This paper analyzes the reasons for the failure of the circulating water system in Taizhou Power Plant , introduces the revamping program of the first and second filters of the water inlet of the circulating pump and the effect after the implementation, and puts forward the further problems after the reformation of the circulating water system Suggest. Overview Taizhou power plant south of Jiaojiang, condenser cooling water from the Jiaojiang water, open circulation, water recycling by the natural conditions of restricted open diversion. Since 1980, the power plant construction has been completed, respectively, one, two, three, four projects a6 aircraft operation, the system layout shown in Figure 1. 1 problems In recent years, due to sediment deposition in the inlet and the forecourt, there is not enough water in the first phase of the pump at the low tide level, resulting in serious air entrainment by the pump, large vibration and low water pressure (the mother pipe pressure is only 0.05MPa). Especially when No. 1 and No. 2 circulating pumps run side by side, the amount of water is obviously insufficient, and the vibration of the pump is increased. The minimum pressure of the effluent is 0.04 MPa. Although annual intake and forebay dredging, but can not solve this problem. In order to ensure the safe operation of the pump, it is necessary to adjust the operation mode of the circulating pump, that is to avoid the simultaneous operation of pumps 1 and 2, so that 1 pump of 2 pumps is in reserve all the year, resulting in the weak links in the safe operation of the circulating water system. 2 reason analysis The influence of circulating water system on safety and economic operation of generating units is mainly reflected in the decrease of condenser vacuum, the destruction of circulating water siphon and the output of generating units. Especially in summer, because of the low vacuum of No.1 and No.2 condensers and the large number of siphon damage of the outlet water, the units have to often run out of force. The reason is that on the one hand the circulating water pressure is low (0.04 ~ 0.05 MPa). Another aspect is one, the second filter is poor. One or three of a filter model ZH-3000, according to 66 Code of water standard design, frameless front inflow structure, put into operation in 1982. Due to low design standards and equipment aging, the following problems exist: (1) The gap between the screen and the screen is too large, about 15 mm. (2) No sealing on both sides of the filter. (3) filter bottom clearance is too large. (4) Skeleton rigidity is low. Resulting in poor interception of pollutants, especially in summer or flood season, a large number of floating garbage and debris from the filter, so that the condenser heat transfer significantly reduced, seriously affecting the condenser vacuum. 1, 2 condenser The original design of the condenser in the plant at the entrance with 2 sets of Φ1400 fixed secondary filter, need to wash, turn on the butterfly flow diversion rinse. After more than ten years of secondary filter has been damaged, in the overhaul has been removed, into a straight tube through the water. In the summer and flood season, a large amount of suspended garbage and debris enter the condenser, affecting the condenser vacuum and sometimes even affecting the siphon of recirculating water outlet, seriously affecting the safe operation of the unit. In order to ensure the safe and economical operation of the unit, it was necessary to clean up and run the backwashing of the condenser during the three trough periods every day to ease the contradiction between the low load and the low vacuum of the steam turbine and reduce the siphon damage of the circulating water. 3 improvement measures In order to increase the safety and economy of generating units, improve the reliability of equipment operation and reduce the labor intensity of equipment maintenance, the existing problems of circulating water system must be solved as soon as possible. After detailed analysis and demonstration, Screen reconstruction program. 3.1 on the transformation of the pump before the pool Four kinds of reconstruction programs were identified: (1) One, two and three stages of the former pool partition wall were partially demolished. (2) One, two and three before the pool partition wall all demolition. (3) In the first and second phase of the project before the pool to open a new inlet. (4) Both the first, second and third stages of the former pool are demolished, while the first and second stages of the forecourt are further opened with water intakes. In order to seek the best effect of the transformation, sediment deposition at least, while reducing the amount of reconstruction works, the four kinds of transformation programs and the original design of hydraulic model tests. First of all, clear water test was carried out to observe the different schemes of operation under different operating conditions, namely the different operating modes of the pump and the water flow field in the forebay of the water inlet under different tide levels, measuring the flow velocity distribution in each main part of the forebay and qualitatively analyzing the water inlet And sediment deposition in the foreclosure may be the situation in order to choose a more reasonable transformation program. The following conclusions are drawn from the clear water test: It is impossible to completely avoid siltation by various reconstruction schemes, but these improvements can all play a role in improving siltation. The first four kinds of programs work best, but the largest amount of construction, operation of the unit during construction is not desirable. The first solution has the obvious effect of improving the existing problems. The original flow velocity is low and the siltation is serious in this area. After the partial wall is removed, the flow velocity in this area obviously increases from 0.076 m / s to 0.29 m / s, The forebay flow rate at low tide when the distribution vector diagram shown in Figure 2. This has a significant effect on improving the pre-siltation of the front pool in the No. 1 and No. 2 pump and the water grab on the No. 1 and No. 2 pumps at the low tide position, and the project volume is the smallest. Water mixing test on this program can determine the inlet flow channel and the forecake in various parts of the deposition. From the test results, the main sedimentation area in the front pool is near the partition wall of the first, second and third phases, and the siltation thickness can be reduced to about 0.7 m near the partition wall after the removal. Through the above test and analysis, decided to use the program 1 (local connectivity method) to solve the problem of the front pool inlet. 3.2 a filter transformation The latest domestic rotary filter carried out a more comprehensive investigation, through careful analysis and comparison decided to use "circular-meshing" rotary filter, the entire replacement. The advantages of "circular meshing" rotary screen are: (1) "arc-mesh" screen structure, the screen can increase the intensity. Stencil mesh plate meshing between mechanical self-sealing principle, the gap remains below 5 mm, so that suspended solids and dirt in the water difficult to filter, improve the filter capacity. (2) screen water resistance is small, excessive water flow. (3) The use of suspension transmission, the traditional insurance overload protection instead of the use of compressed spring compression deformation, the trip switch off, overload protection, when the exclusion of overload factor, the spring automatically reset , You can connect the power to the normal operation of the filter, easy maintenance. (4) improve manufacturing accuracy, smooth operation, flexible, low noise, no jamming phenomenon. 3.3 secondary filter transformation I have used the plant more than the second filter type, a fixed, core-rotating, sewage bucket rotary and so on. According to the actual usage and the research on the usage of the same type of unit, it is believed that the net core rotary secondary filter is more suitable for our factory. However, the second core mesh filter meshing original design for gear transmission, easy to damage the pinion, easy to enter the gear chamber caused by transmission jam, so the choice of turbocharger drive mesh core rotating secondary filter. As the core of the second filter mesh than the original fixed secondary filter shape is much larger, only the secondary filter shift installed in the pump outlet. In the pump outlet valve wells, 1, 2, and 3 circulating jellyfish tubes arranged in parallel on the 3rd Φ1800 secondary filter, this program more provincial investment, construction period is short. The original valve wells 1,2,3 circulating jellyfish pipe part of the pipeline, the valve replacement, retain the original expansion and anti-door, the second filter is arranged in the pump outlet against the door and the electric door, two In front of the secondary filter and before the electric butterfly valve, an expansion joint is added, and the outlet pump and the valve of the pump are arranged in the new switching valve well as shown in FIG. 3. 4 after the transformation effect During the overhaul of Unit 1 in the first half of 2001, the above transformation plan was implemented. Underwater construction of the former pool connectivity project is more difficult, using underwater blasting, but does not affect the safe operation of nearby pump. Project lasted more than 90 days, so that one or two former pool and the three former pool connected. In addition to the 1st, 2nd and 3rd pumps, filters were changed one by one. Reconstruction of the secondary filter civil works in the overhaul before the implementation and most of the completion of the overhaul of the pipeline, filter reconstruction, the installation of three secondary filters. At the lowest tide level, the adjacent circulating pumps 1, 2, and 9 were operated at the same time, and the normal pressure of the circulating pump was up to 0.08 MPa. However, the first circulating pump had air sound and the mother Tube vibration is too large, indicating the total water intake is insufficient, but the situation than before the transformation has significantly improved the normal operation of the parent pipe pressure at 0.08 ~ 0.12 MPa, under various tide positions can be flexibly arranged to follow the pump Operation mode. At the same time, the water pressure of the condenser is increased to 0.06 ~ 0.09 MPa, which achieves the expected purpose of the reform. 5 Suggestions for further improvement Due to the partial redirection of the upstream Jiaojiang River, it affected the flow change of front water along the inlet of the circulating pump of the power plant, and the siltation of the water inlet became more and more serious. In particular, the third phase of the water inlet is the most serious. At the lowest tide level, the siltation of the third phase inlet seriously affected the inflow of water through the third phase of the pump. In addition, as the first and second pump is axial flow pump (Model 50ZLQ-50), the third is a mixed flow pump (Model 1400HLQ-16), mixed flow pump head high flow, there is a water grab phenomenon, resulting in No. 1 pump Run-time due to low water levels caused by circulating water entrained air, import and export pipeline vibration and other issues. The factory has been prepared to thoroughly clean the inlet, to solve the problem of insufficient water. It is suggested that regular dredging of the inlet and the forebay should be strengthened in the future. At the same time, regular measurements should be made on the flow pattern and siltation of the water front and provide a scientific basis for better settling the siltation problem in the future. In the pump running mode, the pump should be regularly replaced by the operation of the portfolio, to avoid the backup pump in the long-term standby caused the siltation of the pump inlet. First and second circulation pump From the overall situation, the low circulation pump, poor operational reliability, circulation pump circulating water flow generally can not reach the rated value, the condenser end margin is larger, the greatest impact in summer. It is suggested that the axial flow pump should be changed into a two-speed mixed flow pump and be operated with high output in summer so as to ensure the safe operation of the circulating water system and reduce the output in autumn and winter so as to save the plant electricity. In addition, the second and third phase of a filter has not been transformed, there are the same problems, 3,6 aircraft original old secondary filter there are problems, and some can not run or canceled. Summer condenser sweeping frequent, affecting the normal operation of the unit. It is recommended to reform old and secondary filters to improve equipment reliability. Only in this way, the whole plant circulating water system operating conditions can be completely improved. Cabinet Stamping Die,washing machine cabinet stamping die,punching mould for cabinet of washing machine,washing machine cabinet stamping tool Wuxi IDO Technology CO.,LTD , https://www.idotechina.com