A non-locking tapered plug valve is provided which prevents taper locking of the plug member by ensuring against pressure responsive plug movement toward the small extremity thereof due to positive or negative hydraulic pressure transients.PLUG VALVES The chambers at each axial extremity of the plug member are of such volumetric relation during positive pressure transients that the chamber at the small extremity of the plug reaches equilibrium with flow passage pressure before the chamber at the large extremity of the plug member thus ensuring that any pressure responsive resultant force acting on the plug member is directed toward its large extremity. To avoid taper locking during a negative pressure transient, Water Power Control Valvesan equalization passage with a check valve is provided to permit unidirectional flow from the large extremity of the valve chamber to the main flow passage.Safety Valves This allows a quicker equalization of pressure between the large extremity of the valve chambers with line pressure, whereas the higher pressure in the small extremity of the valve chamber creates a force on the plug member away from the taper locking direction.

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