This article will take an in-depth look at centrifugal pumps.
The article will bring more understanding on topics such as:
This section delves into the basics of centrifugal pumps, encompassing their design, construction, and functional principles.
A centrifugal pump is a type of hydraulic mechanism that converts mechanical energy into hydraulic energy through the application of centrifugal force on the fluid. It functions by spinning a component to impart velocity to the liquid, thereby converting it into flow. The effectiveness of a centrifugal pump depends on its intricate system of mechanical components working in harmony.
This mechanical assembly includes the pump's shaft, which is supported by bearings, a sealing system that curtails extensive leakage, structural parts that withstand operational loads and stresses, and wear surfaces that allow the pump to be maintained and restored to its original state.
Essential components included in each pump are:
This is the core part of the pump that turns along with the impeller when attached. The shaft connects to the prime mover to receive power and is perfectly aligned with the ball bearing.
This component consists of backwards-curved vanes attached to the electrical motor shaft. The impeller, this rotating piece, is positioned within a sealed casing. As it spins, it transfers velocity to the liquid.
The casing is a sealed passage surrounding the impeller, converting the velocity imparted by the impeller into pressure energy before the liquid exits into the delivery pipe. It serves as a protective enclosure for the system, transforming the velocity generated into a consistent flow. In centrifugal pumps, three main types of casings are used: volute casing, vortex casing, and casing with guide blades.
This casing type encapsulates the impeller and features a design that gradually increases the flow area, reducing liquid velocity while boosting pressure as it traverses through the casing.
This casing includes a circular chamber between the impeller and the volute casing. After leaving the impeller, the fluid enters the vortex chamber before advancing to the volute casing. This configuration effectively converts velocity energy into pressure and typically offers performance advantages over the volute casing.
This casing variety features blades arranged around the impeller. These guide blades are engineered to smoothly direct the water from the impeller, minimizing turbulence. As water flows through the guide vanes, it passes through an expanding passage, facilitating the conversion of velocity into pressure before exiting through the delivery pipe.
The suction pipe has two ends: one connects to the pump's inlet, with the other end submerged in the water source, such as a sump. At the lower end, a foot valve is installed to open only upward, allowing unidirectional flow. A strainer is positioned at the suction pipe's end to prevent debris from entering the system.
The delivery valve, comprising two terminals, connects to the pump's outlet at one end, while the other end is responsible for transporting water to the desired height or location.
Selecting the appropriate materials for centrifugal pumps involves evaluating factors such as strength, abrasion and corrosion resistance, casting and machining traits, ease of repair and welding, and cost-effectiveness.
Centrifugal pumps are constructed from a range of materials, including cast iron, cast steel, stainless steel, bronze, brass, carbon structural steel, composite materials, alloy steel, and non-metallic substances.
Consider the following factors when selecting materials for centrifugal pumps:
Centrifugal pumps come in various types, including:
These pumps run on 12 V DC and offer a maximum flow rate of 330 GPH. They come equipped with alligator clips, a battery cable, and an on/off switch for easy operation. The pump can handle water heights as low as 1/8 inch with the suction strainer and lift water up to 40 feet. It includes a 3/4 inch garden hose adapter at both the inlet and outlet, a 6-foot suction hose, a replacement gasket, and an extra impeller. The pump's lightweight design allows for portability, and a carrying handle can be attached for added convenience.
Chemical pumps are designed specifically for use in pumping chemicals that are resistant to corrosive materials, which makes it suitable for handling corrosive and abrasive industrial liquids such as paint, fuel, solvent, bleach, and many others. A pump that contradicts the chemical can result in brittleness or dissolving, swelling, and ultimately it will leak and fail. Special consideration needs to be given to the materials of a chemical transfer pump, along with the concentration and temperature of the fluid being handled. Whenever there is required a chemical dosing pump, one for tank to tank transfer or a barrel emptying pump, the pump can be tested.
Radial centrifugal pumps direct the fluid outward at a 90-degree angle from the impeller relative to the suction direction. These pumps are prevalent and feature a horizontal suction flange with fluid exiting through a vertical discharge flange. The discharge is perpendicular to the pump’s shaft. This design is typically chosen when there is a need to increase discharge pressure while managing flow limitations. Consequently, radial centrifugal pumps are characterized by low flow rates and high pressures. They are commonly used in industries such as gas and oil.
Axial flow centrifugal pumps allow the fluid to move parallel to the pump shaft, similar to how a propeller functions. These pumps are particularly suited for applications requiring high flow rates with minimal pressure heads. They are commonly used in water circulation and dewatering systems due to their ability to handle large volumes of fluid efficiently.
Mixed flow centrifugal pumps combine both axial and radial flow characteristics, providing a balance between the two types of pumps. This design allows mixed flow pumps to handle larger flow rates while achieving a moderate increase in pressure head. They offer versatility for applications requiring both significant flow and pressure.
In a single-suction centrifugal pump, fluid enters through the inlet and is guided towards the impeller eye, which serves as the entry point for the impeller. As the fluid exits the impeller, centrifugal force generates the necessary pressure.
When the flow rate becomes too high for single-suction pumps to handle effectively, double suction centrifugal pumps are employed. These pumps are designed with an impeller that allows fluid to enter from both sides, unlike the single-sided entry of a standard pump. Despite the name "double suction," the pump still has only one flange each for discharge and suction. The primary distinction lies in the design of the casing and impeller.
Centrifugal pumps with a single volute casing direct the fluid from the impeller into a single volute that encircles the impeller entirely. This volute features a single cut-water that channels the fluid towards the pump outlet. Single volute casings are commonly used in refinery centrifugal pumps.
Portable pumps designed for dewatering applications are often used to handle large volumes of water mixed with both soft and hard solids, such as mud, twigs, leaves, sand, and sludge. These trash pumps are typically heavy-duty centrifugal pumps with larger discharge openings and deeper impeller vanes compared to other types. They can process materials with suspended particulates that might clog other pumps and can move hundreds to thousands of gallons per minute. Trash pumps are constructed with large discharge openings and pump housings, and they are available in materials like cast iron, steel, aluminum, and stainless steel. Many of these pumps feature roll cages for added durability.
Semi-trash pumps are a variant with smaller openings and are not designed to handle large solids or high concentrations of solids. For rigorous pumping tasks involving solid-laden slurries or water, regular trash pumps are more appropriate. Trash pumps come in several types, including syringe pumps, progressive cavity pumps, sanitary pumps, and positive displacement pumps.
They are also known as deep well turbine pumps. These are vertical axis or mixed flow centrifugal pumps which include stages of stationary bowls and rotating impellers to process the guide vanes. Vertical pumps are used whenever the level of water pumping is below the volute centrifugal pump limits. Vertical pumps are costly and are more complicated to refurbish and fit. The design of the pressure head mainly depends on the impeller’s length as well as on the speed of its rotation. The pressure head designed with just one impeller is not that suitable. The different types of vertical pumps are:
Other related types of pumps include vertical sumps, vertical turbine pumps, process pumps, and industrial pumps.
The well pump plays a central role in a water well system by moving water upwards into the household or designated water system. Currently, jet pumps and submersible pumps are the most commonly used types. Both utilize centrifugal force to elevate water. Impellers, which are spinning rotors, create a vacuum that pushes the water up through the well casing and into the distribution system. The choice of well pump depends on the water needs of the household and the well’s depth.
Jet pumps are installed above ground and lift water from the well using a suction pipe, with an impeller generating a vacuum. This vacuum drives water through a small nozzle. Jet pumps need to be primed with water before they can function properly. Shallow well jet pumps are designed for wells up to 25 feet deep, while deep well jet pumps can handle depths of up to 150 feet.
Submersible well pumps offer a broad range of operational depths, making them suitable for wells as shallow as 25 feet and as deep as 400 feet. As their name implies, these pumps are installed below the water level within the well. Unlike jet pumps that draw water from above, submersible pumps primarily focus their energy on pushing water upward.
These pumps are typically cylindrical and include a pump motor along with multiple impellers to move water up through the pump and into the drop pipe. Due to their robustness, efficiency, and adaptability to varying well depths, submersible pumps are the preferred choice in most contemporary well systems.
This chapter will explore the uses and advantages of centrifugal pumps, as well as cover their maintenance procedures.
Centrifugal pumps are utilized in a variety of applications, including:
The advantages of centrifugal pumps are as follows:
Some of the limitations of centrifugal pumps include:
Maintaining centrifugal pumps includes the following tasks:
A centrifugal pump is a machine that changes kinetic energy into the fluid’s pressure head. The external power from a diesel generator or electric motor then turns the pump impeller. Under the influence of the centrifugal force, the fluid enters the impeller reaching its tip and leaving the volute casing. There are many types of centrifugal pumps for example chemical pumps, vertical pumps, and trash pumps to mention only a few. They can be classified according to flow type), based on the number of stages (single stage and multi-stage pumps), and also on the type of volute (single and double volute).
Maintaining the pump is easy; most of the measures are given in the manufacturer’s guide. If used and maintained properly the centrifugal pumps can last long and are less costly. Choose a pump that is compatible with what needs to be used for example when pumping hazardous chemicals, a chemical pump is advised.
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