Plug valves

Claim 1

A PLUG VALVE FOR CORROSIVE FLUIDS AND THE LIKE COMPRISING A VALVE BOGY INCLUDING MEANS DEFINING A BORE AND PORTS OPENING INTO SAID BORE IN ANGULARLY SPACED RELATION, A VALVE PLUG ROTATABLY MOUNTED IN SAID BORE AND HAVING A PASSAGE THERETHROUGH ADAPTED FOR ALIGNMENT WITH SAID BODY PORTS, OPERATING MEANS FOR ROTATING SAID PLUG SELECTIVELY BETWEEN OPEN AND CLOSED POSITIONS, SAID PLUG BEING OF SUFFICIENTLY SMALLER RADIAL DIMENSION THAN SAID BORE TO ESTABLISH AN ANNULAR CLEARANCE SPACE BETWEEN THE MATING SURFACES OF SAID PLUG AND OF SAID BORE, AT LEAST ONE OF SAID MATING SURFACES BEING TAPERED IN THE ORDER OF 1* TO 5* TO PROVIDE FOR VARIATION OF SAID CLEARANCE SPACE IN RESPONSE TO APPROPRIATE MOVEMENT OF SAID PLUG IN SAID BORE ALONG THE LONGITUDINAL AXIS THEREOF, MEANS MOUNTED ON ONE OF SAID MATING SURFACES AND RELATIVELY MOVABLE WITH RESPECT TO THE OTHER OF SAID MATING SURFACES FOR MAINTAINING A FLUID TIGHT SEAL BETWEEN SAID PLUG AND SAID BODY IN THE CLOSED POSITION OF SAID PLUG AND FOR SURROUNDING THE CONNECTING PORTIONS OF SAID PORT AND SAID PASSAGES IN THE OPEN POSITION OF SAID PLUG, SAID SEAL MEANS INCLUDING A CORROSION RESISTANT MATERIAL OF RELATIVELY LOW COEFFICIENT OF FRICTION WITH RESPECT TO SAID PLUG AND SAID BODY AND HAVING A THICKNESS DIMENSION SUFFICIENT TO MAINTAIN SAID MATING SURFACES IN SPACED RELATION, AN ELASTICALLY COMPRESSIBLE SEALANT INTERPOSED BETWEEN SAID SEAL MEANS AND SAID PLUG IN A LONGITUDINAL FACE TO ESTABLISH A FLUID TIGHT SEAL THEREBETWEEN, AND MEANS OPERATIVE ON SAID PLUG TO URGE SAID PLUG IN A LONGITUDINAL DIRECTION CREATING A RADIALLY DIRECTED FORCE SUFFICIENT TO EFFECT A SEAL BETWEEN SAID SEAL MEANS AND SAID OTHER MATING SURFACE, SAID RADIALLY DIRECTED FORCE BEING INSUFFICIENT TO EFFECT A SEAL BETWEEN SAID SEAL MEANS AND SAID ONE MATING SURFACE IN THE ABSENCE OF SAID INTERPOSED SEALANT FOR REDUCING THE FRICTION BETWEEN SAID SEAL MEANS AND SAID OTHER MATING SURFACE THEREBY REDUCING THE TURNING TORQUE REQUIRED FOR SAID OPERATING MEANS.