Abstract: This paper introduces the structure design, working principle, characteristics, design method, test results and practical application of chemical self-priming pipeline pump, which shows that it has obvious practicability and promotion value. CLC number: TQ 051.21 Document code: B. Symbol Description q V - pump rated volume flow, m 3 / h H - pump rated head, m n-- pump rated speed, r / min NPSH - Pump NPSH, m n s - pump specific rotation D o - impeller inlet side diameter, m D - pipeline diameter, m D 2 - impeller diameter, m K u2 - Impeller exit circumference coefficient K D2 - Impeller outer diameter correction coefficient b 2 - Impeller exit width, m K b2 - Statistic coefficient of impeller exit width Z - Number of impeller blades F 8 - Maximum cross-sectional area of ​​vortex chamber, m 2 F i - area of i -th section, m 2 K v3 - Coefficient of flow velocity in the spiral vortex chamber K f8 - Coefficient of correction of the cross section of the swirl chamber S - Area of ​​the return orifice, m 2 K s - empiric coefficient of return orifice V c - volume of reservoir, m 3 V q - volume of gas-liquid separation chamber, m 3 β 1 - impeller blade inlet mounting angle, (°) β 2 - Angle of exit of impeller blades, (°) N - pump shaft power, kW η - pump efficiency,% H s - pump self-priming height, m t s - Pump self-priming time, s δ - impeller blade thickness, m h 1 - Pump inlet and outlet centerline height, m h 2 - pump body height, m d - pump inlet diameter, m C - pump inlet height margin, m Centrifugal pumps have been widely used in the process of refining or transferring chemical products. However, in some negative pressures (such as the unloading and unloading of liquid steel in tank trucks, the liquid transfer in underground tanks, the unloading of liquids in Haihe Port Terminal And car tank liquid transport, etc.) occasions, because it does not breathe empty self-priming performance, unable to 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 infusing fluid, but can not be used in the open air (can not shorten the infusion distance) and is constrained by the pump room. 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 q V = 50 m 3 / h, H = 80 m, n = 2950 r / min, NPSH ≤ 4 m, D = 80 mm. 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 Combined with 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 pipeline 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 hinge-type structure, the sealing surface material selection of PTFE, platen 0Cr23Ni28M o3Cu3Ti. 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 liquid, supporting power selection 45kW. 1. Volute 2. Rolling bearings 3. Reservoir 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 split coupling 12. Pump shaft 13. Box 14. Mechanical seal seat 15. Mechanical seal 16. Pump cover 17. Impeller ring 18. Centrifugal impeller 19. Pump Figure 1 chemical self-priming pipeline pump structure 2 working principle As the suction chamber and the pump inlet and outlet at a certain height, so before starting pump has stored 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 to 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 main structural features ①using the internal structure of the pump itself without any external auxiliary device to complete the 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. (1) In the formula, K u2 is selected according to β 2 and n s [1], and K D2 is generally taken as 1.01-1.05. (2) Among them, K b2 = (0.74 ~ 0.81) (n s / 100) 5/6 , n s is small, K b2 is large. Z = (1.1 to 1.8) D 2 1/2 (3)    (4) In the formula, K v3 is decided by ns, n s is bigger than K v3 [1] . K f8 is generally taken as 1.1 to 1.3, and each cross-sectional area is F i = (i / 8) F 8 . S = πK s 2 (q V / n) 2/3 / 4 (5) Among them, K s = 1.1 ~ 1.8, q V hours, whichever is greater. q V / 3.6 ≤ V c ≤ q V / 1.8 (6) Where, ns hour to take a large value, otherwise take a small value. V q ≥ (0.5~0.7) V c (7) In the formula, ns is big, and vice versa. h 1 = h 2 + D 2 + d + C (8) In the formula, C generally takes 0 ~ 100mm, n s takes a large value. The hydraulic structure of the pump set 6 parameters in Table 1. Table 1 hydraulic structural design parameters ns D 0 / mm D 2 / mm b 2 / mm Z δ/ mm β 1 / (°) β 2 / (°) F 8 / mm 2 S / mm 2 V c / dm 3 V q / dm 3 h 1 / mm d / mm 47.73 75 255 8 6 6 twenty one 38 1380 720 19.5 7.2 620 80 5 test results The pump was self-priming and hydraulically tested at room temperature in a depth of 9 m and on a closed C-test bench. The results are shown in Table 2, Table 3, FIG. 2 and FIG. 3. The test results show that the pump performance indicators have reached the design requirements. Table 2 self-priming performance H s / m 2.0 3.0 4.0 5.0 6.0 6.5 7.0 7.5 8.0 8.3 8.7 t s / s 26 33 40 53 72 90 108 136 161 182 224 Table 3 design point hydraulic performance q V / m 3. h -1 H / m n / r . min -1 N / kW η /% NPSH / m 50.06 79.8 2950 20.19 53.9 3.55 Figure 2 pump self-priming time and self-priming height curve Figure 3 pump hydraulic performance curve 6 practical application 2 sets of 80HGZB-80 chemical self-priming pipe pump was sent to Daqing Chemical Auxiliary Plant in September 1996 for the pick-up and drop of sulfuric acid and alkali in railway tank cars. In about 4.5m high negative pressure under the conditions of loading and unloading, to overcome the air resistance, about 2min to complete the suction liquid emptying task, into the normal infusion work, about 80min unloading liquid tank, the effect is excellent . The pump has been used for more than 2 years, everything is normal. 7 Conclusion 80HGZB-80 chemical self-priming pipe pump with self-priming performance, stable operation, reliable work, low noise, less leakage, easy maintenance and replacement of seals and so on. At the same time, the time for loading and unloading the liquid is shortened, the turnover rate of the tanker truck is increased, the production efficiency is improved, and the promotion value is certain. I also developed a 50HGZB-32 chemical self-priming pipe pump, and has been applied to the corresponding chemical industry. Article ID: 1000-7466 (1999) 06-0031-03 About the author: Instrument Group (1956 -), male (Han), Shandong Juancheng, senior engineer, graduated from Zhejiang Institute of Technology in 1982, received a bachelor's degree, has long been engaged in pump design and technical management Author: Instrument Group: Yiwu City, Zhejiang Province Light Industry Corporation, Yiwu, Zhejiang 322000 Wang Jimin: Second Petrochemical Pump Factory in Yiwu, Zhejiang Province, Yiwu, Zhejiang 322000 references [1] off wake? Pump theory and design [M] Beijing: Mechanical Industry Press, 1987 [2] Jin Shude, Chen Zichang modern pump design method [M] Beijing: Weaponry Industry Press, 1993? ns D 0 / mm D 2 / mm b 2 / mm Z δ/ mm β 1 / (°) β 2 / (°) F 8 / mm 2 S / mm 2 V c / dm 3 V q / dm 3 h 1 / mm d / mm 47.73 75 255 8 6 6 twenty one 38 1380 720 19.5 7.2 620 80 H s / m 2.0 3.0 4.0 5.0 6.0 6.5 7.0 7.5 8.0 8.3 8.7 t s / s 26 33 40 53 72 90 108 136 161 182 224 q V / m 3. h -1 H / m n / r . min -1 N / kW η /% NPSH / m 50.06 79.8 2950 20.19 53.9 3.55