Turbine main valve-2

Release time:

2024-07-22

2. Conditions for installation of main valve

3. Technical requirements of main valve

1) the main valve shall be simple in structure, reliable in operation, small in size and light in weight.

2) the main valve shall be equipped with a tight sealing device to reduce water leakage when it is closed, so as to facilitate the maintenance of components behind the valve.

3) the structure and strength of the main valve and its operating mechanism shall meet the operation requirements and be able to withstand the water pressure and vibration under various working conditions without excessive deformation. In case of an accident of the water turbine generator set, the main valve shall be able to close rapidly under a certain hydrodynamic pressure. The closing time shall meet the requirements of the allowable runaway speed duration of the water turbine generator set and the allowable water hammer pressure of the pressure pipeline, generally not more than 2min; the closing time of the butterfly valve with a diameter of less than 3m, the gate valve with a diameter of less than 1m and the ball valve shall not be more than 1min. The main valve only used to cut off water flow during turbine maintenance can be closed for a longer time, but it must be closed in still water.

4) when the main valve is in the fully open position, the resistance to water flow shall be as small as possible.

Type of main valve

The main valves of hydraulic turbine mainly include butterfly valve, ball valve and gate valve.

1. butterfly valve

Butterfly valve is the most widely used hydraulic turbine main valve.

(1) the butterfly valve is divided into vertical shaft and horizontal shaft according to different device modes. Both types of butterfly valves are in good operation and have been widely used. There is no obvious difference between the two kinds of valves in hydraulic performance, and the manufacturer generally determines the layout form according to their experience and the needs of users.

1) vertical shaft butterfly valve. The valve shaft position in the valve body is vertical, and the valve servomotor and operating mechanism are installed on the upper part of the valve body. Although the thrust bearing is required to support the weight of the valve, resulting in a more complex structure, the overall layout is relatively compact, accounting for a small area of the plant. This is conducive to moisture-proof and monitoring, inspection and maintenance of the operating system, but the lower bearing is easy to deposit sediment, which needs to be cleaned regularly to avoid abrasion or even valve sinking.

2) horizontal shaft butterfly valve is shown in Figure 3-5. The valve shaft position in the valve body is horizontally arranged. Servomotor and operating mechanism are installed on one side of the valve body, and also on both sides of the valve body, with simple structure. As the resultant force center of water pressure falls below the centerline of the valve shaft, when the valve body leaves the middle position, the horizontal shaft butterfly valve will automatically close. However, the servomotor and operating mechanism of horizontal shaft butterfly valve occupy a larger space, and the combination surface of the valve body is mostly in the vertical position, so the operation and maintenance is not as convenient as the vertical shaft type. But its operating mechanism can use the concrete foundation as the foundation without the thrust bearing supporting the valve, so its structure is relatively simple.