Viscosity is the property of a fluid that resists the force causing it to flow. Because viscosity can significantly impact pumping performance and results, understanding it is essential. Disregarding viscosity could lead to the purchase of a pump that is too large, which is expensive to buy and run and can take up a lot of space. Conversely, if the pump is too small, it may not be able to complete the job at hand, or it can stall, which can burn out electrical components. There are two types of fluid in terms of viscosity: Newtonian and non-Newtonian fluids. The viscosity of Newtonian fluids, such as water or alcohol, is not greatly affected by the pumping action and will not exhibit a significant change in flow or pressure over time. When pumping non-Newtonian fluids, such as nondrip paint or toothpaste, the viscosity changes during the process. This change can cause fluid resistance leading to underperformance or cavitation, which can ruin the material and pump equipment. But viscous fluids are not going away anytime soon. So how does one address viscosity so that the integrity of the material remains intact? While pressure and flow correction methods can help keep things flowing when the viscosity changes, selecting the right pump at the outset can eliminate the need for adjustments later.
Select the right pump early on to prevent later adjustments.
ARO
04/30/2018
Table 1. An energy cost balance sheet for the operating system
Because of these factors, understanding viscosity is critically important when determining how to size a pump and the diameter of the pipeline to use. To better understand, see Table 1 above, which illustrates the degree of viscosity (measured in centipoise) for several materials.
Image 1. Diaphragm pump viscosity correction factor for viscous fluids (Images courtesy of ARO)