Abstract: A valve having a body with an inlet duct, an outlet duct and a plug rotatably disposed in the body. The plug has a port to provide for fluid communication between the inlet and outlet ducts and is movable between an open position wherein the port at least partially registers with both the inlet and outlet ducts to pass fluid through the valve to a closed position wherein no part of the port registers with the ducts, thereby preventing fluid from passing through the valve. The valve has a pressurizable seal between the body and plug, when the plug is at both the open and closed positions. To actuate the seal, a closed hydraulic system is provided. A regulator piston is urged against the pressure of the hydraulic system with a preselected force to regulate the hydraulic pressure. The valve also includes a mechanism to compensate for hydraulic fluid thermal expansion.

Abstract: A rotary plug valve has hydraulically actuated seals for sealing between a valve body and a rotatable valve plug. The valve plug is rotated to open or close the valve. A valve handle for turning the plug can be rotatably uncoupled from the valve plug when the valve is closed and turned relative to the plug toward an overtravel position to actuate a hydraulic piston to pressurize the seals. A second piston regulates pressure to the seals and prevents overpressurization.

Abstract: A plug valve, especially for use in lines carrying abrasive materials and materials at high temperatures and pressures. The valve body is rotatable in a valve casing having inlet and outlet ducts to bring a port in the valve body into communication with the inlet and outlet ducts. Recesses are provided in the valve body wall for closely fitted sealing plugs. The outer faces of these plugs conform to the wall of the valve body. A fluid reservoir within the valve body is connected to the recesses by passageways. A moveable piston is provided in the reservoir to force hydraulic fluid under controllable pressure into the spaces between the rear wall of the recesses and the sealing plugs, thereby permitting the sealing plugs to be maintained in fluid-tight contact with the inner wall of the casing.