Abstract: The characteristics and application range of Francis pump are discussed. The structure and main characteristics of SEZ Francis pump are analyzed with the example of Slender West Lake water pump station in Yangzhou. The application of this pump in pumping station is introduced.
Key words: pumping station, mixed flow pump, structure, application
Foreword
Mixed flow pump used in farmland irrigation and drainage, flood control, drainage, sewage treatment, power stations (coal-fired power plants, nuclear power plants, storage power plants, tidal power plants) and other cooling systems. Francis pumps typically have a specific rotational speed in the range of 300-500; their caliber is 100-1 500 nun and some are up to 6 000 mm; their heads are 3-30 m up to 60 m; their flow rates are 200-2 000 Us or Larger, speed 100-1 450 r / min, mixed-flow pump in terms of performance and structure, between the centrifugal pump and axial flow pump. Compared with centrifugal pump and axial flow pump, the main advantages of the mixed flow pump are simple structure, small volume, light weight, small area, stable performance, stable power, small change of power when the head is changed, and easy speed regulation.
At present, it is very important to strengthen the research and development of the stick flow pump, especially to develop a large mixed flow pump with good anti-cavitation performance, advanced structure and stable operation in order to meet the pump needs of the South-to-North Water Diversion Project.
1 SEZ vertical mixed flow pump features
1.1 vertical mixed flow pump the main form
Vertical Francis pump impeller submerged in water, start without vacuum, and the motor installed in the upper, well-ventilated, will not be submerged by the flood, which is horizontal pump can not and the advantages. Vertical Francis pump with high efficiency, cavitation performance, small size, easy maintenance advantages. According to different structures, can be divided into guide vane and volute two. Vertical vane pump can be divided into the rotor can be pumping double shell type (K type) and the rotor can not pumping the single-shell type (B type). According to the installation method, it can be divided into single base type and double base type. The single base type motor and pump are installed on the same basis, while the double base type motor and pump are respectively installed on their own basis. In order to meet the different use of the blade is divided into two types of fixed and adjustable. At present, the main models are LKX type (fixed blade, rotor can), LBS type (fixed blade, rotor can not pumping), LBX type (fixed blade, the rotor can not be pumping, the outlet pipe installed in the pump base), LKX type Fixed blades, pump rotor can be pumping, the outlet pipe installed on the basis of the pump), TKK (adjustable blades, the pump rotor pumping, the outlet pipe installed under the pump base), LT (adjustable blades, pump rotor Pumping, outlet pipe installed on the basis of the pump) several, for selection.
1.2 SEZ vertical mixed flow pump features
SEZ vertical mixed flow pump is a new type of mixed flow pump, which has the advantages of high lift, high flow rate, high efficiency and wide adaptability (the change of motor power is small when the lift change is large.) SEZ, vertical mixed flow The pump adopts an upper supporting way, the motor and the pump are connected as a whole, so the installation is extremely convenient, the unit vibration is small and the operation is smooth. The structure of the SEZ vertical mixed flow pump is shown in FIG.
SEZ vertical mixed flow pump has the following characteristics.
(1) can be pumping core structure.
The most prominent feature of the SEZ vertical mixed flow pump is the drawable core structure, which includes the impeller chamber, guide vane, impeller, guide bearing, shaft, intermediate connector, sheath tube and other components. It can be extracted from the pump body as a whole, without removing the outer cylinder and the connecting pipe can be easily removed the overall core-pulling, which brought great convenience to maintenance Draw core structure shape shown in Figure 2.
(2) ceramic guide bearing.
The guide bearings used on the vertical pump above the water level in the sump, before starting the pump without being put into normal operation, these bearings will be lack of water lubrication if they are not supplied with water from outside, The lubrication of water can easily lead to bearing wear. SEZ-type vertical mixed flow pump guide bearing ceramic material is very wear-resistant, when the pump into normal operation, the pump itself can pump the muddy water for cooling and lubricating, the wear and tear is very small, is a promising promotion Muddy water lubrication of bearings, to simplify the structure of the pump has great significance. The materials chosen for this ceramic bearing are mainly aluminum oxide (AlO), zirconium oxide (ZrO), silicon carbide (SiC), silicon nitride (SiA). These materials still have good properties under poor lubrication conditions Of the thermal conductivity and wear resistance.According to the test, this structure of the bearing has been operating safely for more than 20,000 h.
Figure 1 SEZ-type vertical guide vane mixed flow pump structure Figure 2 sez vertical vane mixed flow pump pumping core structure
(3) automatic exhaust device.
In the pump system when the water pipe is longer, the pipeline accumulates a lot of air, the presence of air will make the start when asked to grow, and caused the start is not stable. The SEZ vertical mixed flow pump is equipped with an automatic exhaust valve device, which can discharge the gas in the pipeline when the unit is started and make the unit run smoothly.
2 Application in Slender West Lake Diversion Pumping Station
2.1 pump station basic situation
Yangzhou Slender West Lake diversion pumping station is located on the west side of Beijing-Hangzhou Grand Canal near Yangzhou Power Plant North and Brick Factory. The project installs SEZ700-595 / 500 vertical guide vane mixed flow pump, with Y3551, -8 type 200 kW motor 4 sets, the design flow of 4 m3 / s.
Four sets of pumps are connected in parallel by the diameter of 1.6 m after the pipeline water, water pipe length of 5.6 km, remittances to protect the lake and flows into the Slender West Lake
2.2 vertical mixed flow pump instead of the original design of centrifugal submersible pump
After the model test, the Slender West Lake Diversion Pumping Station under the design conditions, the single pump design flow Q = 1.0 m3 / S, the total head H = 11.14 m, the normal starting lift H = 15.87 m, the most unfavorable starting lift H start = 18.25 m. The original design selection of 700GQ4000-20-315 submersible centrifugal pump, submersible centrifugal pump biggest advantage is the need to build water pumping station, it is more suitable for urban drainage land tension. Cost analysis shows that the price of submersible pumps is far higher than the price of ordinary pumps and motors. Considering that the Slender West Lake Diversion Pump Station is located in the outskirts of the city, land is not a major factor in pumping station investment, whereas the diversion pumping station has to build a beautiful pumping station to become a sightseeing spot.
In addition, because the submersible centrifugal pump in the water blocking the motor and water conditions are relatively poor, the pump efficiency is low. Taking into account the diversion pumping station perennial use, there must be higher efficiency can be reduced
Low operating costs. The diving centrifugal pump itself, poor water conditions, the export of the motor blockage, especially the original design of the motor power, the water pump plugging a larger role, resulting in effluent efficiency. According to a preliminary analysis, the efficiency of submersible pumps to reduce about 5% of ordinary pump.
Taking into account the above factors, coupled with centrifugal pump head deviate from the pumping station design conditions more, so the selection of the SEZ vertical mixed flow pump. This new type of mixed flow pump has the characteristics of high efficiency, good cavitation performance, stable power change, small power change when the lift is changed, and convenient maintenance. In particular, the vertical mixed flow pump does not need to be evacuated during start-up and has little auxiliary equipment. The electric motor is located on the ground floor. The utility model has the advantages of good ventilation, lighting, good heat dissipation and convenient overhaul. The upper machine room is only equipped with a vertical motor. . Therefore, the use of vertical mixed flow pump is the best choice for local conditions. So after comparing a variety of pump-type programs, the final selection of SEZ700-595500 vertical vane-type mixed flow pump.
2.3 vertical mixed flow pump disassembly order
2.3.1 installation of pump cylinder
(1) The first part of the cylinder (including the inlet horn and external pipe) hanging man pump well and put it on the support beam.
(2) The second part of the cylinder (external pipe) hanging on the first part of the cylinder and assembled.
(3) lifting the first and second parts of the cylinder and the bottom plate, removing the outer pipe out of the support beam, lowering the cylinder, with I-beam support at the outer pipe office.
(4) Similar to the first and second part of the cylinder installation method, step by step in turn installed the entire pump cylinder.
3.3.2 pump core part of the installation
(1) Assemble the draw-off core including impeller room, guide vane, impeller, guide bearing, shaft, intermediate connector, sheath pipe and other parts, and place it vertically to prevent it from falling down.
(2) The assembly of the pumping part of the core pulled out of the pumping cylinder, and the use of I-beam in the water elbow support good.
(3) Lift the shaft of the pump (rigid shaft should be installed at the shaft end) and the coupling at the pump shaft end should be well connected, and the reaming bolt and nut should be tightened.
(4) lifting the shaft sleeve, bearing bracket, jacket tube aligned to the bearing bracket and screw the relevant bolts, nuts and so on.
(5) Lift the whole core pulling component, remove the supporting beam, and slowly lower it to the outer cylinder body so that the cone surface of the impeller chamber is aligned with the lower cone surface of the outer pipe sealing ring. Disassemble the pump in the reverse order.
2.4 Pump Station Test
The efficiency, vibration, noise and frequency spectrum of vertical Francis pump units in Slender West Lake pumping station under different operating conditions were tested on site. From Unit 1 to Unit 4, respectively, running 4 machines to L machine, the main test data shown in Table 1. Through observation and test data analysis, the entire unit runs very smoothly and meets the requirements of design conditions.
3 Conclusion
SEZ-type vertical mixed flow pump has the advantages of stable operation, high efficiency, good cavitation performance, small change of power when the lift changes, and easy maintenance of the core-pulling structure. It not only combines the advantages of centrifugal pump and axial flow pump, Also overcome the shortcomings of both. So SEZ T4 vertical mixed flow pump has a very broad application prospects.
1 The electrical system used by the machine has reliable control performance and strong anti-interference ability.
2 High precision Thrust Ball Bearing and tapered roller bearing are adopted in the spindle of machine, with high rotary precision and the large bearing capacity.
3 The machine tool has the function of two axis linkage, which can be used for turning various types of surfaces.
4 The speed of the worktable adopt two level of gears, gear reducer and motor with frequency converter to achieve stepless speed change, very convenient to adjust and operate.
5 The machine feed shaft adopts precision ball screw and linear guide rail, so that the machine has the characteristics of high precision and high rigidity.
6 The machine tool is equipped with five station electric knife, which has the function of automatic knife change.
7 The machine is equipped with large flow water cooling unit and high-lift pump to ensure good cooling effect.
8 The machine has closed housing (except the top of the slide), and the workspace is completely protected by screen seal. It can also easily open the protective door and is highly accessible when operation.
9 The machine use centralized lubrication, circular lubrication and other methods, supply oil to each lubricating point, reduce friction resistance, reduce temperature rise and reduce surface wear..
10 The Z shaft adopts the hydraulic balance oil cylinder to balance the weight of the slide table and the tool holder. The balance ability is strong and the stability is good, thus the life of the screw and the guide rail can be improved.
11 The operation procedures of the machine are very simple, the degree of automation is high, and the unstable factors of human error can be reduced to the lowest level.
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