Abstract: A fail-safe system is used in a control unit for opening and closing guide vanes of a pump-turbine apparatus operable in both of pump operation mode and turbine operation mode. The fail-safe system has a wire carried by a rotatable sheave adapted for transmitting an information concerning an opening degree of the guide vanes, a weight suspended from one end of the wire, an operation rod disposed below and in alignment with the weight in the direction of action of the force of gravity, and a change-over valve adapted to be switched by the operation rod. When the wire is cut off accidentally, the weight drops onto the operation rod to depress the latter to switch the change-over valve so that a servo-motor is switched to make the guide vanes close at predetermined rates of change of the opening degree in respective operation modes.

Abstract: A rotary type pumping machine such as a pump turbine in a pumped storage hydro-electric plant, wherein, when the pumping operation of the runner of the machine is started, compressed air is introduced into the runner chamber to depress the water surface in the runner chamber to facilitate the start up of the runner and, when the runner is accelerated to a predetermined speed, the air in the runner chamber is discharged through an air discharge valve to commence the pumping operation. Water pressure available in the water passageway on upper reservoir side of the runner chamber is applied to the valve closing mechanism of the air discharge valve. The valve opening force exerted by a valve operating mechanism and acting on the valve opening mechanism of the air discharge valve is selected to be greater than the valve closing force generated by the water pressure applied to the valve closing mechanism of the air discharge valve.