Working principle and advantages of centrifugal pump Why should the outlet gate valve be closed when the centrifugal pump is operating

Working principle and advantages of centrifugal pump Why should the outlet gate valve be closed when the centrifugal pump is operating

Because the centrifugal pump by impeller inlet vacuum water absorption, so before starting should be in the pump and suction pipe grouting diversion channel, or vacuum pump, in order to exclude gas vacuum, and the pump body and suction pipe must be strictly sealed, can not leak steam, or forming a vacuum, may not suck water. Before the pump starts, the pump and the inlet are filled with water. After the pump runs, under the action of centrifugal force caused by the high-speed operation of the impeller, the water in the impeller passage is broken up to the four sides, and the water in the reservoir is sucked into the suction pipe at the edge of the external atmospheric pressure to supplement this space.
Because the centrifugal pump by impeller inlet vacuum water absorption, so before starting should be in the pump and suction pipe grouting diversion channel, or vacuum pump, in order to exclude gas vacuum, and the pump body and suction pipe must be strictly sealed, can not leak steam, or forming a vacuum, may not suck water.
1. Working principle of centrifugal pump
Before the pump starts, the pump and the inlet are filled with water. After the pump runs, under the action of centrifugal force caused by the high-speed operation of the impeller, the water in the impeller passage is broken up to the four sides, pressed into the vortex shell, the impeller channel produces a vacuum, and the reservoir water is sucked into the edge suction pipe under the external atmospheric pressure to supplement this space. Then the suction water is also thrown out by the impeller through the vortex shell and into the outlet. It is not difficult to see that, if the centrifugal pump impeller continues to rotate, it can continue to absorb water and kill the well, and the water will continue to rise from the bottom to the height or distance. In general, centrifugal pump is mainly because under the action of centrifugal force formed by the high-speed operation of the impeller, the water is lifted to the high altitude, so the name centrifugal pump.
2, the general characteristics of centrifugal pump
(1) The flow trend of water along the centrifugal pump is to suck in the radial direction of the impeller, and flow out vertically in the axial direction, that is, the direction of flow in and out of each other into 90¡ã.
(2) Because the centrifugal pump by the impeller inlet of the vacuum water absorption, so before starting should be in the pump and suction pipe grouting diversion channel, or vacuum pump, in order to exclude gas vacuum, and the pump body and suction pipe must be strictly sealed, can not leak steam, or forming a vacuum, may not suck water.
(3) Because the inlet of the impeller is unlikely to produce a vacuum, the relative height of the centrifugal pump suction shall not exceed 10 meters, plus the loss along the water flow through the suction pipe, the specific allowed installation of the relative height (the pump center line from the relative height of the suction surface) is far less than 10 meters. If the assembly is too high, generally do not absorb water; In addition, because the mountain area than the plain area of the atmospheric pressure is low, so the same pump in the mountain area, especially in the high mountain area installation, the relative height of the assembly should be reduced, otherwise it can not suck water.
Water pump has different main uses, different types of transportation of liquid substances, not the same platform flow, not the same category of pump head, therefore, the structure of nature is not the same, raw materials are not the same, summed up, can be roughly divided into:
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Why should the outlet gate valve be turned off when the centrifugal pump is operating? After the pump has achieved the highest speed, the outlet valve should be gradually opened to gradually increase the water output, so that the motor current will gradually increase to the rated voltage. The water in the pump inlet pipe opened the pump before is static, such as suddenly accelerated, the back of the water “can not keep up”, will let the working pressure of the inlet plummet, so that the water vaporization, and then centrifugal pump time. (Because the centrifugal pump is to use the pump impeller to promote the rotation of water to form a centripetal force, and the quality of steam (gas) is very light, according to F=ma, the centripetal force is not large, so that the pump can not send out the water).
Centrifugal pump has a remarkable characteristic: when the working pressure (pump head) is relatively low, its total flow will be very large, so it can be known from the characteristic parameters of centrifugal pump. The pump power is positively related to the total flow, when the pump starts, there is no pressure in the pipeline, it leads to the pump flow is very large, the pump power is very large, coupled with the motor, centrifugal pump rotation part from the stop to high-speed operation, must be a large instantaneous speed, this will inevitably lead to the starting current is very large, so the way to turn off the outlet valve, The pump does not export the water flow when starting, so that the pump power is small, when the pump does the highest speed, gradually open the outlet valve, gradually increase the water output, so that the motor current gradually increase to the rated voltage.
On the other hand, the water in the pump inlet pipe opened the pump before is static, such as suddenly accelerated, behind the water “can not keep up”, will let the working pressure of the inlet plummet, so that the water vaporization, and then centrifugal pump time. (Because the centrifugal pump is to use the pump impeller to promote the rotation of water to form a centripetal force, and the quality of steam (gas) is very light, according to F=ma, the centripetal force is not large, so that the pump can not send out the water).