KEY TO PUMP SELECTION NORMAL VARIABLES IN PUMP SELECTION LOCATION FUNCTION TYPE OF HYDRAULIC SERVICE FLUID CHARACTERISTICS CHEMICAL IDENTITY OF THE FLUID ABSOLUTE VISCOSITY AT PT AND 60 (CENTIPOISES) ;KINEMATIC VISCOSITY (CENTISTOKES) ;SAYBOLT SECONDS UNIVERSAL (SSU) SPECIFIC GRAVITY OF THE FLUID AT PT AND 60 PUMPING TEMPERATURE AND VAPOR PRESSURE AT PT PERSONALITY OF THE FLUID HYDROLICS OF THE SYSTEM( 1:pump & line calculation sheet ) PRESSURE ;BAROMETRIC,GAUGE,ABSOLUTE PRESSURE HEAD ;HEAD FT =2.31 X PRESSURE(PSI) / SP GR STATIC HEAD VELOCITY HEAD ;KINETIC ENERGY OF A FLOWING FLUID = V 2 /2G SUCTION LIFT ;MANOMETER READING AT THE PUMP SUCTION MINUS THE VELOCITY HEAD TOTAL DISCHARGE HEAD TOTAL HEAD HEAD LOSSES NPSH ;CAVITATION EVIDENT INCREASED NOISE,LOSS OF DISCHARGE HEAD,REDUCED FLUID FLOW CALCULATING NPSH NPSH CORRECTION FACTORS FOR PUMPING HYDROCARBONS
;WATER HYDROCARBON VAPOR PRESSURE ;WATER BASED NPSHR > HYDROCARBON BASED NPSHR Vp NPSH reduction NPSH required CORRECTED NPSH required = NPSH required at WATER - NPSH reduction NPSH reduction >1/2 NPSH required at WATER CORRECTED NPSH required=1/2 NPSH required at WATER NPSH reduction <1/2 NPSH required at WATER CORRECTED NPSH required=npsh required at WATER NPSH reduction ;NPSHR PUMP IMPELLER PRESSURE DROP
POSITIVE SUCTION ;TOTAL HEAD = (DIS GAUGE HEAD+DIS VELOCITY HEAD) - (SUC GAUGE HEAD+SUC VELOCITY HEAD) ;TOTAL SUC HEAD = SUC STATIC HEAD + SUC SURFACE PRESS HEAD SUC FRICTION HEAD LOSS = (DIS GAUGE HEAD+DIS VELOCITY HEAD) ;TOTAL DIS HEAD = DIS STATIC HEAD + DIS SURFACE PRESS HEAD + DIS FRICTION HEAD LOSS = (SUC GAUGE HEAD+SUC VELOCITY HEAD) ;NET POSITIVE SUC HEAD = TOTAL SUC HEAD ABSOLUTE - VAPOR PRESSURE ABSOLUTE ACCELERATION HEAD ;REQUIRED TO ACCELERATE THE FLUID IN THE SUCTION LINE NPSH = hp hvpa hst hfs ha < 2 > Effect of throttling a valve on the pump discharge head capa Effect of changes in the static head pump ( ) 3 SPECIAL PROBLEMS CENTRIFUGAL PUMPS BELOW 5% ENTRAINED GAS REGENERATIVE TURBINE PUMPS 50% ENTRAINED GAS RECIPROCATING OR ROTARY PUMPS VIRTUALLY NO LIMIT VISCOUS FLUIDS ; REDUCE EFFICIENCY AND INCREASE HP REQUIREMENT CORRECTION FACTORS ARE AVAILABLE TO PREDICT PERFORMANCE AT VARIOUS
VISCOSITIES( 4 ) SLURRIES (SOLID/LIQUID MIXTURES) ;PUMP SOLID IMPART ENERGY PRESSURE ENERGY. PUMP EFFICIENCY ;CENTRIFUGAL PUMP,OTHER THAN REGENERATIVE TURBINE TYPES, ARE BEST SUITED FOR SLURRIES AND MIXTURES WITH OVER 50% BY WEIGHT STEPS IN PUMP SELECTION FIRST STEP ;ANALYZE THE PUMP S FUNCTION AND INSTALLATION,AND DEVELOP SYSTEM CHARACTERISTICS NORMAL CENTRIFUGAL CAPABILITIES 500SSU 5% ENTRAINED GAS POSITIVE DISPLACEMENT PUMP CENTRIFUGAL PUMP SLURRIES HANDLING SPEED 1800RPM SOLID VOLUME 3 TO 5% SPECIAL SLURRY PUMP SPECIFIC SPEED ;HIGHER SPEED PUMP HORIZONTAL PUMP 12 TO 14 STAGES PRACTICAL LIMIT VERTICAL PUMP ;LIFT STATION,SUMP,INHERENT MIXED OR AXIAL FLOW ;IMPELLER SUBMERGING NPSH ;UNUSUAL HIGH HEAD LIGHTER DUTY CHEMICAL PUMP OR API STD FOR REFINERY SERVICE ;API 2 ~3 ; LIGHTER DUTY CHEMICAL PUMP
MATERIALS OF CONSTRUCTION DUCTILE IRON CAST STEEL CAST IRON CHROME & CHROME- NICKEL ALLOY STEEL BRONZE NICKEL-BASE ALLOYS CAST IRON CHEMICAL PUMP STD CAST IRON 2 TO 2.5 REFINERY OR HIGH P SERVICE PRODUCT FLAMMABLE OR TOXIC GOOD CORROSION RESISTENCE TO MILD CAUSTIC AND COLD NON-CORROSIVE SOLUTION ACID SOLUTION HIGH T, CORROSION, EROSION MILD T CONCENTRATED, HOT, CAUSTIC SOLUTIONS OR FLUIDS WITH HIGH CHLORIDE CONTENTS CENTRIFUGAL PUMP IMPELLER TOUGHER MATERIAL WEAR RINGS
CAST IRON AGAINST CAST IRON CAST IRON OR BRONZE RING AGAINST CHROME STAINLESS STEEL 50SSU AND ABOVE LESS VISCOUS LIQUID ROTARY DESIGN(GEAR,SCREW, VANE ) ADVANTAGE ;LOW NPSH REQUIREMENT ;PRODUCE HIGH SUCTION LIFTS ;VISCOUS LIQUID PUMPING EFFICIENCY ;HIGH HEADS AT A WIDE RANGE OF CAPAVITIES ;EXTENSIVE SPEED RANGE,GENERALLY LIMITED ONLY BY THE FLUID S VISCOSITY ;SELF PRIMING ;COMPRESSOR (29IN Hg PRODUCE ) VANE DIFFERENTIAL P 50PSI CAPA 375GPM LIQUID VISCOSITY LIMIT 100,000SSU LIQUID POOR LUBRICATING QUALITIES GEAR 650GPM 350PSI 5MILLION SSU VISCOSITIES HANDLING PUMP PUMPING LIQUID 100 TO 500SSU TOP SPEED 1,200RPM SCREW 4000GPM 3000PSI 100MILLION SSU OPERATE AT HIGHER SPEEDS BECAUSE OF RELATIVELY LOWER FLUID VELOCITIES RECIPROCATING PUMP CAPABILITIES DIAPHRAGM TYPE CONTROLLED VOLUME APPLICATIONS 600GAL/HR 3500PSI FOR SIMPLEX UNITS PLUNGER PUMPS METERING 1000GAL/HR 7500PSI PISTON PUMPS MAXIMUM PERFORMANCE 600GPM 750PSI PLUNGER TYPE SHORTER SERVICE LIFE PULSATION IS INHERENT DAMPENER MULTIPLE ENDS
SELECTING THE RIGHT PUMP SPECIFIC SPEED AS A GUIDE Ns = ( N Q ) / H 3/4 THIS HELPS IN RATING ALL CENTRIFUGAL PUMPS SELECTION FOR BEST EFFICIENCY TYPICAL FEED PUMP ;ATM, CLEAN LIQUID, NON-VOLATILE OR TOXIC, AMPLE NPSH, NO SOLID, VICOSITY ABOUT LIKE WATER Ns ESTIMATED EFFICIENCY Ds.Ds D ( ):TABLE 1
PUMP SELECTION FOR VOLATILE LIQUIDS FIG2 EXAMPLE LIQUID VAPOR PRESSURE STORED IN A SPHERE OR DRUM RATHER THAN AN ATMOSPHERIC TANKS TABLE2 THE HIGHER VALUE OF NPSHA MAKES POSSIBLE A MORE EFFICIENT PUMP SELECTION. GOOD PUMP SELECTION NPSH AVAILABE GUIDELINE Nss = N Q/H 3/4 S H S = [(N Q)/ Nss] 4/3 Nss, RPM Q Hs PLOTTING CENTRIFUGAL PUMP Nss 7000 TO 13000 OR HIGHER AVAILABLE. 15000 INDUCER-TYPE IMPELLER( NPSHR ) DOUBLE SUCTION IMPELLERS WILL GIVE LOWER NPSHA FOR THE SAME FLOW AND SPEED THAN SINGLE SUCTION TYPES WHEN THE CURVES IN FIG 3 ARE USED FOR DOUBLE SUCTION IMPELLERS, THE VALUE FOR Q MUST BE DIVIDED IN HALF
SELECTION OF PUMPS FOR LARGE CAPACITIES SYSTEM PIPING APPARATUS SIZE HEAD FLOW 10. VOLATILE LIQUID HANDLING FIG3 5000 GPM SINGLE-SUCTION PUMP AT 3550RPM IS NOT REALISTIC 50FT NPSHR UNREASONABLE AND UNACCEPTABLE SINGLE SUCTION AT 1760RPM DOUBLE SUCTION TYPE Nss 11000 RPM 1760 NPSHR 16FT(?) NPSHA > NPSHR + TWO OR THREE FT FLOW 1760RPM LOWER SPEED SINGLE STAGE 1180RPM PUMP TOTAL HEAD REQUIREMENT MULTI STAGE PUMP TOTAL FLOW TWO OR MORE UNIT HIGHER CAPACITY SINGLE SUCTION DOUBLE SUCTION REALISTIC NPSHR LOWER SPEED TOTAL HEAD REQUIREMENT MUTIL STAGE TOTAL FLOW (FIG3 ) DOUBLE SUCTION SINGLE SUCTION FLOW NPSHR PUMPS FOR HIGHER PRESSURES
250GPM 2625FT MULTI STAGE HORIZONTAL CENTRIFUGAL PUMP FIG1 10STAGES 3550RPM Ns 860 EFF 70% D 7.07IN SHAFT DESIGN,SHAFT DEFLECTION,INTERSTAGE CLEARANCES CRITICAL SPEEDS: 10STAGES HORIZONTAL PUMP VERTICAL SHAFT PUMP SHAFT DEFLECTION AND CRITICAL SPEED 12 STAGES VERTICAL TYPE Ns 987 D 6.78IN EFF 71% POPULAR VERTICAL- OR HORIZONTAL- SHAFT PUMP AT HIGHER SPEED ONE STAGE PUMP SPEED RESTRICTION INDUCE TYPE INPELLER NPSHR LOWER RECIPROCATING PUMP MOST EFFICIENT MAINTENANCE FLOW PULSATION ACCUMULATOR OR DAMPNER 50GPM 2625FT 5000GPM 2652FT RECIPROCATING PUMP HIGH SPEED PARTIAL EMISSION TYPE CENTRIFUGAL ONLY SOLUTION 3550RPM REASONABLE MULTI STAGE CENTRIFUGAL PUMP DESIGN HORIZONTAL MULTISTAGE CENTRIFUGAL PUMP VIABLE ALTERNATIVE PUMPS FOR VISCOUS LIQUIDS KINEMATIC VISCOSITY(CST)=ABSOLUTE VISCOSITY(CP)/SP GR OF LIQUID SSU = 4.62 X CST (ABOVE 250 SSU) VISCOSITY ( )
VISCOUS LIQUID PUMPING BEST CHOICE POSITIVE DISPLACEMENT PUMP ROTARY PUMP RECIPROCATING PUMP ROTARY PUMP-GEAR,SCREW OR LOBE TYPES VISCOUS LIQUID BEST PERFORMANCE THE HIGHEST VISCOSITIES TYPE LOW VISCOSITY SLIP ROTARY PUMP HIGHER VISCOSITY RATED CAPA PUMP CAPA RECIPROCATING PUMP REDUCED SPEED VISCOUS LIQUID BEST PERFORMANCE DISCHARGE PRESSURE 500PSI RECIPROCATING PUMP BEST CHOICE CENTRIFUGAL PUMP 1000SSU VISCOSITY SCREW TYPE ROTARY CENTRIFUGAL PT ROTARY PUMP VISCOSITY EFFICIENCY 400 ROTARY PUMP UPPER OPERATING LIMITS DIRVER EXTERNAL TIMING GEAR SCREW PUMP PUMP VISCOSITY CAPA VISCOUS CONDITION OVERSIZE VISCOSITY SLIP :FOUR STUFFING BOXES POSITIVE DISPLACEMENT PUMP OUTPUT THROTTLE ( )
PUMPS FOR SLURRY SERVICE EITHER CENTRIFUGAL OR POSITIVE-DISPLACEMENT PUMPS CAN HANDLE A MIXTURE OF SOLIDS AND LIQUIDS, SOMETIMES CALLED TWO-PHASE FLOW, OR SLURRY PUMPING. SLURRY SERVICE CENTRIFUGAL PUMP CLEAN LIQUID PUMPING LAW PRINCIPLE PUMP MIXTURE SOLID ;SP GR OF THE SOLIDS, THE FLUID, THE MIXTURE, CONCENTRATION BY VOLUME(Cv), CONCENTRATION BY WEIGHT( Cw) ;SOLID NATURE ABRASION WEAR MATERIAL ;CLEAN WATER PUMP PERFORMANCE SP GR, CONCENTRATION OF SOLIDS, VISCOSITY OF MIXTURE, SLIP DERATED ;PUMP CLEAR LIQUID PUMPING SLOW WEAR ABRASION LONGER LIFE SLURRY PUMP AFFINITY LAWS RPM1/RPM2 = Q1/Q2 = 3 H1/H2 )= 3 HP1/HP2) VARIABLE SPEED, AND PROVISION FOR SELECTING ANY EXACT SPEED, ARE EXTREMELY IMPORTANT FOR SLURRY PUMPS SLURRY-PUMP SELECTION : EXAMPLE
SPEED VARIATION FOR SLURRY-PUMPS VARIABLE-SPEED DRIVES VARIABLE-PITCH V BELT OR CHAIN DRIVES VARIABLE-SPEED ELECTRIC MOTORS, SUCH AS D C MOTORS, OR TWO-SPEED OR MULTI SPEED WOUND ROTOR A C MOTOR EDDY-CURRENT COUPLINGS,WHERE SPEED OF THE OUTPUT SHAFT TO THE PUMP WILL BE VARIED ELECTRICALLY HYDRAULIC COUPLING (FLUID COUPLING),WHERE THE HYDRAULIC- FLUID MECHANISM VARIES THE OUTPUT- SHAFT SPEED LIMITATIONS ON SLURRY PUMPS INITIAL INVESTMENT VARIATIONS IN FLOW RATE, HEAD WEAR PUMP PERFORMANCE REQUIED RATE OF FLOW AND HEAD PUMP SYS CALCULATION ERROR CORRECTION SPECIAL DESIGN HEAD DEVELOPED PER IMPELLER 180 TO 220FEET IMPELLER-TIP SPEED SEVERE-ABRASIVE SERVICE 3500 TO 4500 FT/MIN (CLEAR LIQUID CENTRIFUGAL PUMP 2~3 ) HIGHEST HEAD OR PRESSURE, REQUIREMENTS WILL PROBABLY REQUIRE RECIPROCATING TYPE PUMPS THICKEST UNPREDICTABLE MIXTURES THAT CANNOT BE PUMPED BY CENTRIFUGAL PUMPS MAY REQUIRE AIR-OPERATED OR MOTOR-OPERATED DIAPHRAGM PUMPS CENTRIFUGAL PUMP RUBBER-LINED OR HARD- METAL PUMP SERVICE
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