CHAPTER-06 PUMPS SUB: FLUIDS MECHANICS AND MACHINERY Prepared By:

CHAPTER-06 PUMPS SUB: FLUIDS MECHANICS AND MACHINERY Prepared By: Ms.Nilesha U.Patil

Program : Mechanical Engineering Course: Fluid Mechanics & Machinery CO- Evaluate performance of pumps.

PUMPS

PRESENTATION OUTLINE Pump Terminology Pump Classification: - Reciprocating Pumps - Rotary Pumps - Centrifugal Pumps Pumping Problems Power and Efficiency Calculations Pump Selection

PUMP TERMINOLOGY Pumping, the addition of energy to a fluid Pumping action creates a partial vacuum while atmospheric pressure forces liquid up. Pump performance, specified in terms of Q and H: H Q / t ( Pd , g Ps , g 2 2 Vd Vs ) ( ) (Z d Z s ) 2g 2g

Displacement, the discharge of a fluid from a vessel Centrifugal Force, used to produce kinetic energy

PUMPS P O S IT IV E D IS P L A C E M E N T P U M P S R E C IP R O C A T IN G P U M P S ROTARY PUM PS P IS T O N P U M P S GEAR PUM PS PLUNGER PUM PS LOBE PUM PS D IA P H R A G M P U M P S SCREW PUM PS CAM PUM PS VANE PUM PS C E N T R IF U G A L P U M P S

RECIPROCATING PUMPS Based on two stroke principles: High pressure, high efficiency Self-priming X Small quantity, vibration, physical dimension, uneven flow Used mainly for handling slurries in plant processes and pipeline applications

P O S IT IV E D IS P L A C E M E N T P U M P S R E C IP R O C A T IN G P U M P S P IS T O N P U M P S PLUNG ER PUM PS D IA P H R A G M P U M P S Two valves and one stuffing box A rotating mechanism for the reciprocating piston Uses suction to raise liquid into the chamber.

P O S IT IV E D IS P L A C E M E N T P U M P S R E C I P R O C A T I N G P U M P S P IS T O N P U M P S PLUNG ER PUM PS D IA P H R A G M P U M P S Two ball check valves on each side Low pressure on the upward part, high pressure on the downward part

P O S IT IV E D IS P L A C E M E N T P U M P S R E C IP R O C A T IN G P U M P S P IS T O N P U M P S PLUNG ER PUM PS D IA P H R A G M P U M P S Rod is moved to push and pull the diaphragm. Can be used to make artificial hearts.

ROTARY PUMPS Positive displacement type High pressure, high efficiency Liquids must be free of solids Handle viscous fluids Used mainly in, oil burners, soaps and cosmetics, sugars, syrup, and molasses, dyes, ink, bleaches, vegetable and mineral oils

R O T A R Y P U M P S G E A R P U M P S L O B E P U M P S S C R E W C A M V A N E P U M P S P U M P S P U M P S Gears create voids as they come out of mesh and liquid flows into the cavities As the gears come back into mesh, the volume is reduced and the liquid is forced out of the discharge port

R O TA R Y P U M P S G E A R P U M P S L O B E P U M P S S C R E W P U M P S C A M P U M P S V A N E P U M P S As the teeth come out of mesh, liquid flows into the pump and is carried between the teeth and the casing to the discharge side of the pump The teeth come back into mesh and the liquid is forced out the discharge port

R O T A R Y P U M P S G E A R P U M P S L O B E P U M P S S C R E W C A M V A N E P U M P S P U M P S P U M P S Fluid is carried between the rotor teeth and the pumping chamber The rotor surfaces create continuous sealing Rotors include bi-wing, tri-lobe, and multi-lobe configurations

R O TA R Y P U M P S G E A R P U M P S L O B E P U M P S S C R E W P U M P S C A M P U M P S V A N E P U M P S Screw pumps carry fluid in the spaces between the screw threads. The fluid is displaced axially as the screws mesh.

R O T A R Y P U M P S G E A R P U M P S L O B E P U M P S S C R E W C A M V A N E P U M P S P U M P S P U M P S Piston slide arm moves around inside a slot in the casing. An eccentric cam rotates the circular plunger (shown in gray) around the edge of the casing, fluid is swirled around the edge to the outlet port. It is not in use now and is mainly of historical curiosity.

R O T A R Y P U M P S G E A R P U M P S L O B E P U M P S S C R E W C A M V A N E P U M P S P U M P S P U M P S The vanes are in slots in the rotor. Rotor spins, centrifugal force pushes the vanes out to touch the casing, where they trap and propel fluid.

CENTRIFUGAL PUMPS WHAT IS CENTRIFUGAL PUMP? WORKING MECHANISM OF A CENTRIFUGAL PUMP ADVANTEGAES AND DISADVANTAGES OF CENTRIFUGAL PUMPS

WHAT IS CENTRIFUGAL PUMP? Convert the mechanical energy into hydraulic energy by centrifugal force on the liquid Constitute the most common type of pumping machinery Used to move liquids through a piping system Has two main components: 1. Stationary componets, casing, casing cover and bearings 2. Rotating components, impeller and shaft Classified into three categories ; Radial Flow, Mixed Flow, Axial Flow

WORKING MECHANISM OF A CENTRIFUGAL PUMP Simplest piece of equipment in any process plant Energy changes occur by virtue of impeller and volute Liquid is fed into the pump at the center of a rotating impeller and thrown outward by centrifugal force The conversion of kinetic energy into pressure energy supplies the pressure difference between the suction side and delivery side of the pump Liquid flow path inside a centrifugal pump

ADVANTAGES OF CENTRIGUGAL PUMPS Advantages Simple in construction and cheap Handle liquid with large amounts of solids No metal to metal fits No valves involved in pump operation Maintenance costs are lower

DISADVANTAGES OF CENTRIFUGAL PUMPS Disadvantages Cannot handle highly viscous fluids efficiently Cannot be operated at high heads Maximum efficiency holds over a narrow range of conditions

PUMPING PROBLEMS Cavitation Reduces the pump capacity Causes metal removal reduced flow loss in efficiency and noise To avoid cavitation NPSH

POWER AND EFFICIENCY CALCULATIONS The power supplied to the pump: (1) Where m mass flow rate, kg/s H total discharge head, N.m/kg efficiency

The power delivered to the fluid: (2) From equations (1) and (2) efficiency:

PUMP SELECTION The amount of fluid The properties of the fluid Type of power supply Cost and mechanical efficiency of the pump

PRESSURE CAPACITY LOW GEAR HIGH HIGHER SMALL OR MODERATE MODERATE OR HIGH LOBE CENTRIFUGAL RECIPROCATING or ROTARY PLUNGER or ROTARY PISTON RIGID SCREW

REFERENCES 1. 2. 3. 4. http://en.wikipedia.org/wiki/Pump www.cheresources.com www.pumpworld.com/contents.htm www.rpi.edu./dept/chem-eng/ Biotech-Environ/PUMPS/intro.html

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