Centrifugal pumps are dynamic workhorses in the world of fluid motion. They operate on a simple mechanism: by converting rotational energy, often from a motor, into hydrodynamic energy, they accelerate liquids in an outward motion from their core to a discharge point.
These pumps are not only efficient but versatile, making them a favored choice across industries for tasks like water supply, sewage systems, petroleum transportation, and numerous other applications. In diving into this guide, you’ll gain an understanding of their design, functionalities, and the nuances to consider when sourcing one for your specific needs.
Popular Types of Centrifugal Pumps
Centrifugal pumps, while varied in designs and applications, can fundamentally be classified based on the number of stages they possess. The stages refer to the series of impellers (or rotors) contained within the pump; each stage adds more energy to the fluid. Let’s delve into the primary classifications:
Classification of Centrifugal Pumps Based on the Number of Stages
- Single Stage Pumps: These pumps feature just one impeller and are the most straightforward in design. They’re ideal for tasks that require a consistent flow rate and don’t need high pressure. Typical applications include water supply, light industrial processes, and heating or cooling circulation. Due to their simpler construction, they are also generally easier to maintain.
- Multistage Pumps: As the name suggests, multistage pumps consist of multiple impellers housed in a series or parallel configuration. Each stage incrementally increases the pressure of the liquid, enabling these pumps to handle more demanding tasks and achieve higher pressures. They’re preferred when a higher head (or pressure) is needed or when pumping across long distances, like in high-rise buildings, industrial plants, or water treatment facilities. Additionally, by distributing the workload across multiple impellers, multistage pumps often have a longer operational lifespan.
Classification of Centrifugal Pumps Based on Design Codes
Design codes play an essential role in the world of centrifugal pumps. These codes, put forth by recognized international standardizing bodies, ensure the quality, durability, and safety of pumps for their intended applications. When selecting a pump, understanding its design code can provide valuable insights into its capabilities, standards of manufacture, and intended use. Here are two of the most widely recognized design codes for centrifugal pumps:
- API 610: Created by the American Petroleum Institute (API), the API 610 is often referred to as the gold standard for centrifugal pumps in petroleum, petrochemical, and natural gas industries. Pumps adhering to this standard are known for their durability, reliability, and capacity to handle high temperatures, pressures, and often aggressive or volatile liquids. They are built with robust designs to withstand the rigorous demands of these industries and often come with features like enhanced sealing and monitoring systems to ensure safe operation.
- ISO 5199 / ISO 2858 / DIN 24256: This set of standards, put forth by the International Organization for Standardization and the German Institute for Standardization (DIN), provides general requirements for single-stage and multistage centrifugal pumps of standard design. ISO 5199 outlines technical specifications for these pumps, ensuring they meet standard dimensions and performance criteria. On the other hand, ISO 2858 (aligned with DIN 24256) focuses on the dimensional interchangability of pumps, ensuring parts like impellers or seal housings are standardized. Pumps under these standards are typically used in general industry, water utilities, and chemical processes, offering a balance between performance, reliability, and cost-efficiency.
Classification of Centrifugal Pumps Based on Types of Volutes
The volute of a centrifugal pump is the casing or chamber that receives the fluid being pumped. It plays a crucial role in converting the kinetic energy of the fluid (gained from the spinning impeller) into pressure energy. The design of the volute can have significant effects on the pump’s efficiency, stability, and its resistance to wear. Among the various designs, the single and double volute configurations are the most commonly employed. Here’s a closer look at both:
- Single Volute: In a single volute design, the fluid discharged by the impeller enters one continuous casing. As the fluid moves through the casing, it gradually decelerates, causing a rise in pressure. While single volute pumps are simpler in design and often more cost-effective to produce, they can introduce radial forces on the impeller. These forces might result in vibration or cause the shaft and bearings to wear unevenly, especially in larger pumps or when operated far from their best efficiency point (BEP).
- Double Volute: Double volute pumps, as the name suggests, have two separate chambers or paths for the fluid, located 180° apart. This design significantly balances the radial forces exerted on the impeller, leading to reduced shaft deflection and even wear on the bearings. As a result, double volute pumps tend to operate more smoothly, especially under varying conditions. They are more commonly found in larger pumps or applications where stability and reduced vibration are paramount.
Classification of Centrifugal Pumps Based on the Number of Suctions
The suction configuration of a centrifugal pump refers to the design in which the fluid enters the pump’s impeller. The number of suctions – either single or double – can influence the pump’s hydraulic performance, flow rate, and life cycle costs. Let’s explore both configurations:
- Single Suction: Single suction pumps have one inlet for the fluid to be pumped. As the impeller rotates, fluid enters from one side only. While these pumps are simpler in design and generally less expensive to produce, they can exhibit an imbalance of radial forces on the impeller. This imbalance can lead to premature wear on the pump’s shaft and bearings, especially at high flow rates or when pumping viscous fluids.
- Double Suction: Double suction pumps are designed with an impeller that allows fluid to enter from both sides, thereby balancing the hydraulic forces on the impeller. This dual-entry design not only reduces the axial thrust but also allows the pump to handle larger flow rates more efficiently than a single suction counterpart. The reduced wear on components translates to longer pump life and reduced maintenance costs over time.
Classification of Centrifugal Pumps Based on Casing Designs
The casing of a centrifugal pump plays a pivotal role in enclosing and directing the flow of fluid, as well as in withstanding internal pressures. One of the key distinguishing features of pump casings is how they are split or segmented. Based on this, centrifugal pumps can be classified into radial split and axial split designs:
- Radial Split: In a radial split casing design, the casing is split perpendicular to the pump shaft, creating a ‘ring’ separation. These types of casings are common in multistage pumps. The primary advantage of radial split casings is their capability to handle higher pressures, making them ideal for high-pressure systems or demanding applications. Their design allows for better containment and strength to withstand the internal stresses, especially in multi-stage configurations where pressures can be notably high.
- Axial Split: Axial split casings are split parallel to the pump shaft. This means the casing is divided into two halves, usually top and bottom, along its length. Single-stage, double suction pumps typically employ this design. One of the major benefits of axial split designs is the ease of maintenance. Components like the impeller and the shaft can be accessed without entirely dismantling the pump or disconnecting it from the piping system, leading to reduced downtime during servicing.
Classification of Centrifugal Pumps Based on Shaft Orientation
The orientation of the pump shaft plays a role in determining the physical configuration and installation footprint of a centrifugal pump. Broadly, centrifugal pumps can be classified based on their shaft orientation into vertical shaft and horizontal shaft configurations:
- Vertical Shaft: These pumps have their shafts vertically oriented, with the impeller submerged directly into the fluid being pumped, often without the need for priming. Vertical shaft pumps are commonly employed in applications where there’s limited ground space or in deep-well pumping situations. Due to their vertical configuration, these pumps are ideal for transferring fluids from lower levels to higher levels, making them particularly suitable for deep wells, sumps, or other below-ground reservoirs. They also tend to have a longer lifespan since the weight is more evenly distributed and there’s less bearing strain.
- Horizontal Shaft: Horizontal shaft pumps, as the name suggests, have their shafts oriented horizontally. This design is more common and is typically used in surface-level pumping applications. They require a certain amount of ground space for installation and might need priming to remove air from the suction line. A significant advantage of horizontal pumps is the ease of maintenance, as they are more accessible than their vertical counterparts. They are widely used in industrial settings, water treatment plants, and other applications where large volumes of fluids need to be transported over relatively short distances.
Classification of Centrifugal Pumps Based on Impeller Position
The position of the impeller in relation to the bearing assembly is important in determining the structural design, dynamic load distribution, and maintenance requirements of a centrifugal pump. Based on the impeller’s positioning, centrifugal pumps can be classified as overhung impeller pumps and between bearing pumps:
- Overhung Impeller Pump: In these pumps, the impeller is positioned at the end of the shaft and is extended away from the main bearing assembly. The bearings are located in the pump casing, and the impeller is said to be ‘overhung’ or ‘cantilevered’. Because of this configuration, these pumps can handle higher flow rates but may face challenges with heavier impellers and higher dynamic loads. Their compact design makes them popular in various industries. However, their bearing lifespan may be slightly reduced due to the cantilevered position of the impeller.
- Between Bearing Pump: This design incorporates the impeller positioned between two bearing sets. This configuration provides better support to the impeller, distributing dynamic loads more evenly across the bearings. This results in reduced shaft deflection and typically leads to a longer bearing life. Between bearing pumps are often chosen for applications requiring higher pressures and where the pump’s stability is a key consideration. Their robust design makes them suitable for handling thicker or more abrasive fluids.
What to Look for When Buying Centrifugal Pumps
When considering the purchase of a centrifugal pump, it’s imperative to account for the various operational parameters that influence its performance, efficiency, and suitability for specific tasks. Here’s a brief breakdown of key aspects you should evaluate:
- Media: Identify the fluid type (e.g., water, chemicals, oil) to ensure pump material compatibility, minimizing corrosion and wear.
- Flow: Gauge the volumetric flow rate, usually in gallons per minute (GPM) or liters per second (L/s), to match your system’s needs.
- Pressure & Temperature: Ensure the pump can handle the system’s pressure and fluid temperature, safeguarding against inefficiency or damage.
- Suction & Discharge Head: Consider the vertical distances the pump elevates and pushes the fluid. These dictate the pump’s required performance range.
- Head Loss: Account for energy losses due to friction in the pump and connected system.
- Total Dynamic Head (TDH): The amount of pressure differential created by a pump while it is operating. It is the difference between the suction pressure and discharge pressure of the pump.
Applications for Centrifugal Pumps
Centrifugal pumps boast a diverse range of applications, driven by their efficiency and adaptability:
- Water Supply for Residential Areas: They play a pivotal role in distributing water to households, ensuring consistent and safe water supply.
- Fire Protection Systems: Centrifugal pumps provide the necessary pressure to deliver water through sprinklers and hydrants, acting as the backbone of many fire suppression systems.
- Sewage/Slurry Disposal: Robust designs handle waste or thick slurry, ensuring seamless and environmentally safe disposal processes.
- Food and Beverage Manufacturing: These pumps ensure the hygienic transfer of liquids, from juices to dairy, integral in maintaining product quality.
- Chemical Manufacturing: Their corrosion-resistant models facilitate the secure transport of aggressive chemicals, safeguarding production processes.
- Oil and Gas Industrial Operations: They’re indispensable in transporting crude oil or refined products efficiently within various stages of production and refining.
Accessories for Centrifugal Pumps
To optimize the performance and lifespan of centrifugal pumps, several accessories are available:
- VFD (Variable Frequency Drive): This electronic controller adjusts the pump’s speed and power supply frequency, enabling energy savings and precise control over pump operations.
- M20 Power Monitor: Essential for real-time monitoring, the M20 power monitor provides insights into the pump’s electrical usage and performance, allowing for timely interventions and maintenance.
- Base Plates: A foundational component, base plates ensure the pump remains stable and vibration-free during operation, prolonging the equipment’s life and preventing wear.
- Pedestal Assembly: This accessory offers a raised platform for the pump, facilitating maintenance access, promoting airflow, and aiding in drainage.
Tips & Tricks
You won’t have much trouble finding a specific type of centrifugal pump on Surplus Record. At the top of all the pages on our website, you’ll see a search bar. Type the phrase “centrifugal pump” into it, click on the category that drops down, and examine the options we have available.
We also work with a variety of dealers who specialize in centrifugal pumps. You can also find dealers in your area or by name who specialize in pumps.
