Brief introduction to technical transformation of hydropower generating unit of Gezhouba Power Plant Wang Jianzhong, Lu Jinyu (Gezhouba Hydropower Plant, Yichang, Hubei 443002) Some improvement measures and transformations have been made for the reasons for this, and good results have been obtained. The governor was replaced with an SJ-shaped relay. Due to the small stiffness and large piston leakage, the four swinging relays were replaced in the retrofit to ensure stable operation of the unit. After the outer edge of the turbine blade is added to the skirt, not only the vibration is reduced, the gap cavitation is reduced, and the efficiency is improved in some working conditions. The thrust bearing bush is replaced with an elastic metal plastic tile, which has a large carrying capacity. The coefficient of friction is small. The installation process is simple, the transformation is successful, but there are still hidden dangers of burning tiles. The anti-wear protective layer of the turbine has received some effects, but the erosion of the strong cavitation zone of the central ring and the blade has not been effective. I: TM312 (263): The operation of the B 1 hydro-generator set is 20 years running, and the overall situation is good. But there have also been some problems. For example, in the initial stage of commissioning, the 170MW unit was not stable enough, and there was a accident of burning the bearing bush; the vibration and swing were large when running in the no-load and low-load areas; the cold vibration of the generator was too large.
After optimization and modification, these defects were eliminated, and no abnormality occurred for a long time under the head of more than 23 m. 125MW unit has been tested by various working conditions and related experts' research and discussion. The output of the unit has potential to be excavated and can exceed the line operation. The turbine output can reach 138MW at rated working point and the generator can reach 134~135MW. Since 1987, the original output limit line has been modified, and the unit has exceeded the force line during the flood season, so that the time with the rated load of the unit is extended by about 60d, and the annual power generation is 700 million to 1 billion kW *h. During the operation, it was found that the output of the unit still had a large margin. Regardless of the 170MW unit or the 125MW unit, after various working conditions, the vibration, swing, the temperature of the three bearings and the stator core and coil temperature are within the allowable range of the design; the average operating hours of the 21 units The number reached 6 000h, the maximum operating hours of the year exceeded 8000h, far exceeding the design value, and the available hours of the unit were more than 7000h; by the end of 2001, the accumulated power generation was 264.6 billion kWh. 2 The sediment wear situation was controlled on the dam of the Gezhouba Water Control Project. The drainage area is 1 million km\about A5a%c of the whole basin, the average annual im300, m3/s runoff is 425.9 billion m3, the measured maximum inflow rate is 72000m3/s, the minimum inflow is 2 kg/m3, and the annual sediment transport is 5.26. The total storage capacity of the billion t is 1.57 billion m3. Since the Gezhouba Hydropower Plant is located in the lower section of the Nanjinguan bend, the sediment is laterally displaced by the circulation of the curve, and the sediment at the bottom is large, and the sediment with large particle size is convex. The right side of the shore moves, and the surface water moves toward the concave side of the river. The distribution of the size of the sediment is proportional to the distribution of the sediment content of the machine. The more the unit on the right bank, the more severe the erosion of the overcurrent components. The law is: the two rivers are small and thin, the river is large and thick, and the river is The sediment concentration of the power plant is 0.94~0.98 times of the average value of the section (Yichang), 1.37 times of the No. 18 machine, 1.6 times of the No. 21 machine, and the No. 18 machine of the machine is the No.1 of the Second River. ~20 times, the 21st machine is 1.2~2.9 times; the maximum particle size is 0.62mm. The annual amount of sand per machine is about 15 million tons. The cavitation and sediment wear of the turbine are mainly manifested by sediment wear and airfoil cavitation on the front and back of the blade; secondly, the “edge†of the outer edge of the blade and head abrasion. Although the ring in the blade and the runner chamber is made of anti-abrasion stainless steel material, the gap cavitation of the blade and the sediment wear of the overcurrent component still exist, and it increases with the increase of the running time. In order to reduce the damage of the flow component of the unit by the sediment flow, the overcurrent components such as the blade, the hub, the connecting body, the drain cone, the movable vane, the fixed vane, the bottom ring, the upper ring and the lower ring are coated with epoxy. Deputy Chief Engineer of Emery Dam Hydropower Plant; Lu Jinyu (1959-) male, Fuyang, Hubei, senior l work! Wang Shi b Ge 5 Zhou Yu. General and engineer of the dam water power plant maintenance branch. _ paint protection layer; blade outer edge plus skirt; provisions 17 ~ 21 unit is not allowed to exceed the force limit line operation, that is, according to the rated load of 125MW; reasonable use of the unit sand bottom hole, sand hole The sand sluice gate greatly reduces the abrasion of the overcurrent components. After 20 years of practice, these methods are effective, extending the service life and maintenance cycle of the overcurrent components and ensuring the stable operation of the unit.
3 Water turbine generator set retrofit 3.1 Problems and treatment measures 3.11170MW unit problems. 1 thrust bearing burn accident; 2 vibration and swing of the unit in the no-load and low-load area; 3 cold vibration of the generator is too large; 4 large shaft seal issuance; 5 blade "X" seal oil leakage; The shear pin is cut, the water guide leaf is out of control, and so on.
Treatment measures. The circumferential eccentricity of the large thrust bearing bush improves the reliability of its operation; eliminates the insulating spacer of the water guiding tile, the size of the large chrome steel spacer, reduces the adjustment gap of the water guiding tile, and enlarges the vacuum breaking valve The spring force and the reinforcing block are added at the gap between the supporting cover and the top cover, and the upper bearing bush support seat is thickened to reduce the vibration and swing of the unit; the improved double-plate seal replaces the end face seal of the large shaft, so that the large shaft The seal can operate reliably; replace the centrifugal top cover pump with a submersible pump to ensure the drainage of the top cover; the large blade "X" seals the tight ring spring force and clearance, changing the size of the "X" seal, effectively solving The problem of oil leakage in the blade; the water guide blade is equipped with a full-close limit stop, and the water guide leaf will not reverse after the shear pin is cut.
There are problems. 1Responsive bearing is easy to damage; 2The oil guide cooler leaks; 3The oil collector floating tile is easy to wear; 4The generator stator core pressure finger is pulled out; 5The flat plate seal operation is unreliable; 6 blade "X"
Sealing oil leakage; 7 shear pin shearing, guide vane out of control; 8 repair seal (air shroud) can not seal; 9 guide vane sleeve leaking; 10 pivot and bamboo 400 copper tile wear, strain, misalignment; control loop The side and bottom anti-wear blocks fall off, the operating frame and the connecting rod connecting pin are released; 3 the top cover pump and its float are unreliable; 1 the three bearings have oil leakage inside the retaining cylinder.
Treatment measures. Replacing the original bearing housing with the integral return bearing seat improves the reliability of the return bearing operation; replacing the box cooler with a serpentine tube cooler, the problem of water leakage is cured; the end face of the floating tile of the oil receiver is reduced Pressure, change the matching clearance, so that the problem of easy wear of the oil floater is alleviated; open the lubricating water tank on the upper and lower rubber flat sealing surfaces and lubricate it to improve the running reliability; replace the liquid centrifugal top with a submersible pump The cover pump makes the operation more reliable; the large blade "X" seals the tightness of the ring gap, changes the size of the "X" seal, and solves the problem of oil leakage of the blade; the guide vane is equipped with a full-close limit stop in the maintenance. Application has played a very good role.
3.2 Governor The whole plant except the governor of No. 21 machine is imported, and the other 20 machines are domestic equipment. The ESC is an analog circuit electro-hydraulic governor; the main problems in the DST line of the cabinet are: 1 bell-type electro-hydraulic converter is poor in oil resistance, easy to block, card issuance, and the position is easy to change; 2 cam type machinery The coordination device has large error and slow operation; the electrical association adjustment and setting value are easy to change; 3 power supply and frequency give the motor action dead zone; 4 electrical connector and adapter terminal contact is unreliable; 5 electrical anti-interference ability is poor, The components are aging and damaged.
In order to solve these problems, and make the governor realize remote and local manual and automatic operation, adapt to the requirements of computer control, and lay the foundation for unattended (less people on duty), the electrical cabinet of 125MW unit of Erjiang Power Plant is selected from Nanjing Automation. The DTJ*150/4*E1 mechanical cabinet produced by SJ is equipped with strong functionality, strong adaptability, strong protection ability and self-checking ability, intelligent debugging, high reliability and good stability of the device. The water energy utilization rate is high; the cabinet adopts standardization, localization and integrated hydraulic components, and the processing precision is high, the control oil pipeline is greatly reduced, the layout is reasonable and simple, the outer cover is beautiful in design, the operation mode is flexible, and the switch has no impact disturbance, which has reached the expected aims.
On this basis, our factory has made a new attempt. The electric cabinet uses the WBST-A microcomputer stepper motor governor developed by Gedianda and the BST*150 mechanical cabinet (the DTJ*150/4*E1 cabinet). The improved version has been modified with 16 machines. The microcomputer of the electric cabinet adopts high-reliability programmable controller and digital frequency measuring board to overcome various problems of the analog circuit. The ladder language is easy to read and easy to modify. The main control functions absorb the current domestic and international speed controllers. The advantages of the whole system are simple structure, perfect function and good performance; the mechanical cabinet is simpler and clearer than DJT*150/4*E1, and the manual automatic switching solenoid valve is cancelled, the load reducing solenoid valve is reduced, and the oil pipeline is less. The electro-hydraulic converter and the medium-indirect force device were replaced by stepping motor and lead screw, thus overcoming the inherent problems of the original mechanical cabinet, and its main technical performance has reached the international advanced level.
3.3 Over-current parts anti-abrasion protection block shear pin shears, water guides will not reverse, etc. Some measures lish solder paste protection exhibition test; -80 US, ester protective layer test unit over-current parts anti-abrasive material test, from 1983 At the time of the overhaul of the No. 3 machine in March of the year, the epoxy mortar anti-wear test was carried out on the flow-through parts of the unit; the spray-welding Nh-3 powder material protective layer test; the castor oil interpenetrating network polymer composite material Protective layer test; epoxy emery protective layer test; cold epoxy protective layer test; cermet protective layer test; Ni67, Ni180A alloy powder HH893-1 type coating protective layer test; double-layer nylon protective layer test; Amide-polyurethane protective layer test; US DP, DL protective layer test; US epoxy emery protective layer test; titanium alloy patch and other materials powder metal spraying test. After 1~2 flood seasons, most of the materials in these tests were not enough due to insufficient adhesion to stainless steel blades or problems in the construction process and defects in the test materials, and even the blades suffered different degrees of abrasion, and the blades were added. Check the repair and polishing workload. The relatively successful test materials are the National Invention Award and the patented Epoxy Emery Anti-Abrasion Material of Shanxi Water Science Institute, Tianjin Institute of Survey and Design, and the Yellow River Water Division. The anti-abrasive material coating on the unit's over-current components The four-year retention of the fixed part (except the ring in the runner chamber) is over 90%; the protection effect on the back of the blade is not ideal, about 80%, and the 4-year retention of the strong cavitation area on the back of the blade is zero. Therefore, the protection of the ring and the back of the blade in the runner chamber is currently a problem to be solved.
3.4 Elastic metal plastic thrust bearing shell Elastic metal plastic thrust bearing bush (hereinafter referred to as “fluoroplastic tileâ€) is adopted by many hydropower plants after the 1990s due to its comprehensive technical index and performance higher than that of the babbitt thrust tile. The tile is processed at the factory once, and does not need to be processed at the installation site, which simplifies the installation process; its friction coefficient is small, the bearing capacity is large, the bearing loss is reduced, and the water-cooled tile system and the high-pressure oil load shedding system are eliminated, simplifying The thrust bearing structure is easy to overhaul, and at the same time reduces water energy and power consumption, simplifies operating conditions and reduces labor intensity. Therefore, in early 1990, our factory introduced three sets of thrust bearings mounted on the 170MW and 125MW units of Erjiang Power Plant from the former Soviet Union. The test and operation results were satisfactory. With the introduction of fluorine plastic tiles in the former Soviet Union, domestic counterparts are optimistic about their application prospects, and have conducted research in succession and successfully tested on thrust bearings of some large and medium-sized units. Our factory has applied the latest domestic scientific research results without exception. It has introduced 11 sets of fluoroplastic tiles installed on the thrust bearings of 125MW units. The early domestic fluoroplastics were relatively stable, and domestically installed from the end of 1996 to the beginning of 1997. The fluoroplastic tile is unstable in operation and a bush burning accident occurs. Two sets of fluoroplastic tiles were burned in Russia, and the casing of the No. 2 machine produced a large accident of worn mirror plates. Both sets of bushings were scrapped; 6 sets of domestic bushings were burnt, and 5 sets of cracks were generated. Plastic tile quality problems. From the situation of burning tiles and the situation of domestic fluoroplastic tiles currently running in our factory: the design and manufacturing process of domestic fluorine plastic tiles need to be further explored and optimized to make them perfect; manufacturers need to establish a set of effective Process guarantee system to ensure the quality of fluoroplastic tile products; also need to select or develop the measurement system of the temperature and oil temperature of the elastic metal plastic bearing bush to prevent the accident from expanding; at the same time, it is necessary to establish an effective operation, Maintenance specification, with 3.5170 MW unit control ring and ring-type relay 170MW unit turbine control ring due to small rigidity and large deformation, the annular relay piston has serious oil leakage. Although it has been treated many times, the fundamental problem has not been solved, which directly affects the stability of the unit. run. To this end, our factory has completely remodeled it, replacing the control ring with small rigidity with the newly designed control ring; replacing the ring relay with 4 back-to-back rocking relays to ensure stable operation of the unit.
3.6 The outer edge of the turbine blade plus the 170MW unit of the skirt. Since the power generation has been put into operation, the flow conditions in the no-load and low-load areas are not good, the vibration of the unit is large, and the normal operation of the unit is restricted, and the gap clearance of the 170MW and 125MW units is severe. . To this end, the relevant tests were conducted at Huazhong University of Science and Technology. Tests have shown that the outer edge of the blade plus the skirt can not only reduce the vibration, reduce the cavitation of the gap, but also improve the efficiency in some working conditions. In 1993, during the extensive overhaul of the 170MW unit, the scientific research results were implemented on the unit. After the start-up operation, the vibration of the unit's no-load and low-load areas was significantly reduced, meeting the requirements of the normal operation of the unit. This achievement has been promoted and applied throughout the plant.
3.7 Oil receiver floating tile In the 21 axial flow propeller turbines of our factory, there are three floating tiles between the oil receiver and the operating oil pipe. The copper tile structure can be self-aligned with the swinging of the operating oil pipe, which can not only improve the sealing performance of the pressure oil, but also slow down the disadvantages of operating the oil pipe, and play the role of isolating the oil path and guiding. However, this type of floating tile did not play its due role during use. During the operation, the wear of the tile surface is extremely serious, which directly threatens the safe operation of the unit. At the beginning of the production of the 125 MW unit, the lower floating dam of the oil receiver showed severe wear. In this part of the design and manufacturing process of the unit, this factor was considered, and some improvements were made, such as operating the oil pipe bracket, changing the size of the floating tile, etc., but this still has not solved the wear problem from the root. There are two main reasons for the analysis.
Positive pressure is too large. Since the upper end surface of the floating tile under the oil receiver is in communication with the operating pressure oil, the lower end surface can be regarded as an oil discharge chamber, which forms a large pressure difference at both ends of the tile, and the positive pressure acting on the floating tile is about 300 kN. It is impossible for the floating tile to perform self-leveling floating under such a large pressure. In fact, the operating oil pipe is swung in the whole position.
Make it run, repair and have a CJ leg 丨 E* touch toe to produce contact friction, rig is the root cause of wear such as processing doubts notebook2 design gap is too small. The design clearance between the floating tile and the operating oil pipe is 00H7//7, that is, the double-sided clearance is between 0.068~0.194mm. The design only considers the seal on the oil circuit, and neglects that the floating tile should also be a guide bearing. A small gap will cause the temperature of the oil to rise and reduce the load carrying capacity of the oil film, which will also cause the journal and the bearing shell to expand. In addition, the operating oil pipe will inevitably have inclination and different degrees of heart during installation. The local pressure will be reduced between the two, and the sealing area of ​​the lower end of the floating tile will be reduced. At the same time, the large matching clearance will be 0.068~0.194. Mm is changed to 0.20~0.25mm; seal oil ring is added; three 5mmX 3mm labyrinth grooves are evenly distributed in the middle of the floating tile.
3.8 Spindle seal The main shaft seal of the turbine adopts double-layer rubber flat seal structure. When the sealing device was just put into operation, the plate was worn four times in less than 2000 hours, and it was forced to be shut down for maintenance. During operation, the water pressure is extremely unstable. The pressure gauge indicates that a vacuum of 2 104 Pa (200 mmHg) sometimes occurs, sometimes a pressure of 0.2 MPa occurs. The water seal device sometimes emits smoke and emits a scorching odor of rubber, and seals often occur. The failure and leakage of water seriously threaten the safe operation of the unit. The main reason is that the design only emphasizes the "sealing" and neglects the necessary cooling lubrication between the two friction surfaces, so that the rubber plate and the anti-wear ring continuously friction and heat, resulting in the wear of the plate. To this end, our factory began to explore its improvement program. First, we opened 24 wedge-shaped grooves on the rubber plate, which were evenly distributed on the circumference of the plate. The wedge-shaped groove was angular, gradually became shallower in the direction of water flow, and did not open the plate radially, the maximum depth. Approximately 25 mm so that the water in the tank enters the plate for lubrication and cooling. In addition, a support plate is arranged under the rubber plate so as to suspend only 20 mm, so that the rubber plate has good flatness without being deformed by self-weight sinking. After this improvement, it has received relatively good results in the operation of each unit. In order to no longer open the wedge groove in the inspection and replacement plate and transfer the groove to the metal anti-wear ring, the sealing device is thoroughly optimized, thus ensuring the safe operation of the unit.
Since the commissioning of the 3.9 water guide vane block unit, due to the large amount of debris in the incoming water, the phenomenon that the individual guide vane shear pins have been cut off has been caused by the timely treatment and has not affected the safe power generation. There have been 13 machine guide vane shear pins that have been cut off and out of control. The unit has reversed about 15~201/min and was forced to close the upstream import work gate and the unit stopped rotating. From the design point of view, the guide vane has self-closing ability, and the opening degree is 58%~40%. During the closing of the uncontrolled vane, the head may collide with the adjacent uncontrolled guide vane tail; the opening is 40%. At ~32%, the tail of the uncontrolled vane may collide with the tail of the adjacent vane; when the opening is below 32%, the uncontrolled vane may collide with the head of the adjacent uncontrolled vane. In the original design, each water guide of the turbine was provided with a limit block that prevented the opening from being excessively welded to the bottom ring.
However, the limit block is only 50mm in length and has a semi-circular arc with a height of about 20mm, and most of them are welded only in the arc segment, and the strength is low, which does not limit the excessive opening of the uncontrolled guide vane. In fact, in this accident, the limit blocks of the uncontrolled vanes were completely knocked out, leaving only the resistance plant to set a solid limit block at the bottom of the guide vane or the bottom ring to prevent the guide vane. Out of control to open or close the opening limit. This program has been implemented on all units.
3.10 runner blade seal unit The runner blade seal device adopts the traditional “in†type seal. At the initial stage of operation, there was a serious oil leakage phenomenon. According to a series of decomposition inspections and maintenance treatments conducted on this issue, our factory believes that the structural design of the type of seal is successful, and the application on the rotary turbine is also feasible, which causes the turbine runner of our factory to leak oil. The key is that the understanding of the sealing device is not sufficient. The selection of some technical parameters in the design is not reasonable, so the sealing effect is not achieved. The reasons for the oil leakage of the unit runner are summarized as follows: 1 The force of the top tight ring spring is too small. 2 The clearance between the top tight ring and the sealing groove is too small. During the operation, the blade sinks due to the self-weight of the blade and the water thrust, so that the top tight ring is partially stuck and the spring force can not be freely moved. Passed to the seal. The inner diameter of the 3"X" seal is too small, and the length of the seal selected by the design is smaller than the circumference of the blade pivot, so that the seal is easily rotated with the pivot during operation, resulting in partial elongation or deformation of the seal. Tearing.
For the above reasons, the following comprehensive treatment measures have been taken during the maintenance: 1 Increase the pressure of the top ring spring to make it equal to the water pressure acting on the seal. 2 Increase the clearance between the top tight ring and the sealing groove, so that the inner and outer gaps of the top tight ring are each 1, to ensure that the top tight ring moves freely after the blade sinks and the copper sleeve wears; 3 increase the inner diameter and diameter of the “X†seal ring After the improvement and optimization of the original order, the unit has undergone repeated emergency shutdown and load rejection tests, and there has been no oil leakage of the runner blades.
4 Problems to be solved further In the past 20 years, the technical transformation of our factory in hydro-generators has been successful. At the same time, we should also see that the operation of thrust bearings is still not reliable enough, and the hidden dangers of bearing burn accidents still exist, especially 170MW units. . The abrasion of the turbine over-current components is intensified, and the treatment means is single, especially the erosion of the strong cavitation zone in the ring and the back of the runner in the runner chamber. So far, there is no effective treatment. The inspection seal (air shroud) does not seal, the pivot and material 400mm copper tile wear, strain, misalignment, the connecting pin of the operating frame and the connecting rod is released, and the oil leakage in the three bearings is still not leaking. A practical and easy to handle on-site inspection. The vibration problem of the generator No. 14 generator has not been solved. The air cooler of the unit, the oil cooler's sediment wear and equipment aging are very serious. In addition to these problems need to be solved, the technical transformation of some equipment is not perfect, and it is necessary to constantly hinder the guide vane resetting to prevent the accidental leg electric oil. Constantly transforming and making power generation equipment operate stably and reliably.
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