Centrifugal pump minimum flow protection line
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The centrifugal pump is equipped with a minimum flow line for protection; a control valve is installed on this line. The control valve on the minimum flow line is adjusted based on the flow rate measured by the orifice flow meter located on the main outlet pipe of the pump. When the flow rate in the main pipe falls below 30% of the pump’s rated flow rate, the control valve on the minimum flow line opens. At what flow rate does this control valve close?
This post was last edited by ylb913 on 2015-11-18 at 16:22. If the normal flow rate at the pump outlet is 30% or more of the rated flow rate, can’t it be turned off then? It won’t turn on if it’s above 30%.
The solution suggested by the poster indicates that 30% corresponds to a point close to the pump’s minimum continuous flow rate; once the flow rate increases, it can be turned off at a point slightly above 30% of the rated flow rate.
Is the minimum circulation line controlled by a control valve? That’s too extravagant. When the main flow rate does not fluctuate frequently, the minimum circulation line is generally kept with the manual valve slightly open; whether this opening degree is appropriate should be determined based on the pressure reading at the pump’s outlet under normal flow conditions.
The minimum flow line is generally not turned off. . . For high-pressure pumps, the minimum flow line should also ensure that the pump is not subjected to excessive pressure in the event of a sudden blockage in the main line.
It’s a return valve, not a minimum flow valve~~ If it opens when the value is below 30%, then it closes when the value is above 30%~~
Generally, a PID regulator is used for regulation in this type of setup. If the pump outlet flow is set at 30% of the rated flow, when the process flow is below 30%, the return valve will open slightly to ensure that the pump outlet flow does not drop below 30% continuously. And when the process flow exceeds 30%, it shuts down automatically. Conclusion: Usually, there is only one set value, and no other valve closing set value as you mentioned exists.
What are the hazards of a pump operating at a flow rate below the minimum level for an extended period? Which types of pumps generally come equipped with protective measures, and what are these protective measures?
According to API610, Edition 8, the minimum flow rate is defined by the following two values: 1) Minimum continuous stable flow rate: the lowest flow rate at which the pump can operate properly without exceeding the noise and vibration limits specified in API610, Edition 8; 2) Minimum continuous thermal limit flow rate: the lowest flow rate that allows the pump to function properly while preventing cavitation caused by the heating of the liquid being pumped, which could otherwise damage the pump. Minimum flow device: If the pump operates under conditions where the minimum flow rate is not reached, it must be equipped with a minimum flow device, such as an automatic leak-back check valve or a bypass pipe, in order to avoid motor vibration, reduce noise, and prevent damage to components caused by the medium.
Reasons for using centrifugal pumps with minimum flow protection: http://wenku.baidu.com/view/49e0b954312b3169a451a447.html
Do motors also have low-load protection, or rather, what types of pump motors come equipped with such protection?