What is Multistage Pump? | Difference Between Single Stage Pump and Multistage Pump

Pump is a mechanical equipment used to transfer fluid from one area to other area. Different types of pumps are used for multiple industrial applications. There are multiple types of pumps and a centrifugal pump is one of them. Centrifugal pumps are the most common types of the pumps. Centrifugal pumps are further divided into multistage pump and single stage pump. In this article, we will deeply discuss different aspects of the multistage and single stage pumps.

What is Multistage Pump?

A multistage pump has more than one impeller. These impellers can be of the same type or of different types. In this centrifugal pump, the fluid is pressurized in more than one stages. Each stage contains an impeller and a diffuser.

The multistage pumps have multiple impellers and diffusers to increase the fluid pressure instead of pistons.  

The main objective of the impeller is to increase the speed of the fluid. In contrast, the diffuser converts the fluid speed into pressure and increases the fluid pressure. This is a more efficient pump than the single stage pump. It produces more pressurized fluid than the single stage pump.

Working Principle of Multistage Pump

A multistage pump works on the angular momentum principle. It uses centrifugal force to move the fluid in and out of the pump. In this pump, the fluid (i.e., water) flows from different stages.

multistage pump
Image Source: Mechanical Boost

It works in the following way:

  1. The impellers of the pump are driven by an electrical motor.
  2. As the motor delivers electrical power to the impeller, the impeller starts rotating and generates vacuum on the inlet side. As the vacuum generates, the fluid starts entering the pump.
  3. As the enters according to the requirement, the inlet and outlet valves close and fluid compressor process starts.
  4. The impeller contains multiple blades. When the fluid strikes the blades, they provide kinetic energy to the fluid and increase the fluid speed.
  5. As the impeller blades increase the fluid speed according to the requirements, the high-speed fluid is sent into the diffuser section.
  6. The diffuser converts the fluid speed into pressure and increases the fluid pressure.
  7. After passing through the diffuser of the 1st stage, the fluid is sent into the 2nd stage for further pressurization.
  8. As the fluid pressure is increased according to the requirements, the outlet valve opens and the fluid is pumped to the desired area.

Types of a Multistage Pumps

The multistage pump has the following major types:

1) Horizontal Multistage Pump

A horizontal centrifugal pump installs in a horizontal direction. It contains a segmented body with modular components between the stages. The rotating components of the pump are fixed between the bearing seats, which enhances the balancing of the rotating components under high pressure conditions. This configuration of the pump prevents it from extreme vibration.

The main disadvantage of the horizontal multistage pump is that it needs more floor space in horizontal direction.  However, it has capability to control more flow rate than vertical multistage pump (without vertical turbo pumps).

The horizontal multistage pumps are ideal for the following applications:

  • Snow making
  • High Pressure Cleaning
  • Reverse Osmosis
  • Boiler Feed
  • Shower

However, this pump requires more maintenance than the vertical multistage pump. The operator needs good knowledge to operate the horizontal pump. According to the brand type and the quality of the construction materials, these pumps may have high initial costs.

Advantages of Horizontal Multistage Pumps

  1. These pumps have high efficiency.
  2. They have capacity to handle more flow rates than the vertical multistage pumps.
  3. They need very low vertical floor space.

Disadvantages of Horizontal Multistage Pumps

  1. The installation of these pumps requires large floor space in the horizontal direction.
  2. They have high maintenance costs.
  3. The operation of these pumps is very complex.

2) Vertical Multistage Centrifugal Pumps

The vertical multistage centrifugal pump is installed vertically. Therefore, these pumps require more installation space in the vertical direction. However, you can easily install them in an area where you have very low space in horizontal direction.

This pump has a vertical shaft on which stages stack on one another. It is ideal for areas with limited space. Another advantage of this pump is that a combination of a single pump body and a motor can supply a high-pressure output.

However, it is important to remember that these types of multistage pumps can’t transfer contaminated fluids and large amounts of solids.

They have small clearance. The applications of the vertical pumps are given below:

  • High pressure bath systems
  • Desuperheater feed
  • Boiler feedwater

Advantages of Vertical Centrifugal Pump

  1. It requires less space in the horizontal direction.
  2. They have an easy installation.
  3. They require less maintenance than the horizontal pumps.

Disadvantages of Vertical Centrifugal Pump

  • They can’t handle large flow rates of fluids.
  • They can’t transfer contaminated fluids.
  • These pumps need large vertical installation space.

Applications for Multistage Centrifugal Pumps

  • Boiler feed
  • Water circulation
  • Reverse osmosis
  • Heating/cooling conditioning
  • Water supply boosting
  • Fire fighting
  • Irrigation

Advantages of Multistage Pump

  • The multistage pump has small diameter of the impeller.
  • These are most efficient pumps
  • They generate more pressure than the single stage pumps.
  • They have tight clearance for high efficiency and best performance.

Disadvantages of Multistage Pump

  1. These are not best to handle solids.
  2. They have priming issues.
  3. These pumps are not best for the contaminated fluids.
  4. They have more moving parts.

Single Stage Pump VS Multistage Pump

Single Stage PumpMultistage Pump
A single-stage pump pressurizes the fluid in just one stage.A multistage pump pressurizes the fluid in more than one stage.
It has only one impeller and diffuser.It has multiple impellers and diffusers.
This pump has lower rotating parts than the multistage centrifugal pump.It has more rotating parts than the single-stage pump.
These pumps require low space for installation.They require large installation space.
They are less efficient.They are most efficient.
A single-stage pump has an easy maintenance and operation.It has complex operation and maintenance.
It has a low maintenance cost.This centrifugal pump has a high maintenance cost.
It requires low maintenance.It needs high maintenance.
It can’t handle much fluid as multistage.It has the capability to handle a large amount of fluid.

Leave a Comment