EUR
en
Due to their relative simplicity of design, centrifugal pumps are the most common pump type in the market. Centrifugal pumps are categorised into either single or multistage pumps, both of which have their uses. What is important to understand is where which should be selected, which ultimately comes down to their working principle and the application in question. So, let’s understand the differences between the two…
The primary difference between single and multistage pumps is their impellers and how this affects operation. Whereas a single stage pump has only one impeller rotating around the shaft, multistage pumps have two or more. This characteristic has several implications for the performance of the pump, which we will go onto now.
The multiple impellers of a multistage centrifugal pump are all installed and rotated on the same shaft, and essentially act like separate pumps. This mean that as the flow progresses from one stage to the next, the head increases approximately by the same amount, resulting in the multistage pump design having much higher pressure capabilities than a single impeller is able to alone.
With the above in mind, multistage centrifugal pumps are often selected when the pressure requirements of the application exceed the capabilities of a single stage pump. For example, perhaps the fluid must be moved over a very large distance with considerable friction loss, which in most scenarios is achieved via multiple impellers. A typical example of this may be providing water supply to the top of tall buildings or towers.Single stage centrifugal pumps are on the other hand the better suited solution in higher flow, lower pressure installations.
As multistage pumps reply on multiple impellers used to impart energy into the fluid being handed, each impeller can be smaller in diameter than it would be alone and can operate with tighter clearances between the impeller and volute. These smaller tolerances mean that each impeller operates closely to its best hydraulic efficiency. The result of this is that multistage centrifugal pumps are able to achieve higher performance with a smaller motor size and using less energy.
Due to the tight impeller clearance with the pump volute, multistage pumps are unable to handle solids and abrasive content unless they are oversized, which is why they are generally used with water and other low viscosity fluids. This combined with their high pressure range, makes multistage water pumps popular in applications including:
Boiler feed
Reverse osmosis
Water supply boosting
Irrigation
Fire fighting
Heating/cooling conditioning
Water circulation
Pump is a mechanical equipment used to transfer fluid from one area to another 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 type of pump. Centrifugal pumps are further divided into the multistage pump and single-stage pump. In this article, we will deeply discuss the multistage pump working, types, and applications.
A multistage pump pressurizes the fluid in more than one stage. Each stage contains an impeller and a diffuser. Therefore, it has more than one impeller.
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.
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. It works in the following way:
The impellers of the pump are driven by an electrical motor.
As the motor delivers electrical power to the impeller, the impeller starts rotating and generates a vacuum on the inlet side. As the vacuum generates, the fluid starts entering the pump.
As the enters according to the requirement, the inlet and outlet valves close, and the fluid compressor process starts.
The impeller contains multiple blades. When the fluid strikes the blades, they provide kinetic energy to the fluid and increase the fluid speed.
As the impeller blades increase the fluid speed according to the requirements, the high-speed fluid is sent into the diffuser section.
The diffuser converts the fluid speed into pressure and increases the fluid pressure.
After passing through the diffuser of the 1st stage, the fluid is sent into the 2nd stage for further pressurization.
As the fluid pressure is increased according to the requirements, the outlet valve opens, and the fluid is pumped to the desired area.
The multistage pump has the following major types:
Horizontal multistage pump
vertical multistage pump
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 the 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 a small clearance. The applications of the vertical pumps are given below:
High-pressure bath systems
Desuperheater feed
Boiler feedwater
It requires less space in the horizontal direction.
They have an easy installation.
They require less maintenance than horizontal pumps.
They can’t handle large flow rates of fluids.
They can’t transfer contaminated fluids.
These pumps need large vertical installation space.
A horizontal multistage pump is installed 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 the horizontal direction. However, it has the capability to control more flow rates than a 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.
These pumps have high efficiency.
They have the capacity to handle more flow rates than vertical multistage pumps.
They need very low vertical floor space.
The installation of these pumps requires large floor space in the horizontal direction.
They have high maintenance costs.
The operation of these pumps is very complex.
Boiler feed
Water circulation
Reverse osmosis
Heating/cooling conditioning
Water supply boosting
Fire fighting
Irrigation
The multistage pump has a small diameter of the impeller.
These are the most efficient pumps
They generate more pressure than single-stage pumps.
They have tight clearance for high efficiency and the best performance.
These are not the best to handle solids.
They have priming issues.
These pumps are not best for contaminated fluids.
They have more moving parts.
Single-Stage PumpMultistage PumpA 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 the most efficient.A single-stage pump has 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.
What are the types of Multistage Pumps?
The multistage pumps have the following types:
Horizontal pump
Vertical pump
What are the multistage pumps used for?
The multistage pumps are used for different applications including:
Boiler feed
Water circulation
Reverse osmosis
Heating/cooling conditioning
Water supply boosting
Fire fighting
Irrigation
A single-stage pump is defined as having one impeller and its related discharge collector that together produce fluid flow when powered by a driver, but due to having just one impeller, there are limits to the performance of a single-stage pump. On the other hand, a multistage pump is one where fluid flows through multiple impellers that are in series, which increases the total head (pressure) generated by the pump. Single volutes, double volutes and diffuser casing designs can all be configured into multistage pumps.
As the fluid flows through each stage, pressure becomes higher than it was in the previous stage. In multistage pumps, the impellers sometimes differ in design but should always be designed to have nearly identical flow characteristics. An example where the impellers will differ is to avoid significant cavitation in low net positive suction head (NPSH) systems. In this case, or others requiring a pressure boost prior to the subsequent stages, the first stage will be designed for low NPSH operation (such as double suction impeller) and effectively operate while increasing the pressure, prior to entering the subsequent stages.
The main purpose for selecting a multistage pump is to efficiently operate in systems that require a high total head. There is no clear-cut delineation when to move to a multistage pump, but multistage pumps are generally selected above 1,000 feet of total head.
While the fact that multistage pumps produce higher head is the most important application consideration, there are other reasons why a multistage pump would be used. All rotodynamic pumps produce noise, and this noise is contributed to by each of the individual components of the pump. Generally, the noise generated by these pumps is by hydraulic effects that are transmitted to the pump case.
Data has shown that multistage pumps will exhibit lower noise levels when compared to single-stage pumps of the same power levels. This is due to the energy being spread out over multiple stages rather than a single stage. Because of this, multistage pumps may be a better fit when high noise level is a concern.
Bookmark
Daniel Féau processes personal data in order to optimise communication with our sales leads, our future clients and our established clients.
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.