Intuitively, a thicker fluid will experience increased hydraulic losses. The reliability of data measurement equipmentīefore going into more detail, it is worth discussing why performance decreases when pumping a viscous fluid.The limited data set used to create the empirical model.The use of a dimensionless number to characterize complex phenomenon.As with many empirical methods, uncertainty inevitably exists and falls into one of the following categories: Viscosity corrections rely on empirical methods using test data to properly account for a pump performance when the service fluid has a different viscosity than the reference fluid, typically water. This article summarizes technical findings and discussion as to why the guideline is acceptable despite the uncertainties. This guideline has an acceptable amount of uncertainty, but it is imperative to understand the uncertainties of this method to ensure its correct application in pumping systems. While it is preferred to use actual performance curve data from pump manufacturers for thicker fluids, ANSI/HI 9.6.7-2015 provides a commonly used guideline to correct pump performance based on viscosity. Engineers who have been correcting the water performance curves when pumping thicker fluids should consider using the American National Standards Institute/Hydraulic Institute (ANSI/HI) 9.6.7-2015 guidelines. Pump manufacturers that only provide water performance curves for pumps should consider providing performance curves for thicker fluids. Likewise, pump power and NPSHr increase as viscosity increases. A more viscous fluid will generally experience a decrease in volumetric flow rate, head and efficiency compared to water at the same pump speed. Due to the importance of centrifugal pump performance in every fluid industry, it is imperative that accurate corrections are used when a centrifugal pump uses a thicker fluid than what the pump manufacturer used to evaluate the performance. Pump performance curves describe the head added to a fluid, pump power and net positive suction head required (NPSHr) at a variety of different volumetric flow rates. But what happens when the fluid’s viscosity significantly deviates from water? This is where engineers need to adjust the pump performance curves to account for the difference in viscosity between water and the actual fluid in the pump. Typically, pump manufacturers use water to obtain the values for their pump performance curves, even if the intended service of the pump is for a fluid with properties that are different from water. For example, a fluid with high viscosity, such as maple syrup, is thicker and resists flow more when compared to a fluid with a lower viscosity, like water. It is a fluid’s resistance to flow and is higher for thicker fluids. Viscosity is a fundamental property of a liquid.

How to perform viscosity curve test