Positive Displacement Pump vs. Centrifugal Pump — What’s The Difference?

In the world of heavy-duty pumps, there are two main types: positive displacement and centrifugal. Each has its own attributes and applications, which you need to understand to ensure you get the right pump for your end-use.

This article will look at positive displacement pumps vs. centrifugal pumps and their differences and similarities.

What Is Positive Displacement?

Positive displacement works by trapping a fixed volume of liquid in a chamber and then forcing the trapped liquid into the discharge pipe. There are two positive displacement water pump types:

  • Rotary positive displacement pumps, including vane pumps, screw pumps, progressive cavity pumps, peristaltic pumps, gear pumps and lobe pumps
  • Reciprocating positive displacement pumps, such as diaphragm pumps and piston pumps

How Do Centrifugal Pumps Work?

centrifugal pump

Centrifugal pumps use a spinning impeller to transfer the kinetic energy from the pump's motor to the fluid, drawing the liquid into the pump at an increased velocity, which helps move the liquid to the pump outlet.

There are two kinds of centrifugal pumps:

  • Axial flow centrifugal pumps, which use a propeller-shaped impeller
  • Radial flow centrifugal pumps, which use a fan-like impeller

What Are Centrifugal Pumps Used For?

Centrifugal pumps are used for a variety of activities, particularly involving low-viscosity fluids in high-flow-rate, low-pressure installations. They're ideal for high-volume situations. Some of the most in-demand centrifugal pump applications include:

  • Petrochemicals
  • Light fuel transfer
  • Irrigation
  • Mining
  • Sea water transfer
  • Industrial water supply

Positive displacement pumps are often used with high-viscosity liquids in applications like:

  • Sewage systems
  • Waste oil disposal
  • Industrial oil supply
  • Foodstuffs
  • Slurries

Centrifugal Pumps vs. Positive Displacement Pumps

When used for the appropriate application, both positive displacement and centrifugal pumps offer high performance levels. But when comparing centrifugal pumps vs. positive displacement pumps, there are several crucial differences to keep in mind.

The chief difference is that positive displacement pumps create flow, and pressure results, while centrifugal pumps create pressure, and flow results. Other critical differences include:

Flow Rate vs. Pressure

The flow rate with centrifugal pumps varies with pressure, whereas the flow rate with displacement pumps remains constant with varying pressures.

Flow Rate vs. Viscosity

As viscosity increases, a centrifugal pump's flow rate will fall, while a positive displacement pump's flow rate will increase for a period and then remain constant.

Efficiency vs. Pressure

A centrifugal pump works well at a specific pressure — efficiency will fall with any deviation from that pressure. But a positive displacement pump continues to operate efficiently, regardless of the pressure.

Efficiency vs. Viscosity

Centrifugal pumps work more efficiently with low-viscosity fluids than positive displacement pumps do. But the efficiency of centrifugal pumps drops dramatically with an increase in viscosity, while the efficiency of displacement pumps remains relatively constant with just a small drop.

The Benefits of a Positive Displacement Pump vs. Centrifugal Pump

positive displacement pump

As a result of the differences outlined above, positive displacement, or PD, pumps offer several benefits, such as the ability to:

  • Manage different levels of viscosity
  • Maintain a higher level of pressure, viscosity and flow
  • Pump at higher rates of pressure
  • Keep a constant flow and speed

Also, the operational pressure doesn't affect their capacity.

Centrifugal pumps have specific benefits as well, including:

  • A simple design that often makes them less expensive than PD pumps
  • Fewer moving parts, which makes them cheaper to repair and maintain
  • Compact set-up, which means they're ideal for situations where space is tight

Because of the lower maintenance costs, centrifugal pumps are well-suited to applications that require constant pumping.

Purchase Your Heavy-Duty Pumps From Dragon Products

Now that we've discussed positive displacement pumps vs. centrifugal pumps, you're ready for the next step. With years of expertise in the oil and gas industry, Dragon Products has an unparalleled understanding of your heavy-duty pump requirements. Contact us today for the assistance you need.

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