Effect of Self - priming Pump Outlet Tube Height on Self - priming Performance

Self-priming pump The experimental study shows that the self-priming time is related to many factors. In addition to the structural characteristics of the pump itself, the installation condition of the inlet pipe has a great influence on the self-priming performance. However, some studies have reported that the condition of the outlet pipe is self- Suction effect, generally considered small, but not to study.
This article is to solve the practical work and found that under certain circumstances, the export pipeline will have an impact on self-priming performance, the results of this study will give the pump design, the user to help
1 self-priming pump outlet section of self-suction water self-priming suction pump self-priming pressure has not been fully established circulating pump body water circulation, but the flow of water and outlet pipe.
In Figure 1 self-priming pump pump out the water runner and the outlet through, the outlet has a window with air and water separation chamber connected to the water from the impeller out of the water runner into the outlet pipe, if the outlet pipe is relatively long 1M) Because the pressure is not enough water will not flow out, water from the window into the gas-water separation chamber, the separation of gas, from the window into the outlet pipe up and discharge. If the outlet pipe is short (Figure 2), the water pressure will drain the water from the outlet pipe and the pump memory will decrease. When reduced to a certain extent, the pump no longer reduce the circulating water, but then little water storage. For the pump body water outlet and pump outlet separately, ask a large gas-water separation chamber self-priming pump body shown in Figure 3b. The impeller out of the water is not directly aligned with the outlet, when the water pressure is low. Water is not easy to come out, observe the structure of the self-priming pump, you can see the self-priming water in the pump above the formation of a large vortex, not easy to overflow, this structure of the outlet pipe has little effect on self-absorption of water a.
2 The amount of water on the self-suction capacity Self-priming pump self-priming by the formation of air-water mixture layer of the impeller, if too little water, air and water mixed platform is very thin, less pumping capacity, very little water can not Effective isolation of import and export chambers, or even similar, the degree of vacuum imported destroyed. Figure 4 is a different amount of water pump inlet vacuum test results. It can be seen from the test that when the pump water is less than 1.6 2, the pump can not continuously pump air. When the water is stored, the vacuum gauge starts to be steadily evacuated when the water is stored. When the water is stored, the vacuum is increased. Save forever added to a certain value. Vacuum no longer increases. This rule for a variety of self-priming centrifugal pumps are the same, but its value varies.
Figure 5 is 4TC-80 pump self-suction vacuum test results. 4TC-80 Flow rate: 7.8 liters / sec Pump body water volume of l3 liters, the factory test, to achieve adequate water requirements. However, the 13L is stored in the pump when it is stationary. In use, it is found that when the water outlet of the 4TC-80 is only 0.3 m high, the water will flush out during self-priming. The downtime will reduce the water storage by 140 mm and reduce the water storage by 72 , Which can be seen from Figure 5, 6 2 dynamic self-priming capacity is very low, the actual water can not be self-priming.
In this case, self-priming is easy when water pushes out of the pump structure. Must increase the water section, so that it can hold the pump out of the self-absorption circulating water does not reduce the self-suction water 4TC-80 pump out of water to 0.9m self-suction capacity of 8m
5 Minimum outlet installation height of From the above analysis we can get the following conclusion, the pump outlet flow through the outlet structure (Figure 3a). Pump efficiency, but easy to wash out of water, must be equipped with a sufficiently high outlet pipe, or stare can cause serious decline in self-priming performance. The pump outlet channel is separated from the outlet, and the water outlet turns, not the outlet structure (Figure 3b). Pump body whirlpool large, pump body water loss is large, but the pump water is not easy to wash out of the water pump, water and gas separation effect, the pump self-priming performance, and not affected by the level of the outlet pipe installation, pump outlet and outlet Open two mouth alignment structure (Figure 3C). Self-absorption of water will be washed out of the pump, pump suction performance also affected by the height of the outlet pipe installation, the impact is less than the structure of Figure 3a.

That is not, for the Figure 3 a white suction pump, the vertical section of the outlet pipe to ensure only enough water it?
Theoretically speaking, the theoretical maximum of the outlet pipe volume is equal to the volume of the pump body. In fact, in the structure of Figure 3a, when the structure is self-priming, some water in the pump gas-water separation chamber and the impeller cavity is circulated and only a part of the water enters the outlet pipe, Then from the water flow by the window into the air-water separation chamber. Therefore, the actual outlet pipe volume is less than the volume of the pump body, and the height of the outlet pipe will be determined by the height of the influx a. The rising height is related to the pump structure. That is, a certain amount of circulating water volume requires a certain height of static pressure loss to the outlet pipe The water flows back through the window. The main influencing factors are the area of ​​the window, the area of ​​the lower return hole, the width of the impeller and the speed of the impeller. If the window is very small, the height will be higher, if the outlet pipe is large, the volume of water is large, if the window and the return hole are small, rising height is high, on the contrary low, large wheel width, linear speed Big, it is also a large c
Specific height can be ascertained by experimental methods, the method is to export a high outlet pipe (1.2 m or so), the pump filled with water, the pump inlet sealed, self-suction pumping boot, look at the water How high the tube rushed, this noble is the influx of height. This height can also be called the minimum water installation height, self-priming performance.
2. Pump outlet and the pump body is not connected to the flow path and streamline self-priming pump, the effluent height of the white suction performance ~ no effect.
3. Pump outlet and the pump flow was connected to the white suction pump, the outlet pipe installation is greater than the minimum water installed Gaura.
4. The minimum installation height of the effluent is related to the size of the pump channel, the size of the backwater hole, the width of the impeller, the speed of the impeller, and the like. Can be obtained by testing the maximum height of self-absorption to determine the installation of small water height.

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