Centrifugal Pumps Tutorial – Classification and Flow Characteristics

⚙️ Centrifugal Pumps Tutorial – Classification and Flow Characteristics

Centrifugal pumps are the most widely used type of pump in industries such as water supply, chemical processing, HVAC, oil & gas, and power generation. Their popularity comes from their simple design, reliability, and ability to handle large volumes of fluid efficiently.  

To understand pump performance and select the right pump for an application, it is important to study centrifugal pump classification. Pumps are classified based on the manner in which fluid flows through the pump casing and impeller.

🔹 Centrifugal Pump Classification by Flow Direction

Centrifugal pumps can be classified into three main types depending on how the liquid moves through the impeller:

1. Radial Flow Pumps

- Working Principle:  

  - Liquid enters at the center of the impeller.  

  - It is directed outward along the impeller blades at a right angle (90°) to the pump shaft.  

- Characteristics:  

  - High head, low flow applications.  

  - Commonly used in boiler feed pumps, high‑pressure cleaning, and water supply systems.  

2. Axial Flow Pumps

- Working Principle:  

  - The impeller pushes liquid in a direction parallel to the pump shaft.  

  - Operates similar to a boat propeller, hence often called propeller pumps.  

- Characteristics:  

  - High flow, low head applications.  

  - Ideal for irrigation, flood control, and cooling water circulation.  

3. Mixed Flow Pumps

- Working Principle:  

  - Combines features of radial and axial flow pumps.  

  - Liquid is pushed outward and at an angle greater than 90° to the shaft.  

- Characteristics:  

  - Balanced performance with moderate head and flow.  

  - Commonly used in municipal water supply, process industries, and HVAC systems.  

According to number of stages

Single stage- One impeller in pump

A single stage centrifugal pump is the simplest type of centrifugal pump, designed with only one impeller mounted on the shaft. The impeller imparts energy to the fluid, converting mechanical energy from the motor into kinetic energy and pressure.

Because of its straightforward design, single stage pumps are widely used in water supply, irrigation, HVAC, and general industrial applications.

🔹 Characteristics of Single Stage Pumps

One Impeller: Only one impeller is used to generate head and flow.

Simple Construction: Easy to install, operate, and maintain.

Moderate Head & Flow: Suitable for applications requiring medium pressure and flow rates.

Cost‑Effective: Lower initial cost compared to multi‑stage pumps.

Compact Design: Requires less space and fewer components

Multi-Stage Centrifugal Pumps

A centrifugal pump with a single impeller that can develop a differential pressure of more than 10 Kg/cm2 between the suction and the discharge is difficult and costly to design and construct. A more economical approach to developing high pressures with a single centrifugal pump is to include multiple impellers on a common shaft within the same pump casing. Internal channels in the pump casing route the discharge of one impeller to the suction of another impeller. The water enters the pump from the top left and passes through each of the stage impellers in series, going from left to right. The water goes from the volute surrounding the discharge of one impeller to the suction of the next impeller. A pump stage is defined as that portion of a centrifugal pump consisting of one impeller and its associated components. Most centrifugal pumps are single-stage pumps, containing only one impeller. A pump containing seven impellers within a single casing would be referred to as a seven-stage pump or, or generally, as a multi-stage pump

🔹 Classification According to Type of Casing

Centrifugal pumps can also be classified based on casing design, which influences efficiency, maintenance, and application suitability.

1. Volute type pump

Volute Casing Pumps  

   - Spiral‑shaped casing that converts velocity energy into pressure energy.  

   - Simple design, widely used in water supply and irrigation.  

2. Vortex type pump

Vortex Casing Pump – Working Principle, Features & Applications

🔹 What is a Vortex Pump?

A vortex pump (sometimes called a vortex casing pump or vortex impeller pump) is a centrifugal pump with a recessed impeller. Instead of pushing liquid directly, the impeller creates a circular swirling motion (vortex) inside the casing. This vortex transfers energy to the fluid, moving it smoothly from suction to discharge.

🔹 Working Principle

The impeller is recessed and does not directly contact solids.

As the impeller rotates, it creates a vortex flow in the casing.

The vortex motion lifts and carries the fluid (and solids) through the pump.

This design minimizes clogging and wear compared to conventional centrifugal pumps

3. Diffuser type pumps

Diffuser Casing Pumps  

   - Equipped with guide vanes around the impeller.  

   - Provides smoother flow and higher efficiency.  

   - Common in high‑capacity and high‑head applications

🔹 Key Takeaways

- Radial flow pumps: High head, low flow.  

- Axial flow pumps: High flow, low head.  

- Mixed flow pumps: Balanced head and flow.  

- Volute casing: Simple, economical design.  

- Diffuser casing: Higher efficiency, smoother flow.  

- Understanding pump classification helps engineers and operators select the right pump for specific applications, ensuring energy efficiency, reliability, and long service life.