Difficulties When Pumping High Viscosity Fluids

Fluid viscosity is an important property of fluids that cannot be overlooked. Learn what viscosity means for your pump selection.
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Pump performance can be substantially impacted when pumping high viscous fluids.  It is important to understand the viscosity of the fluid to be transferred prior to purchasing a pump.  The EDDY Pump Corporation is a premier industrial pump manufacturer.  EDDY slurry pumps are specifically designed for highly viscous applications, and they excel in extremely harsh environments.  

This article includes:

  • Types of Viscosity Found in Fluids
  • The Difficulty Pumping High Viscosity
  • How to Determine the Right Pump for Viscosities
  • Choosing Pipe Sizes
  • More Information on Slurry Pumps
Viscosity can be defined as the property of a fluid that resists the force tending to cause the fluid to flow. Basically, the viscosity is a measurement for how quickly a liquid flows. As you can imagine, trying to pump fluid much thicker than water can be challenging for many pumps, and outright impossible for others.
Animation of how the EDDY Pump outperforms centrifugal pumps when it comes to pumping high viscosity fluids.

Types of Viscosity Found in Fluids

In simple terms, liquid generally can be divided into two categories: Newtonian liquids and Non-Newtonian liquids. Non-Newtonian liquids can be further divided into two categories, depending on their properties: Thixotropic or Dilatant.

Newtonian Liquid

Liquids that exhibit constant viscosity regardless of shear rate or agitation. These fluids have a linear relationship between viscosity and shear stress and viscosity is only affected by temperature. Water or alcohol would be prime examples of Newtonian fluids.

Non-Newtonian Liquid

Thixotropic or Shear Thinning
Liquids that exhibit reduced viscosity when agitated or mixed are referred to as shear thinning or thixotropic. Paint is a good example of a shear thinning liquid.

Dilatant or Shear Thickening
Liquids that exhibit increased viscosity when agitated or mixed are referred to as dilatant or shear thickening. Quicksand is a famous example of a dilatant.

The Difficulty Pumping High Viscosity

For high viscosity fluids, centrifugal pumps are not ideal because of the close critical tolerances and lack of ability to mix thixotropic materials to provide a shear thinning effect. Without this thinning effect, the viscosity is not naturally reduced by the action of the pump, causing the pump to require more and more power as the viscosity is increased.

As the viscosity increases, the pump performance needs to be adjusted to match the properties of the liquid and the resistance to shear. Pumping viscous liquid usually means a reduction in flow and head, as well as a significant increase in power needed to move the fluid.

Typical Liquid Viscosities

Below is a list of substances and their viscosities; these are to be used as comparison examples only. To pump some of these specific materials listed require certifications due to the critical nature and requirements of the substance.


Typical liquid Centipoise
Water 1 1 31
Milk 3 4 40
No. 4 fuel oil 12.6 15.7 80
Cream 20 20.6 100
Vegetable oil 40 43.2 200
SAE 10 oil 88 110 500
Tomato juice 180 220 1,000
SAE 30 oil 352 440 2,000
Glycerine 800 1,100 5,000
Honey 1,500 2,200 10,000
Glue 3,000 4,500 20,000
Mayonnaise 5,000 6,250 28,000
Molasses B 8,640 10,800 50,000
Sour cream 15,000 19,000 86,000

How to Determine the Right Pump for High Viscosity

First, you should try to determine the viscosity of the material you need to pump. The best way to accomplish this is to use a device called a viscometer. However, viscometers only measure viscosity under a single flow condition. For liquids with viscosities that can vary depending on flow, an instrument called a rheometer is used. Therefore, rheometer can be considered as a special type of viscometer.

The process of measuring viscosity with a rheometer is done by applying a force to the fluid and determining how long it takes for the fluid to move a specific distance. The end result is a method for measuring viscosity so that the most suitable pump can be chosen for an application.

The EDDY Pump makes a great choice for pumping highly viscous material. The EDDY Pump’s geometric rotor acts as a mixer on thixotropic materials and provides a shear thinning effect enabling the pump to move high viscosity liquids much more efficiently than other pumps. The EDDY Pump’s ability to pump concentrated solids is perfect for moving viscous materials with less than 5% free liquid; an impossible task for traditional centrifugal pumps.

Choosing Pipeline Size

Viscosity is critical in determining the selection and sizing of piping, valves, and motors. Using a friction loss chart will detail friction loss data for a given flow rate, pipe size, and fluid viscosity, helping you select the right components for your job. This information combined with available viscosity data will allow a proper analysis of the fluid process system characteristics. Once the fluid process system has been designed and the pump operating parameters defined, the proper pipeline selection can be made. When handling viscous fluids, it can be challenging to determine how they behave. Experience is paramount, as there is no substitute for actually working with these materials out in the field and seeing how they operate.

More Information on Slurry Pumps

The EDDY Pump Corporation offers a full line of products that are specifically designed for high viscous fluids. If you are pumping slurry, high solids, extremely viscous material, paste, high abrasives (sand & gravel) and material filled with solids, then you found the best-suited pump for the job. Go to:

More Information on Slurry Pumps

The EDDY Pump Corporation offers a full line of products that are specifically designed for high viscous fluids.  If you are pumping slurry, high solids, extremely viscous material, paste, high abrasives (sand & gravel), and material filled with solids, then you found the best-suited pump for the job.  Go to:  https://eddypump.com/products/slurry-pumps/ Or Call Us!

Eddy Pump For High Viscosity

Order or Get Selection Help

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