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1 Introduction Huangpu River in Shanghai Water Plant built in 1987, two raw water pumping station, that is, Linjiang pumping station and Yan Qiao pumping stations, each equipped with six large vertical concrete volute mixed flow pump, responsible for the upper reaches of the Huangpu River water quality than the Good raw water is delivered to the respective waterworks in Shanghai by two relay stations, with a daily delivery capacity of 3.5 million tons. Since its commencement of operation to 1997, ten years gradually exposed some problems, Changsha Pump Factory Co., Ltd. should be required by the owners and in cooperation with the relevant departments in Shanghai, the two pumping stations to transform (nearly 30 million investment in the transformation funds). From 1998 to 2001, 12 cement elbow-inhaled volute-flow mixed-flow pumps have all been transformed into wet-pit sink suction diagonal-flow pumps, greatly improving the operation efficiency and reliability of the pump sets, resulting in significant energy-saving effects and Economic benefits. 2 Pumping Station Basic Situation Linjiang Pumping Station and Yanqiao Pumping Station used 1800HLWB-12 vertical mixed flow pump. The installation form of the pump is shown in Figure 1. The structural features are as follows: elbow cement suction runner, cement volute mixed flow pump, semi-adjustable, semi-open impeller, impeller chamber embedded in cement matrix, floating ring shaft seal, pump motor rigid shaft coupling pump rotor Axial force by the motor thrust bearing. Pump design point performance parameters: Q = 7.792m3 / s, H = 12.2m, n = 300r / min, m = 87.2%, supporting motor power 1600kW. 3 the original pumping station main problems (1) low operating efficiency. According to the field calculation, the pump operation efficiency is only 60% ~ 70%. The reason is that the gap between the vane and the impeller chamber can not meet the design requirements (0.8 ~ 1.0mm). (2) poor sealing reliability. The original pump shaft seal with floating ring seal structure, poor sealing stability. Therefore, during operation, a submersible pump was placed on the pump cover and a full-time inspector was set up on the level. Once it is found that the pump leaks too much, immediately start the submersible pump pumping leak water to prevent the pump house was submerged. (3) short pump maintenance cycle. When the original pump is running for about one year, strong vibration, big seal leakage, greatly reduced pump efficiency and other problems must be shut down for maintenance. (4) blade cavitation damage. When overhauling each year, the impeller blades have cavitation damage to the pits. Each time the overhauls are repaired and polished, the maintenance personnel are labor-intensive and the working environment is poor. 4 transformation programs and implementation of the main problems for the original pumping station, the pump performance, pump structure, pump suction runner, the basis of the installation of the pump redesign, that is, wet pit sink suction vertical ramp pump, only the original package The motor is unchanged; however, the motor mounting base layer rearranges the anchor bolt. After the transformation of the pump room structure and inflow channel plan shown in Figure 2. According to the past operation and the analysis of the characteristics of the pump device, the design parameters of the new pump are determined as follows: flow Q = 9m3 / s; head H = 12m; speed n = 300r / min = 3.65nQ1 / 2 / H3 / 4U510. Use L500 excellent hydraulic model for model conversion design, the new pump model is set to 88LKSE-18J. The theoretical performance shown in Figure 3 double-dotted line. Physical pump after real machine test, the performance parameters to meet the design requirements, the test performance curve shown in Figure 3, solid line. 5 structural characteristics of the pump after the transformation Figure 4 shows the modified vertical ramp pump structure, compared with the original pump-type structure, its structural features are: (1) was the original cement-type mixed-flow pump; now (2) The original pump impeller chamber embedded in the cement fixed, and the corresponding parts of the blade is spherical; the impeller chamber can be extracted with the pump rotor parts, and the corresponding parts of the blade cone, so replacement, repair (3) The standard elevation of cavitation of the original impeller is about -1.95m, the standard elevation of cavitation of impeller is about -3.5m and the elevation of impeller is reduced by 1.55m. Therefore, under the same suction water level, the cavitation of the device The amount of increase of 1.55m, is conducive to avoiding the occurrence of cavitation; (4) The original impeller cantilever length of about 1.1m, the impeller is only about 0.6m in length. So the lower part of the pump bearing greatly improved the stress conditions, extending bearing life, help reduce the swing of the impeller and reduce the blade and impeller room between the wear and tear; (5) the new pump in the coupling between the pump coupling An adjusting nut can adjust the relative height position of the impeller conveniently through the pump shaft. During installation and maintenance, it is convenient to adjust the clearance between the impeller blades and the impeller chamber so that the clearance always maintains the designed value, so that the operating efficiency of the pump is not affected (6) The new pump shaft seal with a general packing seal, the part of the pump at the highest point, less leakage, and the leakage of water can be discharged into the sump, without the need to set up a special post inspection and drainage ; (7) The new pump rotor parts can be drawn from the top, pump maintenance work can be installed in the motor base layer, without drilling into the pump repair welding, grinding, not only to ensure the quality and efficiency of maintenance; and greatly improve the overhaul working environment. 6 Conclusion The technical transformation of the pilot since 1998, until 2001, all completed, put into operation the longest four years. Field test results compared with the original pump test results: (1) pump operating efficiency up to 88%. In the annual delivery of 800 million cubic meters of water in the circumstances, compared with the original pump can save electricity 9.6 million yuan expenditure. If the 3500,000 tons / day design load operation, annual savings of up to more than 14 million yuan in electricity costs, the transformation of the investment funds can be recovered within three years; (2) 3 to 4 years a new pump overhaul, overhaul The period is extended by 3 to 4 times, and the maintenance workload and maintenance cost are correspondingly reduced; (3) The vibration intensity of the unit is below 5 mm / s, the shaft seal leakage is normal, the safety and reliability of operation are improved, and the maintenance and operation positions are reduced; (4) No cavitation damage on the blades has been found since 4 years of operation; (5) The working environment and labor intensity of operation and maintenance personnel have been improved and lightened.