Cent Pumps Presentation

11

A technical presentation byA technical presentation by

Jyoti Swarup Jyoti Swarup Tripatra Engineering & ConstructionTripatra Engineering & Construction

Centrifugal Pumps Centrifugal Pumps SelectionSelection

On 29th April 2010

T:\Pumps\Cent Pumps presentation

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Centrifugal Pumps Selection Centrifugal Pumps Selection ContentsContents

Positive Displacement Pumps are "constant flow machines".

Centrifugal Pumps are "constant head machines".

1.1. Definitions & ClassificationsDefinitions & Classifications2.2. Performance CurvePerformance Curve3.3. Affinity LawsAffinity Laws4.4. Specific speedSpecific speed5.5. NPSHA, NPSHR and CavitationNPSHA, NPSHR and Cavitation6.6. Suction EnergySuction Energy7.7. Viscosity and multi-pump operationViscosity and multi-pump operation8.8. Selections & ExampleSelections & Example

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Selection – various types of pumpsSelection – various types of pumps

Types of pumpsTypes of pumps Centrifugal Pumps - Use centrifugal force to push

the fluid through the outlet. Metering Pumps - Bellows, diaphragm, peristaltic,

piston, and syringe pumps that pull the fluid through the inlet valve into a chamber, close the inlet valve, and then push the fluid through the outlet valve.

Positive Displacement Pumps - Bellows, double-diaphragm, gear, piston, progressing cavity, rotary lobe, rotary vane, and peristaltic pumps - fixed cavity that the fluid is pushed through by rollers, gears, or impeller. It leaves a void or vacuum which pulls in more fluid.

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Centrifugal PumpsCentrifugal PumpsMost commonly used machine (next to electric motors)Most commonly used machine (next to electric motors)Consist of a set of rotating vanes, enclosed within a housing or casing, used Consist of a set of rotating vanes, enclosed within a housing or casing, used to impart energy to a fluid through centrifugal forceto impart energy to a fluid through centrifugal forceTwo main parts: Two main parts:

a rotating element which includes an impeller and a shaft, and a rotating element which includes an impeller and a shaft, and a stationary element made up of a casing (volute or solid), stuffing box, a stationary element made up of a casing (volute or solid), stuffing box, and bearingsand bearings..

Classified by API Std 610-10Classified by API Std 610-10thth edition as edition as OverhungOverhung OH1 to OH6OH1 to OH6Between bearingsBetween bearings BB1 to BB5BB1 to BB5Vertically suspendedVertically suspended VS1 to VS7VS1 to VS7

API Standard 610- Tenth edition 2004 (ISO 13709: 2003 identical)API Standard 610- Tenth edition 2004 (ISO 13709: 2003 identical)

Centrifugal Pumps for petroleum, petrochemical and natural gas industriesCentrifugal Pumps for petroleum, petrochemical and natural gas industries

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Characteristics of Centrifugal pumpCharacteristics of Centrifugal pump

Pumps offer high flow rates, low pressures, and pulseless flow at a low price—ideal for general transfer applications.

Simple design means quick installation, low maintenance, and easy repair.

Most centrifugal pumps must be gravity fed or utilized with a priming chamber; some are self-priming.

Can control the flow rate by restricting the flow at the outlet with a nozzle or valve, (H vs Q is drooping)

In smaller pumps, can restrict the outlet indefinitely without damaging the pump.

Centrifugal pumps should not be run dry.

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API Std 610, Oct 2004 (1/2)API Std 610, Oct 2004 (1/2)Centrifugal Pumps for Petroleum, Petrochemical and Natural Gas Industries - Tenth Edition; ISO 13709 Adoption

Introduction .........................................................................................vi

1 Scope ...............................................................................................1

2 Normative references ...................................................................... 1

3 Terms and definitions ...................................................................... 4

4 Classification and designation .......................................................... 9

5 Basic design .................................................................................. 16

6 Accessories ................................................................................... 55

7 Inspection, testing, and preparation for shipment .......................... 64

8 Specific pump types ...................................................................... 71

9 Vendor's data ................................................................................ 84

Annexures

Bibliography........................................................................................181

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API Std 610, Oct 2004 (2/2)API Std 610, Oct 2004 (2/2)Centrifugal Pumps for Petroleum, Petrochemical and Natural Gas Industries - Tenth Edition; ISO 13709 Adoption

Annex A (informative) Specific speed and suction-specific speed ............... 90

Annex B (normative) Cooling water and lubrication system schematics ...... 91

Annex C (normative) Hydraulic power recovery turbines ........................... 102

Annex D (normative) Standard baseplates .................................................106

Annex E (informative) Inspector's checklist .................................................108

Annex F (normative) Criteria for piping design ............................................110

Annex G (informative) Materials class selection guidance ..........................124

Annex H (normative) Materials and material specifications for pump parts..126

Annex I (normative) Lateral analysis ............................................................136

Annex J (normative) Determination of residual unbalance............................142

Annex K (normative) Seal chamber runout illustrations ................................148

Annex L (informative) Vendor drawing and data requirements .....................149

Annex M (informative) Test data summary....................................................158

Annex N (informative) Pump datasheets.......................................................162 88 of 69 of 69

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Foot-mounted OH1Centre-line supported

OH2

Vertical in-line with bearing

bracketOH3

Rigidly-coupled Vertical in-line OH4Vertical in-line OH5

High-speed integrally-geared

OH6

Horizontal

Close-coupled

Flexibly coupled

Centrifugal PumpsCentrifugal Pumps

OverhungOverhung

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FLOWSERVEModel ERPN Overhung, Single stage, Process pump per API 610Centerline supported casing (OH2); Double VoluteRenewable Wear ring for casing and impeller

IN-LINE IN-LINE FIRE PUMPFIRE PUMP

OH4OH4

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Axially-split BB1Radially-split BB2Axially-split BB3

Single-casing BB4Double-casing BB5

Radially-split

1- and 2- stage

Multistage


Between BearingBetween Bearing

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DMX API 610 (BB3) 10th Edition, Between Bearing Axially Split Multistage, Double Volute, Opposed impeller

API 610 (BB1) Between Bearing Axially Split

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Diffuser VS1Volute VS2

Axial-flow VS3Line-shaft VS4Cantilever VS5

Diffuser VS6Volute VS7

Ve

rtic

all

y -

S

us

pe

nd

ed Single-

casing

Discharge through column

Separate discharge

Double-casing


Vertically SuspendedVertically Suspended

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FLOWSERVE

VPC (VTP-Can) Vertical Turbine, Double Casing Pump

Open or Enclosed line shaft construction

Option: Solid shaft or hollow shaft motor

Pressure upto 150 bar

Flow upto 160,000 m3/hr

VS6

FLOWSERVE

QL, Vertical, wet pit

Enclosed line shaft construction

Twin volute casing

Double suction impeller

Option: Solid shaft or hollow shaft motor

Pressure upto 70 bar

Column size 100 to 1200 mm

VS2

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A CENTRIFUGAL PUMP ANIMATION

• This animation shows fluid particles (represented by gray balls) enter the eye of the impeller and after they turn 90 degrees.

• At this point they are at the entrance of the volume formed by two adjacent impeller vanes.

• The rapid rotation of the vanes displaces the fluid particles by moving them in a radial direction into the pump volute and are decelerated and pressurized.

• Check out the direction of rotation.

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Positive Displacement Pumps (1/2)Positive Displacement Pumps (1/2)

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Positive Displacement Pumps (2/2)Positive Displacement Pumps (2/2)

Lobe pump

Multiplex pump

Progressive cavity pump

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ApplicationsApplicationsgeneral purpose fluids, general purpose fluids, pure water, pure water, sludge and sewage, sludge and sewage, slurry, slurry, high viscosity fluids, high viscosity fluids, power generation, power generation, the paper industry, the paper industry, the petroleum industry, the petroleum industry, chemicals and corrosives, chemicals and corrosives, gravel and solid materials, gravel and solid materials, high temperature materials, high temperature materials, and and marine applications. marine applications.

Fluid Properties (1/4)Fluid Properties (1/4)The properties of the fluids being pumped can significantly affect the choice of pump. Key considerations include:

1. Acidity/alkalinity (pH) and chemical composition: Corrosive and acidic fluids can degrade pumps, and should be considered when selecting pump materials.2. Operating temperature: Pump materials and expansion, mechanical seal components, and packing materials need to be considered with pumped fluids that are hotter than 200°F (93°C).

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Fluid Properties (2/4)Fluid Properties (2/4)

3. Solids concentrations/particle sizes: When pumping abrasive liquids such as industrial slurries, selecting a pump that will not clog or fail prematurely depends on particle size, hardness, and the volumetric percentage of solids.4. Specific gravity: The fluid specific gravity is the ratio of the fluid density to that of water under specified conditions. Specific gravity affects the energy required to lift and move the fluid, and must be considered when determining pump power requirements.

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Fluid Properties (3/4)Fluid Properties (3/4)5. Vapor Pressure: A fluid’s vapor pressure is the force per unit area that a fluid exerts in an effort to change phase from a liquid to a vapor, and depends upon the fluid’s chemical and physical properties.

Proper Consideration of the fluid’s vapor pressure will help minimize the risk of cavitation.

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Fluid Properties (4/4)Fluid Properties (4/4)6. Viscosity: The viscosity of a fluid is a measure of its resistance to motion. Since kinematic viscosity normally varies directly with temperature, the pumping system designer must know the viscosity of the fluid at the lowest anticipated pumping temperature. High viscosity fluids result in reduced centrifugal pump performance and increased power requirements. It is particularly important to consider pump suction-side line losses when pumping viscous fluids

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PUMP COMPONENTSPUMP COMPONENTS

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Electric Motors - RPMElectric Motors - RPMDescriptionDescription SingaporeSingapore USAUSA

Electric Supply Electric Supply Frequency, HzFrequency, Hz

50 Hz50 Hz 60 Hz60 Hz

2 Pole Motor 2 Pole Motor speed, RPMspeed, RPM

3000 / 29503000 / 2950 3600 / 35503600 / 3550


1500 / 14601500 / 1460 1800 / 17501800 / 1750


1000 / 9701000 / 970 1200 / 11601200 / 1160

n poles, RPMn poles, RPM Supply Freq x 2 x 60 / n PolesSupply Freq x 2 x 60 / n Poles

For 3-phase AC motor, HP (output) = 1.73 x Current x Voltage x Eff. x P.F. / 746For 3-phase AC motor, HP (output) = 1.73 x Current x Voltage x Eff. x P.F. / 746

Power Factor (P.F.) = KW / KVAPower Factor (P.F.) = KW / KVA Torque in lb-ft = HP x 5250 / RPMTorque in lb-ft = HP x 5250 / RPM

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HeadHeadEnergy content of liquid per unit weightEnergy content of liquid per unit weight

Relationship with pressureRelationship with pressure

Head in ft = psi x 144 / w, w Sp. weight lbf/ftHead in ft = psi x 144 / w, w Sp. weight lbf/ft33 (for Water Sp. Wt. w = 62.3 lbf/ft(for Water Sp. Wt. w = 62.3 lbf/ft33))

Hence Head in ft = psi x 2.31 / Sp. Gr.Hence Head in ft = psi x 2.31 / Sp. Gr.

[Head in m = kPa / (9.81 x Sp. Gr.) ][Head in m = kPa / (9.81 x Sp. Gr.) ]

Velocity Head ft = VVelocity Head ft = V22/2g, /2g,

g = 32.17 ft/sg = 32.17 ft/s22, V in ft/s, V in ft/s

[Velocity Head m = V[Velocity Head m = V22/2g, /2g,

g = 9.81 m/sg = 9.81 m/s22, V in m/s ], V in m/s ]

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Pressure, Liquid Height (Head) and Specific Pressure, Liquid Height (Head) and Specific Gravity RelationshipGravity Relationship - FPS units- FPS units

Water s.g.1.0

100 psi

HCls.g. 1.2

120 psi

Crude s.g. 0.8

80 psi

231 ft

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Why use Head ?Why use Head ?The main reason for using head instead of pressure to measure a The main reason for using head instead of pressure to measure a centrifugal pump's energy is that the pressure from a pump will change if centrifugal pump's energy is that the pressure from a pump will change if the specific gravity (weight) of the liquid changes but the head will not the specific gravity (weight) of the liquid changes but the head will not change. change.

Many Different Types of Pump Head Total Static Head - Total head when the pump is off Total Dynamic Head (Tot System Head) - Total head when the pump is on Static Suction Head - Head on the suction side, with pump off, if the head is higher than the pump impeller Static Suction Lift - Head on the suction side, with pump off, if the head is lower than the pump impeller Static Discharge Head - Head on discharge side of pump with the pump off Dynamic Suction Head/Lift - Head on suction side of pump with pump on Dynamic Discharge Head - Head on discharge side of pump with pump on

The definitions of Pump Head vary in literature !

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Pump Performance CurvesPump Performance Curves

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Performance CurvesPerformance CurvesShut off head – for parallel Shut off head – for parallel operation to be > 110% of rated operation to be > 110% of rated head.head.Min. continuous stable flow Min. continuous stable flow (% of BEP)(% of BEP)Rated operating point flow to be Rated operating point flow to be 80% to 110% of BEP (preferred 80% to 110% of BEP (preferred range 70% to 120% of BEP)range 70% to 120% of BEP)Best Efficiency point (BEP) – Best Efficiency point (BEP) – flow rate at which highest flow rate at which highest efficiency is achievedefficiency is achievedEnd of curveEnd of curve

Minimum continuous stable flow Minimum continuous stable flow % increases as Suction Specific % increases as Suction Specific speed increases.speed increases.

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Typical performance curves – Typical performance curves – centrifugal pumpscentrifugal pumpsRelationship at a Relationship at a

given RPM betweengiven RPM between Flow Flow Dynamic HeadDynamic Head EfficiencyEfficiency NPSH requiredNPSH required BHP requiredBHP required

BHP = Flow (GPM) BHP = Flow (GPM) X TDH (FT) x X TDH (FT) x SG / 3960 x EFF. SG / 3960 x EFF. (%) (%)

[BKW = Flow [BKW = Flow (m(m33/hr) x TDH /hr) x TDH (m) x SG / 367 x (m) x SG / 367 x EFF. (%) ]EFF. (%) ]

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Characteristics CurvesCharacteristics CurvesFigures are non-dimensional curves which indicate the general shape of the characteristic curves for the various types of pumps – radial, mixed and axial flow.

They show the head, brake horsepower, and efficiency plotted as a percent of their values at the design or best efficiency point of the pump.

MIXED MIXED FLOWFLOW

RADIAL RADIAL FLOWFLOW

AXIAL AXIAL FLOWFLOW

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Affinity LawsAffinity LawsThe generated pump head depends upon the exit fluid velocity at impeller periphery, which is V = x D X N, where D = Imp. diameter, N = RPM.Head V² , Head D² or Head N²

For given D, H1/H2 = N1² / N2²

For given N, H1/H2 = D1² / D2²Capacity Q a D or Capacity Q a N

For given D, Q1/Q2 = N1 / N2

For given N, Q1/Q2 = D1 / D2

Power D³ or Power N³

Affinity laws also may be loosely applied to NPSHR & Pump Affinity laws also may be loosely applied to NPSHR & Pump shaft deflections (square law) and pump wear rates (cubic law)shaft deflections (square law) and pump wear rates (cubic law)

Affinity Laws

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Capacity

Diff

Hea

d

N1

N2

H1

H2

Q2 Q1

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Affinity Laws - ExampleAffinity Laws - ExampleA pump operating in Singapore at 2950 RPM (2 pole motor, 50 Hz) A pump operating in Singapore at 2950 RPM (2 pole motor, 50 Hz) generates 100 mgenerates 100 m33/hr at 100m differential head./hr at 100m differential head.Same pump in USA operating at 3540 RPM (60 Hz) will generate Same pump in USA operating at 3540 RPM (60 Hz) will generate approximatelyapproximately

Flow 100 x 3540 / 2950 = 120 mFlow 100 x 3540 / 2950 = 120 m33/hr and/hr andHead 100 x (3540/2950) ² = 144 mHead 100 x (3540/2950) ² = 144 m

Power ratio PPower ratio P22/P/P11 = N = N22³/ N³/ N11³ = 1.728³ = 1.728

Variable speed operationVariable speed operation For varying flow or

pressure, a variable speed drive may be used.

Using affinity laws, one can calculate the flow rate & head at any given operating speed.

The drives may be using hydraulic couplings, variable frequency drive, or a steam/ gas turbine for variable speed operation.

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System head requirement(no valve)

Pump curvefor Di

H (ft)

q (gpm)

q* (desired) q produced by pump with no flow control

RPM1

Advantage: Lower operating Cost

RPM2

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Specific Speed (Specific Speed (API 610, 10API 610, 10thth ed., Annex A ed., Annex A))At Best Efficiency Point, Max. Impeller diameterAt Best Efficiency Point, Max. Impeller diameter

NNss = N (Q) = N (Q)0.50.5 / ( / (gg H) H)0.750.75

Ns Specific Speed, Ns Specific Speed, dimensionlessdimensionlessN Rotative speed RPMN Rotative speed RPMQ total pump flow mQ total pump flow m33/sec /sec

(Alternate Q m(Alternate Q m33/sec per impeller /sec per impeller eye)eye)

H Head per stage, mH Head per stage, mExample: Q = 100 mExample: Q = 100 m33/hr /hr (0.0278 m(0.0278 m33/sec) H = 100m, /sec) H = 100m, RPM 2950, Ns=15.55 SI unitsRPM 2950, Ns=15.55 SI unitsConversion to US units x 51.64 Conversion to US units x 51.64 = 802.9= 802.9

Specific speed vs. Specific speed vs. EfficiencyEfficiency

Even though Specific Speed is dimensionless, ignoring “g” in above equation had made it dimensioned quantity

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Specific Speed Calculation Check Specific Speed Calculation Check (for FPS units)(for FPS units)

Flow 100 mFlow 100 m33/hr (Q = 440.3 USGPM)/hr (Q = 440.3 USGPM)Head 100m (H = 328.08 ft)Head 100m (H = 328.08 ft)Pump RPM N = 2950Pump RPM N = 2950

NNss = N (Q) = N (Q)0.50.5 / (H) / (H)0.750.75 = 2950 (440.3) = 2950 (440.3)0.5 0.5 / / (328.08)(328.08)0.750.75 = 802.9 (US units) = 802.9 (US units)

Specific Speed of impellers is indicative of Specific Speed of impellers is indicative of its shape and characteristics as shown in its shape and characteristics as shown in next slide.next slide.

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Comparison of pump profilesComparison of pump profilesRadial flow – low specific speedRadial flow – low specific speed

Mixed flow – intermediate specific speedMixed flow – intermediate specific speed

Axial flow – high specific speedAxial flow – high specific speed

D1D1

D2/D1 > 2 D2/D1 = 1.5 to 2 D2/D1 < 1.5 D2/D1 = 1

D2D2

4/3H

QNNs

Specific speeds in US units

Specific SpeedSpecific Speed High Ns pump impellers have inlet diameters (D1) that

approach or equal the outlet diameter (D2), and relatively large open flow passages.

Low Ns pump impellers have outlet diameters (D2) that are much larger than the inlet diameters (D1) and relatively narrow flow passages.

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NNet et PPositive ositive SSuction uction HHeadeadNPSHANPSHA: Net Positive Suction Head available is the : Net Positive Suction Head available is the total suction head available from pump centerline less total suction head available from pump centerline less the vapor pressure of the liquid in ft (m) absolute – the vapor pressure of the liquid in ft (m) absolute – determined by purchaser at rated flow.determined by purchaser at rated flow.

NPSHRNPSHR: Net Positive Suction Head required is a : Net Positive Suction Head required is a performance characteristics of the pump, determined by performance characteristics of the pump, determined by the vendor by testing with water (3% loss of head, first the vendor by testing with water (3% loss of head, first stage head in a multi stage pump)stage head in a multi stage pump)

NPSHA > NPSHRNPSHA > NPSHR through the range of operation to through the range of operation to prevent detrimental cavitation.prevent detrimental cavitation.

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NPSHA CalculationsNPSHA CalculationsCalculation of system Net Positive Suction Head Available for typical suction conditions.

NPSHA = NPSHA = a) PB- (VP+Ls+hf)

b) PB+ LH - (VP+hf)

c) p - (VP+Ls+hf)

d) p + LH - (VP+hf)

a ba b

c dc d

Note: Enclosed sheet is a sample NPSH and Note: Enclosed sheet is a sample NPSH and H calculationsH calculations

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Suction Specific Speed (API 610)Suction Specific Speed (API 610)At Best Efficiency Point, Maximum Impeller Diameter.At Best Efficiency Point, Maximum Impeller Diameter.

NNssss = N (Q) = N (Q)0.50.5 / (NPSHR) / (NPSHR)0.750.75

NNssss Suction Specific Speed, dimensionless Suction Specific Speed, dimensionlessN Rotative speed RPMN Rotative speed RPMQ pump flow per impeller eye mQ pump flow per impeller eye m33/sec /sec NPSHR Net Positive Suction Head required at best NPSHR Net Positive Suction Head required at best eff. Point, max. impeller diameter, meff. Point, max. impeller diameter, mExample Q = 100 mExample Q = 100 m33/hr (0.0278 m/hr (0.0278 m33/sec) NPSHR = /sec) NPSHR = 5m, RPM 2950, Single suction impeller N5m, RPM 2950, Single suction impeller Nssss=147.0 (SI =147.0 (SI units)units)Conversion to US units x 51.64 = 7593Conversion to US units x 51.64 = 7593

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NPSHR and marginsNPSHR and margins NPSHR of a pump is the NPSH that cause NPSHR of a pump is the NPSH that cause

the total head (Ist stg head of multistage the total head (Ist stg head of multistage pumps) to be reduced by 3%, due to flow pumps) to be reduced by 3%, due to flow blockage from cavitation vapor in the blockage from cavitation vapor in the impeller vanes. impeller vanes.

NPSHR is not the point at which cavitation NPSHR is not the point at which cavitation starts. (that level is referred to as incipient starts. (that level is referred to as incipient cavitation).cavitation).

The NPSH at incipient cavitation can be The NPSH at incipient cavitation can be from 2 to 20 times the 3% NPSHR value, from 2 to 20 times the 3% NPSHR value, depending on pump design. depending on pump design.

The higher ratios are associated with high The higher ratios are associated with high suction energy pumps or pumps with large suction energy pumps or pumps with large impeller inlet areas. impeller inlet areas.

a pump running at an NPSHA equal to the NPSHR is already cavitating!a pump running at an NPSHA equal to the NPSHR is already cavitating!

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CavitationCavitationCutaway view of a pump Cutaway view of a pump volute shows the passage volute shows the passage of flow through the of flow through the impeller.impeller.

Top curveTop curve System pressure (System pressure (PsPs) > ) > fluid vapor pressure; fluid vapor pressure; cavitation cannot occur.cavitation cannot occur.

Bottom curveBottom curve PsPs < the vapor pressure < the vapor pressure as it enters the impeller as it enters the impeller eye. This will cause eye. This will cause cavitation.cavitation.

One cubic foot of water at room temperature becomes 1700 cu. Ft . of vapor at the same temperature.

Cavitation exists in high percentage of pumps, however acceptable life can be achieved.

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Cavitation typesCavitation types1.1. Low NPSHA: Low NPSHA: Fluid Vaporizes at impeller inletFluid Vaporizes at impeller inlet2.2. Low Flow Low Flow (suction recirculation and discharge recirculation)(suction recirculation and discharge recirculation)3.3. Air Injection Air Injection (air leaks or entrained gases)(air leaks or entrained gases)4.4. Turbulence Turbulence (Excessive, due to high velocity, bends, TEE at (Excessive, due to high velocity, bends, TEE at

inlet)inlet)

Symptoms of Cavitation:1. "Pumping gravel" cavitation noise 2. Failure history: repeated seal or bearing failures 3. Rapid decrease in discharge pressure when attempting to

increase rates 4. High vibrations 5. Lower than expected discharge pressure 6. Repeated impeller replacements

Suction CavitationSuction Cavitation Suction Cavitation: The pump suction is under a low

pressure condition where the liquid turns into a vapor at the eye of the pump impeller.

This vapor carried to the discharge side of the pump no longer sees vacuum and is compressed back into a liquid by the discharge pressure.

This imploding action occurs violently and attacks the face of the impeller which will remove large chunks of material from its face causing premature failure of the pump.

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Suction Energy (Old)Suction Energy (Old)Prediction, when cavitation may cause problems can be based on “Suction Prediction, when cavitation may cause problems can be based on “Suction Energy”. Energy”.

Following formula approximates the Graph in Hydraulic Institute Standard on Following formula approximates the Graph in Hydraulic Institute Standard on NPSH Margin (ANSI/HI 9.6.1- 1998):NPSH Margin (ANSI/HI 9.6.1- 1998):

Suction Energy (SE) ≈ (De x N x NSuction Energy (SE) ≈ (De x N x NSSSS x s.g.) x s.g.)

De = Impeller Eye Diameter (inches) N = Pump Speed (RPM)De = Impeller Eye Diameter (inches) N = Pump Speed (RPM) NNSSSS = Suct. Sp. Speed ...RPM x (GPM) = Suct. Sp. Speed ...RPM x (GPM)0.50.5/(NPSHR)/(NPSHR)0.750.75

s.g. = Specific Gravity of Liquids.g. = Specific Gravity of Liquid

De = Suction Nozzle Diameter x 0.9De = Suction Nozzle Diameter x 0.9 (is a good approximation for End Suction Pumps)(is a good approximation for End Suction Pumps)

De = Suction Nozzle Diameter x 0.75De = Suction Nozzle Diameter x 0.75 (is a good approximation for Side/Double Suction Pumps)(is a good approximation for Side/Double Suction Pumps)

(This HIS code 9.6.1 has since been withdrawn now, and thus some slides are (This HIS code 9.6.1 has since been withdrawn now, and thus some slides are now removed from this presentation. A description of various terms of suction now removed from this presentation. A description of various terms of suction energy are as in next three slides.)energy are as in next three slides.)

http://www.gouldspumps.com/cat_technews.ihtml?pid=9&lastcatid=41&step=4http://www.gouldspumps.com/cat_technews.ihtml?pid=9&lastcatid=41&step=4

Suction Energy (1/3)Suction Energy (1/3)Pumps with high suction energy level are generally more likely to suffer from cavitation damage. However, there are many factors that contribute to this and no precise definition has been established. These factors typically include:

1. The peripheral velocity at the outside diameter of the impeller eye. Values above approximately 120-ft/sec are considered high suction energy.

2. The suction speed S of the pump. S = nQ0.5/(NPSH)0.75 where n = rpm, Q = gpm and NPSH = feet. Values above about 12,000 are considered high energy.

3. The specific gravity of the liquid pumped. The higher the level, the higher the suction energy.

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Suction Energy (2/3)Suction Energy (2/3)4. Thermodynamic properties of the liquid. Cold water is one of

the highest energy liquids, followed by high temperature water and hydrocarbons.

5. The geometry of the pump inlet. Side suction pumps are considered higher suction energy than end suction.

6. The overlap of the impeller vanes. Impellers with two or three vanes have higher suction energy than four or more vanes.

7. The incidence angle between the inlet impeller vanes and the approaching liquid. The greater the angle, the greater the turbulence and suction energy level. This value may have to be obtained from the pump manufacturer.

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Suction Energy (3/3)Suction Energy (3/3)8. The geometry of the inlet piping to the pump. Piping turns

and pipe size changes add to the suction energy of the pump.9. Operation away from the best efficiency point (BEP) of the

pump. At reduced rate of flow, the pump may operate in its suction recirculation region, which considerably increases suction energy.

This is a complex situation and a single equation or relationship has not been developed which will accurately tie all of these factors together. Manufacturers can often provide installation lists of pumps that are operating successfully.

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Viscosity correction for Viscosity correction for Centrifugal PumpsCentrifugal Pumps

Example: Pump at 750 GPM, 100 ft diff head, Viscosity 1000 SSU, Sp. Gr. 0.90

CQ = 0.95, CH = 0.92 for 1.0 QNW, C = 0.635

QW = 750 / 0.95 = 790 GPM

HW= 100 / 0.92 = 109 ft

Select pump for water capacity 790 GPM @ 109 ft head. If selected pump eff. 81%, than viscous eff. = 81% x 0.635 = 51.5%

Pump BHP = (750 x 100 x 0.90) / (3960 x 0.515) = 33.1 HP

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Pumps in Series and Parallel (1/2)Pumps in Series and Parallel (1/2)Pumps in Series

Flow rate Q is same for bothTotal Head = HA + HB

Pumps in ParallelHead H is same for bothTotal Flow = QA + QB

Pumps in Series and Parallel (2/2)Pumps in Series and Parallel (2/2)

When two (or more) pumps are arranged in serial, their resulting pump performance curve is obtained by adding their heads at same flow rate as indicated in the figure below.

When two or more pumps are arranged in parallel their resulting performance curve is obtained by adding their flowrates at the same head as indicated in the figure below.

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Composite Performance Curves – 3600 RPMComposite Performance Curves – 3600 RPM

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Pump Pump RPMRPM

BEP Flow, BEP Flow, GPMGPM

BEP Head, BEP Head, ftft

36003600 490490 400400

18001800 256256 100100

12001200 170170 4343

Pump 3X2X10 operating characteristics at variable speed

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Pump Performance parameters at Pump Performance parameters at various speedsvarious speeds

For a given Centrifugal Pump For a given Centrifugal Pump Model 3 x 2 x 10, performance at Model 3 x 2 x 10, performance at BEP @ Max Impeller diameter:BEP @ Max Impeller diameter:

3600 RPM, 68 HP,3600 RPM, 68 HP,

Q= 490 GPM @ Q= 490 GPM @ H = 400 ftH = 400 ft

1800 RPM, 8.4 HP,1800 RPM, 8.4 HP,

Q= 258 GPM @ Q= 258 GPM @ H = 100 ftH = 100 ft

1200 RPM, 2.4 HP,1200 RPM, 2.4 HP,

Q= 170 GPM @ Q= 170 GPM @ H = 44 ftH = 44 ft

Selected Centrifugal pump model Selected Centrifugal pump model for flow capacity 200 GPM @ 80 for flow capacity 200 GPM @ 80 ft diff head:ft diff head:

3600 RPM, 3 x 2 x 6, 3600 RPM, 3 x 2 x 6, 70%, 70%,

NPSHR = 6.2 ft, Imp. diam 5.3”NPSHR = 6.2 ft, Imp. diam 5.3”

1800 RPM, 3 x 2 x 10, 1800 RPM, 3 x 2 x 10, 78%, 78%,

NPSHR = 5.5 ft, Imp. diam. 9.0”NPSHR = 5.5 ft, Imp. diam. 9.0”

1200 RPM, 4 x 3 x 13, 1200 RPM, 4 x 3 x 13, 63%, 63%,

NPSHR = 4.8 ft, Imp. diam 13”NPSHR = 4.8 ft, Imp. diam 13”

Goulds 3196 Pump CurvesGoulds 3196 Pump CurvesManufacturers provide series of pumps to cover broad ranges of capacities, heads, and suction and discharge piping diameters. Most pumps can be equipped with different diameter impellers and can be operated at different speeds to change capacities.

The 60 Hz curves provided (T:\PUMPS) are for a few variations of the Goulds pump model 3196 process pump, at 1180, 1750 and 3550 RPM. Pump sizes are denoted with 3 numbers.

Discharge Diameter

Inches

Suction Diameter Inches

Casing Diameter

Inches

3 x 4 - 7

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Pump SelectionPump SelectionGoal is to find a pump whose curve matches the piping system head vs. flow rate curve. We can fit our process conditions 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?

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ExamplesExamplesExample 1: Please select centrifugal pumps for following duties

1. Capacity 250 USGPM, Diff Head 200 ft, Sea Water Sp Gr 1.03, 50 Hz Electric Supply, NPSHA 15 ft.

2. Capacity 36 m3/hr, 41.5m Dhead, Crude Oil Sp Gr 0.80, 60 Hz electric supply, NPSHA 2.5m2a The best efficiency point of above pump at 50 Hz operation.

Show Pump Model, RPM, Eff., Rated BKW, Driver rating, NPSHR, Impeller Diameter, Shut Off Head, Specific Speed, Suction Specific Speed, Nozzle sizes and ratings, in the given format.

Please note Model Goulds 3196 is taken as an example only, it is not a suitable model for service.

6262 of 69 of 69Refer Goulds Model 3196 / Bell & Gossett curves available in T:\pumps directory

Example 2 Please select suitable centrifugal pumps for following duties

1. Capacity 6000 USGPM, Ps 20 psig, Diff head 200 ft, Hydrocarbon Sp. Gr. 0.9, NPSHA 18 ft

60 Hz Electric Supply

2. Capacity 500 m3/hr, Ps 150 kPa, Diff head 20m, Diesel Oil Sp. Gr. 0.85, NPSHA 3.5 m, 50 Hz

2a. The best efficiency point of above selected pump at 60 Hz operation.

Show Pump Model, RPM, Eff., Rated BKW, Driver rating, NPSHR, Impeller Diameter, Shut Off HeadSpecific Speed at BEP,Suction Specific Speed at BEP, Nozzle sizes and ratings, BKW @ End of Curve

(Please note Model Bell & Gosset series VSX is taken for example only, it is not a suitable model for service)

Codes and Standards (1/2)Codes and Standards (1/2)

ASME B 73.1, 2001ASME B 73.1, 2001 Specification for Horizontal End Specification for Horizontal End Suction Centrifugal Pumps for Chemical Process-Suction Centrifugal Pumps for Chemical Process-Replaces B73.1M (R2007) Replaces B73.1M (R2007)

ASME B 73.2, 2003ASME B 73.2, 2003, Specification for Vertical In-, Specification for Vertical In-Line Centrifugal Pumps for Chemical Process Line Centrifugal Pumps for Chemical Process (R2008)(R2008)

ASME B 73.3, 2003ASME B 73.3, 2003, Specification for Sealless , Specification for Sealless Horizontal End Suction Metallic Centrifugal Pumps Horizontal End Suction Metallic Centrifugal Pumps for Chemical Process (R2008)for Chemical Process (R2008)

ASME PTC 8.2, 1990ASME PTC 8.2, 1990, Centrifugal Pumps , Centrifugal Pumps

API Std 610, 10API Std 610, 10thth ed., 2004 ed., 2004 Centrifugal Pumps for Petroleum, Centrifugal Pumps for Petroleum, Petrochemical and Natural Gas Industries-Tenth Edition; ISO 13709 Petrochemical and Natural Gas Industries-Tenth Edition; ISO 13709 Adoption Adoption

API Std 682, 3API Std 682, 3rdrd ed. 2004 ed. 2004, Pumps Shaft Sealing Systems for Centrifugal , Pumps Shaft Sealing Systems for Centrifugal and Rotary Pumps-Third Edition; ISO 21049 Adoption; Errata: November and Rotary Pumps-Third Edition; ISO 21049 Adoption; Errata: November 10, 2006 10, 2006

API Std 685, Ist ed., 2000API Std 685, Ist ed., 2000 Sealless Centrifugal Pumps for Petroleum, Sealless Centrifugal Pumps for Petroleum, Heavy Duty Chemical, and Gas Industry Services Downstream Segment, Heavy Duty Chemical, and Gas Industry Services Downstream Segment, Errata 10/2007Errata 10/2007

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Codes and Standards (2/2)Codes and Standards (2/2)

There are many other codes There are many other codes available for Centrifugal available for Centrifugal pumps from various pumps from various international organizations as international organizations as

BSI, ENBSI, EN DIN, DIN, JIS, JIS, AWWA, AWWA, ISO, ISO, GOST, GOST, ASHRAE etc.ASHRAE etc.

BSI BS EN 22858, 1993BSI BS EN 22858, 1993 End-Suction Centrifugal Pumps (Rating 16 Bar) - End-Suction Centrifugal Pumps (Rating 16 Bar) - Designation, Nominal Duty Point and Dimensions Second Edition; (CEN Designation, Nominal Duty Point and Dimensions Second Edition; (CEN EN 22858: 1993) EN 22858: 1993)

NFPA 20, 2010NFPA 20, 2010, Standard for the Installation of Stationary Fire Pumps for , Standard for the Installation of Stationary Fire Pumps for fire protection : fire protection :

NFPA 20H, 2010NFPA 20H, 2010 Stationary Fire Pumps Handbook - Third Edition Stationary Fire Pumps Handbook - Third Edition

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Hydraulic Institute Standards (1/3)Hydraulic Institute Standards (1/3)

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Unit ConversionsUnit ConversionsSome unit conversions (for ready Some unit conversions (for ready

reference)reference) Flow mFlow m33/hr = 4.403 USGPM/hr = 4.403 USGPM Flow mFlow m33/hr = 0.2778 liter/sec/hr = 0.2778 liter/sec Flow mFlow m33/hr = 0.5886 ft/hr = 0.5886 ft33/min/min Head 1 m = 3.2808 ftHead 1 m = 3.2808 ft Head 10.19m WC = 1 bar Head 10.19m WC = 1 bar

pressurepressure Power 1 KW = 1.341 HPPower 1 KW = 1.341 HP Accel. due to gr. g = 9.806m/sAccel. due to gr. g = 9.806m/s2 2 = =

32.17 ft/s32.17 ft/s22

Sp. speed in US units = 51.64 x SI Sp. speed in US units = 51.64 x SI units (API 610)units (API 610)

Some formulas (for ready reference)Some formulas (for ready reference) USGPM = 449 x CFSUSGPM = 449 x CFS Pipe Vel. ft/sec = GPM x 0.321/ (ID in)Pipe Vel. ft/sec = GPM x 0.321/ (ID in)22

BHP = GPM x H x Sp Gr / 3960 / Eff.BHP = GPM x H x Sp Gr / 3960 / Eff. BKW = mBKW = m33/hr x H,m x Sp Gr/ 367 / Eff./hr x H,m x Sp Gr/ 367 / Eff. Head H = VHead H = V22/2g/2g Ns = N Q Ns = N Q ½½ H H ¾¾

Nss = N Q Nss = N Q ½½ NPSHR NPSHR ¾¾

QQ11/Q/Q22 = N = N11/N/N22, H, H11/H/H22 = N = N1122/N/N22

22

psi = head in ft x Sp Gr / 2.31psi = head in ft x Sp Gr / 2.31 kPa = head in m x Sp Gr / 0.102kPa = head in m x Sp Gr / 0.102

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Books on Centrifugal PumpsBooks on Centrifugal Pumps

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Thank YOU

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Composite ratingcharts for the

“Goulds 3196”family of pumps

Bell & Gossett VSX 1780 RPM

Base Mounted – Double Suction

Bell & Gossett VSX 1180 RPM

Base Mounted – Double Suction

Manufacturer’s pump characteristics

Index of pumpsfrom

Goulds PumpsInc

Affinity law - NPSHR5/1

2

1

1

2

1

1

D

D

Cent Pumps Presentation

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