Regarding the minimum flow line of the pump
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Hello everyone. I would like to ask whether the issue of a minimum flow rate line exists only with centrifugal pumps? For example, my plunger-type or diaphragm-type metering pumps can adjust the flow rate on their own; for instance, the flow rate range is 0~50 L/H. In this case, isn’t the concept of a minimum flow rate relevant anymore? Thank you all:D
I’ve never heard of flow lines. In principle, when the flow rate of a centrifugal liquid pump is below a certain value, the pressure exerted will cause the temperature of the liquid to rise. Pressure energy is converted into thermal energy, until the liquid vaporizes. So there must be a minimum flow rate. On a macro level, the minimum flow rate is achieved as long as the pump body temperature is not high. As for positive-displacement liquid pumps, they can only regulate the output volume through backflow. But it also cannot be in a reflux state for a long time, as this will cause energy conversion and the generation of heat. For reference.
The metering pump allows adjustment of the stroke, has no minimum flow requirement, and it’s fine to set it to 0
Metering pumps do not require backflow control; adjusting the stroke is sufficient. The minimum flow line for centrifugal pumps refers to the lowest flow rate that can be achieved at the pump’s outlet when the process requires a very low outlet flow rate (i.e., when the pump’s outlet valve is opened wide). This minimum flow rate directs the fluid from the pump’s outlet back to the pump’s inlet tank. This flow is not sent outside the pump but rather returned to its inlet; the purpose of this is to prevent the pump from being overloaded. As the pump operates, it generates heat, which can raise the temperature of the fluid and lead to cavitation. High fluid temperatures can easily cause damage to the seals, as well as vaporization at the moving and stationary rings, resulting in dry friction.