PUMP BASICS

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pump basic

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PUMP BASICS Prepared by A.Prasad Roshan prasadroshan1982gmail.com You can download from http://www.authorstream.com/prasadroshan/1

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 WHAT IS PUMP It converts mechanical energy in to hydraulic energy water or other fluids at in motion • NEED OF PUMP .  To increase the flow rate  To increase the pressure.  To move the fluid from lower elevation to higher elevation

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PUMP IS A DEVICE USED TO  MOVE LIQUID FROM LOW PRESSURE AREA TO HIGH PRESSURE AREA. Ex: boiler feed water Multistage centrifugal pump  TO MOVE LIQUID FROM LOWER ELEVATION TO HIGHER ELEVATION. But higher to lower by gravity flow Ex: all the process pump centrifugal pump  TO INCREASE THE FLOW RATE OF LIQUID Ex: all the process pump centrifugal pump  TO INCREASE PRESSURE OF THE LIQUID Ex: CAR washer pump piston pump  TO CIRCULATE THE FLOW OF LIQUID IN CLOSED SYSTEMS  Ex: Sealing water liquid in LIQUID ring vacuum pump centrifugal pump Purpose of Pumps

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Pump adds energy pressure to a fluid Pumps can deliver: 1 high pressure 2 Low pressure 3 low flow 4 high flow

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5 © UNEP 2006 Introduction Objective of pumping system What are Pumping Systems US DOE 2001 • Transfer liquid from source to destination • Circulate liquid around a system

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Pumps in OXIDE PRODUCTION FACILITY a Back pull out type centrifugal pumps 91 nos b vertical or pit pump 06 nos c air operated double acting diaphragm 04 no pump d Multistage centrifugal pump 01no e Liquid ring vacuum pump 04nos Pumps in Sponge PRODUCTION FACILITY a Back pull out type centrifugal pumps 06Nos b vertical or pit pump nil c air operated double acting diaphragm 2nos pump d Roots pump 4nos e Oil sealed rotary piston type vacuum pumps 4nos Pumps in Utility Fire a Back pull out type centrifugal pumps b vertical or pit pump c gear pump d Screw pump d Multistage centrifugal pump 02nos Pumps in work shop a Triplex piston type Reciprocating pump 01no

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Cross section view of Centrifugal pump Fixed bearing Floating bearing

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Introduction • Main pump components • Pumps • Prime movers: electric motors diesel engines air system • Piping to carry fluid • Valves to control flow in system • Other fittings control instrumentation What are Pumping Systems a. Pump casing b. Pump shaft c. Impeller d. Volute e. Stuffing box f. Stuffing box gland g. Packing h. Lantern Ring i. Impeller wearing ring j. Pump casing wearing ring

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PISTON PUMPS PLUNGER PUMPS DIAPHRAGM PUMPS RECIPROCATING PUMPS GEAR PUMPS LOBE PUMPS SCREW PUMPS CAM PUMPS VANE PUMPS ROTARY PUMPS POSITIVE DISPLACEMENT PUMPS CENTRIFUGAL PUMPS PUMPS

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Centrifugal pump or Constant head machine is Adding energy to fluid is continuously Positive displacement pump is Adding energy to fluid is intermediately

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CENTRIFUGAL PUMPS CLASSIFICATION According to types of flow 1 Radial flow 2 Axial flow 3 Mixed flow According to suction type 1 Single suction 2 Double suction According to number of Impellers 1 Single 2 Multiple According to Impeller type 1 Open 2 Semi open 3 Closed

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According to types of CASING 1 Volute 2 Vortex According to priming 1 Non self Priming type 2 Self priming According to case split 1 Horizontal back pull out type 2 vertical According to bearing support 1 Over hung ie cantilever type 2 Between bearing ie simply supported According to pump shaft orientation 1 Horizontal mounted 2 Vertical mounted

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According to suction/delivery nozzle orientation 1 End suction/top discharge 2 Top suction/top discharge 3 side suction/side discharge According to pumped fluid sealing method 1 Gland packing 2 Mechanical seal According to horizontal shaft mounting 1 Foot mounted 2 Center line mounted According to shaft to impeller 1 Direct motor shaft ie mono block 2 Indivisible shaft ie pump shaft + motor shaft

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Mostly our centrifugal pumps are Side suction top discharge back pull out type radialy casing spilt single suction cantilever type bearing support radial type of liquid flow single impeller volute type casing horizontally shaft mounted mechanical seal type sealing method

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

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Nature of Fluid to be handled Temperature Viscosity Corrosive Nature Abrasion nature Vapour pressure NPSHa Particulars of the duty required from the pump Rate of flow- Min / Normal / Max Inlet condition- Flooded/Lift Head to be developed by the pump Type of pump and drive required Horizontal / Vertical Preference for gland packing / mechanical seal. Turbine / motor / VSD/ Autostart

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Special operational requirements Application like Boiler feed water Marine altitude humidity ambient temperature pump in parallel/series Material of Construction. Shaft – 304L Impeller-304L wet casing – 304L Body- carbon steel sleeve- 304L Miscellaneous Water for cooling / flushing / sealing Any other liquid for sealing.

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Cross section view of Centrifugal pump

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 Pumping the addition of energy to a fluid  Pumping action creates a partial vacuum while atmospheric pressure forces liquid up. Displacement the discharge of a fluid from a vessel Centrifugal Force used to produce kinetic energy

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PUMP TERMINOLOGY  Atmospheric Pressure  Absolute Pressure  Vacuum  Specific Gravity  Vapor Pressure  Suction Head  Suction Lift  Total Dynamic Head  Net Positive Suction Head

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PUMP TERMS Atmospheric pressure Absolute Pressure Vacuum Specific gravity Pressure of atmosphere on earth Sum of Available Pressure Atm-pressure Full or partial elimination of atmospheric pressure Ratio weight of any liquid to weight of water of same volume.

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Vapor pressure Liquid can get vapor by TWO WAYS 1 heating 2 Reduce pressure

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Suction Head

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Suction lift

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Total dynamic head

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Net Positive Suction Head To avoid cavitations in centrifugal pumps the pressure of the fluid at all points within the pump must remain above saturation pressure. The quantity used to determine if the pressure of the liquid being pumped is adequate to avoid cavitations is the net positive suction head NPSH. The net positive suction head available NPSHA is the difference between the pressure at the suction of the pump and the saturation pressure for the liquid being pumped. The net positive suction head required NPSHR is the minimum net positive suction head necessary to avoid cavitations.

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eye Suction discharge pressure bubbles Liquid stage

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Centrifugal Pumps Centrifugal Pumps

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Three basic components:  Volute casing body  or Diffuser  Impeller  or impellers  Driver motor

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Centrifugal Pumps Vanes Direction of rotation

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 Convert the mechanical energy into hydraulic energy by centrifugal force on the liquid  Has two main components: 1. Stationary componets casing casing cover and wear ring 2. Rotating components impeller and shaft  Classified into three categories Radial Flow Mixed Flow Axial Flow

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ACCORDING TO MECHANICAL CONSTRUCTION IMPELLERS ARE CLASSIFIED IN TO OPEN – FOR LOW HEAD PUMPS FOR SEWAGE CONCRETE SERVICE. SEMI-OPEN – FOR ABRASIVE AND SLURRY SERVICE FOR MEDIUM HEADS. CLOSED TYPE – FOR CLEAR LIQUIDS FOR HIGH HEAD PUMPS SINGLE SUCTION IMPELLER AND DOUBLE SUCTION IMPELLER. ACCORDING TO FLOW IMPELLERS ARE CLASSIFIED IN TO AXIAL FLOW – LOW HEAD HIGH VOLUME. RADIAL FLOW- HIGH HEADCOMPARATIVELY LESS VOLUME MIXED FLOW – MEDIUM HEAD MEDIUM VOLUME.

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Centrifugal Pumps Single suction impeller

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Centrifugal Pumps • Open • Semi-open • Closed - Single suction - Double suction • Non-clogging • Axial flow • Mixed flow

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Centrifugal Pumps Rotation Impeller Blades V t V r V s V r Radial Velocity V t Tangential Velocity V s Vector Sum Velocity

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Centrifugal Pumps Suction Eye Cutwater Arrows represent the direction of water flow Discharge Nozzle

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Centrifugal Pumps

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Centrifugal Pumps

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AXIAL SPLIT TYPE

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Centrifugal Pumps Typical Split Case Pump- Section View

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Centrifugal Pumps VSC Pump- Section View

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Mono block centrifugal pump

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 Impeller  Suction nozzle  Casing  Shaft  Shaft sleeve  Gland packing or mechanical seal  Bearings  Discharge nozzle

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WORKING PRINCIPLE 1CONVERTING PRIME MOVER ENERGY INTO VELOCITY ENERGY by means of shaft impeller 2 CONVERTING VELOCITY ENERGY INTO PRESSURE ENERGY by means of volute casing.

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Liquid flow path inside a centrifugal pump Generation of Centrifugal Force The process liquid enters the suction nozzle and then into eye center of a revolving device known as an impeller. When the impeller rotates it spins the liquid sitting in the cavities between the vanes outward and provides centrifugal acceleration. As liquid leaves the eye of the impeller a low- pressure area is created causing more liquid to flow toward the inlet. Because the impeller blades are curved the fluid is pushed in a tangential and radial direction by the centrifugal force.

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Conversion of Kinetic Energy to Pressure Energy The key idea is that the energy created by the centrifugal force is kinetic energy. The amount of energy given to the liquid is proportional to the velocity at the edge or vane tip of the impeller. The faster the impeller revolves or the bigger the impeller is then the higher will be the velocity of the liquid at the vane tip and the greater the energy imparted to the liquid. This kinetic energy of a liquid coming out of an impeller is harnessed by creating a resistance to the flow. The first resistance is created by the pump volute casing that catches the liquid and slows it down. In the discharge nozzle the liquid further decelerates and its velocity is converted to pressure

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One fact that must always be remembered: A pump does not create pressure it only provides flow. Pressure is a just an indication of the amount of resistance to flow.

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The main reason for using head instead of pressure to measure a centrifugal pumps energy is that the pressure from a pump will change if the specific gravity of the liquid changes but the head will not change. 10meter water column is 1kg/cm2 Sp. Gravity 1 760mm of Hg is 1kg/cm2 Sp. Gravity 13.6 Since any given centrifugal pump can move a lot of different fluids with different specific gravities it is simpler to discuss the pumps head and forget about the pressure. A given pump with a given impeller diameter and speed will raise a liquid to a certain height regardless of the weight of the liquid.

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 IN A CENTRIFUGAL PUMP THE ROTARY PART WHICH ROTATES WITH THE SHAFT IS KNOWN AS IMPELLER THE STATIONARY PART WHICH SURROUNDS THE IMPELLER IS KNOWN AS CASING.  THE CASING IS FIRST FILLED WITH LIQUID TO REMOVE ENTRAPPED AIR OR GAS IN THE CASING THIS PROCESS IS KNOWN AS PRIMING. IN CASE OF FLODDED SUCTION PUMP THERE IS NO NEED OF PRIMING.

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CENTRE PART OF THE IMPELLER IS KNOWN AS EYE. THE EYE OF THE IMPELLER IS CONNECTED TO THE SUCTION PIPE.WHEN THE IMPELLER ROTATES INSIDE THE CASING DUE TO CENTRIFUGAL FORCE THE LIQUID INSIDE THE IMPELLER IS THROWN AWAY HENCE THE LIQUID WILL GAIN KINETIC ENERGY.SO THE LIQUID AT THE TIP OF THE IMPELLER WILL HAVE MAXIMUM VELOCITY ENERGY THIS VELOCITY ENERGY OF LIQUID IS THEN CONVERTED IN TO PRESSURE ENERGY BY THE STATIONARY CASING. THE CASING IS OF VOLUTE SHAPE INCREASING CROSS SECTIONAL AREA.HENCE THE VELOCITY ENERGY IS GRADUALLY CONVERTED IN TO PRESSURE ENERGY. AS THE LIQUID FROM THE CENTRE OF THE IMPELLER IS THROWN AWAY VACCUM WILL BE CREATED AT THE EYE OF THE IMPELLER AND TO FILL THIS VACCUM FRESH LIQUID WILL BE DRAWN THROUGH THE SUCTION PIPE.THIS PROCESS CONTINUES UNTILL THE IMPELLER IS ROTATING.

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 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

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 Cannot handle highly viscous fluids efficiently  Cannot be operated at high heads  Maximum efficiency holds over a narrow range of conditions

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 Preliminary checkup  Lubrication oil in bearings – static / forced  Check for free rotation of the shaft  Cooling water to bearing / oil coolers  Seal water flow / seal liquid / gland water  Coupling and its guard  Close drain valves  Open Suction valve  Check whether Discharge valve is in closed condition  Open Spillback valve  Prime the pump – suction head / suction lift  Check for leaks in gland area and casing flange

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Affinity laws For a fixed speed Q1 / Q2 D1 / D2 H1 / H2 D1 / D2 2 P1 / P2 D1 / D2 3 For a fixed Diameter Q1 / Q2 N1 / N2 100/Q2 1750/3500 200M3/HR H1 / H2 N1 / N2 2 100/H2 1750/35002 400M P1 / P2 N1/ N2 3 5/P2 1750/35003 Q1Q2 – Flow rate M3/hr H1H2 - Head Mts D1D2 - Diameter of the impeller mm N1N2 - Speed.rpm Impeller Trimming...

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CAVITATION 1 Formation of bubbles inside the pump 2 Growth of bubbles 3 Collapse of bubbles 4 Cavitations Vapor pressure is the pressure required to keep the liquid in a liquid state. If pressure applied to surface of liquid is not enough to keep molecules good-looking close together Molecules will be free to separate roam as a vapor. Vapor pressure is dependent upon the temperature of liquid.

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eye Suction discharge pressure bubbles Liquid stage

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Cavitations in a centrifugal pump has a significant effect on pump performance. Cavitations degrades the performance of a pump resulting in a fluctuating flow rate and discharge pressure. Capitation can also be destructive to pumps internal components. When a pump capitates vapor bubbles form in the low pressure region directly behind the rotating impeller vanes. These vapor bubbles then move toward the oncoming impeller vane where they collapse and cause a physical shock to the leading edge of the impeller vane. This physical shock creates small pits on the leading edge of the impeller vane. Cavitations can also cause excessive pump vibration which could damage pump bearings wearing rings and seals.

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Damaged impeller due to cavitations

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Misalignment Misalignment - The most common vibration problem. Unlike unbalance does not have a single vibration symptom. As a result it should always be considered as a possibility. Definition of Perfect alignment - Shaft centerlines are parallel and intersect. Angular Misalignment Offset orParallel Misalignment Shaft centerlines intersect but are not parallel Shaft centerlines are parallel but do not intersect.

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Misalignment of pump shaft motor shaft

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SHAFT RUN OUT SHAFT DIAL GAUGE

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AXIAL PLAY CHECKING

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Mechanical causes of vibration Unbalanced rotating components. Damaged impellers and non concentric shaft sleeves are common. A bent or warped shaft. Pump and driver misalignment. Pipe strain. Either by design or as a result of thermal growth. The mass of the pump base is too small. Thermal growth of various components especially shafts. Rubbing parts. Worn or loose bearings. Loose hold down bolts. Loose parts. Product attaching to a rotating component. Damaged parts. Hydraulic causes of vibration Operating off of the best efficiency point BEP of the pump. Vaporization of the product Impeller vane running too close to the pump cutwater.

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Method of alignment aFeeler gauge bStraight edge method cRim face method dReverse indicator method Method of calculation aFormulae method bGraph method

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RIM FACE ALGNMENT CALCULATION a Mount dial indicator on moveable unit with touching dial plunger touching the non-moveable unit. b Zero indicator point on top of coupling radial reading axial reading R A 0 0 +0.01’’ +0.05’’ +0.05’’ -0.01’’ +0.04’’ +0.06’’ D diameter of indicator point R Radial reading A axial reading L1 Inboard leg L2 Outboard leg

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L2 Out board leg S1 Shims needed for L1 S2 Shims needed for L2 Formula S1 L1 A + ½ R D S2 L2 A + ½ R D CONSIDER L1 8’’ L2 16’’ D 2’’ A +0.04’’ R +0.06’’ S1 8/2 0.04’’ + 0.06/2 +0.019’’ S216/20.04’’ +0.06/2 +.035’’

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 An expanding cavity on the suction side and a decreasing cavity on the discharge side.  Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses. POSITIVE DISPLACEMENT PUMP

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Classification of positive displacement pump.

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 Positive displacement type CHigh pressure high efficiency DLiquids must be free of solids CHandle viscous fluids  Used mainly in oil burners soaps and cosmetics sugars syrup and molasses dyes ink bleaches vegetable and mineral oils

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GEAR PUMPS LOBE PUMPS SCREW PUMPS CAM PUMPS VANE PUMPS ROTARY PUMPS  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

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 Meshing gears separate creating vacuum  Atmospheric pressure forces liquid inward to fill the vacuum

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 Liquid is delivered in large volumes with less number of pulses than in gear pump  Not dependent on discharge pressure

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 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 GEAR PUMPS LOBE PUMPS SCREW PUMPS CAM PUMPS VANE PUMPS ROTARY PUMPS

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 Screw pumps carry fluid in the spaces between the screw threads.  The fluid is displaced axially as the screws mesh. GEAR PUMPS LOBE PUMPS SCREW PUMPS CAM PUMPS VANE PUMPS ROTARY PUMPS

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Function of positive displacement pump

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 Suction stroke and delivery stroke alternatively occurs creating vacuum

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 Diaphragm an elastic substance usually rubber  Used for low pressure application like removing water from trenches

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ROTODYNAMIC  High speed  Discharge decreases with increase in delivery head  No slip or leakage loss  Continuous flow  Low initial maintenance costs  Compact symmetric in design  Efficient for heads up to 60m in single stage POSITIVE DISPLACEMNT  Low speed  Discharge does not change with variation in delivery head  Losses due to slip leakage  Pulsating flow  High initial maintenance cost  Large in size oblique  Efficient for high heads over 60 m

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Thank you

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