When to Choose Positive Displacement vs. Centrifugal Pumps in Hygienic Applications

Selecting the right pump technology is one of the most important decisions in hygienic process design. While both centrifugal and positive displacement pumps are widely used, they operate on fundamentally different principles—and choosing the wrong type can lead to inefficiencies, product damage, or unnecessary operational challenges.

Understanding how each technology behaves under real operating conditions – not just in theory, can help processors make more confident, informed decisions.

Centrifugal pumps are typically the preferred choice for low-viscosity fluids, especially those similar to water (generally below ~100–200 cP). Their design enables smooth, continuous flow with relatively simple construction and low maintenance requirements. In hygienic systems, they are commonly used for transferring water, CIP solutions, and other low-viscosity liquids where high flow rates are required.

However, centrifugal pumps rely on velocity to generate flow, which makes them sensitive to changes in system conditions. As system resistance increases, flow rates decrease. This means that in systems with variable backpressure—such as long piping runs, filtration systems, or heat exchangers—flow can become inconsistent. Maintaining performance often requires careful system design or the use of variable frequency drives (VFDs).

Positive displacement pumps operate differently, moving a fixed volume of product with each rotation. This makes them better suited for higher-viscosity fluids (often above ~500 cP and well into the thousands or up to a million cP or more) or applications where consistent flow is required regardless of system pressure. Products such as yogurt, sauces, creams, or concentrates benefit from the steady, predictable flow these pumps provide.

They are also a strong choice for shear-sensitive products, where maintaining texture, particle integrity, or emulsion stability is important. Because positive displacement pumps operate at lower speeds and do not rely on high velocity, they can reduce the risk of product degradation.

That said, these advantages come with tradeoffs. Positive displacement pumps require proper system protection, such as pressure relief valves, because they will continue to generate flow even if downstream restrictions increase. They may also involve more complex maintenance compared to centrifugal designs, depending on the application and pump type.

In many hygienic systems, the decision is not purely based on viscosity—it also depends on how the process operates. For example, applications involving entrained air, foaming, or intermittent flow (such as tank emptying or CIP return) can challenge traditional centrifugal pumps. In these cases, selecting a pump that can handle varying inlet conditions becomes just as important as viscosity considerations.

This is where newer technologies, such as twin screw pumps, have introduced a hybrid approach. These pumps can handle a wide range of viscosities while also operating at higher speeds for CIP, allowing them to function as both a process pump and a cleaning pump. In systems where reducing equipment count or simplifying piping is a priority, this flexibility can offer meaningful advantages.

Ultimately, the choice between centrifugal and positive displacement pumps comes down to a combination of factors:

• Viscosity of the product
• Required flow consistency
• System pressure variability
• Sensitivity of the product to shear
• Presence of air or vapor in the process
• Cleaning requirements and system design

In simpler terms:

• If the application involves low-viscosity, high-flow transfer with stable conditions, a centrifugal pump is often the most efficient solution.
• If the process requires consistent flow, handles higher viscosities, or needs gentle product handling, a positive displacement pump is typically the better choice.
• If the system must handle multiple duties (process + CIP) or variable conditions, a hybrid approach like a twin screw pump may be worth considering.

Taking the time to evaluate these factors early in the design process can help avoid common performance issues and reduce the need for future system modifications. Have additional questions on which pump type is right for you? Contact you local authorized Fristam distributor or one of our application experts for additional information.