Aspects to Pay Attention to for Slurry Pumps to Run Stably and Efficiently in Series

The advantage of slurry pumps in series is that multiple pumps are arranged in one pump station, which is convenient for installation, maintenance, operation and management, with a total low cost, it can realize overall automatic management. The following aspects should be noted when selecting slurry pumps in series:

•  Selection of working conditions of slurry pumps in series

The total head and flow rate of clean water required under the current working conditions are calculated, and a single-stage slurry pump is selected based on this. When selecting a single-stage slurry pump, it is strictly forbidden to exceed the maximum working pressure that the single-stage pump can withstand. After the single-stage pump is selected, the performance curve of the series pump is obtained by superimposing the performance curve of the single-stage slurry pump. It should be noted that when selecting the quantity of pumps in series, it is not appropriate to calculate according to the highest head of a single pump. Although the number of pumps is reduced and the initial construction cost can be lowered, it is not economical calculating from the perspective of long-term operation, because the higher the head of the slurry pump, the higher the slag speed. In the future, the life (T) of the wear parts of the slurry pump (impeller, volute liner, mechanical seal, etc.) is approximately proportional to the cube of the pump speed (R³).

• Speed regulation of slurry pumps in series

In long-distance slurry transportation applications, considering the changes in actual working conditions and the errors in pump selection calculations, speed regulation device such as hydraulic coupling, variable frequency inverter are generally installed. The speed regulation device is normally installed on the first or last stage pump.

•   Key design points of series slurry pump station:

1.  When the axial load between wear-resistant pipes is higher than the operating load of single-stage pumps, special telescopic pipes should be designed to connect the pipes to reduce the transmission of loads.
2. The overall layout of slurry pumps and wear-resistant pipes should make the discharge of each pump correspond to the suction of the secondary pump to reduce pipe support and axial loads.
3. A shaft seal water pump that provides sufficient packing sealing water should be installed in the pump station.

• Starting method of series pumps

For slurry pumps that are connected in series, the discharge pipeline is as long as kilometers to tens of kilometers. When the pumps are started, the resistance of the empty pipes is zero. If the slurry pump system is started directly, it is easy to cause a large instantaneous flow due to the small resistance, which will cause cavitation and motor overload.

To overcome the above problems, the following two starting methods are recommended:

1. The pump is stationary, feed clean water into the pump chamber from the highest point, and then start the pump at the same time. This is also the most commonly used starting method.
2.  Limit the flow of the slurry pump system to pour clean water, and then start the pump stage by stage. The flow at the beginning should be controlled at about 25% of the rated flow.