DXP Pacific Industrial Pumps

Understanding Fluid Viscosity in Your Pump System

The viscosity of the process media is a very important factor when it comes to selecting the best pump for the application. Cortech Engineering has put together this guide to help you understand fluid viscosity as it relates to industrial pumps.
Viscosity, Defined and Measured
By definition, viscosity is the property of a liquid that causes it to resist to shear stress. Fluid viscosity, along with fluid density, acidity, corrosiveness and quantity will all impact how you choose the right pump options and configurations.
It is common to express fluid viscosity in relation to density using measurements such as absolute viscosity or kinematic viscosity, which uses Saybolt Seconds Universal (SSU). SSU refers to the time it will take for a measured quantity of liquid to drain from a container with a measured orifice at the bottom (at a specific temperature). We won’t go into all the complex mathematics here, but the point is, there are ways to measure and determine the exact viscosity of any liquid being processed.
Fluid Viscosity in Industrial Pumps
The impact of fluid viscosity will be different based on the type of pump being used. Let’s look at some examples:

  • Centrifugal: A centrifugal pump will be affected by viscous liquids because it increases the friction as the impeller rotates. This causes more resistance, reduced efficiency, increased input power and reduced head and flow rate.


  • Positive Displacement (Reciprocating or Rotary): These types of pumps are generally more effective when processing more viscous fluids. Higher viscosity liquids will reduce the leakage flow, otherwise known as “slip,” which can increase the volumetric efficiency.

Finding the Right Pump for Your Application
Since different pumps are designed for different purposes, not all fluids and applications will be the same. It is important to find the right pump for the situation and configure it precisely to provide the desired flow rate for the specific process fluid.
For help in selecting the best pump for your industrial application, whether the fluid being processed is highly viscous or not very viscous at all, contact Cortech Engineering today. Our engineering experts can walk you through all your options, crunch the numbers and get you set up with the best pumps from the world’s leading pump manufacturers.