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Chemical self-priming pipeline pump design and application CLC number: TQ 051.21 Document code: B Symbol Description qV - pump rated volume flow, m3 / h H - pump rated head, mn - pump rated speed, r / min NPSH - Pump NPSH, m ns - Pump RPM rpm - Impeller inlet side diameter, m D - Pipeline diameter, m D2 - Impeller outside diameter, m Ku2 - Impeller exit circumference factor KD2-- impeller diameter correction coefficient b2-- impeller exit width, m Kb2-- impeller exit width statistical coefficient Z-- impeller blade number F8-- vortex chamber maximum cross-sectional area, m2 Fi - i cross-sectional area, m2 Kv3 - Spiral vortex chamber flow coefficient Kf8 - Swirl chamber section correction factor S - Backflow hole area, m2 Ks - Backflow hole empirical coefficient Vc - Liquid storage chamber volume, m3 Vq - Gas-liquid separation chamber volume, m3 β1 - inlet angle of impeller blades, (°) β2 - angle of exit of impeller blades, (°) N - shaft power of pump, kW η - pump efficiency,% Hs - self-priming pump height, m ts - pump self-absorption time, s δ - impeller blades Degree, m h1 - pump inlet and outlet centerline height, m ​​h2 - pump height, md - pump inlet diameter, m C - pump inlet height margin, m in the process of chemical products refining or transfer process Centrifugal pump applications have been quite popular, but in some negative pressure (such as the loading and unloading of railroad tank car, underground tank liquid transfer, the unloading of the Haihe terminal liquid and automobile tank liquid transport, etc.) occasions, Because it does not inhale emptying self-priming performance, can not achieve infusion function. In addition, most chemical products are corrosive. For these special occasions, such as the combination of suction-suction equipment and infusion equipment unloading, it is bound to increase equipment investment and the operation is complicated. At present, the horizontal self-priming centrifugal pump that has been developed has the functions of suctioning air and transfusion, but can not be used outdoors (can not shorten the transfusion distance) and is constrained by the pumping station. Therefore, it is difficult to achieve the purpose and effect of discharging liquid. In response to the above status quo, according to the request of the user, the author successfully developed a chemical self-priming pipeline pump, and won the national patent. Take 80HGZB-80 type chemical self-priming pipeline pump as an example, expounds the characteristics of its research and design, and introduces some situations of online operation. 1 Design requirements and structure type 1.1 Design requirements qV = 50m3 / h, H = 80m, n = 2950r / min, NPSH ≤ 4m, D = 80mm. Transmission medium for sulfuric acid, hydrochloric acid and alkali, require pump self-priming mechanism, both self-absorption and infusion, the pump is vertical, pump import and export diameter should be the same level. 1.2 Structure Type Combination of ordinary pipeline pump pump and self-priming pump self-priming mechanism, taking into account the corrosive conditions, designed as shown in Figure 1 outside the mixed chemical self-priming pipe pump. Design considerations: ①corrosive gasification factors, in order to protect the internal structure of the motor and to avoid environmental pollution, the use of outdoor use and with a flange of the explosion-proof motor. ② Where the liquid over-current contact with the parts are used 0Cr23Ni28Mo3Cu3Ti anti-corrosive materials. Pump shaft through the heat treatment to HB269 ~ 302. ③ All gaskets are PTFE, screw plugs and fasteners are used 3Cr13. ④ pump one-way door with a hinged-type structure, the sealing surface material selection of PTFE, platen 0Cr23Ni28Mo3Cu3Ti. ⑤ support the use of rolling bearing shaft, and its design in the mechanical seal above, isolated corrosive media. Rolling bearings and pump shaft for a larger gap with the convenience of mechanical seal seat disassembly, installation and maintenance. ⑥ pump seal corrosion-resistant, wear-resistant and medium pressure resistant 108u-055-type mechanical seal. ⑦ pump import and export design in the same horizontal line, the wrong 180 °. ⑧ coupling split rigid rigid split coupling, you can get rid of the motor shaft and pump shaft, leaving an axial space, mechanical seal seat and other parts can be removed. ⑨ Taking into account the different temperature and density of liquids, supporting power selection 45kW. 1. Volute 2. Rolling bearings 3. Liquid storage chamber 4. Pump outlet 5. Gas-liquid separation chamber 6. Explosion-proof motor 7. Pump inlet 8. Unidirectional door 9. Import seat 10. Suction chamber 11. Rigid-to-open Coupling 12. Pump shaft 13. Tank 14. Mechanical seal seat 15. Mechanical seal 16. Pump cover 17. Impeller port ring 18. Centrifugal impeller 19. Pump 2 working principle As the suction chamber and the pump inlet and outlet in a certain Height, so before the pump has been stored in a certain amount of liquid. When the pump is started, the impeller rotates at a high speed and sucks in the liquid storage chamber and the air in the suction pipe under the action of centrifugal force. The gas-liquid mixture is discharged into the gas-liquid separation chamber through the impeller, the tongue and the diffusion chamber of the pressurized water chamber , The lighter gas is separated from the mixed gas liquid due to the reduced flow rate and escapes through the pump outlet while the heavier liquid returns to the volute through the return hole in the box body and the pump body and returns to the impeller and mixes again with the gas , Continue to participate in the separation of exhaust. According to this cycle, until the pump and suction tube gas are all exhausted, that is to complete the process of self-absorption, the pump will be put into normal infusion operation. 3 The main structural features ①The use of the pump itself within the structure without any external auxiliary device can be completed self-priming function, set the self-absorption and infusion functions as one, novel structure. ② The use of vertical structure, small footprint, reducing pipelines in the pipeline attachment. ③ In the whole process of self-priming and infusion, the cooling and lubrication of the mechanical seal are all realized by the liquid being transported without additional liquid and additional piping. ④ The use of split rigid on the open coupling, without removing the motor and the shell, you can replace the rolling bearings and mechanical seals and other parts, disassembly and maintenance quite convenient. ⑤ impeller axial force by their own structural balance, without additional parts. 4 Hydraulic Design The pump design method and centrifugal pump is basically the same. However, due to the particularity of its structure and the different hydraulic losses, the following parameters should be amended and supplemented in the design of specific parameters, otherwise the design requirements will not be reached.