Pump Construction (Part2)

Continuing our exploration of building and pump types, this article will focus on the most noteworthy attributes of the centrifugal pump. We will then delve deeper into the various types of pumps.

This article will explore the centrifugal pump, highlighting its key features and various types. Centrifugal pumps are a critical component of many industrial operations, and it is important to understand their differences and capabilities in order to make the best selection for a given application. We will go over all of the essential information regarding centrifugal pumps to help you make an informed decision.

Characteristics of the centrifugal pump

Centrifugal pumps are a type of rotodynamic pump that uses a rotating impeller to increase the pressure and flow of a fluid. They are widely used in many industrial and commercial applications due to their simple design, relatively low cost, and ability to handle a wide range of liquids. Characteristics of centrifugal pumps include high efficiency, low maintenance, self-priming capabilities, and the ability to handle high pressure. They are also capable of operating at high speeds, making them ideal for many applications.

The number of stages

Depending on the number of impellers in the pump, a centrifugal pump can be either a single-stage pump or a multistage pump.

Multistage pumps are ideal for applications requiring higher pressure than single-stage pumps can provide. These pumps are often used in HVAC/R (heating, ventilation, air conditioning, and refrigeration) systems and solar energy systems to move water or other fluids. Additionally, these pumps can also be used to transfer oil and other viscous fluids.

The multistage pump design can provide improved efficiency and performance. They are typically more reliable and require less maintenance than single-stage pumps due to their ability to pump a higher volume of fluid at a lower speed. This, in turn, reduces wear and tear and extends the life of the pump.

HVAC/R technicians should be familiar with the different types of pumps and their uses in order to ensure they are selecting the correct pump for their application. They should also understand the importance of proper installation and maintenance to maximize the efficiency and longevity of the pump.

The position of the pump shaft

The pump shaft plays an important role in the operation of a pump, as it is the part of the pump which drives the motion of the liquid or gas through it. The position of the pump shaft must be properly aligned in order to ensure efficient operation and prevent damage to the pump. In order to ensure the correct position of the pump shaft, it is important to use specialized tools to measure and adjust the position of the shaft as needed. This helps maintain the optimal performance of the pump and can prevent costly repairs.

Single-stage and multistage pumps come with horizontal or vertical pump shafts. These pumps are normally designated horizontal or vertical pumps.

Horizontal pumps are typically used in applications where there is a large amount of fluid to be moved. The advantage of a horizontal pump is that it requires less energy to move the fluid since it has a larger diameter impeller. Vertical pumps, however, are more efficient at moving smaller amounts of fluid with less power.

In the HVAC/R & Solar industry, pumps are often used to move water for cooling, heating, and other purposes. Horizontal pumps are ideal for applications where the amount of water being moved is large, while vertical pumps are more suitable for applications with smaller amounts of fluid.

The choice of pump also depends on the type of application, as well as the size and power requirements. For instance, in HVAC/R & Solar applications, a single-stage or multistage pump may be needed to generate enough pressure to move the water. The size, power, and performance of the pump should also be taken into account for the most efficient operation.

Single-suction or double-suction impellers

Single-suction and double-suction impellers are two types of pump impellers used to move fluids. Single-suction impellers feature one side with an inlet that sucks in water, while double-suction impellers have two inlets that pull in water from either side. Single-suction impellers tend to have higher speed and efficiency, while double-suction impellers offer more stability and are often used in larger pumps. Both types of impellers are important components of any fluid-moving system, and choosing the right one for the job is essential for optimal performance.

Depending on the construction of the impeller, a pump can be fitted with either a single-suction impeller or a double suction impeller.

Single suction impellers draw liquid from one side of the pump while double suction impellers draw liquid from both sides. Typically, double suction impellers provide more efficient operation and increased capacity over single suction impellers. This is because double suction impellers reduce the amount of turbulence and friction at the impeller itself, resulting in greater flow rates.

For HVAC/R & Solar industry professionals, choosing the appropriate impeller for the job is essential. The impeller must be selected based on the operating conditions of the application to ensure that the pump’s performance meets the requirements of the system. Additionally, understanding the differences between single and double suction impellers can help professionals make informed decisions when selecting the right pump for the job.

Coupling of stages

The two different pump stages arrangements are series and parallel, as shown in Figure 1. Both arrangements have their own advantages and disadvantages, and each is suitable for different applications. When selecting a pump, it is important to consider these two options to determine which will best suit your needs. Properly optimizing pump stages can help improve system efficiency and performance.

Figure 1 – Twin pump with parallel-coupled impellers

Construction of the pump casing

The construction of the pump casing is a critical step in the manufacturing process. Using high-quality materials and precision manufacturing techniques, a well-constructed pump casing ensures reliable performance and long-term durability.

We distinguish between two types of pump casing: Volute casing and return channel casing with guide vanes.

Volute casing is a cylindrical-shaped casing with a spiral-shaped interior. It is designed to be able to contain the pressure of the fluid while keeping the flow rate steady. The main advantage of this type of casing is that it helps to reduce energy losses and it is also easy to produce. On the other hand, return channel casing with guide vanes is used for higher flow rates and is more efficient than volute casing. It consists of a guide vane in the return channel which is used to direct the flow in such a way that it increases the efficiency of the pump. This type of casing is usually more expensive than volute casing due to its complexity.

No matter what type of casing you choose, it is important to ensure that it is properly designed and constructed according to the requirements of the specific application. The right casing can help to ensure that the pump operates safely and efficiently, thus optimizing the performance of the HVAC/R & Solar system. On the other hand, a poorly designed and constructed casing can lead to increased energy losses and reduced efficiency. Therefore, it is essential to assess the various types of casings available and make an informed decision based on the specific requirements of the application.

Most common end-suction and in-line pump types

End-suction pumps are designed with a 90° angle between the inlet and the outlet, allowing the liquid to run directly into the impeller. In-line pumps take the liquid through the pump in-line, with the suction and discharge pipes opposite one another and directly mounted in the piping system. Split-case pumps have an axially divided pump housing, while horizontal and vertical pumps differ in the orientation of the pump shaft. Single-stage and multistage pumps are distinguished by the number of impellers, while long-coupled and close-coupled pumps differ in the way they are connected to the motor.

End-suction pump types
  • End-suction pump = The liquid runs directly into the impeller. Inlet and outlet have a 90° angle.
  • In-line pump = The liquid runs directly through the pump in-line. The suction pipe and the discharge pipe are placed opposite one another and can be mounted directly in the piping system
  • Split-case pump = Pump with an axially divided pump housing.
  • Horizontal pump = Pump with a horizontal pump shaft.
  • Vertical pump = Pump with a vertical pump shaft.
  • Single-stage pump = Pump with a single impeller.
  • Multistage pump = Pump with several series-coupled stages.
  • Long-coupled pump = Pump connected to the motor by means of a flexible coupling. The motor and the pump have separate bearing constructions.
  • Close-coupled pump = A pump connected to the motor by means of a rigid coupling.
In-line pump types

The various types of pumps offer a range of options for different applications. End-suction pumps are generally used for supplying water and other liquids in domestic and industrial applications. In-line pumps are used for transporting liquids in high-pressure and high-flow conditions. Split-case pumps are used when the liquid needs to be pumped from a lower to a higher level.

Horizontal and vertical pumps are used to move liquid in both horizontal and vertical directions. Single-stage and multistage pumps are designed to cater to specific pressure requirements. Long-coupled pumps are suitable for applications that require a higher level of noise reduction and vibration isolation. Close-coupled pumps are ideal for applications that demand a more compact design. All these pumps are essential components of modern HVAC/R and solar energy systems, and at hvac-eng.com, we provide comprehensive information on the best pumps and their applications.


What are the key characteristics of centrifugal pumps?
Centrifugal pumps are characterized by their ability to convert kinetic energy into pressure energy, resulting in a high flow rate and low pressure rise. They are also known for their simplicity, reliability, and low maintenance requirements. Additionally, centrifugal pumps are typically compact and lightweight, making them ideal for applications where space is limited. Other key characteristics include their ability to handle low-viscosity fluids, high efficiency, and low noise levels.
How do centrifugal pumps differ from positive displacement pumps?

Centrifugal pumps and positive displacement pumps operate on different principles. Centrifugal pumps use centrifugal force to accelerate fluid, increasing its kinetic energy, which is then converted into pressure energy. In contrast, positive displacement pumps use a mechanical seal or diaphragm to displace a fixed volume of fluid, resulting in a constant flow rate. Positive displacement pumps are better suited for applications requiring high pressure and low flow rates, while centrifugal pumps are ideal for high-flow, low-pressure applications.

What are the advantages of using centrifugal pumps in industrial operations?

Centrifugal pumps offer several advantages in industrial operations, including high efficiency, reliability, and low maintenance requirements. They are also capable of handling large volumes of fluid, making them ideal for applications such as water supply, wastewater treatment, and industrial processes. Additionally, centrifugal pumps are relatively inexpensive compared to other types of pumps, and their simplicity makes them easy to install, operate, and maintain.

How do the different types of centrifugal pumps (e.g., radial, mixed, and axial flow) differ?

The main difference between radial, mixed, and axial flow centrifugal pumps lies in their impeller design and flow characteristics. Radial flow pumps have an impeller that pushes fluid radially outward, resulting in a high pressure rise and low flow rate. Mixed flow pumps have an impeller that pushes fluid both radially and axially, resulting in a moderate pressure rise and flow rate. Axial flow pumps have an impeller that pushes fluid axially, resulting in a low pressure rise and high flow rate. Each type is suited for specific applications, such as radial flow pumps for boiler feedwater and axial flow pumps for irrigation systems.

What factors should be considered when selecting a centrifugal pump for a specific application?

When selecting a centrifugal pump, several factors should be considered, including the required flow rate, pressure rise, fluid properties (e.g., viscosity, density), and operating conditions (e.g., temperature, suction pressure). Additionally, the pump’s efficiency, power consumption, and maintenance requirements should be evaluated. It is also essential to consider the pump’s compatibility with the piping system and any relevant safety and regulatory requirements.

How can centrifugal pump performance be optimized and maintained?

Centrifugal pump performance can be optimized and maintained by ensuring proper installation, operation, and maintenance. This includes regular cleaning and inspection of the pump and its components, as well as monitoring performance indicators such as flow rate, pressure, and power consumption. Additionally, optimizing pump speed, adjusting impeller trim, and ensuring proper alignment and coupling can help maintain peak performance. Regular maintenance, such as bearing replacement and seal inspection, can also help extend the pump’s lifespan.