Specifying Equipment for High Viscosity Materials

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Specifying Equipment for High Viscosity Materials: It’s All About the Bore (and More!)

We promise not to bore you, but when it comes to specifying equipment for transferring and dispensing high-viscosity, dense pastes, a lot of it really is about the bore.

Well, it’s not entirely about the bore, but it’s definitely a major factor. Transferring thick paste-like materials can present unique challenges, and understanding how to handle them efficiently is key to smooth operations.

Let’s break it down: thick, viscous materials don’t behave the same way as low-viscosity liquids when moving through pipes, hoses, or pumps. For example, when a thick paste flows through a hose, it creates more friction against the inner walls than a thin liquid would. This increased friction results in lower throughput, meaning reduced flow the other end of the hose. Fortunately, there are several strategies to help overcome these challenges and increase the flow of high-viscosity materials.

  1. Shear Action: Making Materials Flow More Easily

One of the primary methods for improving the flow of viscous products is shear action—typically achieved through stirring or agitation. When certain materials are subjected to shear forces, their viscosity decreases, and they become more fluid. This phenomenon is known as shear thinning. A classic example is hand cream: when you rub it between your hands, the cream becomes runnier and spreads more easily.

However, not all materials are shear thinning. Some materials remain unaffected by shear action, while others are shear thickening, meaning their viscosity increases when subjected to shear. When specifying equipment for such materials, it’s essential to consider the material’s behaviour under shear forces. If the material is shear thinning, applying agitation can help. However, for materials that are shear thickening or shear stable, high-intensity agitation should be avoided.

Another consideration is the recovery of shear-thinning materials. After agitation or shear stress, these materials should return to their original viscosity when the shear stops. If the material is specifically formulated for a particular viscosity, it’s important to ensure that the viscosity can recover once agitation ceases. Excessive shear energy can permanently alter the product’s characteristics.

Pumping systems inherently introduce shear energy as materials are drawn through moving parts. For shear-thinning materials, this can be beneficial, as it aids flow. However, for shear-thickening materials, low-shear methods are preferred to prevent altering the product’s consistency.

  1. Heat: Making Materials Flow More Freely

Another effective strategy for enhancing the flow of viscous materials is heat. Most high-viscosity materials become runnier and easier to flow when they are heated. Of course, this only works if the material can be heated without damaging its properties. For products that can tolerate heat, incorporating heater jackets on tanks, heated hoses, or heated pumps and valves can make a significant difference in flow rates. By maintaining a consistent, elevated temperature, you can ensure that the material flows more easily through the system.

However, care must be taken to ensure that the heating process does not alter the product in ways that would make it unsuitable for its intended use. For example, some materials may degrade, change color, or lose their desired properties if overheated.

  1. Increased Pressure: Pushing Materials Through

Increasing the pressure of the material flowing through the pipes or hoses is another way to increase throughput. By raising the pressure, you force more material through the system at a faster rate. However, this strategy has its limits. There are maximum pressure ratings for hoses, fittings, and pumps, and pushing beyond those limits can cause equipment failure. Therefore, while increased pressure can help to move thick materials, it’s important to observe pressure ratings and make sure they are not exceeded.

  1. Increase Bore: The Key to Efficient Flow

When dealing with high-viscosity products, increasing the bore of pipes, hoses, and equipment is often the most effective way to improve flow. Larger bore pipes reduce frictional loss, meaning that the material can move more freely without the need for excessive heat or pressure. This is particularly useful for thick, dense pastes where friction is a major obstacle.

While increasing the bore size is a highly effective solution, it can sometimes result in large and cumbersome hoses or pipes. However, in many cases, the benefits of increased flow and reduced friction outweigh the drawbacks of larger equipment.

  1. Specifying Equipment for High-Viscosity Materials

When specifying equipment to handle thick, high-viscosity pastes, there are several key factors to consider:

  • Bore Size: Large bore inlet and outlet ports, as well as large bore fluid paths, are essential for maintaining optimal flow rates and reducing friction.
  • Pump Type: Choose pumps that are capable of handling high-viscosity materials without causing damage or excessive shear. Positive displacement pumps, for example, are often a good choice for thick pastes.
  • Agitation or Shear Methods: For shear-thinning materials, agitation can help reduce viscosity. For shear-thickening or shear-stable materials, opt for low-shear transfer methods.
  • Temperature Control: Integrating heat sources like heated hoses or tank jackets can reduce viscosity and make materials flow more easily.
  • Pressure: Ensure the equipment is rated to handle the pressures necessary to move viscous materials effectively, but don’t push beyond the limits of the system.

Conclusion

In summary, specifying equipment for high-viscosity materials is a balancing act of several factors, with the bore size being a critical consideration. By understanding how viscosity behaves under shear forces, heat, and pressure, you can select the right equipment and strategies to achieve optimal flow. Whether it’s increasing the bore, applying shear action, or introducing heat, there are multiple approaches that can help you handle dense, high-viscosity pastes more effectively. With the right specifications, you can ensure that your material transfer and dispensing systems run smoothly, efficiently, and cost-effectively.