High viscosity liquids are “thick” fluids that resist flow—such as honey, syrups, molten chocolate, polymers and many adhesives. Viscosity often changes significantly with temperature, and thixotropic liquids can become less viscous when agitated or sheared. AxFlow helps customers pump high viscosity and thixotropic liquids reliably by selecting the right positive displacement pump technology—and by supporting projects with viscosity measurement using our rheometer.
AxFlow supply proven pumping and fluid-handling solutions for high viscosity and thixotropic liquids—helping customers move thick products reliably, minimise shear, and maintain consistent process performance. With technologies ranging from positive displacement pumps for very high viscosities to specialist support such as viscosity measurement, we match the right pump and configuration to your product, temperature range, and duty conditions.
Why high viscosity changes pump selection
As viscosity increases, centrifugal pumps become progressively less effective and can recirculate fluid within the pump head. For thicker products, a positive displacement pump is typically required. Pumps for high viscosity duties commonly use larger inlets and slower running speeds, improving efficiency and reducing shear compared with centrifugal designs.
Here are the typical maximum viscosties of most common pump types.
- AODD pumps: up to 20,000 cP
- Centrifugal pumps: up to 200 cP
- Circumferential piston pumps: up to 1,000,000 cP
- Eccentric disc pumps: up to 3,000 cP
- Gear pumps: up to 1,000,000 cP
- Metering pumps: up to 5,000 cP
- Peristaltic hose pumps: up to 25,000 cP
- Peristaltic tube pumps: up to 10,000 cP
- Rotary lobe pumps: up to 700 cP
- Rotary vane pumps: up to 22,000 cP
As the density and thickness of a fluid increases, it becomes increasingly difficult to flow and pump with a centrifugal pump. Typically the thicker the fluid a different technology is required being positive displacement pumps, as with a centrifugal pump the thicker the fluid is the more it recirculates within the pump head.
Pumps which handle high viscosity fluids typically have larger inlets, run slower, and are consequently more efficient with such fluids than a centrifugal pump. Pumping high viscosity liquids require careful handling to prevent changes to its consistency, ensure parts of the liquid do not separate out and that solids remain in suspension.
The secret to handling viscose fluids sucessfully is a wide range of pump types something that AxFlow has in abundance.These are supported by our UK and international expertise and ability to measure fluid viscosities with our rheometer.
We are also able to supply systems that incorporate mechanical pump feeders and bridge breakers.
Why is viscosity an important factor when selecting a pump
Viscosity is an highly important factor to consider when selecting a pump because it directly affects the pump's ability to efficiently transport liquids or fluids.
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Viscosity Variation with Temperature: Viscosity changes with temperature, affecting the fluid's flow properties. Effective pumping solutions must accommodate variations, ensuring consistent performance across different temperature ranges.
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Resistance to Flow: Highly viscous fluids resist flow, making it challenging to pump them efficiently. As viscosity increases, traditional centrifugal pumps become less effective, necessitating alternative technologies for successful pumping.
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Preventing Separation and Suspension Issues: Certain viscous fluids contain solids or particles. Careful handling is vital to prevent separation, ensuring uniform consistency and suspension of solids within the liquid.
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Cavitation Risk: High-viscosity fluids can increase the risk of cavitation, which occurs when the pressure in the pump drops to a level where the fluid vaporizes and forms cavities or bubbles.
- Maintenance and Longevity: The viscosity of the fluid can also impact the wear and tear on pump components. High-viscosity fluids may cause more significant wear on impellers, seals, and bearings, potentially leading to increased maintenance requirements and shorter pump lifespan.
Examples of Highly Viscous Fluids
- Molasses
- Molten chocolate
- Polymer melts
- Adhesives and sealants
- Lubricating grease
Pumps which handle high viscosity typically have larger inlets, run slower, and are consequently more efficient with such fluids than a centrifugal pump. Some high viscosity liquids require careful handling to prevent changes to its consistency, ensure parts of the liquid do not separate out and that solids remain in suspension.
Successful handling of highly viscous fluids involves understanding viscosity changes, selecting appropriate pump types, and implementing precise operational techniques. With a wide array of pump technologies and expertise, AxFlow ensures efficient and reliable solutions for pumping challenges posed by viscous substances, ensuring consistency and quality across various industrial applications.
