The installation of centrifugal pump is analysed skills -

by:J&T     2020-06-05
01. Working principle of centrifugal pump

pump start before the pump first inflow tube filling with water. When the fast rotating impeller, the impeller of the liquid in the impeller blades driven followed spin, so that the liquid obtained the centrifugal force, and along the blade passage from the center of the impeller outward movement, and then from the end of the blade was thrown into the volute chamber within the pump casing or diffusion tube ( Or wheel) 。 When the liquid flow to the diffusion tube, as a result of the flow area gradually expanded, slows down, can will be part of the kinetic energy is converted into the static head, the pressure rise, the final out of the discharge pipe pressure. At the same time, because of the liquid in the center of the impeller was thrown produced partial vacuum, thus absorbing liquid pool of liquid from the suction pipe under the action of a liquid level pressure flowing inside the suction water pump. Continuous rotating impeller, liquid continuously by the absorption liquid pool to high or pressure vessel. To sum up, the centrifugal pump was able to transport liquid, mainly by the effect of centrifugal force, the so called centrifugal pump.

02。 The characteristics of the centrifugal pump

1. Gas bound phenomenon: centrifugal pump starts, if the pump is no priming or priming, air will be inside the pump shell, because of low air density of rotation to produce centrifugal force is small, the impeller center to the storage tank formed by low voltage to the liquid suction pump, centrifugal pump can transport liquid is started. This phenomenon is called chi bound, said no self-priming centrifugal pump capacity, so you have to the shell before starting the filling of liquid.

2。 Cavitation phenomenon: if a centrifugal pump in operation, its flow section of the local area, Usually impeller blade inlet somewhere later) For some reason, pumping the liquid pressure is reduced to the temperature of liquid pressure, the liquid at the begin to boil, to produce a large amount of steam, bubble formation, when the liquid containing a large number of bubbles within the impeller forward high, bubble around the high pressure liquid bubble dramatically narrow and fracture. Condensed during the bubble burst at the same time, the liquid particle filling holes at high speeds, in this moment of strong water hammer effect, and with the impact of the high frequency on metal surface impact stress can amount to several hundred to several thousand atmospheric pressure, impact frequency up to tens of thousands of times per second, constantly hitting the impeller and other components, make its surface show honeycomb or spongy, serious when wall thickness breakdown, cause centrifugal pump noise and vibration, serious when, the flow rate and pressure head and efficiency of the centrifugal pump dropped significantly.

03。 The installation of centrifugal pump technique

1. The installation of chemical centrifugal pump technology is the key to determine the chemical centrifugal pump installation height ( The suction) , the height is refers to the water surface by chemical centrifugal water pump impeller axis vertical distance, is not to be confused with it and allow the vacuum suction height, chemical centrifugal pump product manuals or nameplate signs allow the vacuum suction height refers to the vacuum chemical centrifugal pump inlet section on value, and it is under the condition of 1 standard atmospheric pressure, water temperature 20 ℃ test measured. It does not consider water pipe supporting future water conditions. So, chemical centrifugal pump mounting height should be allowed on the vacuum suction height after the suction pipe head loss, the remaining portion of the values, it is to overcome the actual water terrain height. Chemical centrifugal pump installation height can't more than calculated value, otherwise, chemical centrifugal pump will pump water.

2。 Reduce the pipeline resistance, therefore, appropriate USES the shortest piping layout, and try to minimize the fittings such as elbow, also can consider the appropriate with larger diameter of the pipe, to reduce tube flow velocity.

3。 It should be pointed out that chemical centrifugal pump installation site elevation and water temperature is different from the test conditions, such as local 300 meters above sea level, or by pumping the water temperature of more than 20 degrees Celsius, the calculated value will be revised. Is that the atmospheric pressure and at different elevation height of the more than 20 ℃ the saturated vapor pressure of water temperature. But, when the water temperature is 20 ℃ below, saturated vapor pressure can be ignored.

4。 Suction piping from the pipe installation technology, requires strict sealing, not leak, leakage, otherwise it will damage chemical centrifugal pump inlet of vacuum degree, reduce chemical centrifugal pump water yield, serious when even tied up. Therefore, to seriously do a good job in pipeline interface ensure the construction quality of pipe connection.

5。 Centrifugal pump export to install the check valve. In production, sometimes there will be a power outage, the problem such as motor fault, causing the running equipment shutdown suddenly, in the export of centrifugal pump check valve installation, in order to prevent the pump suddenly shut down, the export pipeline within the liquid will not go back to the water pump, the impeller inversion, formation water hammer effect, resulting in damage of impeller and mechanical seal, etc.

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