Chemical Self - priming Pipeline Pump Design and Application

CLC number: TQ051.21

Document code: B.

Symbol Description

qV - pump rated volume flow, m3 / h

H - pump rated head, m

n-- pump rated speed, r / min

NPSH - Pump NPSH, m

ns - pump than the number of revolutions

Do-- impeller inlet side diameter, m

D - pipeline diameter, m

D2 - impeller diameter, m

Ku2 - Impeller exit circumference factor

KD2 - impeller diameter correction factor

b2 - impeller outlet width, m

Kb2 - impeller exit width statistics coefficient

Z-- impeller blades

F8 - vortex chamber maximum cross-sectional area, m2

Fi - i th cross-sectional area, m2

Kv3 - Velocity factor in the spiral vortex chamber

Kf8 - eddy chamber section correction factor

S - return hole area, m2

Ks - return hole experience coefficient

Vc - reservoir volume, m3

Vq - gas-liquid separation chamber volume, m3

β1 - impeller blade inlet placement angle, (°)

β2 - impeller blade exit angle, (°)

N - pump shaft power, kW

η - pump efficiency,%

Hs - self-priming pump height, m

ts - pump self-absorption time, s

δ - impeller blade thickness, m

h1 - pump import and export center line height, m

h2 - pump 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 operation complexity. However, horizontal self-priming centrifugal pumps, which have been developed at present, can not be used in the open air (can not shorten the infusion distance) though they have the functions of suctioning air and infusing fluids and are constrained by pumping stations. Therefore, it is very difficult to achieve the purpose and effect of liquid discharging. 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

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: ① corrosive 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 liquids, supporting power selection 45kW.

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

① using 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 is 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.

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