Selection of pump motor power
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When the pump is operating normally, the density of the medium is lower than that of water; therefore, when selecting the power of the pump motor, is it necessary to take the density of water into account in the calculations? To be more specific, although under normal conditions the density of the fluid in the pump is lower than that of water, which means a pump with relatively lower power is sufficient, it is still necessary to consider scenarios such as the plant’s water operation when selecting the power capacity of the pump for use with water as the fluid.
Check what the shaft power is, and multiply it by a coefficient.
The motor power generally needs to be calculated by multiplying the shaft power by a coefficient； Does your coefficient refer to the shaft power calculated based on a normal medium or based on water?
If we have a pump that uses liquefied gas, it can’t pump water; it trips as soon as we try to pump water.
1. When selecting a pump, it is necessary to specify the operational requirements, such as full flow rate with a low-density medium as the first operating condition, as well as second and third operating conditions, so that the selected pump can cover all of these conditions. In other words: if a pump designed for transporting low-density media is used to move water, it is necessary to specify the operating conditions clearly. 2. A safety factor should be applied when selecting the motor, with more emphasis placed on the long-term safety of the motor itself, as well as taking into account appropriate fluctuations in the flow rate of the medium. 3. When selecting high-power, low-density medium pumps, if we take into account the conditions associated with water as the medium, it will lead to significantly higher costs for the motor; therefore, operators are required to use a low flow rate when pumping water in order to address this issue.
For pumps whose medium density is much lower than that of water, the selection criteria for motors are as follows: 1. The motor power under the rated operating conditions of the process medium; 2. The motor power at the head corresponding to the minimum flow rate during water testing. Note: The motor margin shall be determined in accordance with API610, and the higher of the two values shall be adopted
When selecting the motor power, the main consideration is the power required by the pump for transporting the process medium. If the power required during water transport is also taken into account, the motor will need to have a higher power capacity, which is a waste in terms of investment. After all, water transport is only temporary. If water transport is taken into account, it is necessary to control the flow rate or use other methods to address it.
Of course, it’s based on your current medium
I basically understand now; thanks to everyone for their generous help! For some low-flow pumps, even if the density of the medium in use is lower than that of water, using a motor designed for water doesn’t result in much of a difference ； If high-density media are used occasionally, measures such as flow adjustment need to be taken to address the issue ； Conduct a comprehensive analysis of the usage of the pump medium, taking all factors into consideration.