Viscosity Chart
How does fluid viscosity affect food processing?
Viscosity is one of the key fluid characteristics to consider when selecting pumps for your food-grade processing systems. In this article, we outline what viscosity is and where common products fall on a viscosity scale so you can make informed decisions during pump selection.
What is viscosity?
Viscosity is a measure of a fluid’s resistance to flow.
Water is less viscous than corn syrup and cooking oil, for example, so on a viscosity scale or comparison chart, water would show lower viscosity than the other fluids.
Some liquids change viscosity when under stress or pressure, such as when they come in contact with a rotating impeller inside a pump. The stress or pressure the liquid encounters is called shear force.
Some liquids become less viscous (thinner) with increased shear, while others become more viscous (thicker) with increased shear.
By comparison, water does not change its viscosity, no matter how much shear is applied.
Temperature is always an important factor in viscosity and therefore in pump sizing, as you can readily imagine when you think about the flow of honey when it’s cold versus when it’s heated up. Positive displacement pumps deliver a constant flow of fluid at a given pump speed. When viscosity increases, however, resistance to flow increases, so to maintain system flow at higher viscosities, pumps require more horsepower.
While nearly all liquids have stated or apparent viscosities—take diesel fuel, motor oil, other lubricants, and paint, for example—our focus is hygienic liquids.
What is high and low viscosity?
“High” and “low” refer to the thickness of a fluid.
- High viscosity means high thickness and high resistance to flow
- Low viscosity means low thickness and low resistance to flow.
Comparing common liquids from low to high viscosity
Examples of high viscosity pumps and low viscosity pumps
| High Viscosity | Low Viscosity | High Solids Concentration | Low Solids Concentration | |
|---|---|---|---|---|
| Centrifugal | ✓ | ✓ | ||
| Self-Priming | ✓ | ✓ | ||
| Rotary Lobe | ✓ | ✓ | ✓ | |
| Diaphragm | ✓ | ✓ | ✓ | |
| Peristaltic | ✓ | ✓ | ||
| Eccentric Disc | ✓ | ✓ | ✓ | ✓ |
Next Steps
As you've seen, viscosity is one of the key fluid characteristics to consider when selecting pumps for your food-grade processing systems. If you need more information about viscosity and how it affects system design, contact CSI today!
ABOUT CSI
Central States Industrial Equipment (CSI) is a leader in distribution of hygienic pipe, valves, fittings, pumps, heat exchangers, and MRO supplies for hygienic industrial processors, with four distribution facilities across the U.S. CSI also provides detail design and execution for hygienic process systems in the food, dairy, beverage, pharmaceutical, biotechnology, and personal care industries. Specializing in process piping, system start-ups, and cleaning systems, CSI leverages technology, intellectual property, and industry expertise to deliver solutions to processing problems. More information can be found at www.csidesigns.com.