Centrifugal vs. Positive Displacement Pumps: Which One Is Better?

The market has two major types of water pumps available. These include centrifugal and positive displacement pumps. It is vital to visit https://garpen.com.au/ and distinguish the two types to ensure you choose the right one for your needs.

Centrifugal Pumps

These pumps are mechanically designed to move fluids through rotational energy from one motor to another. It lets water enter the rotating impeller along the system’s axis and cast it out through centrifugal force along the circumferences of an impeller’s vane tips.

Uses of Centrifugal Pumps

The applications of centrifugal pumps include industrial, municipal, residential, and commercial operations. They offer efficient pumping of fluids and a high flow rate, making them suitable for irrigation, air conditioning, general water supply, and water circulation.

Pros

  • Ideal for low-medium viscosity liquids
  • Low maintenance and simple design
  • High flow rates

Cons

  • Not suitable for viscous liquids
  • Inconsistent flow of liquids at a variable pressure

Positive Displacement Pumps

These pumps transport liquids by trapping part of the liquid and forcing it into a discharge line. Two to three spindles moving in the opposite direction create a function of displacing, trapping, and pumping fluids.

You can find several types of positive displacement pumps, including linear, reciprocating, and rotary. People have been using linear positive pumps to draw up liquids. Perfect examples include chain pumps and rope pumps.

Reciprocating positive pumps use one or several diaphragms, plungers, and oscillating pistons. Their valves restrict the motion of water in the right direction, making them ideal for an application that requires you to maintain a low flow rate against more resistance.

Lastly, rotary positive pumps often use a rotating principle to make a vacuum that captures and draws in water. Good examples include progressive cavity, rotary, lobe, peristaltic, vane, screw, and gear pumps. You can use a progressive cavity pump to transfer highly viscous liquids like sludge, dirt, or grit in more challenging applications.

When to Use Positive Displacement Pumps?

You choose positive displacement pumping systems depending on their capability to deal with higher viscosity liquids at a relatively low flow and high pressure since pressure doesn’t affect their efficiency. While a centrifugal pump is the most widely used pump because of its simplicity, a positive displacement pump is a great solution to deal with complex situations that a centrifugal pump can’t deal with, all thanks to the capability of running at any point on the curve.

Pros

  • Self-priming ability
  • Ideal for viscous liquids
  • Consistent pressure and flow

Cons

  • Sensitive to changes in pressure
  • Limited flow rates

What Are the Key Differences between the Two?

Both types of pumps move fluid, but they work differently and in unique ways. Here is how you can see the difference between the two types of water pumps:

1. Applications

Centrifugal pumps handle larger volumes of water, produce lower rates, and throttle the rates over a broad range. Because of these characteristics, they are ideal for petroleum, industrial production, agriculture, and more municipal power generation through generators.

On the other hand, positive displacement pumps do better in applications that deal with high viscosity and high pressure. They are also suitable for consistent performance, making them ideal for:

  • Paint spraying
  • Oil production
  • High force washing
  • Chemical injection

2. Transfer Mechanisms

Every pump works better with various kinds of fluids. Centrifugal pumps can’t deal with viscous liquids because of their frictional losses, while positive displacement pumps deal with highly viscous liquids, and their rate of flow increases as the liquids get thicker.

Positive displacement pumps also deal with shear-sensitive liquids that change when you apply pressure, stress, or force. However, centrifugal pumping systems can’t deal with such because their impellers present many risks.

3. Suction-Lift

A positive displacement pump will be an ideal option if you need suction-lift. The pump creates a vacuum on the side of the suction by using a cavity with changing volume to suck in a particular fluid amount through a pipe.

The cavity volume is reduced to push fluids out at high pressure via a discharge pipe. Centrifugal pumps don’t create a vacuum. This means they can’t lift fluid into a suction port, but manufacturers have designed specialized self-priming pumps.

4. Maintenance

A centrifugal pump needs less maintenance than a positive displacement pump. Due to their simplicity in design, a centrifugal pump is easy to repair and disassemble.

On the other hand, a positive displacement pump needs regular inspections and maintenance to ensure it works efficiently and correctly. It has many moving parts that you should regularly check and lubricate.

5. Inlet Conditions

A centrifugal pump needs a particular liquid amount to create different pressures. This means dry pumps won’t be able to start on their own. Once started, a centrifugal pump must meet a specific inlet pressure requirement that a manufacturer recommends.

Because a positive displacement pump stirs fluid by contracting and expanding its volume, you create pressure at the inlet, enabling your pump to prime on itself.

6. Flow Characteristics

The flow rate in centrifugal pumps differs with changes in the system pressure. As discharge pressure reduces, the flow rate increases. This makes it suitable for applications with a higher flow rate and low-medium viscous liquids.

On the other hand, positive displacement pumps offer a constant flow rate irrespective of the changes in their system pressure. This makes them perfect for applications that require a steady flow rate or need you to handle viscous liquids.

7. Efficiency

In general, a positive displacement pump is less efficient when compared to a centrifugal pump, especially with a higher flow rate. On the other hand, a centrifugal pump is more efficient at a higher flow rate. This makes a centrifugal pump more suitable for large-scale pumping tasks compared to a positive displacement pump.

Final Touches

You may choose between a positive displacement pump and a centrifugal pump, depending on specific applications and needs. Both have unique strengths and capabilities under specific processing circumstances. So, to make the right decision, first determine where you intend to use your water pump while considering factors like efficiency, flow characteristics, inlet conditions, maintenance, transfer mechanisms, and suction lift.