Design and application of self priming pipeline pu

Abstract: This paper introduces the structural design, working principle, characteristics, design method, test results and practical application of chemical self-priming pipeline pump, which shows that it has obvious practicality and popularization value

Chinese Library Classification Number: tq051.21

document identification code: b

symbol description

qv - rated volume flow of pump, perpendicularity measurement of M3 hollow pier/h

h - rated lift of pump, m

n - rated speed of pump, r/min

npsh - NPSH of pump, m

ns - specific speed of pump

do - diameter of impeller inlet side, m

d - NPSH of pump.Pipeline diameter, m

d2 - impeller outer diameter, M

ku2 -- impeller outlet circumference coefficient

kd2 -- impeller outer diameter correction coefficient

b2 -- impeller outlet width, m

kb2 -- Statistical coefficient of impeller outlet width

z -- number of impeller blades

f8 -- maximum cross-sectional area of vortex chamber, m2

fi -- I cross-sectional area, m2

kv3 -- velocity coefficient in spiral vortex chamber

kf8 -- cross-sectional correction coefficient of vortex chamber

s -- reflux hole area, M2

ks -- empirical coefficient of reflux hole

vc -- volume of liquid storage chamber, m3

vq -- volume of gas-liquid separation chamber, m3

β 1 - setting angle of impeller blade inlet, (°)

β 2 - setting angle of impeller blade outlet, (°)

n - shaft power of pump, kw

η—— Pump efficiency,%

hs - pump self-priming height, m

ts - pump self-priming time, s

δ—— Impeller blade thickness, m

h1 - pump inlet and outlet centerline height, m

h2 - pump body height, m

d - pump inlet inner 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 pressure occasions (such as the unloading of railway tank car liquid, the reverse delivery of underground tank liquid, the unloading of Haihe wharf liquid and the transfer of truck tank liquid, etc.), because it does not have the self-priming performance of suction and emptying, it cannot realize the infusion function. In addition, most chemical products are corrosive. For these special occasions, such as the joint unloading of air suction equipment and infusion equipment, it is bound to increase equipment investment, and the operation becomes complex. At present, the horizontal self-priming centrifugal pump that has been developed has the functions of empty suction and infusion, but it cannot be used in the open air (the infusion distance cannot be shortened), and it is constrained by the pump room, so it is difficult to achieve the purpose and effect of liquid unloading. In view of the above situation, according to the requirements of users, the author successfully developed a chemical self-priming pipeline pump, and obtained a national patent. Taking 80HGZB-80 chemical self-priming pipeline pump as an example, this paper expounds the characteristics of its development and design, and introduces some operating conditions

1 design requirements and structural type

1.1 design requirements

qv=50m3/h, h=80m, n=2950r/min, NPSH ≤ 4m, d=80mm. The transmission medium is sulfuric acid, hydrochloric acid and alkali. The pump is required to be equipped with a self-priming mechanism, which can both self-priming and infusion. The pump is vertical, and the inlet and outlet diameters of the pump should be on the same horizontal line

1.2 structural type

combined with the integration of ordinary pipeline pump, machine and pump and the self-priming mechanism of self-priming pump, after considering the corrosive situation, an external mixing chemical self-priming pipeline pump is designed as shown in Figure 1. The main considerations in the design are: ① corrosive medium gasification factors. In order to protect the internal structure of the motor and avoid polluting the environment, explosion-proof motors with flanges suitable for outdoor use are adopted. ② All parts in contact with liquid overcurrent are made of 0cr23ni28mo3cu3ti corrosion-resistant materials. The pump shaft reaches hb269 ~ 302 through heat treatment. ③ All gaskets are made of polytetrafluoroethylene, and plugs and fasteners are made of 3Cr13. ④ The one-way flap of the pump adopts a hinged structure, which seals the software and hardware environment with good development of the new material industry. The material is polytetrafluoroethylene, and the pressing plate is 0cr23ni28m o3cu3ti. ⑤ The shaft is supported by rolling bearings and designed on the mechanical seal to isolate corrosive media. However, due to its high price, complex protection and high energy consumption, the bearing and pump shaft are matched with a large clearance, which is convenient for the disassembly, installation and maintenance of the mechanical seal seat. ⑥ The pump seal adopts 108u-055 mechanical seal which is corrosion-resistant, wear-resistant and medium pressure resistant. ⑦ The inlet and outlet of the pump are designed on the same horizontal line, and the phase is staggered by 180 °. ⑧ The coupling adopts a split rigid split coupling, which can disconnect the motor spindle and pump shaft, leaving an axial space, and the mechanical seal seat and other parts can be taken out. ⑨ Considering the different temperature and density of the liquid, the supporting power is 45KW

2 working principle

since the suction chamber and the inlet and outlet of the pump are at a certain height, a certain amount of liquid has been stored in the pump before starting. When the pump is started, the impeller rotates at a high speed. Under the action of centrifugal force, the air in the liquid storage chamber and the suction pipeline is sucked together. The gas-liquid mixture is discharged into the gas-liquid separation chamber through the impeller, the tongue and the diffusion pipe of the water pressure chamber. Due to the reduction of flow rate, the lighter gas is separated from the mixed gas-liquid and escapes through the pump outlet, while the heavier liquid returns to the volute through the return hole connected between the box and the pump body and returns to the impeller, Re mix with gas and continue to participate in the separation of exhaust gas. According to this cycle, until all the gas in the pump and suction pipe is discharged, that is, the self-priming process is completed, and the pump is put into normal infusion operation

3 main structural features

① the self-priming function can be completed by using the internal structure of the pump itself without any external auxiliary devices, which integrates the self-priming and infusion functions. Automotive exterior parts are the parts that use the most plastic materials in automotive parts. The system structure is novel. ② The vertical structure is adopted, and the floor area is small, which reduces the pipeline accessories in the pipeline system. ③ In the whole process of self suction and infusion, the cooling and lubrication of the mechanical seal are realized by the conveyed liquid, without additional liquid and additional pipes. ④ With separate rigid split coupling, rolling bearings, mechanical seals and other parts can be replaced without disassembling the motor and housing, which is quite convenient for disassembly and maintenance. ⑤ The axial force of the impeller is balanced by its own structure, and no additional parts are required

4 hydraulic design

the design method of this pump is basically the same as that of centrifugal pump. However, due to the particularity of its structure and different hydraulic losses, the following parameters should be modified and supplemented in the specific parameter design, otherwise it will not meet the design requirements