Spherical vale is used for medium and large power station with the head more than 250m, and has tightly closing and little leakage and the sealing device is not easy to wear.There is hardly any hydraulic loss when it is fully open. The required operating torque is very small when it is started and stopped, and it can be used for emergency closing of dynamic water. The amplitude of spherical valve is smaller than the amplitude of  butterfly valve, but the valve has  large volume,  complex structure, large weight, and  high cost. Spherical valve is generally operated by hydraulic or oil pressure .

 

　　

 

　　

 

　　

 

Sluice valve is commonly used in small power station with a pipe diameter of less than 1m and a high working head. Sluice valve has the advantages of simple structure, convenient maintenance, low cost, small hydraulic loss when fully opened, and good sealing when fully closed, and sluice valve does not start or stop by itself due to the impact of water flow. Therefore, lock device is not required. However, the volume and dead weight are large, when the valve is started and stopped,the required operating force is large, the time is long, and the vibration is strong when the dynamic water is closed.

Sluice valve is composed of valve body, valve cover, valve stem and gate etc. According to the type of valve seat, sluice valve has wedge-shaped seat type and parallel seat type. The wedge-shaped seat type gate is divided into single gate and double gates, and the double gates is divided into two structures: rising stem and non-rising stem.

 

　　

 

　　

 

　　

 

Butterfly valve, called butterfly valve for short, and is widely used in power stations with head below 200m. The butterfly valve mainly consists of cylindrical valve body, discus-shaped valve disc which can rotate around shaft in the valve body, and other accessory parts.

When the butterfly valve is closed, the valve body contact with around the valve disc, to close the passage of water flow. When the valve is opened, the valve disc is parallel to the water flow direction, and the water flows around both sides of the valve disc. The butterfly valve has the advantages of small overall dimension, light weight, simple structure, low cost, convenient operation, and rapid closing under dynamic water. However, the valve disc has the disadvantages of affecting the flow state of water flow, causing hydraulic loss, and large water leakage.