How to correctly adjust the impact of small flow multi-stage centrifugal pump flow on the water pump, and adjust the impact of pump flow on the water pump, belongs to the head water pump. Therefore, it is inevitable to adjust the pump flow. Therefore, when adjusting, we should pay attention to some issues and methods of adjustment.

Because improper adjustment methods can have a serious impact on the effectiveness of the adjustment and the performance of the water pump. Of course, the adjustment of flow rate has nothing to do with the price of the water pump.

Changing the characteristic curve, according to the laws of proportion and cutting, both methods of changing the pump speed and structure (such as cutting the outer diameter of the impeller method) can change the characteristic curve of the pump, thereby achieving the goal of adjusting the flow rate (while changing the pressure head).

When the operating condition of the pump is less than the rated flow rate of the pump, if it is not too small, it is only a decrease in efficiency, a waste of electrical energy, and mechanical failures are still rare. Once the deviation reaches a certain limit, it will cause noise and vibration, and the pump performance may become unstable.

In China, the attention paid to this issue is far less than in foreign countries, with only a focus on the energy loss caused by "big horses pulling small cars". However, there is still a certain gap in understanding the mechanical failures caused by low flow operation. API 610 in the United States has specifically emphasized and stipulated the minimum operating flow rate for centrifugal pumps.

Namely:

The minimum continuous stable flow rate refers to the minimum flow rate that a pump can operate under the noise and vibration limits specified in the API610 standard.

The minimum continuous thermal control flow rate refers to the minimum flow rate that can maintain operation without being damaged by the temperature rise of the pumped liquid.

There are many methods for calculating temperature rise. In Japan, the proposed calculation of temperature rise is based on the fact that the power provided by the driving machine is mainly used for conveying liquids, in addition to overcoming mechanical losses from bearings and shaft seals. Once the pump is running at a low flow rate in a semi closed state, a significant portion of the power of the driving machine will be converted into heat to raise the fluid temperature. Assuming that the pump casing does not dissipate heat outwards, the power of the driving machine is fully converted into heat.