What is the optimal equipment for protein lines to achieve reliable transfer, predictable flow rates, and consistent texture? It often comes down to the choice of a positive displacement pump vs. centrifugal pump.
Proper equipment selection relies on understanding how your product behaves and the specific details of your workflows. Here’s what you should know before making a decision.
Understanding Centrifugal and Positive Displacement Pumps
Positive displacement (PD) and centrifugal pumps are both common pieces of equipment for protein transfer. However, they operate on different principles. A centrifugal pump has a spinning impeller that accelerates material and converts mechanical energy into kinetic energy and pressure. The output is determined by a curve, so it enables flexible operation when flow rate and pressure vary due to valves, discharge piping length, and other criteria.
The major difference between a positive displacement pump vs. centrifugal pump is that PD pumps move a fixed volume each cycle. The pump traps volume on the suction side and then pushes it to the discharge port. With the same volume transferred each time, the flow rate remains steady. Processes can operate at higher pressure with PD pumps, but this also requires additional design considerations.
Both types of pumps can be adapted for sanitary service, but they each have their own applications. Centrifugal designs are useful for low-viscosity fluids and high-capacity transfer. Positive displacement pumps, meanwhile, can tackle much thicker fluids and deliver consistent flow under varying pressure.
Positive Displacement Pump vs. Centrifugal Pump for Protein Processing
Before choosing a pump to support your process, you should have a clear understanding of what positive displacement and centrifugal pumps have to offer. Pump behavior, controls, cleaning, and maintenance access, as well as your unique product, will all factor into making the right choice.
Benefits of a Centrifugal Pump
Centrifugal pumps could be the right fit if you work with:
- Thin liquids or low-viscosity fluids at high flow rates
- Low-pressure duty flow
- Processes in which minor flow variation is acceptable
- Schedules with heavy clean-in-place or transfer service
Why Choose a PD Pump
Positive displacement pumps may be a better choice when handling:
- Highly viscous fluids with constant flow
- Fluids that are sensitive to shear
- Processes that require precise metering
- Cases that require self-priming capability
Each type of pump has its ideal applications, so carefully consider these criteria before making your selection.
Factors to Consider When Choosing Between Positive Displacement and Centrifugal Pumps
Here are a few key aspects of food processing that may impact your decision between these two types of pumps.
Viscosity and Performance in Industrial Pumps
Protein-processing facilities typically handle a wide range of fluids. While brines might behave like thin liquids, protein slurries can be incredibly viscous, and there are many examples in between. Viscosity varies by shift and over time, and has a major impact on pumping performance.
Thick fluids tend to result in poor centrifugal performance. The rising internal friction requires higher speeds to maintain the flow rate, increasing heat, shear, and wear. Positive displacement pumps perform better with high-viscosity fluids. They maintain consistent flow under varying discharge pressure, stabilizing feed when batches vary in thickness.
Shear Sensitivity and Texture
Many emulsified meat products and blended proteins are sensitive to shear. The high-speed impeller inside a centrifugal pump creates significant local velocity gradients, leading to high shear that can damage product in certain applications. However, some models implement unique impeller designs and operating speeds to limit shear.
Positive displacement pumps operate at lower speeds and have controlled clearances, limiting shear and its effects. A variety of PD pump designs can preserve particulates and limit fluid velocity to protect sensitive products.
Flow Rate and Line Integration
Flow control is often one of the most important pump requirements for protein processing. Packaging, injection, and forming all require constant flow rates. Positive displacement pumps are an excellent option for repeatable yields and stable timing.
Centrifugal pumps are well-suited to processes where variation isn’t a major concern. They allow for precise output control through throttling and speed adjustments. For consistent performance, make sure any elements in the same pipeline as the pump aren’t creating major pressure changes.
Safety Protections and Installation Considerations
Reliable suction priming is a primary design goal when installing centrifugal pumps. For this reason, positive displacement pumps are a solid choice in certain applications with a higher suction lift.
However, their operating conditions mean that overpressure can occur rapidly if not accounted for in design. As such, discharge relief paths are necessary to ensure safety. Regardless of the pump type you go with, you’ll need to verify discharge pressures.
In food-processing operations, hygienic fittings and the practical reality of inspection, service, and washdown all combine to guide equipment selection.
Choosing the Right Pumps for Your Processes
Pump selection is critical for achieving smooth operations and consistent quality in protein processing. When making a choice, you’ll need to carefully consider factors like viscosity, shear, and flow.
The knowledgeable team at FPEC can offer clear guidance to help you choose machines that are suited to your facility. Contact us today to schedule a consultation and learn more about which pumps might be best for your operations.
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