TOPIC :PUMPING SYSTEM (OIL TANKER) MODULE 1 :PUMPS & PUMPING SYSTEMS Pumps & Pumping Systems Presentation from theEnergy Efficiency Guide for Industry 2 UNEP 2006 Training Agenda: Pumps Introduction Type of pumps Assessment of pumps Energy efficiency opportunities INTRODUCTION PUMPING SYSTEM ACCOUNTS FOR NEARLY 20% OF THE WORLDS ELECTRICAL ENERGY DEMAND PURPOSE OF PUMPS Transfer of liquid from one place to another place Circulate liquid around a system e.g. cooling & lubrication pumps MAIN COMPONENTS OF PUMPING SYSTEMS PUMPS PRIME MOVERS PIPING VALVES PUMP & PIPE FITTINGS , INTRUMENTATION & CONTROLS END USE EQUIPMENTS 4 UNEP 2006 Introduction 20% of worlds electrical energy demand 25-50% of energy usage in some industries Used for Domestic, commercial, industrial and agricultural services Municipal water and wastewater services What are Pumping Systems 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 6 UNEP 2006 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 End-use equipment Heat exchangers, tanks, hydraulic machines What are Pumping Systems 7 UNEP 2006 Introduction Head Resistance of the system Two types: static and friction Static head Difference in height between source and destination Independent of flowPumping System Characteristics destination source Static head Static head Flow 8 UNEP 2006 Introduction Static head consists of Static suction head (hS): lifting liquid relative to pump center line Static discharge head (hD) vertical distance between centerline and liquid surface in destination tank Static head at certain pressure Pumping System Characteristics Head (in feet) = Pressure (psi) X 2.31 Specific gravity 9 UNEP 2006 Introduction Friction head Resistance to flow in pipe and fittings Depends on size, pipes, pipe fittings, flow rate, nature of liquid Proportional to square of flow rate Closed loop systemonly has friction head (no static head) Pumping System Characteristics Friction head Flow 10 UNEP 2006 Introduction In most cases: Total head = Static head + friction head Pumping System Characteristics System head FlowStatic head Friction head System curve System head Flow Static head Friction head System curve 11 UNEP 2006 Introduction Pump performance curve Relationship between head and flow Flow increase System resistance increases Head increases Flow decreases to zero Zero flow rate: risk ofpump burnout Pumping System Characteristics Head Flow Performance curve for centrifugal pump 12 UNEP 2006 Introduction Pump operating point Pumping System Characteristics Duty point: rate of flow at certain head Pump operating point: intersection of pump curve and system curve Flow Head Static head Pump performance curve System curve Pump operating point 13 UNEP 2006 Introduction Pump suction performance (NPSH) Cavitation or vaporization: bubbles inside pump If vapor bubbles collapse Erosion of vane surfaces Increased noise and vibration Choking of impeller passages Net Positive Suction Head NPSH Available: how much pump suction exceeds liquid vapor pressure NPSH Required: pump suction needed to avoid cavitation Pumping System Characteristics CARGO PUMPING SYSTEM 1. WORKING PRINCIPLES OF DIFFERENT TYPES OF PUMPS AND THEIR USES 2. WORKING PRINCIPLE OF CENTRIFUGAL PUMP 3. DESCRIPTION AND CHARATERISTICS OF CENTRIFUGAL PUMP 4. DESCRIPTION OF FRAMO PUMP 5. PIPING SYSTEM FOR OIL TANKERS DIRECT SYSTEM , RING MAIN SYSTEM , CRUCIFORM SYSTEM , FREE FLOW SYSTEM 6. DISCUSSION/EXPLANATION OF ACTUAL PIPING SYSTEM OF AN OIL TANKER 7. LOADING & DISCHARGING PROCEDURES FOR AN OIL TANKER 8. STRIPPING SYSTEM , VAC-STRIP/CENTI-STRIP SYSTEM 9. PARALLEL/SERIES RUNNING OF PUMPS , EFFECT OF SHORE CHARACTERISTICS ON PUMPING RATE 10. CARGO HEATING SYSTEM AND REQUIREMENT 15 UNEP 2006 Training Agenda: Pumps Introduction Type of pumps Assessment of pumps Energy efficiency opportunities TYPES OF PUMPS PUMPS ROTODYNAMIC POSITIVE DISPLACEMENT CENTRIFUGALOTHERROTARY RECIPROCATING GEAR PUMP SCREW PUMP VANE PUMP LOBE PUMP PISTON PUMP DIAPHRAGM PUMP PROGRESSIVECAVITY PUMP PERISTALTIC PUMP EDUCTOR-JET PUMP AXIAL PISTON PUMP RADIAL PISTON PUMP SOLENOID PUMP 17 UNEP 2006 Type of Pumps Classified by operating principle Pump Classification DynamicPositive DisplacementCentrifugal Special effect Rotary ReciprocatingInternal gearExternal gearLobeSlide vaneOthers (e.g. Impulse, Buoyancy)PumpsDynamicPositive DisplacementCentrifugal Special effect Rotary ReciprocatingInternal gearExternal gearLobeSlide vaneOthers (e.g. Impulse, Buoyancy)Pumps18 UNEP 2006 Type of Pumps Positive Displacement Pumps For each pump revolution Fixed amount of liquid taken from one end Positively discharged at other end If pipe blocked Pressure rises Can damage pump Used for pumping fluids other than water 19 UNEP 2006 Type of Pumps Positive Displacement Pumps Reciprocating pump Displacement by reciprocation of piston plunger Used only for viscous fluids and oil wells Rotary pump Displacement by rotary action of gear, cam or vanes Several sub-types Used for special services in industry 20 UNEP 2006 Type of Pumps Dynamic pumps Mode of operation Rotating impeller converts kinetic energy into pressure or velocity to pump the fluid Two types Centrifugal pumps: pumping water in industry 75% of pumps installed Special effect pumps: specialized conditions 21 UNEP 2006 Type of Pumps Centrifugal Pumps How do they work? (Sahdev M) Liquid forced into impeller Vanes pass kinetic energy to liquid: liquid rotates and leaves impeller Volute casing converts kinetic energy into pressure energy 22 UNEP 2006 Type of Pumps Centrifugal Pumps Rotating and stationary components (Sahdev) 23 UNEP 2006 Type of Pumps Centrifugal Pumps Impeller Sahdev) Main rotating part that provides centrifugal acceleration to the fluid Number of impellers = number of pump stages Impeller classification: direction of flow, suction type and shape/mechanical construction Shaft Transfers torque from motor to impeller during pump start up and operation 24 UNEP 2006 Type of Pumps Centrifugal Pumps Casings Volute Casing (Sahdev) Functions Enclose impeller as pressure vessel Support and bearing for shaft and impeller Volute case Impellers inside casings Balances hydraulic pressure on pump shaft Circular casing Vanes surrounds impeller Used for multi-stage pumps WORKING PRINCIPLES Liquid is taken from one end and positively discharged at the other end for every revolution. Positive displacement pumps are widely used for pumping fluids other than water, mostly viscous fluids. Fixed quantity of liquid is pumped after each revolution. So if the delivery pipe is blocked, the pressure rises to a very high value, which can damage the pump. POSITIVE DISPLACEMENT PUMP ROTO-DYNAMIC PUMP Liquid is forced into the impeller either by atmospheric pressure or by static head The vanes of impeller pass kinetic energy to the liquid, thereby causing theliquid to rotate. The liquid leaves the impeller at high velocity. The impeller is surrounded by a volute casing or in case of a turbine pump a stationary diffuser ring. The volute or stationary diffuser ring converts the kinetic energy into pressure energy. Positive Displacement Pumps To move fluids positive displacement pumps admit a fixed volume of liquid from the inlet into a chamber and eject it into the discharge.

Positive displacement pumps are used when higher head increases are required.Generally they do not increase velocity. Positive Displacement: Reciprocating Piston:up to 50 atm Plunger: up to 1,500 atm Diaphragm: up to 100 atm, ideal for corrosive fluids Efficiency 40-50% for small pumps, 70-90% for large pumps Positive Displacement: Reciprocating (plunger) Positive Displacement: Rotary Gear, lobe, screw, cam, vane For viscous fluids up to 200 atm Very close tolerances Positive Displacement: Rotary GEAR PUMP INTERNAL GEAR PUMP Two gears coming out of mesh creates vacuum causing inflow ofprocess liquid while on the other end two gears coming into mesh squeeze out the liquidforcing it out into the piping Lubrication of gears is by the process liquid itself Used for pumping of viscous liquidsOnboard use is for pumping of Fuel oil , Diesel Oil & Lube Oil LOBE PUMP Two lobes coming out of mesh creates vacuum causing inflow ofprocess liquid on suction side Two lobes coming into mesh squeeze out the liquidforcing it out into the piping on the discharge side Usually use timing gear for driving the driven lobe shaft Lubrication of gears is by the process liquid itself Used for pumping of viscous liquids Could be bi-lobe or multi-lobe design Onboard use is in usually in flowmeters Working Principle of Tri-lobe pump 33 GEAR PUMP VANE PUMP Vanes move in and out on the machined slots inside the eccentric rotor inside the circular casing Vane moving outwards creates increase in volume of vane chamber causing inflow of liquid through suction ports Vane moving increates decrease in volume of vane chamber causingsqueezing out of liquid through discharge ports Sealing & lubrication between the vane tips& casing is by the process liquid Can be used as Variable Displacement Pumps Lubrication of gears is by the process liquid itself Used for pumping of viscous liquids 35 VANE PUMP SCREW PUMP Twin screw& tri-screw pumps are quite common Driven screw could be direct driven or timing gear driven Screws coming out of mesh create vacuum causing inflow of liquid on suction side Screws coming into mesh cause squeezing out of the liquid on the discharge sideLubrication & sealing between the moving screws & casing is caused by the process liquid Used for pumping viscous liquid Used as Main Lube Oil Pumps onboardPROGRESSIVE CAVITY PUMP Also called eccentric screw pump , or cavity pump Transfers fluid by means of the progress, through the pump, of a sequence of small, fixed shape, discrete cavities, as its rotor is turned.Volumetric flow rate is proportional to the rotationUsed in fluid metering and pumping of viscous or shear sensitive materials.Rotor is made of high alloy stainless steel , while stator(casing) is made of hardened rubber Rotor is attached to the drive shaft through universal coupling Used as sludge and bilge pump onboard RECIPROCATING PISTON PUMP Reciprocating piston causes suction and discharge alternately Pump could be single acting or double actingFlow is pulsating , accumulator is used on the discharge side to smoothen the pulsating pressure Intake stroke : Suction valves are opened, and fluid is drawn into the cylinderDischarge stroke : Suction valves close, the discharge valves open, and fluid is forced out of the cylinder.Double acting pump is of crosshead type Slow speed and low capacity pump Used as Bilge pump and OWS pump COMPONENTS OF RECIPROCATING PUMP TWO STAGERECIPROCATING PUMP RECIPROCATING CAM PUMP Eccentric cam pushes the plunger up to create a discharge .Discharge check valve opens and suction side check valve closes Spring pushes the plunger down to create suction . Suction check valve open and discharge side check valve closes Commonly used as cylinder lubricator pump onboard SINGLE ACTING DIAPHRAGMPUMP Basically a single acting plunger pump Diaphragm is actuated by trapped liquid between the plunger and the diaphragm Both the suction and discharge sides have check valves Both the suction and discharge sides have diaphragm dampers (accumulators) DOUBLE ACTING PUMP Double acting reciprocating twin-diaphragm pump Pneumatically operated pump commonly known as Wilden pump Inner side of the diaphragm chamber comes in contact with airOuter side of the diaphragm chamber handles process liquid Driving air inlet and exhaust is controlled by a control valveControl valve shifts with diaphragm movement towards the end of the stroke which reverses the air inlet and exhaust ports Can be used for pumping a variety of fluids Special material pump ( teflon ) comes for pumping highly corrosive liquid PERISTALTIC OR ROLLER PUMP Offers contamination-free pumping and relatively low maintenance The fluid is contained within a flexible tube fitted inside a circular pump casing Rotor with a number of rollers attached to the external circumference compresses the flexible tube Part of tube under compression closes thus forcing the fluid to be pumped to move through the tube As the tube opens to its natural state after the passing of the cam fluid flow is induced to the pump Chemical compatibility of the tubing with the process liquid is the most important criteria while choosing this pump SOLENOID PUMP Also known as electromagnetic pump Commonly used as metering pumps for dosing applications Stroke length and frequency determine the flow rate Usually diaphragm operated with diaphragm attached to the spring loaded plunger Solenoid energizes to push the plunger and hence the diaphragm out to create discharge stroke Solenoid de-energizes , the spring causes the plunger to retract casing diaphragm to take suctionUsed as Boiler & Fresh Water Generator chemical dosing pump , Fuel oil additive dosing pump and Boiler & incinerator Pilot burner pump onboard VARIABLE DELIVERY PUMPS AXIAL PISTON PUMP Axial Piston Pump also known as Swash Plate type of pump Plungers attached through slipper pads to the swash plate Angle of tilting of swash plate determines the flow rate Delivery can be varied from zero to maximum in both the directions RADIAL PISTON PUMP Radial piston pump also sometimes called Janey pump Pump stroke is varied by means of eccentric floating ring Delivery cane be varied from zero to maximum in both the directions Both these pumps are used for high pressure hydraulic applicationsUsed onboard for windlass ,mooring winches , Hatch cover pumps , steering gear pumps & hydraulic cranes 45 PISTON PUMP Rotodynamic pumps There are three different types of rotodynamic pumps: Axial-flow pumps Centrifugal pumps Mixed flow pumps Axial-flow Pumps IntroductionAn axial-flow pump uses a screw propellerto axially accelerate the liquid. The outletpassages and guide vanes are arrangedto convert the velocity increase of theliquid into a pressure.As distinct from the centrifugal pump, the axial flow pumpabsorbs the maximum power at zero flow. Axial-flow Pumps A mechanical seal prevents leakage where the shaft leaves the casing. A thrust bearing of the tilting padtype is fitted on the drive shaft. Theprime mover may be an electricmotor or a steam turbine. Axial-flow Pumps Applicabilitywith The axial flow pump is used where large quantities of water at a low head are required,or example in condenser circulating. The efficiency is equivalent to a low lift centrifugal pump, and the higher speed fs possible enable a smaller driving motor to be used. The axial-flow pump is also suitable for supplementary use in a condense scoop circulating system, since the pump will offer littleresistance to flow when idling. With scoop circulation, the normal movement of the ship will draw in water; the pump would be in use only when the ship was moving slowly or stopped. The pump is reversible and this, in conjunction with highcapacity flow, makes it suitable for trimming and heeling duties as well. Axial-flow Pumps The impellerThe pump casing is of gunmetal for condenser cooling duties and cast iron for heeling and trimming pumps. The impellers are of aluminium bronze and guide vanes of gunmetal are arranged immediately after the impeller, the pump shaft beingofstainless steel. Quick quiz Which part of the pump is the screw propeller? Click on the screw propeller. If you are not sure go to the previous screen to refresh your memory. Centrifugal pumps In this part of the lesson we will take a closer look at Centrifugal pumps Centrifugal Pump Symbols CENTRIFUGAL PUMPS WORKING MECHANISM OF CENTRIFUGAL PUMP Centrifugal Pumps Most common type of pumping machinery.There are many types, sizes, and designs from various manufacturers who also publish operating characteristics of each pump in the form of performance (pump) curves.The device pictured on the cover page is a centrifugal pump. Pump curves describe head delivered, pump efficiency, and net positive suction head (NPSH) for a properly operating specific model pump. Centrifugal pumps are generally used where high flow rates and moderate head increases are required. Centrifugal pumps - theory and characteristics Centrifugal pump duties are usually for the movement of large volumes of liquid at low pressures, although higher pressures can be achieved with multi-staging. Energy input Energy transformations inside the Dump Velocity and pressure levels Fluid flow Click on an item to jump to it. Centrifugal pumps - theory and characteristics A centrifugal pump can be further defined as a machine which uses several energy transformations in order to increase the pressure of a liquid. The energy input into the pump is typically the fuel source energy used to power the driver. Centrifugal pumps - theory and characteristics Energy input Most commonly, this is electricity used to power an electric motor. Alternative forms of energy used to power the driver include high-pressure steam used to drive a steam turbine. Fuel oil used to power a diesel engine. High-pressure hydraulic fluid used to power a hydraulic motor. Compressed air used to drive an air motor. Regardless of the driver type for a centrifugal pump, theinput energy is converted in the driver to a rotating mechanical energy, consisting of the driver output shaft, operating at a certain speed, and transmitting a certain torque, or horsepower. Centrifugal pumps - theory and characteristics The remaining energy transformations take place inside the pump itself. The rotating pump shaft is attached to the pump impeller, which rotates in a volute housing. The impeller imposes a centrifugal force, which imparts kinetic energy to the fluid. Kinetic energy is a function of mass and velocity (K.E = $Sv7.Raising a liquids velocity increases its kinetic energy.This causes the fluid to accelerate out of the impeller with this increased velocity.The volute casing or diffuser provides gradually widening passages i.e. an expansion of the flow area, which reduces the fluid velocity and this energy is converted into pressure. Centrifugal pumps - theory and characteristics Velocity and pressurelevels Fluid flow A particular feature of centrifugal pumps is that the power absorbed is a minimum at zero flow, and therefore can be started up against a closed valve. By increasing the size of the impeller, and/or the speed of pump rotation, we can achieve larger pumping rates. The diagram illustrates that velocity and pressure levels vary as the fluidmoves along the flow path in a centrifugal pump. Centrifugal pumps - theory and characteristics The fluid flow causes a vacuum to be formed in the pump suction, which will draw fluid into the impeller suction. Thus fluid flow will occur from the suction to discharge. The liquid enters the centre or 'eye' of the impeller axially, changes direction and flows radially out between the vanes. If the pipeline leading to the pump inlet contains a non-condensable gas such as air, then the pressure reduction at the impeller inlet merely causes the gas to expand, and suction pressure does not force liquid into the impeller inletCentrifugal pumps - theory and characteristics Consequently, no pumping action can occur unless this non-condensable gas is first eliminated, a process known as priming the pump. Hence we need a fluid flow through the impeller in order to achieve a vacuum. Thus when these pumps are not primed, or loose suction during operation they will not self-prime themselves. In order to prime or re-prime these pumps we can use a priming system If vapours of the liquid being pumped are present on the suction side of the pump, this results in Cavitation, which can cause loss of prime or even serious damage to the pump. CENTRIFUGAL PUMPS WORKING MECHANISM Converts rotational energy of prime mover to kinetic energyand finally to pressureenergy of process fluid Impeller imparts kinetic energy to the process liquid by centrifugal force Pump is not self primingAir ejector/vacuum pump is required to create partial vacuum inside the pump casing to draw in the process liquid Alternatively pump casing is to be filled with process liquid for priming Movement ofprocess liquid by centrifugal action causes the liquid to move to the tip of the impeller This causes vacuum at the eye of the impeller Vacuum at eye of the impeller causes inflow of Process fluidProcess liquid exits the impeller tip at a high velocity tangential to the vane tip Diffuser ring or volute casing has increasing cross section and act as a divergent nozzleKinetic energy is converted to pressure energy , the velocity of flow decreases while the pressure increases while passing through volute casing/diffuser ring Fluid is discharged under pressure through the outlet piping Comparisons: Centrifugal larger flow rates not self priming discharge dependent of downstream pressure drop down stream discharge can be closed without damage uniform pressure without pulsation direct motor drive less maintenance wide variety of fluidsComparisons: Positive Displacement smaller flow rates higher pressures self priming discharge flow rate independent of pressure utilized for metering of fluids down stream discharge cannot be closed without damage bypass with relief valve required pulsating flow gear box required (lower speeds) higher maintenance Advantages of centrifugal Pump Very efficient Produce smooth and even flow Reliable with good service life Disadvantages Loss of priming easily Efficiency depends upon operating design head & speed. Centrifugal Pumps Advantages simple and cheap uniform pressure, without shock or pulsation direct coupling to motor discharge line may be closed can handle liquid with large amounts of solids no close metal-to-metal fits no valves involved in pump operation maintenance costs are lower Disadvantages cannot be operated at high discharge pressures must be primed maximum efficiency holds for a narrow range of operating conditions cannot handle viscous fluids efficiently COMPONENTS OF CENTRIFUGAL PUMP CASING IMPELLER SHAFT BEARINGS SHAFT SEAL OR GLAND PACKING COUPLING Main components of a centrifugal pump are: COMPONENTS OF CENTRIFUGAL PUMP VOLUTE CASING (TOP HALF) CASING BOLTS CASING (TOP HALF) IMPELLER (DOUBLE SHROUD) WEAR RING WEAR RING MOTORCOUPLING PUMP COUPLING BEARING HOUSING (DRIVE END) BEARING HOUSING(FREE END) GLAND COVER SHAFT SLEEVE WITH GLAND PACKING PUMP SHAFT COUPLING BOLTS NECK BUSH VOLUTE CASING (LOWER HALF) Centrifugal pumps-component parts Centrifugal pumps-component parts This is a vertical , single stage ,single entry, centrifugal pump for general marine use . The mainframe and casing, together with a motor support bracket, house the pumping element assembly. The volute casing is split in two halves along a vertical plane. Since the suction and discharge nozzles are provided in the rear half of the casing, the rotating element can be taken out by removing only the front half casing without disturbing the rest of the pump. Centrifugal pumps - component parts The pumping element is made up of a top cover, a pump shaft, an impeller, a bearing bush and a sealing arrangement around the shaft. The sealing arrangement may be a packed gland or a mechanical seal and the bearing lubrication system will vary according to the type of seal. Replaceable wear rings are fitted in the casing around the top and bottom faces of the impeller. The motor support bracket has two large apertures to provide access to the pumping element, and a coupling spacer is fitted between the motor and pump shaft to enable the removal of the pumping element without disturbing the motor or vice versa VOLUTE CASING Volute casing converts the processliquid kinetic energyto pressure energy The sectional area of the volute increases from minimum to a maximum at the discharge This area is caled the cut-throat area The cut-throat area of the volute corresponds to theminimum working clearencebetween impeller & casing Cut-throat area prevents internal leakage from high pressure area to low pressure area Volute casing may be vertically or horizontally split Volute casing may be single or double entry Another classification is Single voluteand double volute casing Double volute casing if properly designed can eliminate the radial thrust on the shaft at BEP (Best Efficiency Point) Impeller Centrifugal Pumps Pump Impeller Vanes Direction of rotation Centrifugal Pumps Typical single suction impeller Centrifugal Pumps Single suction impeller Centrifugal Pumps Impeller Types Open Semi-open Closed - Single suction - Double suction Non-clogging Axial flow Mixed flow Centrifugal Pumps Full Diameter Impeller Rotation Impeller Blades Vt Vr Vs Vr = Radial Velocity Vt = Tangential Velocity Vs = Vector Sum Velocity Centrifugal Pumps Impeller and volute Suction Eye Cutwater Arrows represent the direction of water flow Discharge Nozzle Centrifugal Pumps Pump Construction Standard construction, any impeller Mechanical seal Internally flushed, seal cavity Variety of seal materials Stuffing box construction, any impeller External flush lines Compression packing rings Single flushed mechanical seal Centrifugal Pumps Standard construction Bell & Gossett Series 1510 Standard Construction CLASSIFICATION OF CENTRIFUGAL PUMPS Centrifugal Pumps can be classified based onvarious factorsSINGLE VOLUTE DOUBLE VOLUTE SINGLE ENTRY DOUBLE ENTRY OPEN SEMI-OPEN CLOSED SINGLE STAGE MULTI-STAGE RADIAL FLOW MIXED FLOW AXIAL FLOW VOLUTE TYPE DIFFUSER TYPE TURBINEOR REGENRATIVE TYPE HORIZONTAL VERTICAL SUBMERSILE CENTRIFUGAL PUMPS CASING IMPELLERSTAGES FLOWPRINCIPLEINSTALLATION Centrifugal Pumps End Suction Pump Series 1510 26 sizes To 4400 gpm To 520 ft TDH To 150 HP To 8x10 General Purpose Motor Centrifugal Pumps Section View Bell & Gossett Series 1510 Standard Construction Gauge Taps Centrifugal Pumps Large, Line Mounted Pump Series 80 Close coupled 18 sizes To 2600 gpm To 410 ft TDH To 60 HP To 8x8 Special Purpose Motor Centrifugal Pumps Multi-stage pumps Bell & Gossett Series 3550 Multi-stage, diffuser design 8 sizes, stainless steel to 600 gpm to 1200 ft to 75 hp, 3500 rpm many options for suction and discharge nozzles Centrifugal Pumps Multi-stage pump Bell & Gossett Series 3550 Diffusers Centrifugal Pumps Vertical Turbine Submersible 48 Models 5 - 14 bowls 40 - 2000 gpm 25 - 300 feet head Lineshaft 88 Models 5-20 bowls 4 Styles 20 - 10,000 gpm 7 - 200 feet headCentrifugal Pumps Double Suction Pump Bell & Gossett Series HSC 37 sizes To 12500 gpm To 840 ft TDH To 1000 HP To 14x18 General Purpose Motor Centrifugal Pumps Typical Split Case Pump- Section View Centrifugal Pumps Double Suction Pump Series VSCS Series VSC 17 sizes To 8000 gpm To 400 ft TDH To 600 HP To 12x14 General Purpose Motor Centrifugal Pumps VSC Pump- Section View Centrifugal Pumps - Double Entry Pumps Centrifugal Pumps - Double Entry Pumps The incoming liquid enters the double impeller from the top and bottom and passes into the volute casing for discharge in the same way as before. A double entry pump has a lower NPSH required characteristic, which will have advantages in poor suction conditions. It should be noted that different impeller sizes could be fitted into a basic pumping element. This enables various discharge head characteristics to be provided for the same basic pump frame. The larger pumps, which are double entry, can achieve flow rates of 10,000 tonns/hour. Centrifugal Pumps - Double Entry Pumps Illustration shows a cross-section through a double entry centrifugal pump. Mixed flow pumps In this type, the pressure is developed partly by centrifugal action and partly by the vanes and, as the name implies, the flow is both axial and radial through the impeller. Centrifugal Pumps Vertical Turbine Pump Driver Discharge Head Column Bowl Assembly Centrifugal pump closely coupled with motor Does not require long drive shaft Motor operates at a cooler temperature. Noiseless operation. High efficiency Smooth and even flow In case of repair full pump to be removed. Submersible Pumps Jet Pumps Combination of a surface centrifugal pump, nozzle and venturi arrangement. Used in small dia bore wells. Simple design Low purchase and maintenance cost. Easy accessibility to all moving parts. Low efficiency. Vacuum Pumps

Vacuum Doesn't Suck! There is no such force as suction. If gas molecules in one "section" of an enclosed volume are removed, then there is a pressure difference between the two "section"and the remain gas molecules will moveand fill the total space but at a lower pressure.

Vacuum pumps (as a single or as a pumping system) create and maintain the conditions appropriate to a required process Different types of vacuum pumps have a characteristic working range in which it will be effective Gas Transfer Vacuum Pump VACUUM PUMPING METHODS Two fundamental types of pumpimg: Gas Transfer Vacuum Pump Entrainment Vacuum Pump Pumps arebased on speeding gas particle into the exit by means of : stream of liquid (aspirator pump) or of vapour (diffusion pump) stream moving surfaces (turbo-molecular pump) electric field (ion pump) -gas entering the inlet is compressed and expelled out the outlet. Positive Displacement Vacuum Pumps Inlet Outlet PUMP Gas VACUUM PUMPING METHODS

Entrainment Pumps based on gas sorption Must be regenerated to empty the trapped gas Inlet PUMP Gas Scroll pump Sliding Vane Rotary Pump Molecular Drag Pump Turbomolecular Pump Fluid Entrainment Pump VACUUM PUMPS Reciprocating Displacement Pump Gas Transfer Vacuum Pump Drag Pump Entrapment Vacuum Pump Positive Displacement Vacuum Pump Kinetic Vacuum Pump Rotary Pump Diaphragm Pump Piston Pump Rotary Piston Pump Roots Pump Dry Pump Adsorption Pump Getter Pump Getter Ion Pump Bulk Getter Pump Diffusion Pump Sublimation Pump The quantity of a gas removed by the pump at a steady state pressure p is a gas flow rate( gas flax) characterized by the throughput QVolume flow rate Expressions for gas flow rate Q

pVVQ ptA=AThroughput and Pumping Speed Q P,V QuantityMass flow rate pV flow rate (pV throughout) Volume flow rate Molar flow rate n=m/M Equation Typical unitskg s-1 mbar L s-1 Pa m3 s-1 M3 h-1,L s-1 mols s-1 mmQtA=A VVQtA=AnnQtA=AThe pumping speed S refers to the volume rate of flow of gas . Gives the total volume evacuated per unit time (L/sec) dtdVpdtpdVpQSpv= = =Pumping speed = S Moving Gases Compression ratio = Pout/Pin Fans:large volumes, small discharge pressure Blowers: compression ratio 3-4, usually not cooled Compressors: compression ratio >10, usually cooled. Centrifugal (often multistage) Positive displacement Fan Impellers Two-lobe Blower Reciprocating Compressor Vacuum Pumps Aspirator or Venturi Pump Bernoullis principle of operation (moving fluid reduces pressure) Pump operation is based on bulk flow of fluids Ultimate vacuum is approximately 24 Torr (vapor pressure of water at 25C) Bernoulli Equation The Bernoulli Equation is a statement of the conservation of energy principle appropriate for flowing fluids. "Bernoulli effect" is the lowering of fluid pressure in regions where the flow velocity is increased. In the high velocity flow through the constriction, kinetic energy must increase at the expense of pressure energy. If the density doesnt change typical for liquids this simplifies to where the pipe is wider, the flow is slower. A fluid can also change its height. By looking at the work done as it moves: This is Bernoullis equation: as the speed goes up, the pressure goes down. How the Venturi Pump Works: Bernoullis Principle describes fluid behavior for varying flow (and height) conditions P + 1/2v2 + gh = Constant P = static pressure, = fluid density,v = velocity conservation of energy for fluid mechanics Giovanni Venturi, created a pump using this effect. A restriction in a fluid line causes a pressure drop due to the velocity increase.How the Venturi Pump Works: No stream Stream How the Venturi Pump Works: Venturi Pump Details Vacuum Range: 50-500 Torr Pros: no moving parts, minimal maintenance Cons: requires an external compressed air source, limited vacuum range Reciprocating pump This is a simple reciprocating pump.If it is to be used as a vacuum pump, the vessel is connected to the intake; If it is to be used as a pressure pump, the vessel is connected to the outlet. The heart operates as a pump.Theory of Operation Mechanical vacuum pumps work by the process of positive gas displacement, that is during operation the pump periodically creates increasing and decreasing volumes toremove gases from the system, and exhaust them to the atmosphere. In most designs a motor driven rotor spins inside a cylindrical stator of larger diameter. The ratio of the exhaust pressure (atmospheric) to the base pressure (lowest pressure obtained at the vacuum pump inlet) is referred to as the Compression Ratio of the pump For example, if a mechanical vacuum pump obtains a base pressure of 15 mTorr, its compression ratio is: outinPKP=For mechanical pumps it is possible to achieve K at a values of about 105 Theory of Operation Pumping speed (S) for the mechanical pumps isfairly constant at pressures from 1atm down to about 1mbarr Pumping speed decreases rapidly below this pressure, and approaches zero at the pump's base pressure. Volume pumps - based on the concept of reducing the pressure by increasing the volume. Old designs were in the form of a piston pump. Modern design a rotary pump. In a single cycle of the pump operation the number of particles in the pumped volume will be reduced by: cc 0VV -Vwhere Vc is the volume of the pump cylinder, Vo is the pumped volume.AllvolumepumpshaveadeadvolumeVswhichdetermines the ultimate pressure (the amount of gas in the dead volume) scVp[Tr] =760VThe pumping volume is lubricated with vacuum oil, which means that in reality: To improve p one should increase the pumping volume and decrease the dead volume. The best way is to reduces the back pressure well below 760 Tr e.g., by multistage pumping.scVp =760 +p (oil v.p.)V Example A simple piston pump has a displacement of 1L (Vp). It is connected to a chamber of 10L (V0 ). If pumping start at 1atm, what will be a pressure in the chamber after 4 complete cycles? In a single cycle of the pump operation the number of particles (n0) in the pumped volume will be reduced to (n1) P N ( )= P 0 ( ) 1VDV|\

|.|NFor four complete cyclesP(4) = 0.656 atm. ( )( )( ) ( )00 0 00 1 0 1 0100 01 0 0 00 0 0; ; ;1pppp pPVPV Pn n n n n V VRT RT RTRTP nVVP P RTP V VPVV V PRTnRVTV V= = A = = ==A| |= = = |\ .Diaphragm pumps A flexible metal or polymeric diaphragm seals a small volume at one end.At the other end are two spring-loaded valves: one opening when the volumes pressure falls below the outside pressure, other opening when the volumes pressure exceeds the outside pressure. A cam ( ( on a motor shaft rapidly flexes the diaphragm, causing gas transferin one valve and out the other. Diaphragm pumps often have two stages in seriesto produce a lower vacuum, or in parallel, to produce a higher pumping speed.In general, diaphragm pumps have low pumping speeds (Dehydrated aluminosilicate: e.g., Na2O Al2O3 nSiO2mH2O Dehydration creates channels with calibrated diameter size, 0.1 nm760 >760 350 >760 760 Water cooled baffleOil is contained and condensed by the diffusion pump. A small amount can escape toward the HiVac area of the system. This "backstreamed" oil is detrimental to the system.To contain it, a water-cooled baffle is located between the diffusion pump and the cold trap. Most back-streamed diffusion pump oil molecules are condensed on the internal water cooled baffle disc and returned to the diffusion pump in the form of liquid oil.Oil Diffusion PumpPotential Problems: Backstreaming of oil vapor can occur if forepressure becomes too large. Backstreaming occurs for pressures of 1 to 10 mTorr. Cold cap on top of multistage jet assembly helps to reduce this. Liquid nitrogen filled cryotrap also helps to reduce this. Maximum tolerable foreline pressure (critical forepressure) must not be exceeded, or pump will dump or blow-out, sending oil up into the chamber. Pump can overheat if cooling water fails Most pumps have a thermal cutout switch. Pumping requires low vapor pressure oil Water, dirt, or other impurities will raise vapor pressure. Only special oils are suitable for diffusion pump use. Example Diffusion pump has a pumping speed of 1000Ls-1 at pin,10-3mbar,falling to 400Ls-1 at pin =10-2mbar.The critical backing pressure pcrit for the pump is 0.4mbar! a) Calculate the minimum size (pumping speed) of the baking rotary pump if diffusion pump is in at 10-2mbar At 10-2mbar the throughput of the diffusion pump is (Qmax)in= pin*SeffDP=10-2mbar*400Ls-1=4mbarLs-1(Qmax)in =(Qmax)back=Seff*pcrit Approximate value of the pumping speed of baking pump is Seff,back=Qmax/pcrit =4mbarLs-1 /0.4mbar=10Ls-1 b) Calculate the minimum size (pumping speed) of the baking rotary pump if diffusion pump is in at 10-3mbar. (Qmax)in= pin*SeffDP=10-2mbar*1000Ls-1=1mbarLs-1 Seff,back=Qmax/pcrit =1mbarLs-1 /0.4mbar=2.5 Ls-1 Turbomolecular Pump The turbomolecular pump was invented in 1958 by Becker Turbomolecular pump imparts a directed momentum to gas molecules through a rapidly rotating blades. Turbine blades rotating at high speed transfer momentum to gas molecules to force them out the exhaust (must be backed). 9,000 to 90,000 rpm motor speeds! - 20 to 60 blades per disk The pump is characterized by a compression ratio and ultimate pressure. Work only in molecular regime, use after roughing pump is spent (< 100 mTorr) Typically 100 to 800 L/sec pumping speeds UHV can be readily achieved (better if used in combination with a titanium sublimation pump). Pumping speed is proportional to the rotor speed and is constant when normal rotation speed is achieved. Turbo pumps have advantages over diffusion pumps: no back-stream oil into the vacuum system at any time can be started and stopped in a few minuets can be directly connected to the chamber without a high vacuum valve.!!!But turbo pump can be noisy and they induce vibration, and the compression ratio for hydrogen and helium are low Turbomolecular Pump The compression ratio of the turbine establishes the base pressure. The compression ratio is higher for higher molecular weights: Approximately: log10K = 1.5 (M)1/2, K-compression ratio For H2, M = 1, so K = 10x1.5 = 30 = very small For hydrocarbons, M = 100, so K = 1015 = very large Base pressure is usually limited by H2. Turbomolecular Pump: Structure 10 to 20 stator/rotator pairs assembled on a single shaft. The blades rotate at 20,000-90,000 rpm. The stators are between the rotors in order to direct thegas molecules. Rotor stator distance is less than 1 mm. The pairs near the inlet are for high throughputwhereas those near the exitare at low pumping speed. Mechanically rotor bearings andmagnetically suspended bearings. No trapping gas. No uncertainty about whether the pump is pumping. If the rotor is turning, it is pumping. Traps, baffles are not required between the vacuum chamber and the pump inlet. Molecule V Moving Wall with Speed V Schematic of the rotor and stator of a turbomolecular pump Inlet Outlet Rotation blades Non-Rotation blades Gas captured by the upper stages is pushed into the lower stages and successively compressed to the level of the fore-vacuum pressure.As the gas molecules enter through the inlet, the rotor, which has a number of angled blades, hits the molecules. Thus the mechanical energy of the blades is transferred to the gas molecules.With this newly acquired momentum, the gas molecules enter into the gas transfer holes in the stator. This leads them to the next stage where they again collide with the rotor surface, and this process is continued, finally leading them outwards through the exhaust.The relative velocity between the rotating blades and stator blades makes it probable that a gas molecule will be transported from the pump inlet to the pump outlet Each blade is able to support a pressure difference. Because this pressure ratio is small for a single stage many stages are cascaded Rotation axis is in the center of the rotorand in the vertical direction.The rotor moves at a high speed such that when a molecule hits a blade ,momentum is imparted to the molecule in a direction almost perpendicular to the blade surface. Turbomolecular PumpsPotential Problems Very high speed rotor blades have close-mating stator blades. Slight imbalances can cause vibration and bearing wear problems. Sudden blast of atmospheric pressure can bend the blades down, causing catastrophic failure, crashing the pump. Lubrication of the high speed rotor is an engineering problem. Circulating oil is most reliable, but pump must be right-side-up. Grease-lubricated bearings are less reliable, but allow pump to be placed at any orientation. Too high of a pressure will cause aerodynamic lift and drag. A mechanical foreline pump must be used Aerodynamic lift can bend blades, causing catastrophic failure. A high voltage combined with a magnetic field causes electrons to travel in a helical path with an energy sufficient to ionize gas atoms. The ions are accelerated so they strike a Ti cathode and become buried in the plate. Sputtered Ti coats everything: tubes, plates, and pump casing. Several pumping mechanisms are possible, including chemical reaction (getter action(, ion burial, and neutral burial (the last two accounting for the pumps ability to pump inert gases). Can be started below 10-6 mbar!!!!. Pumping speed is gas dependent and drops off below 10-9 mbar. A little less expensive than turbo pumps. Ion pump for UHV (and high HV) Single cell from ion pump Cathode Anode Ion pump for UHV (and high HV) Diode Pump: High pumping speed for getterable gases low speed for noble gases (no getter action). Argon instabilities when buried Ar is released from cathodes at high gas loads. Noble (or Differential) Diode Pump: The two cathodes are made of different materials, Ti and Ta Ta is also a getter (slightly less active). When ions impinge onTa, the higher mass of Ta results inmore energetic neutrals, which penetrate deeper (less Coulomb interaction), both in anode and pump wall. Triode Pump: Glancing incidence collisions with Ti grid cathode increase Ti sputter yield and yield of neutrals, both leading to increased burial. Ion pump for UHV (and high HV) A anode B- magnetic flix line produced by a permanent magnet attached to the outside of the pump,K1,K2- cathode plates made of Ti , in contact with pump walls 1- electron () in a spiral track,2- gas molecules (), ionized gas particles() 3-sputtered Ti ( ), 4- implanted buried, gas particles, 5- gas particles incorporated into sputtered Ti

Ion pump for UHV (and high HV) Diode-type sputtering ion pump-pumping mechanism A sputtering ion pump consist of a large number of such cells Ions generated in cell impinge on the cathode plates and sputter Ti. The amount sputtered is roughly proportional to the pressure in the pump. This material adheres to the surface of anode, opposite cathode and getters reactive gases. Some ionized particles penetrate well into the cathode. This mechanism of pumping is effective for all types of ion As cathode sputtering proceedssuch particles are released giving rise to gas pressure Ion pump for UHV (and high HV) Triode-type sputtering ion pump-pumping mechanism A anode, B- magnetic flux line produced by a permanent magnet attached to the outside of pump, K- Ti cathode in the form of grid, behind K is a collector target plate F at anode potential 1- electron () in a spiral track,2- gas molecules (), ionized gas particles() 3-sputtered Ti ( ), 4- implanted buried, gas particles,Triode-type sputtering ion pump has a grater efficiency for pumping noble gases It is due to geometry of the system favors grazing incidence of the ions from the discharge on the cathode grid. This increases the sputtering yield and the number of ions that are neutralized and reflected. These ions travel to the target plate with high energy and implant themselves but! With negligible sputtering. Ions which are not neutralised cannot move against the electricalfield betweenK and F and return towards K The enhanced pumping speed for noble gases is because the sputtering is less at F and the reemergance of implanted particles is reduced Ion Pumps Pump life depends on quantity of gas pumped> 20 years at 10-9 mbar The nominal pumping speed of ion pump is given by the max in the pumping speed curve for air GasH2 H2OCH4O2 ArHe Relative pum..speed % 14580100802530 Example A chamber is fitted with a triode ion pump with pumping speed Sair=100Ls-1A gas mixture containing 5%CH4+10%O2 in N2 is admitted. A required total pressure in the chamber is 10-6mbar -Calculate the flow rate of the gas mixture . Ptot=PCH4+PO2+PN2=1*10-6mbar= QCH4/SCH4+QO2/SO2+QN2/SN2= =5*10-2*Qtot/SCH4+0.1*Qtot/SO2+0.85*Qtot/SN2 SN2=Sair=100Ls-1, SO2=0.8Sair, SCH4=Sair,(see the table above) 1*10-6mbar=5*10-4Qtot+1.25*10-3Qtot+8.5*10-3Qtot=10.25*10-3Ls-1Qtotmbar Qtot=9.76*10-5mbarLs-1 Getters and Gettering Gettering is the process of removing impurities from the active track regionsPhysical getters are in cryostats where a zeolite material is used to physically absorb and hold water vapor.If a zeolite material is placed at liquid nitrogen temperature it will absorb and hold gases. Chemical getters provides a pumping action by a chemical reaction where a chemically active gas combines with a chemically active metal to form a low vapor pressure solid compound.The chemically active metal can be an element or an alloy that can be called a getter metal (GM) These reactions with active gases are fairly straightforward.They all form a low vapor pressure ceramic compoundThe active gas is permanently removed from the vacuum chamber.The inert gases are not pumped at all due to they are inert and will not react with GM Hydrogen (H2) does not react to form a chemical compound but merely dissolves in GM to form a solid solution.How To Use Getters There are two separate categories of chemical getters:i- evaporable, ii-non-evaporable. Evaporable getters are used in electron tubes: when the tube is pumped down a slug of getter metal is heated to a high temperature to evaporate it so that it can subsequently condense on the tubes inner surfaces to forms a high surface area reactive coating that will remain as an in situ pump after the tube is pinched off. Titanium sublimation pump (TSP) : heating titanium/molybdenum alloy filament to 1450o C Ti sublimes and then condenses into a thin film on the inner surface of the chamber The lifetime of Ti film is dependent upon the gas load it is required to pump The pumping speed of is directly proportional to the total surface area of the film. The pumping speed will decline as it reacts the gas in the chamber The Ti source will become saturated with H2 when it cooled after sublimation temperature, and re-heating releases the hydrogen.How To Use Getters Non-evaporable getters (NEG) remain in the solid state. Usually it is zirconium alloys in any solid form: chunks or pellets or thin films bonded to metallic substrates. Getter Activation process is required for NEGs: - NEG exposed to air has skin of oxides, nitrides, etc over its surface.-NEG bulk will be saturated with dissolved H2. NEG will be essentially inert and will not provide getter-pumping surface. Getter Activation the process to prepare the getter surface for pumping.It is done in situ by heating under vacuum after being installed. During heating skin layer will diffuse into the NEGs bulk and the H2 will be driven out of solid solutionThe time and temperature required for activation will vary with the specific getter alloy,The vacuum level required is at least 10-4 torr H2 remaining in the chamber will be re-pumped by the getter, Gases will be removed from the vessel by reaction on the NEGs surface until enough gas is reacted to once again skin over the surface andreacted skin begins to act as a barrier for furtherdissolution of H2.The higher temperature will result in pumping and diffusion into the bulk taking place at the same time as sort of a continuous activation cycle.Depending upon the actual NEG alloy in use, a compromise temperature must be chosen that trades-off diffusion rate for H2 retention.Re-activation is required each time the NEG material sees air or any other active gas .When an active gas encounters a hot NEG material, an exothermic reaction occurs that can run away in terms of temperature and present a very real safety problem. In a cycled system, the chamber can be released to argon instead of an active gas, or the getter can be contained within a separate housing that can be isolated from the chamber by an appropriate valve. How To Use Getters Getter Pumps An important class of getter pumps are the Non Evaporable Getters (NEGs) These are alloys of elements like Ti, Zr, V, Fe, Al which after heating in vacuum present an active surface where active gases may be gettered Traditionally, the getters take the form of a sintered powder either pressed into the surface of a metal ribbon or formed into a pellet Getter pumps In recent times, thin films of getter material have been formed on the inside of vacuum vessels by magnetron sputtering These have the advantage of pumping gas from the vacuum chamber by gettering and of stopping gases from diffusing out of the walls of the vessels Titanium Sublimation Pumps (TSP) a type of getter pump When a gas molecule impinges on a clean metal film, the sticking probability can be quite high. For an active gas with the film at room temperature, values can be between 0.1 and 0.8. For noble gases and hydrocarbons sticking coefficients are very low (essentially zero) Evaporated films, most commonly of titanium or barium, are efficient getters and act as vacuum pumps for active gases. Example UHV chamber evacuated by turbomolecular pump (TMP) backed with oil-rotary pump and Titanium Sublimation Pump (TSP). A total pressure of 4*10-9mbar is achieved and this consists of 50%Ar+50%H2. . On reaching this pressure the valve to the TSP is closed and pressure in chamber rise up to 8*10-9mbar. - Calculatethe new partial pressure of H2 in the system, taking in account that Noble gases will not be pumped by TSP Ptot=PAr+PH2=2*10-9mbar(PAr)+2*10-9mbar(PH2) AP=8*10-9mbar -4*10-9mbar=4*10-9mbarnew PH2=2*10-9mbar+4*10-9mbar=6*10-9mbar - Calculate the pumping speed of TSP for H2, if the effective pumping speed of TMP is 100Ls-1 InitiallyPtot=4*10-9mbar=PAr+PH2 or For Ar PAr=Qpv,Ar/100Ls-1Q With TSP closed off With TSP open 2, , 9, , ,4 10pv H pvAreff TMP eff TMP eff TSPQ QmbarS S S= ++2 227 1, , , 91 1 17 1,2 10;8 10100 100 1006 10pVAr pVH pVHtotpVHQ Q QmbarLsP mbarLs Ls LsQ mbarLs += = +=7 1 7 191 1,7 19 1,1,2 10 6 104 10100 1006 102 10 ; 200100eff TSPeff TSPeff TSPmbarLs mbarLsmbarLs Ls SmbarLsmbar S LsLs S = ++= =+Starting the system ( all off): 1.start BP 2.open V1 3.open DP water 4.wait until G1 reads below 10-1 Tr 5.turn on DP heater 6.fill lq. Nitrogen trap 7.wait until the DP warms up (20-40 min.) DP diffusion pump BP primary (backing) pump V1 backing valve V2 bypass valve V3 - vent (air inlet) valve V4 high vacuum valve G1 fore-vacuum gauge G2 high vacuum gauge OPERATING A DIFFUSION PUMP VACUUM SYSTEM Pumping down (initial pressure in the chamber 760 Tr, all in the pump start-up positions): close V3 close V1 open V2 wait until G2 reading goes below ~ 10-2 Tr close V2 open V1 slowly open V4 wait until G2 reads the desired pressure DP diffusion pump BP primary (backing) pump V1 backing valve V2 bypass valve V3 - vent (air inlet) valve V4 high vacuum valve G1 fore-vacuum gauge G2 high vacuum gauge Venting the chamber: close V4, open V3 Stopping the system. pump down the chamber.close V4 turn off DP heater stop lq. Nitrogen refill wait 20-40 min for the DP to cool down close V1 stop BP close DP water OPERATING A DIFFUSION PUMP VACUUM SYSTEM 189 UNEP 2006 Training Agenda: Pumps Introduction Type of pumps Assessment of pumps Energy efficiency opportunities 190 Assessment of pumps Pump shaft power (Ps) is actual horsepower delivered to the pump shaft Pump output/Hydraulic/Water horsepower (Hp) is the liquid horsepower delivered by the pump How to Calculate Pump Performance Hydraulic power (Hp): Hp = Q (m3/s) x Total head, hd - hs (m( x (kg/m3( x g (m/s2( / 1000 Pump shaft power (Ps): Ps = Hydraulic power Hp / pump efficiency Pump Pump Efficiency (Pump):Pump= Hydraulic Power /Pump Shaft Power UNEP 2006 hd - discharge headhs suction head, - density of the fluidg acceleration due to gravity 191 UNEP 2006 Assessment of pumps Absence of pump specification data to assess pump performance Difficulties in flow measurement and flows are often estimated Improper calibration of pressure gauges & measuring instruments Calibration not always carried out Correction factors used Difficulties in Pump Assessment PUMPING SYSTEM CHARACTERISTICS STATIC HEAD Resistance of the system which is to be overcome to initiate the flow is called head. "Head" may be simply defined as any resistance to the flow of a pump. Static head isthe difference in height between the source and destination of the pumped liquid Static Head can be divided into two parts : Static Suction Head (Hs) :Also called the suction lift.It is the vertical distance fromsurface of liquid at source (can be positive or negative) Static Discharge Head (Hd) : Vertical distance between pump centreline to destination STATIC HEAD STATIC HEAD VERSUS FLOW PUMPING SYSTEM CHARACTERISTICS FRICTION HEAD The pressure drop due to resistance of flow in the pipe and fittings is called the friction head Friction head is effected by the flow and increases with increase in flow FRICTIONAL HEAD VS FLOW SYSTEM HEAD VS FLOW TOTAL DYNAMIC HEAD (TDH) OR SYSTEM HEAD TDH = STATICDISCHARGE HEAD STATIC SUCTION HEAD+FRICTION HEAD PUMPING SYSTEM CHARACTERISTICS PUMP PERFORMANCE CURVES Head and flow determine the performance ofa pumpPUMP OPERATING POINT The pump operating point is determined by the intersection of the system curve and the pump curve PUMP PERFORMANCE CURVEPUMP OPERATING POINT Pump Curves For a given pump 1. The pressure produced at a given flow rate increases with increasing impeller diameter. 2. Low flow rates at high head, high flow rates at high head. 3. Head is sensitive to flow rate at high flow rates. 4. Head insensitive to flow rate at lower flow rates. Pump Curve - used to determine which pump to purchase. - provided by the manufacturer. Pump Curve Pressure increases with diameter Low flow at high head Head sensitive to flow at high flow rates CHARACTERISTICS CURVES TOTAL HEAD (M) FLOWRATE(LPM) %AGE EFFICIENCY SHAFT POWER CENTRIFUGAL PUMP PERFORMANCE CURVES Total head reduces with increasein flow rate Power required increases with increase in flow rate Efficiency increases with increase in flow rate and reachespeak before falling down DSM measures to reduce consumption in pumps Demand side management measures Use of friction less foot valve. Use of HDPE pipes Use of appropriate capacitor. Use of higher size suction pipe compared to delivery pipe. Overall Efficiency = Hydraulic power ( P2) X 100/ Power input ( P1) Pump efficiency. =Hydraulic power ( P2) X 100/ Power input to pump shaft ( P3) Hydraulic Power ( P2) = Q X Total Head ( hd - hs ) X p X g / 1000 Q = discharge in m/sPump Performance calculation p = density of fluid inkg/ m g = acceleration due to gravity ( m/s) P1 =1.732 X V X I X pf P3=P1 Xeff.of motor. Key Parameter for determining efficiency Flow Head Power Flow Measurement Techniques Tracer Method Ultrasonic flow measurement Tank filling method Installation of online flow meter Determination of total head Suction headmeasured from pump inlet pressure gauge reading Discharge head This is taken from the pump discharge side Pr. gauge Pumps: (Monoblock Pumps used for Drinking water) Sl.NoITEMPump1Pump2 1 MakeBeacon Beacon 2Capa hp/kW5 (3.7)5 (3.7) 3 Pipe sizes S/D65/50 mm 65/50 mm 4 Head25 m 25 m Typical name plate details of pump 5Discharge 8 L/s8 L/s 6Amps 88 7Overall Efficiency 47% 47 % Typical name plate details of pump PUMP EFFICIENCY CALCULATION SHEET SL.NO. ITEM Pump1Pump2Units 1Voltage406 407volts 2Current 6.0 6.6amps 3P.F 0.83 0.82 4Power input3.53.48 KW Typical performance calculations 5Dis. Head 22.2 22.2m 6Suc.Head 2.2 2.2m 7discharge 8 8L/s 8Hyd.Power1.571.57 KW 9Pump Effi. 44.8545.10 Typical performance calculations 1.Replace the existing discharge line with the 50 mm dia pipes to reduce the friction losses. 2.Provide water level switch to switch off the pump sets as soon as the Tank is filled. 3.Replace the existing pump sets with high efficiency pump sets. Typical observations/ Recommendations Size pump correctly Operate close to the best efficiency point. Size all piping and valves correctly Avoid all leakages. Factors to be considered from user side Flow control Strategies Varying speed Pumps in parallel stop/start control Flow control valve By pass control valve Trimming impeller Use of VFDS Energy conservation opportunities in pumping Operate pump near best efficiency point. Replace old pumps by energy efficient pumps Reduce system resistance by pressure drop assessment and pipe size optimization. Provide booster pump for few areas of higher head. Energy conservation opportunities in pumping Conduct water balance to minimize water consumption. Ensure availability of instruments like pressure gauges, flow meters. Repair seals and packing to minimize water loss. Avoid valves in discharge side as far as possible. Operatepumpsetduring non-peak hours. CHARACTERISTICS CURVES SYSTEM CURVE: System curve is the change in flow with respect to head of the system. PUMP PERFORMANCE CURVE : is the change in flow with the total head developed by the pump BEST EFFICIENCY POINT (BEP) When system curve is superimposed on pump curve it crosses at the pump BEP BEP is the pumping capacity at maximum impeller diameter ,or the point at which the efficiency of the pump is highest Obtaining exact flow rate as per BEP is not practically possible Flow rate deviation from BEP results in loss of performance and pump instability Flow rate can be matched corresponding to the BEP by following methods : a) Adjusting the pump speed b)Adjusting the pump impeller diameter c) Changing the impeller design d)Adjusting the system resistance e)Modifying static head f) Providing a system bypass flow route Pump Specification Recall Mechanical Energy Balance ( )2422 2VKDLfpz gVWi((

+ +A+ A +A=okgm N -( )cic cgVKDLfpgz ggVW2422 2((

+ +A+A+A=omflblb f t -Both equations describe work that must be supplied to system Pump Head What happens if the MEB is multiplied through by g (gc/g)? ( )((

((

+ +A+ A +A=24212 2VKDLfpz gVg gWioWhat are the units (SI)? 22mskgm N -2223mss kgm kg--= m =W/g has units of length and is known as the pump head ^ Example Tank A 2 Tank B 1 3 Why do we choose point 2 rather than 3 for MEB? What kind of valve to uses to control flow rate?Example Tank A 2 Tank B 1 3 gVKDLfgpz Hi24 12((

+ + +A+ A =Mechanical Energy Balance (in terms of head) ||.|

\|+ =gVH22min|Head vs. Flow Rate ||.|

\|+ =gVH H22min|gp gz HcA+ A =mingVKDLfi24 12((

+ +Quadratic In V or q System Response What happens when flow control valve is closed? Resistance (f) increases Flow rate decreases Need more head to recover flow rate Tank A 2 Tank B 1 3 System Response Valve Open Constant Head Response Constant Flow Response Valve Closed Pump Curves Pump manufacturers supply performance curves for each of their pumps.These are normally referred to as pump curves.These curve are generally developed using water as the reference fluid. The following can be read directly from a pump curve: Head vs. flow rate information for any fluid Pump efficiency for any fluid Pump horsepower for system operating with water Pump Performance Curves Developed Head Impeller Diameter Efficiency Flow Rate NPSH Horsepower http://capsicum.me.utexas.edu/ChE354/resources.html Power Input For fluids other than water: qWm P=|.|

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\|-=minshp slb f tf tlbgalf tmingalqlblb f tggHhp Pfmmfc60 55048 . 71) (33q W mPower Input Easier Way fluidwaterfluidwaterfluidGr SpPP. . = =Note:A less dense fluid requires less horsepower Example Q = 300 gpm Di= 10 Di= 10 Di= 10 Head(ft) = (%) = P(hp) = Head(ft) = (%) = P(hp) = Head(ft) = (%) = P(hp) = Pump Selection Goal is to find a pump whose curve matches the piping system head vs. flow rate curve.We can superimpose the previous head-flow rate curve on the manufacturers pump curves. To select a specific pump from a product line, find the pump with the highest efficiency that does not require the use of the largest impeller diameter.This will allow for future production expansions. Suppose that we have a process that requires a flow rate of 300 gpm and has a head requirement of 60 ft. at that flow rate.Can a 3x4-10 model 3196 Goulds pumps be used? Example Impeller Diameter = For Desired Q Head = How do can you force the system to operate on the pump curve? NPSH and Cavitation NPSH = Net Positive Suction Head Frictional losses at the entrance to the pump cause the liquid pressure to drop upon entering the pump. If the the feed is saturated, a reduction in pressure will result in vaporization of the liquid. Vaporization = bubbles, large volume changes, damage to the pump (noise and corrosion). Pressure Profile in the Pump NPSH To install a pump, the actual NPSH must be equal to or greater than the required NPSH, which is supplied by the manufacturer. Typically, NPSH required for small pumps is 2-4 psi, and for large pumps is 22 psi. To calculate actual NPSH NPSHactual= Pinlet-P* (vapor pressure) Pinlet = P(top of tank, atmospheric) + gh - 2fLeqV2/D NET POSITIVE SUCTION HEAD (NPSH) NPSH is the difference between suction head and the vapour pressureof the liquid at that point NPSHa NPSH available isthe difference between the suction head availableand the saturated vapour pressure of liquid at the pump suction NPSHr NPSH required is the NetSuction Head as required by the pump in order to prevent cavitation for safe and reliable operation of the pump.Net Positive Suction Head (NPSH) Associated with each H-Q location on the pump curve is a quantity that can be read called NPSH. An energy balance on the suction side of the fluid system (point 1 to pump inlet) with pinlet set to the vapor pressure of the fluid being pumped gives a quantity called NPSHA (net positive suction head available). ( )inletinletiv cz zVKDLfp pggNPSHA +((

|.|

\|+ = 12124Net Positive Suction Head The requirement is that: NPSH NPSHA>Otherwise (if NPSHA < NPSHpump), the pressure at the pump inlet will drop to that of the vapor pressure of the fluid being moved and the fluid will boil. The resulting gas bubbles will collapse inside the pump as the pressure rises again.These implosions occur at the impeller and can lead to pump damage and decreased efficiency. Cavitation What if NPSHactual < NPSHrequired? INCREASE NPSHactual cool liquid at pump inlet (T decreases, P* decreases) increase static head (height of liquid in feed tank) increase feed diameter (reduces velocity, reduces frictional losses) (standard practice) Centrifugal Pumps - Cavitation When the pressure falls below the vapour pressure of the liquid at agiven temperature, boiling occurs and small bubbles of vapour are formed. These bubbles will grow in the low-pressure area and implode when they are transported to an area of pressure above vapour pressure. The termgiven to this local vaporisation of the fluid is Cavitation. Centrifugal Pumps - Cavitation The collapsing of the bubbles is the area of Cavitation we are concerned with, as extremely high pressures are produced, which causes noise and erosion of the metal surface. The area of pipeline ... This cavitation effect... To reduce cavitation ... Click on an item to jump to it. Centrifugal Pumps - Cavitation When the pressure falls below the vapour pressure of the liquid at agiven temperature, boiling occurs and small bubbles of vapour are formed. These bubbles will grow in the low-pressure area and implode when they are transported to an area of pressure above vapour pressure.The term given to this local vaporisation of the fluid is Cavitation. Centrifugal Pumps - Cavitation The collapsing of the bubbles is the area of Cavitation we are concerned with, as extremely high pressures are produced, which causes noise and erosion of the metal surface. The area of pipeline where Cavitation mainly occurs is the pump suction, where the liquid is subjected to a rapid rise in velocity, and hence a fall in static pressure. Centrifugal Pumps - Cavitation When the pressure falls below the vapour pressure ofthe liquid at a given temperature, boiling occurs and small bubbles of vapour are formed. These bubbles will grow in the low-pressure area and implode when they are transported to an area of pressure above vapour pressure. The term given to this local vaporisation of the fluid is Cavitation. The collapsing of the bubbles is the area of Cavitation we are concerned with, as extremely high pressures are produced, which causes noise and erosion of the metal surface. Centrifugal Pumps - Cavitation This Cavitation effect on the pumpcan cause damage on the casing and impeller. During Cavitation, a liquid/vapour mixture of varying density is produced. This results in fluctuations in pressure (caused by the liquid column being drawn in), and causes fluctuations in the discharge pressure, pump power absorbed (shown on the ammeter), and hence pump revolutions.

Centrifugal Pumps - Cavitation When the pressure falls below the vapour pressure of the liquid at a given temperature, boiling occurs and small bubbles of vapour are formed. These bubbles will grow in the low-pressure area and implode when they are transported to an area of pressure above vapour pressure. The term given to this local vaporisation of the fluid is Cavitation. Centrifugal Pumps - Cavitation The collapsing of the bubbles is the area of Cavitation we are concerned with, as extremely high pressures are produced, which causes noise and erosion of the metal surface. To reduce Cavitation we must reduce the 'losses' on the suction side, hence reduce the pipeline friction and NPSH. This means reducing the pump flow rates. To reduce 'losses' on starting, the pump should be started against a closed discharge valve NPSH Do not use NPSH to size or select a pump unless all else fails.Pump selection is governed by H vs. Q requirements of system.When NPSHA is too small, it might be increased by: Increasing source pressure (not usually feasible) Cooling liquid to reduce vapor pressure (not usually feasible) Raise elevation of source reservoir Lower elevation of pump inlet Raise level of fluid in reservoir If NPSHA Cant Be Increased If the pump must be modified to achieve proper NPSH: Larger slower-speed pump Double suction impeller Larger impeller eye Oversized pump with an inducer Example 1 5 ft 150 ft 2 5 ft L = 5 ft, 6 inch Sch40 L = 300 ft, 5 inch Sch40 globe valve (open) P1 = 16 psia P2 = 16.1 psia P3 = 16 psia Use Goulds 3x4-10@3560 RPM Flow = 600 gpm of benzene 60F Data for benzene:PVap = 7.74 psia = 50.1 lbm /ft3 = 0.70 cP 3 Centrifugal pumps - Priming Centrifugal pumps although suitable for most general marine duties, suffer in one very important respect; they are not self priming and require some means of removing air from the suction pipeline and filling it with the liquid. Centrifugal pumps - Priming Where the liquid to be pumped is at a higher level than the pump, opening an air release cock near the pump suction will enable the air to be forced out as the pipeline fills up under the action of gravity. This is often referred to as "flooding the pump". Alternatively, an air-pumping unit can be provided to individual pumps or as a central priming system connected to several pumps. The water ring or liquid ring primer can be arranged as an individual unit mounted on the pump and driven by it, or as a motor driven unit mounted separately and serving several pumps, known as a central priming system. Centrifugal Pumps - Central Priming System Centrifugal Pumps - Central Priming System Where several pumps require a priming aid, for example a cargo pumping system or a number of engine room pumps, a central priming system is often used This reduces the number of priming pumps, saving spares, maintenance and cost. With this system a central priming unit consisting of two or more liquid ring primer pumps is arranged to pull a vacuum on a central tank.The tank has connections to float chambers in each of the suction lines for the system pumps isolated by either manually operated or solenoid operated valves. The priming pumps are controlled by the vacuum ofcentral tank, cutting in and out as required according to demand. As a system pump is required the priming connection is opened manually or automatically until good suction is achieved. The illustration shows a typical central priming system, including tank, valves, gauges and switches. Pump Selection from Many Choices of Characteristic Curves 1. Examine pump curves to see which pumps operate near peak efficiency at desired flow rate.This suggests some possible pipe diameters. 2. Compute system head requirement for a few diameters. 3. Compute V for some diameters.For water V in the range of 1 10 ft/s is reasonable (see ahead). 4. Re-examine pump curves with computed headand pipe diameters.This may give a couple of choices. 5. Pick pump with highest efficiency. Centrifugal Pumps Whats suitable? Impeller Single suction or double suction. Volutes Base mounted or in-line. Internally flushed or stuffing box. Single stage or multi stage. Packing, seal or wet rotor. Centrifugal pumps - selection The selection of Centrifugal pumps depends mainly upon duty and thespace available. The duty points are: Flow and total head requirements. This will govern the speed of rotation, impellerdimensions, number of impellers and type e.g. single or, double inlet, Range of temperature of fluid to be pumped. If suction capability is insufficient to accommodate supply conditions due for example to high inlet temperature Cavitation can occur Centrifugal pumps - selection Viscosity of the medium to be pumped, Type of medium, e.g. corrosive or non-corrosive, this would affect the choice of material (although for salt and fresh water the difference is often just the casing). Materials for salt water could be, casing-gunmetal (cast iron for fresh water), impeller-aluminium bronze, shaft-stainless steel, casing bearing ring seals-leaded bronze. Centrifugal pumps - selection The selection of Centrifugal pumps depends mainly upon duty and the space available.

The space points are: With vertically arranged pumps less floor space is required, this usually means that no hydraulic balance is necessary, impeller access is simple and no pipe joints have to be broken. Centrifugal pumps - selection A typical engine room pump could be a vertical, in-line, overhung (i.e. suction and discharge pipes are in a straight line and the impeller is supported, or hung, from above), either base or frame mounted. From which the impeller can be removed without splitting the casing, breaking pipe joints or removing the electric motor. Selection of Pipe Size Optimum pipe size depends mainly on the cost of the pipe and fittings and the cost of energy needed for pumping the fluids. Cost of materials increase at a rate proportional to about D1.5, while power costs for turbulent flow varies as D4.8.One can find correlations giving optimum pipe diameter as a function of flow rate and fluid density, however the optimum velocity is a better indicator as it is nearly independent of flow rate. Optimum Pipe Size For turbulent flow of liquids in steel pipes larger than 1 in. 36 . 01 . 012mVopt=3] [] [] [ft lbs lb ms ft Vmmopt===Remember Maximize pump efficiency Power input (hp) should be minimized if possible Selected impeller diameter should not be largest or smallest for given pump.If your needs change switching impellers is an economical solution NPSH required by the pump must be less than NPSHA Outline Pipe routing Optimum pipe diameter Pressure drop through piping Piping costs Pump types and characteristics Pump curves NPSH and cavitation Regulation of flow Pump installation design Piping and Pumping Learning Objectives At the end of this section, you should be able to Draw a three dimensional pipe routing with layout and plan views. Calculate the optimum pipe diameter for an application. Calculate the pressure drop through a length of pipe with associated valves. Estimate the cost of a piping run including installation, insulation, and hangars. List the types of pumps, their characteristics, and select an appropriate type for a specified application. Draw the typical flow control loop for a centrifugal pump on a P&ID. Describe the features of a pump curve. Use a pump curve to select an appropriate pump and impellor size for an application. Predict the outcome from a pump impellor change. Define cavitation and the pressure profile within a centrifugal pump. Calculate the required NPSH for a given pump installation. Identify the appropriate steps to design a pump installation. References Appendix III.3 (pg 642-46) in Seider et al., Process Design Principals (our text for this class). Chapter 12 in Turton et al., Analysis, Synthesis, and Design of Chemical Processes. Chapter 13 in Peters and Timmerhaus, Plant Design and Economics for Chemical Engineers. Chapter 8 in McCabe, Smith and Harriott, Unit Operations of Chemical Engineering. Pipe Routing The following figures show a layout (looking from the top) and plan (looking from the side) view of vessels. We want to rout pipe fromthe feed tank to the reactor. Plan View 50 ft feed tank reactor 40 ft steam header 35 ft piping chase 60 ft reactor feedtank piping chase 50 ft 35 ft steam header 30 ft 45 ft 40 ft 10 ft Layout View: Looking Down reactor 50 ft feed tank reactor 40 ft steam header 35 ft piping chase 60 ft Plan View = out = in reactor feedtank steam header 30 ft 85 ft 20 ft 60 ft 35 ft 10 ft 10 ft Layout View Pipe Routing Exercise Form groups of two. Draw a three dimensional routing for pipe from the steam header to the feed tank on both the plan view and the layout view. Size the Pump globe valve check valve 200 ft 150 ft 1. Determine optimum pipe size. 2. Determine pressure drop through pipe run. 100 gpm Optimum Pipe Diameter The optimum pipe diameter gives the least total cost for annual pumping power and fixed costs.As D, fixed costs , but pumping power costs.

Optimum Pipe Diameter Cost/(year ft) Pipe Diameter Total Cost Annualized Capital Cost Pumping Power Cost Optimum Example Two methods to determine the optimum diameter: Velocity guidelines and Nomograph. Example:What is the optimum pipe diameter for 100 gpm water. Using Velocity Guidelines Velocity = 3-10 ft/s = flow rate/area Given a flow rate (100 gpm), solve for area. Area = (t/4)D2, solve for optimum D. Optimum pipe diameter = 2.6-3.6 in. Select standard size, nominal 3 in. pipe. Nomograph -Convert gpm to cfm 13.4 cfm. -Find cfm on left axis. -Find density (62 lb/ft3) on right axis. -Draw a line between points. -Read optimum diameter from middle axis. 3.3 in optimum diameter Practice Problem Find the optimum pipe diameter for 100 ft3 of air at 40 psig/min. A = (s/50ft)(min/60 s)(100 ft3/min) = 0.033 ft2 0.033 ft2 = 3.14d2/4 d = 2.47 in Piping Guidelines Slope to drains. Add cleanouts (Ts at elbows) frequently. Add flanges around valves for maintenance. Use screwed fitting only for 1.5 in or less piping. Schedule 40 most common. Calculating the Pressure Drop through a Pipe Run Use the article Estimating pipeline head loss from Chemical Processing (pg 9-12). AP = (t/144)(AZ+[v22-v12]/2g+hL) Typically neglect velocity differences for subsonic velocities. hL = head loss due to 1) friction in pipe, and 2) valves and fittings. hL(friction) = c1fLq2/d5 c1 = conversion constant from Table 1 = 0.0311. f = friction factor from Table 6 = 0.018. L = length of pipe = 200 ft + 150 ft = 350 ft. q = flow rate = 100 gpm. d = actual pipe diameter of 3 nominal from Table 8 = 3.068 in . hL due to friction = 7.2 ft of liquid head Loss Due to Fittings K= 0.5 entrance K = 1.0 exit K=f(L/d)=(0.018)(20) flow through tee K=3[(0.018)(14)] elbows K=0.018(340) globe K=0.018(600) check valve Sum K = 19.5 hL due to fittings = c3Ksumq2/d4 = 5.7 ft of liquid head loss due to fittings. hLsum=7.2 + 5.7 ft of liquid head loss Using Bernoulli Equation AP = (t/144)(AZ+[v22-v12]/2g+hLsum) AP = (t /144)(150+0+12.9)= 70.1 psi due mostly to elevation.Use AP to size pump. elevationvelocityfriction and fittings Find the Pressure Drop check valve 400 ft 50 ft 400 gpm water 4 in pipe Estimating Pipe Costs Use charts from Peters and Timmerhaus. Pipe Fittings (T, elbow, etc.) Valves Insulation Hangars Installation $/linear ft Note: not 2003 $ EFFECT OF SPEED Q N, Flow rate is proportional to rotational speed H N2 , Head is proportional to square of rotational speed P N3 , Power is proportional to cube of rotational speed Variable Speed Pumps Advantage:Lower operating cost Disadvantage:Higher capital cost System head requirement (no valve) Pump curve for Di H (ft) q (gpm) q* (desired) q produced by pump with no flow control RPM1 RPM2 Affinity Laws In some instances complete sets of pump curves are not available.In this instance the pump affinity laws allow the performance of a new pump to be determined from that of a similar model. This can be useful when modifying the operating parameters of an existing pump. Affinity Laws ||.|

\|=121 2DDq q||.|

\|=121 2RPMRPMq q2121 2||.|

\|=DDH H2121 2||.|

\|=RPMRPMH H3121 2||.|

\|=DDhp hp3121 2||.|

\|=RPMRPMhp hp5 1211211||.|

\|=DDqqPARALLEL & SERIES OPERATION Regulating Flow from Centrifugal Pumps Usually speed controlled motors are not provided on centrifugal pumps, the flow rate is changed by adjusting the downstream pressure drop (see pump curve). Typical installation includes a flow meter, flow control valve (pneumatic), and a control loop. Typical Installation FT FC FV operator set-point Designing Pump Installations use existing pump vendor, note spare parts the plant already stocks. select desired operating flow rate, maximum flow rate. calculate pressure drop through discharge piping, fittings, instrumentation (note if flow control is desired need to use pressure drop with control valve 50% open). add safety factor to calculated head 10 psig spec pump for 20 psig, 150 psig spec pump for 200 psig. using head and flow rate, select impeller that gives efficient operation in region of operating flow rate. vertical location of pump compared to level of influent tank (NPSH). if want to control flow rate spec and order flow meter and flow control valve also. 295 UNEP 2006 Training Agenda: Pumps Introduction Type of pumps Assessment of pumps Energy efficiency opportunities 296 UNEP 2006 Energy Efficiency Opportunities 1. Selecting the right pump 2. Controlling the flow rate by speed variation 3. Pumps in parallel to meet varying demand 4. Eliminating flow control valve 5. Eliminating by-pass control 6. Start/stop control of pump 7. Impeller trimming297 UNEP 2006 Energy Efficiency Opportunities 1. Selecting the Right Pump Pump performance curve for centrifugal pump BEE India, 2004 298 UNEP 2006 Energy Efficiency Opportunities 1. Selecting the Right Pump Oversized pump Requires flow control (throttle valve or by-pass line) Provides additional head System curve shifts to left Pump efficiency is reduced Solutions if pump already purchased VSDs or two-speed drives Lower RPM Smaller or trimmed impeller 299 UNEP 2006 Energy Efficiency Opportunities 2. Controlling Flow: speed variation Explaining the effect of speed Affinity laws: relation speed N and Flow rate Q o N Head H o N2 Power P o N3 Small speed reduction (e.g. ) = large power reduction (e.g. 1/8) 300 UNEP 2006 Energy Efficiency Opportunities Variable Speed Drives (VSD) Speed adjustment over continuous range Power consumption also reduced! Two types Mechanical: hydraulic clutches, fluid couplings, adjustable belts and pulleys Electrical: eddy current clutches, wound-rotor motor controllers, Variable Frequency Drives (VFDs) 2. Controlling Flow: speed variation 301 UNEP 2006 Energy Efficiency Opportunities Benefits of VSDs Energy savings (not just reduced flow!) Improved process control Improved system reliability Reduced capital and maintenance costs Soft starter capability 2. Controlling Flow: speed variation 302 UNEP 2006 Energy Efficiency Opportunities 3. Parallel Pumps for Varying Demand Multiple pumps: some turned off during low demand Used when static head is >50% of total head System curve does not change Flow rate lower than sum of individualflow rates (BPMA) 303 UNEP 2006 Energy Efficiency Opportunities 4. Eliminating Flow Control Valve Closing/opening discharge valve (throttling) to reduce flow Head increases: does not reduce power use Vibration and corrosion: high maintenance costs and reduced pump lifetime (BPMA) 304 UNEP 2006 Energy Efficiency Opportunities 5. Eliminating By-pass Control Pump discharge divided into two flows One pipeline delivers fluid to destination Second pipeline returns fluid to the source Energy wastage because part of fluid pumped around for no reason 305 UNEP 2006 Energy Efficiency Opportunities 6. Start / Stop Control of Pump Stop the pump when not needed Example: Filling of storage tank Controllers in tank to start/stop Suitable if not done too frequently Method to lower the maximum demand (pumping at non-peak hours) 306 UNEP 2006 Energy Efficiency Opportunities 7. Impeller Trimming Changing diameter: change in velocity Considerations Cannot be used with varying flows No trimming >25% of impeller size Impeller trimming same on all sides Changing impeller is better option but more expensive and not always possible 307 UNEP 2006 Energy Efficiency Opportunities 7. Impeller Trimming Impeller trimming and centrifugal pump performance (BEE India,2004) 308 UNEP 2006 Energy Efficiency Opportunities Comparing Energy Efficiency Options ParameterChange control valve Trim impellerVFD Impeller diameter 430 mm375 mm430 mm Pump head71.7 m42 m34.5 m Pump efficiency75.1%72.1%77% Rate of flow80 m3/hr80 m3/hr80 m3/hr Power consumed 23.1 kW14 kW11.6 kW Centrifugal pumps - losses When assessing the amount of power needed to operate a centrifugalpump you must always take into account the various losses. Centrifugal pumps - losses - Friction loss in bearings and glands, surfaces of impeller and casing. Some impellers are highly polished to minimize friction loss. - Head loss in pumps due to shock at entry and exit to impeller vanes and eddies formed by vane edges. - Leakage loss in thrust balance devices, gland sealing and clearances between cut water and casing and bearing seals. Centrifugal pumps - losses A characteristic curve for a centrifugal pump isobtained by operating the pump at rated speedwith the suction open and thedischarge valve shut. The discharge valve is then opened in stages to obtain differentdischarge rates and total head corresponding to them. The data can then be represented graphically as a curve. The illustration shows the characteristic curves for three different types of pumps. Centrifugal pumps - losses Losses can be caused by: Failure to deliver Capacity reduction Excessive vibration Failure to deliver caused by loss of suction may be due to Insufficient supply head Air leakage at suction pipe (e.g. valve open to empty bilge, etc) Loss of priming facility or leaking shaft gland Centrifugal pumps losses Capacity reduction could be the result of A damaged sealing ring Leaking gland Obstruction (valve partly closed/foreign body) Incorrect rotational speed Excessive vibration may be caused by Loose coupling Loose impeller Bearing damaged Impeller imbalance Centrifugal pumps - hydraulic balance To control the axial movement of the rotating assembly, a balance piston is arranged to counteract the effect of the thrust of the impellers,especially in the multistage pumps. Centrifugal pumps - hydraulic balance The arrangement keeps the rotating assembly in its correct position under all conditions of loading .Water at the approximate pressure of the pump discharge passes from the last stage of the pump between the impeller hub and the balance restriction bush C into the annular space B dropping in pressure as it does so .The pressure of water in the chamber B tends to push the balance piston towards the drive end.When the thust on the balance piston overcomes the drive and the impeller thrust the gap A between the piston and balance ring widens and allows water to escape .This in turn has the effect of lowering the pressure in chamber B allowing the rotating assembly to move back towards the pump end . Theoretically this cycle will be repeated with a smaller movement each time until the thrust on the balance piston exactly balances the other axial forces acting on the assembly. In practice the balancing of the forces is almost instananeous and any axial movement of the shaft is negligible. Centrifugal pumps - maintenance When the pump is due for overhaul, it will be necessary to dismantle it to its component parts to examine them for wear. The following procedures are intended as a general guide only, and your attention should be drawn to the manufacturer's operational instructions regarding specific pump requirements before commencing to dismantle the pump. Centrifugal pumps - shaft sealing Centrifugal Pumps Seals Shaft Process Fluid Leakage Environment Vessel Wall Centrifugal pumps - shaft sealing To connect the motor to the impeller, the shaft has to pass through an aperture in the casing. To allow the shaft to rotate freely in the casing aperture there needs to be a gap, but this gap needs to be closed off to stop air from being drawn in from atmosphere or liquid from leaking out during operation. There are two common methods. Packing Mechanical seal The role of the pump, its speed and the type of liquid being pumped all play a part in deciding which application works best. PUMP SEALS MECHANICAL SEAL GLAND PACKING Stationary type seal Lantern ring supplies process liquid for sealing , cooling and lubrication Gland packing runs normally on shaft sleeve Small leakage is allowed and is actually required to prevent damage to packing & sleeve Slight imbalance/eccentricity doesnt effect the seal function Can withstand slightly abrasive process liquids Used for low pressure systems or on suction sides Insensitive to installation errors Wear of shaft or shaft sleeve takes place Consists of rotating & fixed element Rotating Seal element is made of Carbon Fixed seal element is made of Ceramic Rotating seal is mounted on rotating shaft and is pushed onto the stationary seal by a spring Process liquid is led to the sealing faces for sealing ,cooling& lubrication No leakage is allowed through the seal Slightest imbalance effects the seal function Abrasives are enemy of mechanical seals Can withstand high system pressures Highly sensitive to installation errors Packing Packing A stuffing box with a soft packing material is the traditional seal for pumps. Normally made from soft impregnated cotton, which takes the form of a length of square cross-section wound spirally onto a tube. This enables the correct length, to suit the external diameter of the shaft, to be manually cut to the correct size. The stuffing box is then repeatedly filled with sections until almost full, the gland can then be tightened down to provide the axial compressive force. This in turn provides the necessary radial compressive force required to seal the gap due to the sloping bottom face of the aperture. If the force is insufficient the stuffing box will leak, if the force is too great, the additional friction, and consequently heat generated by the rotating shaft can damage the soft packing and/or shaft. Centrifugal Pumps Packing Shaft Process Fluid Leakage Environment Vessel Wall Centrifugal Pumps Stuffing box with packing Centrifugal Pumps Packing Installation Centrifugal Pumps Bypass Flush Line Bell & Gossett Series HSC-S Centrifugal Pum