Why Shear Rates Matter More Than Ever In Pump Selection
- 5 days ago
- 3 min read
Selecting a pump has traditionally been driven by two primary considerations: flow rate and pressure. However, as process industries increasingly handle complex, high-value and shear-sensitive fluids, a third factor is becoming critical – shear rate.
This was one of the key messages delivered by Michael Tekneyan, Head of Development Digital Products at NETZSCH Pumps & Systems, during a recent talk on shear-sensitive fluid handling. According to Tekneyan, many process fluids can be negatively affected when subjected to excessive shear during pumping. Shear-sensitive fluids are found across a wide range of industries, including environmental and energy applications, chemicals, paper production, oil and gas, and battery manufacturing.
“Any time a fluid is moved through a pump, energy is introduced into that fluid,” he explained. “The way the pump conveys the fluid, as well as the speed at which it operates, directly influences the shear applied to the product.” He said shear rate describes the deformation a fluid experiences when subjected to different velocities within a flow path. In simple terms, high fluid velocities moving through small gaps generate higher shear rates, while lower velocities through larger gaps generate less shear.
Although some fluids remain largely unaffected, many non-Newtonian fluids respond significantly to shear. Shear-thinning fluids experience a reduction in viscosity as shear increases, while shear-thickening fluids become more viscous under higher shear conditions.These changes can have a direct impact on process performance, product quality and pumping efficiency, he said.
Looking beyond flow and pressure
While calculating shear rates in pipelines is relatively straightforward, determining what happens inside a pump is considerably more complex. To address this challenge, NETZSCH uses computational fluid dynamics (CFD) simulations to model fluid behaviour inside its pumps. These simulations allow engineers to visualise pressure distribution and calculate shear rate distributions throughout the pumping process.
One of the outcomes of this work, said Teknayan, is the development of shear rate histograms. These graphs illustrate the percentage of fluid exposed to different levels of shear inside a pump. The histograms provide a new way of comparing pump technologies beyond conventional performance criteria. For example, two pumps may deliver the same flow rate and differential pressure, yet expose the fluid to vastly different shear conditions. Understanding these differences can be particularly valuable when handling products that are sensitive to viscosity changes or excessive shear.“ The traditional selection process focuses on flow and pressure requirements,” said Tekneyan. “But if the fluid is shear sensitive, understanding the shear rate distribution can become just as important.”
A greenfield advantage
Tekneyan believes the greatest opportunity lies during greenfield project development, where engineers have the flexibility to evaluate technologies before equipment is specified. By incorporating shear rate analysis into the pump selection process, project teams can identify technologies better suited to protecting fluid integrity while still meeting process requirements.
While reducing pump speed is one method of lowering shear rates, it is not always practical because it also affects flow rate. Instead, selecting the most appropriate pump technology for a specific application often delivers better results. NETZSCH currently applies this approach across its range of progressing cavity pumps, rotary lobe pumps, multi-screw pumps and peristaltic pumps.
The role of digitalisation
The company is also exploring how digital technologies can provide operators with greater visibility into shear-related performance. As part of ongoing research and development activities, NETZSCH has developed proof-of-concept systems capable of calculating and displaying live shear rate distributions using operational pump data.
Through an IoT-enabled dashboard, operational data such as pump speed, flow rate, pressure and temperature can be analysed in real time to calculate a live shear-rate distribution, creating what Tekneyan describes as a “virtual sensor”. Because shear rate cannot currently be measured directly using a physical sensor, these calculations offer a potential pathway for operators seeking greater control over sensitive processes.According to Tekneyan, the concept could be particularly valuable in facilities handling multiple products or batch processes where fluid characteristics and shear sensitivity vary from one production run to another.
A growing consideration
Although shear-related issues are not encountered every day, Tekneyan noted that customers increasingly investigate shear effects when unexplained process problems occur.
Importantly, pumps are not always the source of excessive shear. Filters, pipework and other process components can also generate high shear conditions, particularly where fluids are forced through small openings at high velocities.
Nevertheless, as process industries continue to work with more specialised and performance-sensitive products, understanding how pumping technology influences shear rates is likely to become an increasingly important part of system design. For engineers responsible for fluid handling systems, the message is clear: selecting a pump based solely on flow and pressure may no longer be enough. Understanding how a pump interacts with the fluid itself could prove equally important in maintaining product quality and process efficiency.
NETZSCH Pumps & Systems,
+27 (0) 11 794 8975,
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