As mentioned above, the elevation of the tailrace deck generally takes traffic requirements into account. Some are as high as the generator floor, and others are much higher than the generator floor. For example, in the river bed and in power plants located behind a dam. , the leakage channel. The water platform may be flooded below the design flood, but the lifting platform must be located above the design and verification flood.
The water leaking from the upper crown of the Francis turbine wheel through the gap of the anti-leakage ring is generally discharged into the tail water through the hole d evacuation to reduce the thrust of the water. discharged through the top cover opening as cooling water for the unit. Using this type of top cover to collect water can turn losses into efficiency. The water ofThe cooling unit must have a certain pressure and flow. To meet this requirement, the water intake of the top cover and the water height of the power plant, the speed of the unit, the diameter of the channel, the size of. the spacing of the anti-leak ring, the presence or absence of leak holes as well as the size and angle of arrangement of the holes. This is related to the structural form of the main shaft seal, the arrangement has a pump on the channel;