Essential Series on Pump Selection and Piping(3)

                                Essential Series on Pump Selection and Piping(3)

3. The Influence of Viscosity

The viscosity of the medium significantly impacts the pump's performance. As viscosity increases, the pump's head curve declines, leading to reduced head and flow rates at optimal operating conditions while power consumption rises, thereby lowering efficiency. Parameters listed in general catalogs typically represent performance for pumping clean water. When handling viscous media, conversion is necessary (correction factors for different viscosities can be referenced in relevant conversion charts). For pumping highly viscous slurries, pastes, or thick liquids, screw pumps are recommended. 

4. Impact of Pipelines

When designing and arranging pipelines, the following matters should be taken into account:

A. Select the pipe diameter appropriately. A larger pipe diameter results in lower liquid flow velocity and reduced resistance loss at the same flow rate, but it comes with higher costs. Conversely, a smaller pipe diameter leads to a sharp increase in resistance loss, requiring higher pump head and power, which in turn raises both costs and operational expenses. Therefore, a comprehensive technical and economic evaluation is necessary.

B. The discharge pipe and its pipe connections shall be designed to withstand the maximum pressure they can bear.

C. Piping layout should be arranged as straight pipes as much as possible, minimizing the number of fittings and reducing pipe length. When bends are necessary, the bending radius of elbows should be 3 to 5 times the pipe diameter, with angles preferably greater than 90 degrees.

D. Valves (such as ball valves or globe valves) and check valves must be installed on the discharge side of the pump. Valves are used to adjust the operating point of the pump, while check valves prevent reverse rotation of the pump and protect it from water hammer damage (when liquid flows backward, it generates significant reverse pressure, which can damage the pump)