Centrifugal pumps work by converting mechanical energy into hydraulic energy using centrifugal force. They are commonly used to lift liquids to higher elevations.
The document discusses key components of centrifugal pumps including the impeller, casing, suction and delivery pipes. It also covers critical concepts such as net positive suction head (NPSH), wearing rings, stuffing boxes, and lantern rings which are used to seal the pump shaft. Cavitation and its damaging effects are also summarized.
This document provides an overview of centrifugal compressors. It begins with introductions to potential and kinetic energy as they relate to compression. It then discusses dynamic compressors like centrifugal and axial compressors. The document outlines the major parts of compressors like casings, impellers, diffusers, and seals. It also describes the cooling, lubrication, and safety systems that support compressor operation. Finally, it discusses operating characteristics, configurations like series and parallel, and performance features of compressors.
Centrifugal compressors work by imparting kinetic energy to a gas stream using an impeller, converting the dynamic energy into increased static pressure. They have advantages like high throughput capacity and efficiency over a wide operating range, but also disadvantages like discharge pressure limitations. Key components include impellers, diffusers, volutes, casings, shafts, bearings, and seals. Surge, a dangerous condition where flow reverses rapidly, must be controlled. Compressors can operate alone or in multi-stage arrangements with intercoolers. Common drivers are steam turbines, electric motors, and gas turbines.
This document provides an overview of the Pelton turbine. It describes the Pelton turbine as an impulse type water turbine invented by Lester Allan Pelton in the 1870s. The key parts of a Pelton turbine discussed include the penstock, runner, casing, spear rod, deflector, nozzle, and brake nozzle. It also briefly discusses the specific speed of turbines and notes that China produces the most hydroelectric power worldwide.
A pump is a mechanical device that transfers rotational energy to liquid to move it from one place to another. There are two main types of pumps: dynamic and positive displacement. A reciprocating pump is a type of positive displacement pump that uses a piston or plunger to trap and move liquid. A rotary pump also positively displaces liquid but does so continuously rather than reciprocating. A centrifugal pump is a type of dynamic pump that uses a rotating impeller to accelerate liquid and convert kinetic energy to pressure energy to move the liquid.
The document discusses cooling towers, including:
1. Types of cooling towers like natural draft, mechanical draft, forced draft, induced draft, cross flow and counter flow towers.
2. Parameters for assessing cooling tower performance including range, approach, effectiveness and cooling capacity.
3. Energy efficiency opportunities like selecting an appropriately sized tower, using efficient fill media to reduce pumping needs, and optimizing fans and motors.
This document provides an overview of centrifugal compressors. It begins with introductions to potential and kinetic energy as they relate to compression. It then discusses dynamic compressors like centrifugal and axial compressors. The document outlines the major parts of compressors like casings, impellers, diffusers, and seals. It also describes the cooling, lubrication, and safety systems that support compressor operation. Finally, it discusses operating characteristics, configurations like series and parallel, and performance features of compressors.
Centrifugal compressors work by imparting kinetic energy to a gas stream using an impeller, converting the dynamic energy into increased static pressure. They have advantages like high throughput capacity and efficiency over a wide operating range, but also disadvantages like discharge pressure limitations. Key components include impellers, diffusers, volutes, casings, shafts, bearings, and seals. Surge, a dangerous condition where flow reverses rapidly, must be controlled. Compressors can operate alone or in multi-stage arrangements with intercoolers. Common drivers are steam turbines, electric motors, and gas turbines.
This document provides an overview of the Pelton turbine. It describes the Pelton turbine as an impulse type water turbine invented by Lester Allan Pelton in the 1870s. The key parts of a Pelton turbine discussed include the penstock, runner, casing, spear rod, deflector, nozzle, and brake nozzle. It also briefly discusses the specific speed of turbines and notes that China produces the most hydroelectric power worldwide.
A pump is a mechanical device that transfers rotational energy to liquid to move it from one place to another. There are two main types of pumps: dynamic and positive displacement. A reciprocating pump is a type of positive displacement pump that uses a piston or plunger to trap and move liquid. A rotary pump also positively displaces liquid but does so continuously rather than reciprocating. A centrifugal pump is a type of dynamic pump that uses a rotating impeller to accelerate liquid and convert kinetic energy to pressure energy to move the liquid.
The document discusses cooling towers, including:
1. Types of cooling towers like natural draft, mechanical draft, forced draft, induced draft, cross flow and counter flow towers.
2. Parameters for assessing cooling tower performance including range, approach, effectiveness and cooling capacity.
3. Energy efficiency opportunities like selecting an appropriately sized tower, using efficient fill media to reduce pumping needs, and optimizing fans and motors.
This document provides information on centrifugal pump classification, installation, maintenance, and troubleshooting. It includes classifications based on ANSI/API standards for overhung, between bearing, and vertically suspended pump designs. The document also details maintenance procedures and checklists for pump systems, mechanical components, electrical systems, diesel engines, and more. Common centrifugal pump problems like low flow are addressed along with potential causes such as air leaks, low speed, and high system head.
This document provides an overview of the scope of work for overhauling a turbine. It outlines the preparation, alignment checks, disassembly, non-destructive testing, fact-finding, reassembly, and commissioning processes. The specific tasks listed include opening bearing pedestals, uncoupling various components, checking alignments, disassembling the high pressure and low pressure turbines and valve blocks, performing non-destructive testing, inspecting individual parts, reassembling components, and conducting final alignment checks and commissioning. Detailed procedures are provided for selected tasks such as opening bearing pedestals and uncoupling various turbine sections.
This document summarizes a parametric study evaluating design parameters for pulsation dampeners on plunger pumps. The study uses a pulsation model to examine the effects of:
1) Pump system configuration, finding that complex piping can significantly impact pulsations compared to just the pump package.
2) Dampener location, finding pulsations generally increase as the dampener moves farther from the pump, and are still high when located next to the pump due to quarter-wave resonances.
3) Dampener neck geometry, finding pulsations decrease with a larger neck diameter and shorter neck length to maximize the dampener's effect.
The study also examines the impacts of fluid compressibility and
Basics of centrifugal. Topics covered are operating principles, energy conversion, components in centrifugal pump, the concept of NPSH, pump rating calculation and affinity laws
Pump Cavitation & Net Positive Suction HeadHasnaın Sheıkh
This document summarizes key concepts related to pump cavitation and net positive suction head (NPSH). It defines cavitation as the formation of vapor bubbles when local pressure inside a pump drops below the vapor pressure of the liquid. Repeated cavitation can damage impeller blades through pitting and erosion. NPSH is introduced to quantify the pressure required to avoid cavitation. NPSH available considers the inlet pressure accounting for piping losses, while NPSH required is provided by pump manufacturers as the minimum pressure needed. The document outlines how NPSH available and required values vary with flow rate and other variables like liquid temperature.
PRINCIPAL OF COOLING TOWER
TYPES OF COOLING TOWER
DIFFERENT TERMS USED IN COOLING TOWER SPECIFICATION
AIR PROPERTIES AND
SIZING OF COOLING TOWER HEIGHT
TYPICAL SPECIFICATION FORMAT / DATASHEET
Types of compressor and application in oil and gas industryajichemix
This presentation covers the type of compressors, its application, capacity control methods, surge control, cooling system, advantage and disadvantage of compressors.
Positive displacement pumps move fluids by trapping a fixed volume and forcing that volume from the suction to discharge side. Reciprocating pumps, like piston pumps, use reciprocating motion powered by engines while rotary pumps use rotating components like gears or lobes. Piston pumps have two check valves and a reciprocating piston powered by translating rotary motion into linear motion. They can be direct or indirect acting, simplex or duplex, and single or double acting. Diaphragm pumps use a flexible diaphragm instead of pistons. Rotary pumps have gears, lobes, screws, cams, or vanes that rotate to trap and move fluid and include gear, lobe, screw, vane, and cam pumps
The document describes the key components and processes in a vapor absorption refrigeration system:
1) An evaporator where refrigerant vaporizes and absorbs heat, 2) An absorber where refrigerant vapor is absorbed by an absorbent, releasing heat, 3) A generator where heat regenerates the refrigerant and absorbent, and 4) A condenser where refrigerant condenses and liquefies. Heat from a heat source like steam drives the process without the need for a compressor.
When altitude increases, water's boiling point decreases as pressure drops. For every 27mmHg increase in pressure, boiling point rises 1°C. Water vaporizes based on temperature and pressure. NPSHa is the available positive suction head, calculated as total suction head minus vapor pressure. NPSHR is the required positive suction head to avoid cavitation. Cavitation can damage pumps when NPSHa is less than NPSHR. Engineers must ensure sufficient margin between liquid and vapor states.
The document discusses the design of dimple jackets for vessels. Dimple jackets allow for construction from light gauge metals while maintaining strength for pressures. Their design begins with an assumed flow velocity between 2-5 ft/s. Dimple jackets are typically more economical than other choices when internal pressure is less than 1.67 times the jacket pressure. However, dimple jackets are not practical for vessels less than 10 gallons. The design of dimple jackets is governed by inspection standards and limited to a pressure of 300 psi and temperature of 700°F. Correlations and estimates are provided for heat transfer coefficients and pressure drop calculations for dimple jacket design.
This document discusses vapor compression refrigeration systems from Sana'a University in Yemen. It covers topics like coefficient of performance, the basic refrigeration cycle with four main components (evaporator, compressor, condenser, expansion valve), processes within the cycle, effects of evaporator and condenser temperatures, examples of cycle analysis, use of flash tanks and accumulators, and multistage compression systems. The document is presented by Dr. Abduljalil Al-Abidi from the Mechanical Engineering department and focuses on vapor compression refrigeration taught to students.
Air compressors:- One of the important device used to compress air at high pressure.
The presentation contains a detailed information about air compressors, classification of air compressors, reciprocating air compressors, rotary type, multistage/ single stage compressors. advantages and lastly application/ uses of air compressors.
Hope You like the presentation.
The document discusses multi-stage centrifugal pumps. It explains that a multi-stage centrifugal pump has two or more impellers to produce a high head. In a series connection, the total head developed is equal to the number of impellers multiplied by the head developed by each impeller. In a parallel connection, multi-stage pumps are arranged in parallel to discharge a large quantity of liquid, with the total discharge equal to the number of pumps multiplied by the discharge from each pump. Some applications of multi-stage centrifugal pumps include pumping water in high-rise buildings, industrial wash down facilities, fire hydrant systems, boiler feed systems, and irrigation.
Centrifugal pumps work by using an impeller to increase the pressure and flow of a liquid. Liquid enters the center of the impeller and is accelerated outward by the curved blades of the impeller. This increases the pressure and flow of the liquid. Calculating the required head of a centrifugal pump involves accounting for static head, pipe friction losses, and adding additional head for safety. Proper pump selection is based on matching the required head and flow rate to the pump performance curves. Cavitation and ensuring adequate Net Positive Suction Head (NPSH) are also important considerations for centrifugal pump operation.
Shell and Tube Heat Exchanger in heat TransferUsman Shah
Shell and tube heat exchangers consist of a bundle of tubes enclosed in a cylindrical shell. Fluids flow through either the tubes or shell to facilitate heat transfer between the two fluids. They are widely used in chemical processes due to their ability to achieve a large heat transfer surface area in a compact volume. Key components include tubesheets, baffles, support rods and segmented baffles which direct fluid flow across the tube bundle for efficient heat transfer. Design considerations include allocating the more corrosive or fouling fluid to the tubeside for easier cleaning and maintenance.
This Presentation is about working principle of Pumps.Basic Presentation regarding pumps , will definitely help beginners to learn pump types , their working , their parts etc.
Centrifugal pumps work by using a rotating impeller to impart velocity energy to fluid and increase pressure. They consist of a casing and impeller on a shaft. As fluid enters the impeller eye, the impeller blades spin and eject fluid outward, increasing pressure. The volute collects and redirects the fluid, converting velocity energy to pressure. During operation, pressure imbalances across the impeller cause both radial and axial thrusts. Radial thrust is balanced through design of the casing and volute. Axial thrust is balanced through methods like balancing holes, wear rings, back vanes, or double suction impellers.
The hydraulic machines which convert the mechanical energy into hydraulic energy are called pumps.”
“If the mechanical energy is converted into pressure energy or kinetic energy by means of centrifugal force
acting on the fluid, the hydraulic machine is called Centrifugal pump.”
This document provides information on centrifugal pump classification, installation, maintenance, and troubleshooting. It includes classifications based on ANSI/API standards for overhung, between bearing, and vertically suspended pump designs. The document also details maintenance procedures and checklists for pump systems, mechanical components, electrical systems, diesel engines, and more. Common centrifugal pump problems like low flow are addressed along with potential causes such as air leaks, low speed, and high system head.
This document provides an overview of the scope of work for overhauling a turbine. It outlines the preparation, alignment checks, disassembly, non-destructive testing, fact-finding, reassembly, and commissioning processes. The specific tasks listed include opening bearing pedestals, uncoupling various components, checking alignments, disassembling the high pressure and low pressure turbines and valve blocks, performing non-destructive testing, inspecting individual parts, reassembling components, and conducting final alignment checks and commissioning. Detailed procedures are provided for selected tasks such as opening bearing pedestals and uncoupling various turbine sections.
This document summarizes a parametric study evaluating design parameters for pulsation dampeners on plunger pumps. The study uses a pulsation model to examine the effects of:
1) Pump system configuration, finding that complex piping can significantly impact pulsations compared to just the pump package.
2) Dampener location, finding pulsations generally increase as the dampener moves farther from the pump, and are still high when located next to the pump due to quarter-wave resonances.
3) Dampener neck geometry, finding pulsations decrease with a larger neck diameter and shorter neck length to maximize the dampener's effect.
The study also examines the impacts of fluid compressibility and
Basics of centrifugal. Topics covered are operating principles, energy conversion, components in centrifugal pump, the concept of NPSH, pump rating calculation and affinity laws
Pump Cavitation & Net Positive Suction HeadHasnaın Sheıkh
This document summarizes key concepts related to pump cavitation and net positive suction head (NPSH). It defines cavitation as the formation of vapor bubbles when local pressure inside a pump drops below the vapor pressure of the liquid. Repeated cavitation can damage impeller blades through pitting and erosion. NPSH is introduced to quantify the pressure required to avoid cavitation. NPSH available considers the inlet pressure accounting for piping losses, while NPSH required is provided by pump manufacturers as the minimum pressure needed. The document outlines how NPSH available and required values vary with flow rate and other variables like liquid temperature.
PRINCIPAL OF COOLING TOWER
TYPES OF COOLING TOWER
DIFFERENT TERMS USED IN COOLING TOWER SPECIFICATION
AIR PROPERTIES AND
SIZING OF COOLING TOWER HEIGHT
TYPICAL SPECIFICATION FORMAT / DATASHEET
Types of compressor and application in oil and gas industryajichemix
This presentation covers the type of compressors, its application, capacity control methods, surge control, cooling system, advantage and disadvantage of compressors.
Positive displacement pumps move fluids by trapping a fixed volume and forcing that volume from the suction to discharge side. Reciprocating pumps, like piston pumps, use reciprocating motion powered by engines while rotary pumps use rotating components like gears or lobes. Piston pumps have two check valves and a reciprocating piston powered by translating rotary motion into linear motion. They can be direct or indirect acting, simplex or duplex, and single or double acting. Diaphragm pumps use a flexible diaphragm instead of pistons. Rotary pumps have gears, lobes, screws, cams, or vanes that rotate to trap and move fluid and include gear, lobe, screw, vane, and cam pumps
The document describes the key components and processes in a vapor absorption refrigeration system:
1) An evaporator where refrigerant vaporizes and absorbs heat, 2) An absorber where refrigerant vapor is absorbed by an absorbent, releasing heat, 3) A generator where heat regenerates the refrigerant and absorbent, and 4) A condenser where refrigerant condenses and liquefies. Heat from a heat source like steam drives the process without the need for a compressor.
When altitude increases, water's boiling point decreases as pressure drops. For every 27mmHg increase in pressure, boiling point rises 1°C. Water vaporizes based on temperature and pressure. NPSHa is the available positive suction head, calculated as total suction head minus vapor pressure. NPSHR is the required positive suction head to avoid cavitation. Cavitation can damage pumps when NPSHa is less than NPSHR. Engineers must ensure sufficient margin between liquid and vapor states.
The document discusses the design of dimple jackets for vessels. Dimple jackets allow for construction from light gauge metals while maintaining strength for pressures. Their design begins with an assumed flow velocity between 2-5 ft/s. Dimple jackets are typically more economical than other choices when internal pressure is less than 1.67 times the jacket pressure. However, dimple jackets are not practical for vessels less than 10 gallons. The design of dimple jackets is governed by inspection standards and limited to a pressure of 300 psi and temperature of 700°F. Correlations and estimates are provided for heat transfer coefficients and pressure drop calculations for dimple jacket design.
This document discusses vapor compression refrigeration systems from Sana'a University in Yemen. It covers topics like coefficient of performance, the basic refrigeration cycle with four main components (evaporator, compressor, condenser, expansion valve), processes within the cycle, effects of evaporator and condenser temperatures, examples of cycle analysis, use of flash tanks and accumulators, and multistage compression systems. The document is presented by Dr. Abduljalil Al-Abidi from the Mechanical Engineering department and focuses on vapor compression refrigeration taught to students.
Air compressors:- One of the important device used to compress air at high pressure.
The presentation contains a detailed information about air compressors, classification of air compressors, reciprocating air compressors, rotary type, multistage/ single stage compressors. advantages and lastly application/ uses of air compressors.
Hope You like the presentation.
The document discusses multi-stage centrifugal pumps. It explains that a multi-stage centrifugal pump has two or more impellers to produce a high head. In a series connection, the total head developed is equal to the number of impellers multiplied by the head developed by each impeller. In a parallel connection, multi-stage pumps are arranged in parallel to discharge a large quantity of liquid, with the total discharge equal to the number of pumps multiplied by the discharge from each pump. Some applications of multi-stage centrifugal pumps include pumping water in high-rise buildings, industrial wash down facilities, fire hydrant systems, boiler feed systems, and irrigation.
Centrifugal pumps work by using an impeller to increase the pressure and flow of a liquid. Liquid enters the center of the impeller and is accelerated outward by the curved blades of the impeller. This increases the pressure and flow of the liquid. Calculating the required head of a centrifugal pump involves accounting for static head, pipe friction losses, and adding additional head for safety. Proper pump selection is based on matching the required head and flow rate to the pump performance curves. Cavitation and ensuring adequate Net Positive Suction Head (NPSH) are also important considerations for centrifugal pump operation.
Shell and Tube Heat Exchanger in heat TransferUsman Shah
Shell and tube heat exchangers consist of a bundle of tubes enclosed in a cylindrical shell. Fluids flow through either the tubes or shell to facilitate heat transfer between the two fluids. They are widely used in chemical processes due to their ability to achieve a large heat transfer surface area in a compact volume. Key components include tubesheets, baffles, support rods and segmented baffles which direct fluid flow across the tube bundle for efficient heat transfer. Design considerations include allocating the more corrosive or fouling fluid to the tubeside for easier cleaning and maintenance.
This Presentation is about working principle of Pumps.Basic Presentation regarding pumps , will definitely help beginners to learn pump types , their working , their parts etc.
Centrifugal pumps work by using a rotating impeller to impart velocity energy to fluid and increase pressure. They consist of a casing and impeller on a shaft. As fluid enters the impeller eye, the impeller blades spin and eject fluid outward, increasing pressure. The volute collects and redirects the fluid, converting velocity energy to pressure. During operation, pressure imbalances across the impeller cause both radial and axial thrusts. Radial thrust is balanced through design of the casing and volute. Axial thrust is balanced through methods like balancing holes, wear rings, back vanes, or double suction impellers.
The hydraulic machines which convert the mechanical energy into hydraulic energy are called pumps.”
“If the mechanical energy is converted into pressure energy or kinetic energy by means of centrifugal force
acting on the fluid, the hydraulic machine is called Centrifugal pump.”
This document provides an overview of centrifugal pumps and reciprocating pumps. It defines key components of centrifugal pumps like impellers and casings, and describes how they work by imparting centrifugal force to increase fluid pressure. It also defines important pump parameters like head, efficiency, specific speed, and NPSH. Cavitation in pumps and methods to prevent it are explained. Performance curves for pumps are introduced. Finally, the working principle and equations for reciprocating pumps are outlined.
This document provides information about centrifugal pumps, including:
- Centrifugal pumps work by using centrifugal force to increase the pressure of a fluid. They have an impeller that spins inside a casing to impart velocity and pressure to the fluid.
- The main parts of a centrifugal pump are the impeller, casing, suction pipe, foot valve, strainer, and delivery pipe. The impeller increases the fluid's velocity and the casing converts the velocity to pressure.
- Centrifugal pumps can be used to lift fluids to high levels by imparting pressure through centrifugal force generated by the spinning impeller. Characteristic curves are used to understand a pump's performance at varying flow rates
Basics Fundamentals and working Principle of Centrifugal Pump.SHASHI BHUSHAN
Basics Fundamentals and working Principle of Centrifugal Pump. Centrifugal pumps are the rotodynamic machines that convert mechanical energy of shaft into kinetic and pressure energy of Fluid which may be used to raise the level of fluid. A centrifugal pump is named so, because the energy added by the impeller to the fluid is largely due to centrifugal effects.
Hello everyone this is N Murali Mohan, working as a assistant professor in JNTUA college of engineering pulivendula, in this chapter covers the all topics, if any topics missing please inform I will correct and then upload.. thank you all
The pdf contains explanation about the centrifugal pumps. It is usually studied by Mechanical or Civil engineering students. This pdf file will help for the students from these fields.
1. Centrifugal pumps work by using centrifugal force to increase the pressure of a liquid. As the liquid moves through an impeller with curved vanes, it is pushed outward and its pressure increases.
2. Key components include an impeller, casing, suction and delivery pipes. Liquid enters the eye of the impeller and is flung outward, gaining pressure and velocity before exiting through the volute casing.
3. Advantages are low cost, high efficiency, uniform continuous flow. Centrifugal pumps are classified by design, number of impellers, entrances, shaft position, liquid handled and specific speed.
A regenerative turbine pump varies from the more familiar centrifugal pump mostly in the design of its impeller. This design difference makes the regenerative turbine pump uniquely suited for low NPSH (Net Positive Suction Head) applications, among others. Regenerative turbine pumps can safely pump liquids close to the boiling point without the detriment of cavitation, and the pump design is suitable for handling highly unstable liquids.
The document provides information about pumps, including their basic functions, main components, classifications, and examples of applications. It discusses how pumps work to increase the energy of liquids and move fluids through mechanical action. Pumps are classified as centrifugal or rotodynamic pumps, which use a rotating impeller to increase fluid velocity, and positive displacement pumps, which work by filling and emptying cavities. Examples of positive displacement pump types include reciprocating, power, and steam pumps. The document also outlines the basic working procedure of a centrifugal pump and provides diagrams to illustrate pump components and operation.
This document discusses centrifugal pumps and how they work to increase fluid pressure. It provides the following key points:
1) Centrifugal pumps, or dynamic pumps, impart kinetic energy to fluid using a rotating impeller, transforming it into pressure energy. Pressure produced is proportional to impeller speed and diameter.
2) An experiment is described where spinning a bottle with a hole produces a pressurized spray, demonstrating centrifugal force.
3) Pump performance curves show total head, flow rate, efficiency, horsepower requirements, and other information to aid in pump selection and sizing for a given system. The operating point is where the system curve intersects the performance curve.
This document provides information about pumps, including their classification, main components, and operating principles. It discusses two main types of pumps - centrifugal pumps and positive displacement pumps. For centrifugal pumps, it describes how the impeller increases the velocity of the fluid to generate pressure and flow. It also explains the priming, startup, and operation procedures for centrifugal pumps. Examples of pump applications like boiler feed pumps, fire pumps, and pool pumps are listed at the end.
Turbo machines are those mechanical devices which either extract energy from or impart energy to, a continuous moving stream of fluid. Pump is one of the most important and widely used turbo machines which basically impart energy to a moving fluid. Mechanical energy developed inside the pump is transferred to the moving fluid as hydraulic energy.
Centrifugal pumps use centrifugal force to raise liquids to higher levels. They work by imparting kinetic energy to the liquid using an impeller. The main parts of a centrifugal pump are the impeller, volute casing, and optional diffuser. The impeller spins and increases the pressure of the liquid flowing through it. The liquid then passes through the volute casing which collects and directs the flow to the outlet pipe. Common pump losses include friction within the impeller and casing as well as leakage losses.
1. The document presents information on centrifugal and reciprocating pumps, including their basic workings, components, uses, and efficiencies.
2. Centrifugal pumps use centrifugal force to accelerate and move fluid outwards from the center to increase pressure, while reciprocating pumps use pistons or plungers that move back and forth to displace fluid.
3. Key components of centrifugal pumps include casings, impellers, while reciprocating pumps have cylinders, pistons, valves. Both are used widely for irrigation, industry, buildings and other purposes.
IRJET- Experimental Setup of Centrifugal PumpIRJET Journal
1. The document describes an experimental setup used to test the performance of a centrifugal pump with a variable drive system.
2. Tests were conducted to generate characteristic curves showing the relationships between head vs discharge, efficiency vs discharge, and input power vs discharge under different pump speeds controlled by a dimmer-stat.
3. The results showed significant changes in the pump's performance when the dimmer-stat was used to vary the speed, as pump characteristics like head and efficiency depend on operating conditions like flow rate and speed.
This document discusses several topics related to hydraulics and hydraulic machines, including:
1) Classical hydraulic jumps and their evaluation in different channel types.
2) Classification of rotodynamic pumps based on their flow patterns and basic equations governing their operation.
3) Pump characteristic curves which graphically represent a pump's performance under different operating conditions using curves for total head, efficiency, power, and net positive suction head against discharge.
This document provides an overview of centrifugal pump training, covering:
- Centrifugal pump theory and how pumps work using atmospheric pressure
- Common pump terms like head, static head, total head, and NPSH
- How to read centrifugal pump curves and understand a pump's operating range
- The information needed to submit a pump inquiry
- How to draw system curves to select the proper pump
- Parallel and series pump operation and cavitation causes
- Explaining NPSH and the affinity laws for pump speed and performance changes
- Troubleshooting pumps using pressure and vacuum gauges
Modal 05: Question Number 9 a & 9 b
Centrifugal Pumps:
i. Classification and parts of centrifugal pump,
ii. Different heads of centrifugal pump
iii. Different efficiencies of centrifugal pump,
iv. Theoretical head – capacity relationship,
v. Minimum speed for starting the flow,
vi. Maximum suction lift,
vii. Net positive suction head,
viii. Cavitation,
ix. Need for priming,
x. Pumps in series and parallel. Problems.
Previous Year Question papers
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The smart irrigation system represents an innovative approach to optimize water usage in agricultural and landscaping practices. The integration of cutting-edge technologies, including sensors, actuators, and data analysis, empowers this system to provide accurate monitoring and control of irrigation processes by leveraging real-time environmental conditions. The main objective of a smart irrigation system is to optimize water efficiency, minimize expenses, and foster the adoption of sustainable water management methods. This paper conducts a systematic risk assessment by exploring the key components/assets and their functionalities in the smart irrigation system. The crucial role of sensors in gathering data on soil moisture, weather patterns, and plant well-being is emphasized in this system. These sensors enable intelligent decision-making in irrigation scheduling and water distribution, leading to enhanced water efficiency and sustainable water management practices. Actuators enable automated control of irrigation devices, ensuring precise and targeted water delivery to plants. Additionally, the paper addresses the potential threat and vulnerabilities associated with smart irrigation systems. It discusses limitations of the system, such as power constraints and computational capabilities, and calculates the potential security risks. The paper suggests possible risk treatment methods for effective secure system operation. In conclusion, the paper emphasizes the significant benefits of implementing smart irrigation systems, including improved water conservation, increased crop yield, and reduced environmental impact. Additionally, based on the security analysis conducted, the paper recommends the implementation of countermeasures and security approaches to address vulnerabilities and ensure the integrity and reliability of the system. By incorporating these measures, smart irrigation technology can revolutionize water management practices in agriculture, promoting sustainability, resource efficiency, and safeguarding against potential security threats.
ACEP Magazine edition 4th launched on 05.06.2024Rahul
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A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
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Centrifugal and gear pump theory dms
1. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
1 Theory of Centrifugal and Gear Pump_
Fig. 1 Classification of Pump
Centrifugal pump is a hydraulic machine which converts mechanical energy into
hydraulic energy (i.e. pressure energy) by the use of centrifugal force acting on the fluid. The
flow of liquid takes place in radial outward direction which is reverse of the inward radial low
reaction turbine. It is used in different areas where fluid is needed to raise from low level to
high level
Total Head in a Centrifugal Pump :
The energy relations in a pumping installation can be understood using the Bernoulli equation.
In Fig. 2,
2. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
2 Theory of Centrifugal and Gear Pump_
Fig. 2 Pump Heads in Pump installation
Considering (1) and (2) , the energy relationship in terms of head can be written as –
Where, V1 and V2 are velocities, P1 and P2 are pressures, and Z1 and Z2 are elevations
from a datum at points 1 and 2 respectively. Hm is the energy imparted to the liquid in moving
it from point 1 to 2 and Hf is the friction loss in the piping system.
The terms in the above equation are to be considered depending on the physical
situation. Considering Fig. 2 the velocities and pressures at points 1 and 2 can be taken as zero
and as such Hm is given by –
Where, hfs and hfd are the total friction losses in the suction side and the delivery side
respectively. When the delivery side is discharging to the atmosphere, the delivery head
𝑉𝑑
2
2𝑔
may
be added to Hm and the pumping head becomes as –
Velocity head
𝑉𝑑
2
2𝑔
is calculated using the relationship V = Q/A where Q is the discharge
and A is the cross-sectional area of the pipe. The head due to frictional losses is calculated by
knowing the pipe lengths on the suction and delivery sides and the pipe fittings and estimating
the frictional losses through them. Standard tables giving the frictional losses through different
pipe fitting are used for the purpose.
Considering points S and d in Fig. 2, the energy imparted by the impeller can be written as
3. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
3 Theory of Centrifugal and Gear Pump_
The above equation is used in testing of the centrifugal pumps. Knowing the rate of
flow and the diameter of the pipe lines in the suction and delivery sides, Vs and Vd values can
be calculated. The pressure or the suction side is negative and is measured using a vacuum
gauge and the pressure on the delivery side is positive and is measured using a pressure gauge.
However, allowance has to be given for the location of the gauges.
Net Positive Suction Head:
In case of centrifugal pumps, installed above the water level, certain amount of energy
is required to move the water into the eye of the impeller. The source of energy available for
this purpose is the atmospheric pressure.
The maximum suction lift of centrifugal pumps is dependent upon the atmospheric
pressure. Atmospheric pressure varies with elevation and at sea level, its value is 1.03
kg/cm2
(14.7 psi) or 10.34 m (34 ft) of water. Theoretically, pump should be able to operate
with this suction lift at sea level.
But because of air leaks past the impeller and through other openings the effective
suction lift is of the order of 6.34 m (18 ft) at sea level and about 4.5 m (15 ft) for most inland
conditions. For obtaining higher pump efficiencies, the suction lift should be as small as
possible.
Fig. 3 Computation of Net Positive Suction Head
Values of the atmospheric pressure at various altitudes, the vapour pressure and specific
gravity of water as a function of temperature can be obtained from standard tables.
The atmospheric pressure and vapour pressure are un-adjustable, but suction lift and
friction head of suction side are able to adjust to be minimum for maximize the NSPHA which
means energy to drive water to pump will be increased.
The amount of energy required to move the water into the eye of the impeller is referred
so as the net positive suction head required (NPSHR). The NPSHR is a function of the pump
4. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
4 Theory of Centrifugal and Gear Pump_
speed, impeller shape, liquid properties and discharge rate. Its value is determined for a
particular condition using laboratory tests.
If sufficient energy is not present in the liquid on the suction side of the pump to move
the liquid into the eye of the impeller, then the liquid will vaporize and what is known as
cavitation will occur. Cavitation could remove metal particles, cause severe vibrations and
damage the functioning of the pump. The occurrence of cavitation should therefore be avoided.
At a given location, for the satisfactory operation of the pump, the NPSHA should be
greater than NPSHR. In order to satisfy this condition the pump may have to be lowered
towards the water surface, or the suction pipe could be changed to reduce the friction loss. If
NPSHA is less than NPSHR, driving energy is not sufficient to requirement air and water will
be pumped together which will damage the pump.
NPSH Design Considerations :
Vapour pressure is strongly dependent on temperature, and thus so will both NPSHR
and NPSHA. Centrifugal pumps are particularly vulnerable especially when pumping heated
solution near the vapour pressure, whereas positive displacement pumps are less affected by
cavitation, as they are better able to pump two-phase flow (the mixture of gas and liquid),
however, the resultant flow rate of the pump will be diminished because of the gas
volumetrically displacing a disproportion of liquid. Careful design is required to pump high
temperature liquids with a centrifugal pump when the liquid is near its boiling point.
The violent collapse of the cavitation bubble creates a shock wave that can carve
material from internal pump components (usually the leading edge of the impeller) and creates
noise often described as "pumping gravel". Additionally, the inevitable increase in vibration
can cause other mechanical faults in the pump and associated equipment.
Principle :
It works on the principle of forced vortex flow. The forced vortex flow means when a
certain mass of fluid or liquid is allowed to rotate by an external torque than there is a rise in
pressure head of the rotating liquid takes place. This rise in pressure head is used to deliver
water from one location to another. It is centrifugal force acting on the fluid that makes it to
flow within the casing.
The rise in the pressure head of the rotating liquid at any point is directly proportional
to the square of the tangential velocity of the rotating liquid.
Mathematically,
How liquid is lifted to high level?
At the outlet of the impeller, radius is more and because of this the rise in the pressure
head is more and the liquid at the outlet discharged with a high pressure head. And because of
this high pressure head, the liquid can be lifted to a very high level.
5. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
5 Theory of Centrifugal and Gear Pump_
Main Parts :
The various main parts of a centrifugal pump are:
Fig. 4 Layout of Centrifugal Pump
1. Impeller :
It is the rotating part of the pump. The impeller is mounted on a shaft and the shaft of
impeller is again connected with the shaft of an electric motor. It is rotated by the motor and
consists of series of backward curved blades.
Impellers of pumps are classified based on the number of points that the liquid can enter
the impeller and also on the amount of webbing between the impeller blades. Impellers can be
either single-suction or double-suction. A single-suction impeller allows liquid to enter the
center of the blades from only one direction. A double-suction impeller allows liquid to enter
the center of the impeller blades from both sides simultaneously. Figure 4.1 shows simplified
diagrams of single and double-suction impellers.
Fig. 4.1 Single-Suction and Double-Suction Impellers
Impellers can be open, semi-open, or enclosed.
6. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
6 Theory of Centrifugal and Gear Pump_
Fig. 4.2 Open, Semi-Open, and Enclosed Impellers
The open impeller consists only of blades attached to a hub. The semi-open impeller is
constructed with a circular plate (the web) attached to one side of the blades. The enclosed
impeller has circular plates attached to both sides of the blades. Enclosed impellers are also
referred to as shrouded impellers. Figure 4.2 illustrates examples of open, semi-open, and
enclosed impellers.
The impeller sometimes contains balancing holes that connect the space around the hub
to the Suction side of the impeller. The balancing holes have a total cross-sectional area that is
considerably greater than the cross-sectional area of the annular space between the wearing
ring and the hub. The result is suction pressure on both sides of the impeller hub, which
maintains a hydraulic balance of axial thrust.
2. Casing :
It is an air tight passage which surrounds the impeller. The design of the casing is done
in such a way that it is capable of converting the kinetic energy of the water discharging from
the outlet of the impeller into pressure energy before it leaves the casing and enters into the
delivery pipe.
Commonly three types of casing are used in centrifugal pump and these are
(i) Volute Casing: It is a spiral type of casing in which the area of flow increases gradually.
The increase in area of flow decreases the velocity and increases the pressure of the liquid that
flows through the casing. The volute casing is shown in figure above:
(ii) Vortex Casing: In vortex casing, a circular chamber is introduced in between the impeller
and casing. This is done in order to prevent the loss of energy due to formation of eddies. The
efficiency of the vortex casing is more than that of the volute casing.
(iii) Casing with Guide Blades: In this casing, the impeller is surrounded by series of guide
blades. The guide blades are mounted on a ring which is called as diffuser. The design of the
guide vanes are kept as such that the water which is leaving the impeller enters the guides
without shock. The area of the guide vanes increases; this helps to decrease the velocity of the
liquid and increases its pressure. After guide vanes, water passes through the surrounding
casing. In most of the cases, the casing remains concentric with the impeller.
3. Suction Pipe with Foot Valve and Strainer :
A pipe whose one end is connected with the inlet of the impeller and the other end is
dipped into the sump of water is called suction pipe. The suction pipe consists of a foot valve
and strainer at its lower end. The foot valve is a one way valve that opens in the upward
direction. The strainer is used to filter the unwanted particle present in the water to prevent the
centrifugal pump from blockage.
7. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
7 Theory of Centrifugal and Gear Pump_
4. Delivery Pipe :
It is a pipe whose one end is connected to the outlet of the pump and other end is
connected to the required height where water is to be delivered.
Centrifugal Pump other Components:
Centrifugal pumps vary in design and construction from simple pumps with relatively few
parts to extremely complicated pumps with hundreds of individual parts. Some of the most
common components found in centrifugal pumps are wearing rings, stuffing boxes, packing,
and lantern rings. These components are shown in Figure 4.3 .
Fig. 4.3 Centrifugal Pump Components
a. Wearing Rings:
Centrifugal pumps contain rotating impellers within stationary pump casings. To allow the
impeller to rotate freely within the pump casing, a small clearance is designed to be maintained
between the impeller and the pump casing. To maximize the efficiency of a centrifugal pump,
it is necessary to minimize the amount of liquid leaking through this clearance from the high
pressure or discharge side of the pump back to the low pressure or suction side. Some wear or
erosion will occur at the point where the impeller and the pump casing nearly come into contact.
This wear is due to the erosion caused by liquid leaking through this tight clearance and other
causes. As wear occurs, the clearances become larger and the rate of leakage increases.
Eventually, the leakage could become unacceptably large and maintenance would be required
on the pump.
To minimize the cost of pump maintenance, many centrifugal pumps are designed with
wearing rings. Wearing rings are replaceable rings that are attached to the impeller and/or the
pump casing to allow a small running clearance between the impeller and the pump casing
without causing wear of the actual impeller or pump casing material. These wearing rings are
designed to be replaced periodically during the life of a pump and prevent the more costly
replacement of the impeller or the casing.
b. Stuffing Box :
In almost all centrifugal pumps, the rotating shaft that drives the impeller penetrates the
pressure boundary of the pump casing. It is important that the pump is designed properly to
control the amount of liquid that leaks along the shaft at the point that the shaft penetrates the
pump casing. There are many different methods of sealing the shaft penetration of the pump
casing. Factors considered when choosing a method include the pressure and temperature of
the fluid being pumped, the size of the pump, and the chemical and physical characteristics of
the fluid being pumped.
8. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
8 Theory of Centrifugal and Gear Pump_
One of the simplest types of shaft seal is the stuffing box. The stuffing box is a
cylindrical space in the pump casing surrounding the shaft. Rings of packing material are
placed in this space. Packing is material in the form of rings or strands that is placed in the
stuffing box to form a seal to control the rate of leakage along the shaft. The packing rings are
held in place by a gland. The gland is, in turn, held in place by studs with adjusting nuts. As
the adjusting nuts are tightened, they move the gland in and compress the packing. This axial
compression causes the packing to expand radially, forming a tight seal between the rotating
shaft and the inside wall of the stuffing box.
The high speed rotation of the shaft generates a significant amount of heat as it rubs
against the packing rings. If no lubrication and cooling are provided to the packing, the
temperature of the packing increases to the point where damage occurs to the packing, the
pump shaft, and possibly nearby pump bearings. Stuffing boxes are normally designed to allow
a small amount of controlled leakage along the shaft to provide lubrication and cooling to the
packing. The leakage rate can be adjusted by tightening and loosening the packing gland.
c. Lantern Ring :
It is not always possible to use a standard stuffing box to seal the shaft of a centrifugal
pump. The pump suction may be under a vacuum so that outward leakage is impossible or the
fluid may be too hot to provide adequate cooling of the packing. These conditions require a
modification to the standard stuffing box.
One method of adequately cooling the packing under these conditions is to include a lantern
ring. A lantern ring is a perforated hollow ring located near the center of the packing box that
receives relatively cool, clean liquid from either the discharge of the pump or from an external
source and distributes the liquid uniformly around the shaft to provide lubrication and cooling.
The fluid entering the lantern ring can cool the shaft and packing, lubricate the packing, or seal
the joint between the shaft and packing against leakage of air into the pump in the event the
pump suction pressure is less than that of the atmosphere.
d. Mechanical Seals:
In some situations, packing material is not adequate for sealing the shaft. One common
alternative method for sealing the shaft is with mechanical seals. Mechanical seals consist of
two basic parts, a rotating element attached to the pump shaft and a stationary element attached
to the pump casing. Each of these elements has a highly polished sealing surface. The polished
faces of the rotating and stationary elements come into contact with each other to form a seal
that prevents leakage along the shaft.
Actual Working :
As the electric motor starts rotating, it also rotates the impeller. The rotation of the
impeller creates suction at the suction pipe. Due to suction created the water from the sump
starts coming to the casing through the eye of the impeller.
From the eye of the impeller, due to the centrifugal force acting on the water, the water
starts moving radially outward and towards the outer of casing.
Since the impeller is rotating at high velocity it also rotates the water around it in the
casing. The area of the casing increasing gradually in the direction of rotation, so the velocity
of the water keeps on decreasing and the pressure increases, at the outlet of the pump, the
pressure is maximum.
Now form the outlet of the pump, the water goes to its desired location through delivery
pipe.
What is priming and why it is necessary?
It is process in which the suction pipe, casing and delivery pipe upto the delivery valve
is filled completely with liquid to be raised from outside source before starting the motor.
Priming is done to remove the air from the pump.
9. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
9 Theory of Centrifugal and Gear Pump_
If air is not removed from the pump than a small negative pressure is created at the
suction pipe and it cannot suck the water from the water sump. So it is advised to fill the pump
with water before starting it.
OR
Priming Centrifugal Pumps
Most centrifugal pumps are not self-priming. In other words, the pump casing must be
filled with liquid before the pump is started, or the pump will not be able to function. If the
pump casing becomes filled with vapours or gases, the pump impeller becomes gas-bound
and incapable of pumping. To ensure that a centrifugal pump remains primed and does not
become gas-bound, most centrifugal pumps are located below the level of the source from
which the pump is to take its suction. The same effect can be gained by supplying liquid to
the pump suction under pressure supplied by another pump placed in the suction line.
What is Cavitation and How it Occurs?
Cavitation is a phenomenon of formation of vapour bubbles of
a flowing liquid in a region where the pressure of the liquid becomes equal or
less than the vapour pressure. When these vapour bubbles reaches into the region
of higher pressure, they collapse and creates high impact pressure. These high
impact pressure created by the vapour bubbles eroded the materials from metallic
surface and produces cavity.
Fig. 5 Basic phenomenon of Bubble formation
For better explanation of the above cavitation phenomenon one must have knowledge
of vaporization and vapour pressure.
What is Vaporization?
The change of liquid phase into gaseous phase is called
vaporization. The vaporization depends upon the prevailing temperature and
pressure condition. It occurs due to the continuous escaping of the liquid
molecules from free surface of the liquid.
What is Vapour Pressure?
In order to understand vapour pressure, let’s take a closed vessel in which a liquid (say
water) is present. Let the temperature of the water is 20o
C and pressure is atmospheric. In this
situation the vaporization of water takes place at 100o
C. As the vaporization of
water starts, the molecules of liquid (vapour) start escaping out from the free surface of the
liquid. The vapour molecules escaping out from the liquid free surface gets collected between
the free surface of the liquid and top of the vessel. These vapour molecules exerts pressure on
the free surface of liquid. This pressure exerted by the vapour is called vapour pressure. Vapour
pressure is also defined as the pressure at which the liquid changes into vapour
10. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
10 Theory of Centrifugal and Gear Pump_
Now, again take a closed vessel filled with a liquid (say water). Let the temperature of
the water is 20o
C and the pressure in the vessel is reduced by some external source. When the
pressure is reduced, the vaporization temperature is also reduced. Let the pressure inside the
vessel is reduced to such an extent that it becomes equal or less than the vapour pressure. In
this situation the boiling of water takes place even though the temperature of liquid is 20o
C.
Thus the boiling of water takes place even at ordinary temperature; if the pressure is reduced
as such it becomes equal to or less than the vapour pressure.
Explanation of Cavitation :
Considered a system in which a liquid (say water) is flowing. When the flowing water
enters into a region where the pressure becomes equal to or less than that of the vapour pressure.
Than the vaporization of water starts and vapour bubbles are formed in the water. When these
vapour bubbles are carried by the flowing liquid in the region of higher pressure they explode.
The explosion of vapour bubbles creates impact pressure of high intensity.
Since the liquid flows over the metallic surface, the high pressure produced by explosion of
vapour bubbles erodes the material from the metallic surface and creates cavity. This
phenomenon is called cavitation. The bursting of the vapour bubbles creates noise and
vibration.
Cause of Cavitation :
Cavitation occurs when pressure of flowing liquid in any region becomes equal to or
less than the vapour pressure.
Effect of Cavitation :
It results in damage to the metallic surfaces and creates cavity.
Creates noise and vibration due to sudden collapsing of vapour bubbles.
It reduces the efficiency of hydraulic machines like turbine and pumps.
Precaution for Cavitation :
The pressure of the liquid in any part of the hydraulic system should not be reduced below its
vapour pressure.
The special materials or coating such as stainless steel and aluminium bronze, which are
cavitation resistance should be used.
Application :
The centrifugal pump is used in almost every field to raise the liquid from low level to
high level. They are mostly used at home for filling water tanks, almost in every industry such
as chemical, automobile, marine, manufacturing, for irrigation etc.
Power Requirements of Pumping:
Power is rate of doing work. If a force or a load moves over a distance, energy is consumed
and work is done, therefore-
Work = Force X Distance and
Rate of Work or power = work / time
The scientific unit of power is the watt (W) and because this is small it is often
expressed as kilowatt (1,000 W). The unit of work or energy corresponding to the Watt is the
joule (J), which is defined as the work done when a force of one Newton (1 N) moves through
a distance of 1 m. (Watts = joules/sec)
11. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
11 Theory of Centrifugal and Gear Pump_
Another unit of power used in case of pumping installations is the horsepower (HP).
This is defined as the work done at the rate of 75 m kilograms per sec. in the metric units or
550 ft.lb. per second in the British units.
The Horsepower is not the same in both units but has the following relationship –
The pump efficiency is calculated from the above formula knowing the other two terms.
Brake horsepower (BHP) refers to the power supplied by the engine or electric motor as its
output. When there is direct drive from the engine or electric motor to the pump and the drive
efficiency being 100 per cent, brake horsepower is equal to shaft horsepower.
Selection of Centrifugal Pumps:
As every pumping installation has different operating head and discharge it is necessary
to select the pump such that it operates under maximum efficiency with the given head and
12. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
12 Theory of Centrifugal and Gear Pump_
giving the required discharge. This is done by plotting what are known as characteristic curves,
both for the well and the pump.
The characteristic curves represent the behaviour of the pump or the well under various
operating conditions with the help of these curves different pumps can be conveniently studied
and compared.
1. Head Capacity Curve:
This curve for a pump shows how much water, a given pump will deliver with a given
head (Fig. 6a). The curve represents the behaviour of the pump at one particular speed, head
being the variable. The length AO in Fig. 6a gives the shutoff head or the head developed when
the discharge valve is closed.
At pump installations where there is considerable delivery head, at the instant of
starting, the pump is not operating against the total head. Since the head is low, the discharge
tends to be high and the engine or motor gets overloaded. Hence at the time of starting, the
discharge valve should be kept closed and gradually opened afterwards.
Fig. 6 Characteristics of Centrifugal Pump
2. Overall Efficiency Curve:
The relationship between the efficiency of the pump and the discharge at a particular
speed is represented by the efficiency curve. Also efficiency curves are obtained for different
speeds of the pump. The general patterns of the curves are shown in Fig. 6b.
3. Break-Horse Power Curve:
The necessary engine or motor horse power needed for a particular pump installation is
obtained from the brake horse power curve. Knowing the head and the discharge and the
efficiency at that discharge, the BHP is calculated and is plotted against discharge (Fig. 6c).
In case a centrifugal pump has to be selected for pumping from an open water source, the total
head has to be calculated for selecting the suitable pump. In case of wells the head-capacity
curve of the well is made use of in the selection of the pump. The head capacity curve for a
given well is constructed from the data obtained when the well is tested.
This curve indicates the amount of water which the well will yield with different
drawdowns. Matching the pump and well characteristics is illustrated in Fig. 7. Let the head-
13. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
13 Theory of Centrifugal and Gear Pump_
capacity curves of the pump and the well intersect at point P. The efficiency can be read from
the efficiency curve. The efficiency obtained should be maximum or near about it.
Specific Speed of Centrifugal Pumps:
The performance of a pump is determined by the ability of its impeller to impart energy
to the water. The design of the impeller therefore, is a basic factor for deciding the type and
structure of the pump. An index to operating characteristics of pumps is the specific speed ns,
expressing the relationship between speed, discharge (Q) and head (Hm).
The specific speed of a centrifugal pump (ns) may be defined as the speed in revolutions
per minutes of a geometrically similar pump of such a size that under corresponding conditions
it would deliver 1 litre of liquid per second against a head of 1 m. The value of specific speed
is useful in comparing the performance of different pumps.
Fig. 7 Matching Pump and well characteristics
Let Hn, Qn, Dn and n represent the head, discharge, diameter and speed of a centrifugal
pump and Hs, Qs, Ds and ns similar values of a model pump.
14. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
14 Theory of Centrifugal and Gear Pump_
ns, however, is not a pure (non-dimensional) number. It depends on the units chosen to express
Qs and Hs. Common units are 1 m for Hs and 1 m3
/sec or 1 m3
/hr or 1 1/s for Qs. In English units
Hs = 1 ft, but Qs may be 1 ft3
/sec, 1 gal/min, etc. As the value of ns increases, the pump type changes
from radial flow to mixed flow type and then to the axial flow type.
Fig. 8 General characteristics of the different types of pumps
Fig. 8 shows the general characteristics of the different types of pumps. It can be seen from
these graphs that in general for low heads and high discharges the axial flow type are more efficient
compared to other types at its normal working speed. In case of single impeller centrifugal pumps
the value of ns varies from 300 to 5,000.
15. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
15 Theory of Centrifugal and Gear Pump_
Affinity Laws:
Total dynamic head (H), discharge (Q) and brake horse power (P) of a pump are related
to size (W, width) and speed (N, rpm) of impeller. Changing the size and speed of the impeller
modifies the operational characteristics of a pump.
This allows pump manufacturers or users to alter the performance of a single pump to
match the system needs or understand the pump performance under different operating
conditions. These relationships are known as affinity laws are given by the following wherein
the subscript zero refers to the original condition.
Eq. 10.15 indicates that a 50 per cent increase in impeller speed, diameter or width will
increase discharge by 50 per cent. Eq. 10.16 shows that a 50 per cent increase in impeller speed,
diameter, or width will increase the head developed by (1.5)2
or 2.25 times.
Eq. 10.17 shows that when speed, diameter, or width increases by 50 per cent, the power
required increases by (1.5)3
or 3.37 times.
Common Troubles of Centrifugal Pumps Installation:
Some of the common troubles that occur with centrifugal pumps installations and the
remedies are listed below:
1. Pump Fails to Deliver Water:
(i) There may be an air leak in the suction line. Threaded connections are a common source.
These should be coated with white lead or pipe cement and tightened.
(ii) Gaskets at the inlet and outlet of the pump may be admitting air. These should be tightened.
(iii) The foot valve or the reflux value may be defective, so that water is not retained in the
suction side. Often the flap in the foot valve does not operate properly. This should be checked
and replaced if necessary.
2. Pump Fails to Develop Sufficient Pressure or Capacity:
(i) The pump speed to be checked to see whether it is as per prescribed speed or not.
(ii) Suction line and foot valve to be checked for any clogging with debris or any other foreign
material.
(iii) The suction lift should be within the prescribed limits.
(iv) A worn-out impeller reduces the capacity of the pump.
3. Pump Takes too Much Power:
16. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
16 Theory of Centrifugal and Gear Pump_
(i) The speed of the pump may be higher than the rated speed.
(ii) The head may be lower than the rated head for the pump, thereby pumping too much water.
(iii) Mechanical defects such as bent shaft, tight stuffing box, misalignment of the pump and
the driving unit should be checked.
4. Pump Leaks Excessively at the Stuffing Box:
(i) The packing material used may be worn out, incorrectly inserted or may not be of the right
kind.
(ii) The shaft may be worn out.
5. Pump is Noisy:
(i) The suction lift may be too high.
(ii) Mechanical defects such as bent shaft, improper alignment between the pumps and the
driving unit, broken or worn-out bearing may cause noise during the operation of the pump.
Centrifugal Pump Operation Summary
There are three indications that a centrifugal pump is cavitation.
Noise
Fluctuating discharge pressure and flow
Fluctuating pump motor current
Steps that can be taken to stop pump cavitation include:
Increase the pressure at the suction of the pump.
Reduce the temperature of the liquid being pumped.
Reduce head losses in the pump suction piping.
Reduce the flow rate through the pump.
Reduce the speed of the pump impeller.
Three effects of pump cavitation are:
Degraded pump performance
Excessive pump vibration
Damage to pump impeller, bearings, wearing rings, and seals
To avoid pump cavitation, the net positive suction head available must be greater than the
net positive suction head required.
Net positive suction head available is the difference between the pump suction pressure
and the saturation pressure for the liquid being pumped.
Cavitation is the process of the formation and subsequent collapse of vapour bubbles in a
pump.
Gas binding of a centrifugal pump is a condition where the pump casing is filled with
gases or vapors to the point where the impeller is no longer able to contact enough fluid
to function correctly.
17. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
17 Theory of Centrifugal and Gear Pump_
Shutoff head is the maximum head that can be developed by a centrifugal pump
operating at a set speed.
Pump runout is the maximum flow that can be developed by a centrifugal pump without
damaging the pump.
The greater the head against which a centrifugal pump operates, the lower the flow rate
through the pump. The relationship between pump flow rate and head is illustrated by
the characteristic curve for the pump.
Centrifugal pumps are protected from dead-heading by providing a recirculation from
the pump discharge back to the supply source of the pump.
Centrifugal pumps are protected from runout by placing an orifice or throttle valve
immediately downstream of the pump discharge and through proper piping system
design.
POSITIVE DISPLACEMENT PUMPS
Positive displacement pumps operate on a different principle than centrifugal pumps.
Positive displacement pumps physically entrap a quantity of liquid at the suction of the pump
and push that quantity out the discharge of the pump.
A positive displacement pump is one in which a definite volume of liquid is delivered
for each cycle of pump operation. This volume is constant regardless of the resistance to flow
offered by the system the pump is in, provided the capacity of the power unit driving the pump
or pump component strength limits are not exceeded. The positive displacement pump delivers
liquid in separate volumes with no delivery in between, although a pump having several
chambers may have an overlapping delivery among individual chambers, which minimizes this
effect. The positive displacement pump differs from centrifugal pumps, which deliver a
continuous flow for any given pump speed and discharge resistance.
There are many types of positive displacement rotary pumps, and they are normally
grouped into three basic categories that include gear pumps, screw pumps, and moving vane
pumps. Out of all positive displacement pump we will discussed only about Gear Pump.
Simple Gear Pump:
There are several variations of gear pumps. The simple gear pump shown in Figure 9
consists of two spur gears meshing together and revolving in opposite directions within a
casing. Only a few thousandths of an inch clearance exists between the case and the gear faces
and teeth extremities. Any liquid that fills the space bounded by two successive gear teeth and
the case must follow along with the teeth as they revolve. When the gear teeth mesh with the
teeth of the other gear, the space between the teeth is reduced, and the entrapped liquid is forced
out the pump discharge pipe.
18. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
18 Theory of Centrifugal and Gear Pump_
Fig. 6 Simple Gear Pump
As the gears revolve and the teeth disengage, the space again opens on the suction side
of the pump, trapping new quantities of liquid and carrying it around the pump case to the
discharge. As liquid is carried away from the suction side, a lower pressure is created, which
draws liquid in through the suction line.
With the large number of teeth usually employed on the gears, the discharge is relatively
smooth and continuous, with small quantities of liquid being delivered to the discharge line in
rapid succession. If designed with fewer teeth, the space between the teeth is greater and the
capacity increases for a given speed; however, the tendency toward a pulsating discharge
increases. In all simple gear pumps, power is applied to the shaft of one of the gears, which
transmits power to the driven gear through their meshing teeth.
There are no valves in the gear pump to cause friction losses as in the reciprocating
pump. The high impeller velocities, with resultant friction losses, are not required as in the
centrifugal pump. Therefore, the gear pump is well suited for handling viscous fluids such as
fuel and lubricating oils.
Other Gear Pumps:
There are two types of gears used in gear pumps in addition to the simple spur gear. One type
is the helical gear. A helix is the curve produced when a straight line moves up or down the
surface of a cylinder. The other type is the herringbone gear. A herringbone gear is composed
of two helixes spiralling in different directions from the centre of the gear. Spur, helical, and
herringbone gears are shown in Figure 7.
Fig. 7 Types of Gears Used In Pumps
19. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
19 Theory of Centrifugal and Gear Pump_
The helical gear pump has advantages over the simple spur gear. In a spur gear, the
entire length of the gear tooth engages at the same time. In a helical gear, the point of
engagement moves along the length of the gear tooth as the gear rotates. This makes the helical
gear operate with a steadier discharge pressure and fewer pulsations than a spur gear pump.
The herringbone gear pump is also a modification of the simple gear pump. Its principal
difference in operation from the simple spur gear pump is that the pointed centre section of the
space between two teeth begins discharging before the divergent outer ends of the preceding
space complete discharging. This overlapping tends to provide a steadier discharge pressure.
The power transmission from the driving to the driven gear is also smoother and quieter.
Positive Displacement Pumps Summary
The flow delivered by a centrifugal pump during one revolution of the impeller depends
upon the head against which the pump is operating. The positive displacement pump
delivers a definite volume of fluid for each cycle of pump operation regardless of the head
against which the pump is operating.
Positive displacement pumps may be classified in the following ways:
Reciprocating piston pump
Gear-type rotary pump
Lobe-type rotary pump
Screw-type rotary pump
Moving vane pump
Diaphragm pump
As the viscosity of a liquid increases, the maximum speed at which a reciprocating positive
displacement pump can properly operate decreases. Therefore, as viscosity increases, the
maximum flow rate through the pump decreases.
The characteristic curve for a positive displacement pump operating at a certain speed is a
vertical line on a graph of head versus flow.
Slippage is the rate at which liquid leaks from the discharge of the pump back to the pump
suction.
Positive displacement pumps are protected from over pressurization by a relief valve on
the upstream side of the pump discharge valve.
Generally used in:
Petrochemicals: Pure or filled bitumen, pitch, diesel oil, crude oil, lube oil etc.
Chemicals: Sodium silicate, acids, plastics, mixed chemicals, isocyanates etc.
Paint and ink.
Resins and adhesives.
Pulp and paper: acid, soap, lye, black liquor, kaolin, lime, latex, sludge etc.
Food: Chocolate, cacao butter, fillers, sugar, vegetable fats and oils, molasses,
animal food etc.
20. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
20 Theory of Centrifugal and Gear Pump_
Difference between Centrifugal Pump and Positive Displacement Pump
Difference between Centrifugal Pump, Reciprocating Pump and Rotary Pump
21. THEORY OF CENTRIFUGAL AND GEAR PUMP_
PROF. SAGAR A. DHOTARE,
ASSISTANT PROFESSOR,
VISHWANIKETAN’S IMEET, KHALAPUR
21 Theory of Centrifugal and Gear Pump_