Guide vane leakage is one of the criteria for judging the installation and maintenance quality of high and medium head hydraulic turbines. Whether it is Francis Turbine or other turbines, the guide vane may leak. During the shutdown of the unit, water leakage from the turbine guide vanes will not only waste water energy resources, but excessive leakage will also affect the normal operation of the unit and cause equipment damage. The specific performance is as follows:
1. Waste of water
Affected by factors such as the reduction of the water supply from the reservoir and the increase in the installed capacity of the power grid year by year, the unit's stand-by time has reached more than 5,000 hours. Based on the leakage before treatment, the power loss of the four units in the year reached 10 million kilowatt hours.
2. Speed up cavitation of guide vanes and flow parts
Due to the existence of the gap between the vane end face and the elevation, when the water flow passes through a relatively narrow vane gap, the water flow speed will change suddenly, which will cause the local pressure to decrease. When the pressure decreases to the vaporization pressure of the current temperature, the air will appear empty. And cavitation, causing damage to the unit's overcurrent components.
3. Affects downtime and even burns tiles
When the unit is stopped, water leakage caused by excessive clearance will have a large jet velocity, especially when the brake air pressure is low or the brake pads are severely worn, the rotating parts of the unit will rotate at low speed for a long time, affecting the The unit shuts down normally, aggravating the wear of each bearing component, and even the bearing bush burned out.
So what is the cause of the leak? Hydraulic Turbine Generator Supplier will come to tell you.
1. Guide vane clearance is too large
In the pre-repair data, most of the guide vane gaps are large, and part of the gap length has exceeded 25% of the total guide vane length. Utilizing the disassembly and overhaul opportunities of the unit, the stainless steel strips of the large and small vertical surfaces of the guide vanes are inlaid with welded stainless steel strips and precision-planed to ensure the sealing requirements of the vertical gaps; under the premise of meeting the technical requirements, the compression stroke of the relay (5 -7 mm).
Casting Guide Vane
After the water guide mechanism is installed and the governor is pressurized, the guide vane surface clearance measurement data is adjusted by reference to the first time after the repair, and the guide vane surface clearance is adjusted by using the 0.05 mm feeler gauge.
2. Guide vane end gap is too large
The surface of the bottom ring is a finished surface. After repeated local repair welding and polishing, the surface of the anti-wear plate of the bottom ring is uneven, which seriously affects the measurement and adjustment of the installation level of the bottom ring. In view of the deformation of the bottom ring, the bottom ring anti-wear plate is returned to the factory for processing 0.30 mm. In order to meet the installation size requirements, a ring groove is processed on the bottom ring anti-wear plate, and an elastic seal is installed to compensate the processing amount. Compensation is made; the end gap is adjusted according to the manufacturer's design lower limit, and the end gap is adjusted according to the lower limit required by the design drawing. At the same time, the guide vanes that affect the end gap are ground, pre-installed, and the entire lower pad of the sleeve is integrated. replace.
After the bottom ring is assembled, the horizontal measurement is performed. The measurement surface of the bottom ring meets the requirements. The parallelism deviation between the top cover and the bottom ring is within 0.05 mm / m, which meets the requirements of the installation technical specifications, and the end surface clearance deviation is small.
3. Guide vane journal seal damaged
The guide vane journal seal is mainly to prevent water in the volute from entering the top cover and to prevent the sediment in the water from entering the sleeve, so as not to wear the journal and the sleeve. It is divided into two types: the middle journal seal and the lower journal seal. Seals are easily damaged during installation and operation, which can cause leakage of the guide vane sleeve. During the maintenance process, it is mainly controlled from two aspects, one is the selection of O-type sealing materials, and the other is the control of the installation quality of seals and water guiding components.
The above is the reason and treatment of the leakage of the turbine guide vane shared by the supplier of Casting Guide Vane, I hope to help everyone.