Working principle of turbogenerator vacuum cut-off valve

The vacuum breaker valve is generally installed on the upper cover of the hydraulic turbine (one on each upstream and downstream side), shaped like a straw hat worn by the farmer's uncle. When the turbine guide vanes are suddenly closed, a vacuum forms in the turbine chamber, causing negative water hammer (water flow returns to the channel chamber), which can easily break the top cover of the turbine and cause a water leak or cause the lighter to lift to damage the equipment. When there is a vacuum, the atmospheric pressure overcomes the spring force in the vacuum cut-off valve, opens the vacuum cut-off valve body, and supplies air to break the vacuum. When the vacuum is destroyed and becomes equal to atmospheric pressure, it automatically closes under the action of the spring, completing a vacuum breaking action.