWEEN THE OPPOSED SURFACES THEREOF, MEANS IN SAID BORE DEFINING A POCKET SURROUNDING EACH OF SAID BODY PORTS, EACH SAID POCKET HAVING RADIAL DIMENSIONS GREATER THAN THE RADIAL DIMENSIONS OF THE PORTIONS OF SAID BORE BETWEEN SAID POCKETS, A POLYTETRAFLUOROETHYLENE INSERT RECEIVED IN SEALING RELATION WITHIN EACH SAID POCKET AND HAVING A PORT THERETHROUGH MATCHING THE BODY PORT, EACH SAID INSERT BEING PROPORTIONED TO PROJECT INTO SAID ANNULAR CLEARANCE AND TO ENGAGE A PORTION OF THE OUTER SURFACE OF SAID PLUG TO MAINTAIN SAID PLUG SPACED FROM SAID BORE, SAID BORE INCLUDING A RADIALLY DISPOSED PERIPHERAL WALL EXTENDING COMPLETELY AROUND EACH POCKET, EACH SAID INSERT AND CORRESPONDING POCKET COOPERATING WITH SAID PLUG TO PROVIDE A RELATIVELY HIGH PRESSURE SEALING AREA COMPLETELY SURROUNDING EACH BODY PORT, MEANS COOPERATING WITH SAID BORE AND SAID PLUG TO PROVIDE A LOW PRESSURE SEAL AREA SURROUNDING SAID HIGH PRESSURE SEAL AREA FOR PERMITTING LATERAL EXPANSION OF EACH SAID INSERT IN RESPONSE TO INCREASES IN TEMPERATURE, EACH SAID POCKET INCLUDING AN EXPANSION SPACE SUBSTANTIALLY COMPLETELY SURROUNDING AND SPACED FROM THE CORRESPONDING BODY PORT, SAID EXPANSION SPACE HAVING A RADIAL DIMENSION GREATER THAN THE RADIAL DIMENSION OF SAID POCKET AND COOPERATING WITH THE PLUG TO PROVIDE A LOW PRESSURE SEAL AREA SPACED FROM THE CORRESPONDING BODY PORT, THE SPACE BETWEEN SAID EXPANSION CHAMBER AND THE CORRESPONDING BODY PORT PROVIDING IN COOPERATING WITH SAID INSERT AND SAID PLUG A HIGH PRESSURE SEALING AREA WHICH SURROUNDS SAID CORRESPONDING BODY PORT, AND MEANS URGING SAID PLUG INTO SAID BORE COMPRESSING EACH SAID INSERT IN SAID POCKET AND BETWEEN SAID BORE AND SAID PLUG TO ESTABLISH A SEAL THEREBETWEEN.