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High-Performance Pumps for Shear-Thinning Slurry Applications
Fluids Handling

High-Performance Pumps for Shear-Thinning Slurry Applications

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Selecting the correct pump for high-density slurry applications can make the difference between reliable long-term performance and frequent maintenance issues. Fluids that change viscosity during operation present a unique engineering challenge and require careful consideration of pump type, motor sizing and operating conditions.

In this latest case study, we take a closer look at a recent project delivered for a client requiring an efficient and reliable solution for transferring a high-density slurry through a recirculation circuit. The application demanded dependable performance whilst handling a difficult fluid with highly variable characteristics.

The slurry consisted of a mixture of barite and bentonite with a consistency similar to drilling mud. It would be pumped continuously through a recirculation circuit for homogenisation and required operating pressures of up to 12 bar with variable flow rates of up to 77m³/h.

Understanding Barite and Bentonite Slurries

Barite and bentonite are both essential minerals used extensively within the oil and gas drilling industry, although they perform very different functions.

Barite is an ultra-dense mineral that is added to drilling fluids to increase their weight. By increasing the density of the drilling mud, barite helps maintain well pressure and prevents uncontrolled formation fluids from entering the wellbore.

Bentonite, by contrast, is a highly absorbent clay that thickens drilling fluids and helps seal the wellbore. Its excellent suspension properties allow it to carry drill cuttings whilst maintaining fluid stability throughout the drilling process.

When combined, barite and bentonite produce a dense, highly viscous slurry that is considerably more challenging to pump than conventional liquids. This meant that selecting the correct pump specification was critical to ensuring reliable performance and long service life.

The Challenge of Shear-Thinning Slurry

One of the most demanding aspects of this application was that the barite and bentonite mixture behaved very differently from standard liquids.

Whilst stationary inside the storage tank, the slurry exhibited a high specific gravity and very high viscosity. However, once shear was applied during pumping, both the viscosity and the apparent resistance to flow reduced significantly. The fluid effectively transformed from a thick paint-like substance into a much more free-flowing liquid.

This behaviour is known as shear-thinning and presents a significant challenge during pump selection. The chosen high-density slurry pump needed to be capable of handling the fluid when it was at its thickest whilst continuing to operate efficiently once the viscosity dropped during circulation.

Designing a pumping system that accommodates these changing characteristics is essential for maintaining consistent flow, reducing wear and achieving maximum operational efficiency.

north ridge pumps Progressing Cavity Pump

How Specific Gravity Affects Pump Performance

Pump performance is typically expressed using performance curves based on water, which has a specific gravity of 1. Since pump flow rate is measured by volume rather than weight, the density of the liquid being pumped has a significant influence on overall system performance.

As specific gravity increases, the pump must generate greater pressure to move the liquid through the system. This results in higher power consumption and increased motor loading, both of which directly influence operating efficiency and energy costs.

Conversely, liquids with lower specific gravity require less pressure and less power, meaning a smaller motor may often be sufficient.

The presence of solids further increases the power required by the pump. Wastewater containing sewage is generally treated as having a specific gravity close to 1 because of its high water content. Dense industrial slurries such as barite and bentonite mixtures can easily reach two or even three times this density, placing substantially greater demands on both the pump and its drive motor.

Understanding these characteristics is vital when specifying industrial slurry pumps, as undersized equipment can quickly become overloaded, whilst oversized equipment may operate inefficiently.

Why Fluid Viscosity Matters

Viscosity is another major consideration when selecting pumps for slurry applications.

If a liquid remains highly viscous whilst standing still and experiences little or no shear, then a positive displacement pump is generally the preferred solution once viscosity exceeds approximately 300cSt.

A centrifugal pump is typically unsuitable for these conditions because its effective viscosity handling is generally limited to around 300cSt. Attempting to pump highly viscous fluids using centrifugal technology often results in poor efficiency, increased wear and inadequate system performance.

High-density fluids also increase the pressure that the pump must develop and the power required from the motor. It is therefore essential that the selected pump is capable of producing sufficient pressure whilst operating efficiently under these demanding conditions.

Careful consideration of viscosity, density, operating pressure and required flow rate ensures reliable long-term operation whilst minimising maintenance and energy consumption.

Our Pump Specification

For this demanding bentonite transfer application, North Ridge Pumps supplied its DN120K4, a heavy-duty industrial progressing cavity pump weighing more than 1.1 tonnes and measuring 3.9 metres in length.

The entire DN range has been designed using a modular construction philosophy, allowing common pump components to be shared across multiple pump models ranging from industrial process duties through to hygienic applications.

The DN Series also features a modular drive connection, enabling the pumps to be coupled directly to a motor, via a gearbox or through a lantern with a bearing housing where higher pressures or continuous 24/7 operation are required.

For this application, the DN120K4 provided the ideal combination of durability, flexibility and pumping performance.

The progressing cavity pump is capable of handling viscosities up to 10,000mPas whilst transferring liquids with specific gravities of up to 3, making it particularly well suited to challenging slurry transfer applications involving drilling muds, mineral slurries and other high-density industrial fluids.

The complete unit was assembled with a 37kW motor incorporating additional fan cooling. This enabled the pump to deliver a broad operating range with flow rates between 19 and 77m³/h whilst operating at relatively low pump speeds of just 60 to 270rpm.

Maintaining lower rotational speeds helps minimise wear on internal components, extending service life and reducing maintenance requirements whilst still delivering the required system performance.

A Critical Component: The Cardan Joint

An important feature of the pump is the cardan joint located within the pump head. This component transmits torque from the motor, gearbox and pump shaft to the pressure-generating rotor.

Widely known as a universal joint or U-joint, the cardan joint is a mechanical coupling that connects rigid shafts whose axes are inclined relative to one another. This allows rotary motion and torque to be transmitted efficiently even where shaft alignment changes during operation, making it particularly effective in demanding industrial pumping systems.

The cardan joint used within the bentonite transfer pump has been engineered without welded components. This enables it to withstand torque levels up to four times higher than its designed operating parameters whilst providing exceptional durability.

Its robust construction also makes it highly suitable for continuous 24/7 industrial operation and pumping pressures of up to 48 bar, offering additional reliability in demanding process environments.

Choosing the Right High-Density Slurry Pump

Applications involving barite, bentonite and other shear-thinning slurries require far more than simply selecting a pump capable of achieving the desired flow rate. Factors including viscosity, specific gravity, pressure requirements, solids content and operating conditions all play an important role in determining the most suitable pumping solution.

A correctly specified progressing cavity pump can deliver reliable performance, reduced maintenance, improved energy efficiency and extended equipment life even under the most demanding operating conditions.

If you have an application involving the transfer of high-density fluids and need help finding the best pumping solution, speak to North Ridge Pumps today.

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About us

North Ridge Pumps are an independent manufacturer and distributor of pumps. Having been established since 1998, we have a vast array of experience having become accustomed to supplying pumps for most processes.

We work within a range of industries both UK and Internationally, specifying pumps for a wide variety of applications from the transfer of corrosive and aggressive chemicals, to dewatered sludge, viscous grease, resin, glues, food and Seawater.

Our pumps range from standard centrifugal and multistage pumps, to immersed and process overhung solid handling pumps. We also supply a wide range of positive displacement pumps including Vane, Piston, Progressing Cavity and Peristaltic enabling us to specify more than one solution for your application, but also ensuring the majority of applications remain within our reach.

We offer the following services:

Technical support – We know at times pump selection is difficult. Pump selections are made with confidence by technical sales engineers who understand your process, ensuring equipment is engineered beyond your needs.

To select the correct technical solution for your requirement, longevity of design is prioritised. If there are existing issues you need assistance with, we work with you to solve these which could be high maintenance costs, frequent service periods, repeated equipment breakdown leading to lost revenue, inconsistent flow rates, clogging or where pumped product is inconsistent.

Application experience – Due to our 20 years of application experience we work with you to ensure our pumps operate according to your desired application. Our experience means we have most likely provided a solution for a similar process previously. With proven results, we know how to achieve your outcome sooner.

As our pumps are completely configurable, we design pumps with materials according to your requirement, and to your required duty point. Pumps are engineered specifically for your process whether they be baseplate mounted, within a mobile frame or in kit form with couplings, hoses, and dispensing nozzle.

Industry knowledge – We have a thorough understanding of a range of industries through experience from supplying the offshore oil and gas market, to paper mills, chemical plants and food manufacturers to name a few.

We not only understand the importance of downtime but also what each process requires and how small design improvements specific to the nature of your industry and application can reduce downtime, facilitate maintenance and improve longevity.

If you have a process or application you require a pump for, or a process which requires improving, get in touch to see how we can help.

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Photo of North Ridge Pumps North Ridge Pumps Follow on X Send an email 26 seconds ago
26 5 minutes read
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