Pumps Presentation

PUMPS

OBJECTIVE

• REVIEW STEPS FOR SELECTING A PUMP

A PUMP IS REQUIRED

• WHEN THERE IS A NEED TO DELIVER A LIQUID FROM ONE POINT TO ANOTHER POINT WITHIN A PIPING SYSTEM, AND

• BY OBSERVATION P1<P2

OR IF P1>P2

BUT P1< (FRICTIONAL LOSSES + P2) FOR A GIVEN FLOW RATE

A PUMP IS A PIECE OF EQUIPMENT THAT IS USED TO ADD ENERGY TO A FLUID.

PROCESS DESIGN REQUIREMENTS

• FLOW RATE(s)• FLUID PROPERTIES• SUCTION CONDITIONS• DISCHARGE CONDITIIONS• REQUIRED HEAD / PRESSURE• DOCUMENTATION

DETERMINE THE PUMPS REQUIRED HEAD

DEFINITIONS

• HEAD (FT)

HEAD IS THE ENERGY PER POUND OF FLUID AND IS USED TO REPRESENT THE VERTICAL HEIGHT BETWEEN TWO POINTS. IT IS ALSO A TERM FOR EXPRESSING THE PRESSURE AS IT RELATES TO THE SPECIFIC GRAVITY OF A FLUID.

• STATIC SUCTION HEAD

HEIGHT OF LIQUID ABOVE OR BELOW THE CENTELINE OF PUMP SUCTION.

• STATIC DISCHARGE HEAD

HEIGHT OF LIQUID ABOVE OR BELOW THE CENTERLINE OF PUMP DISCHARGE.

• FRICTION HEAD

SUM OF THE ENERGY LOSSES IN SUCTION AND DISCHARGE LINE.

• TOTAL DYNAMIC HEAD (TDH) (USED TO SIZE PUMP)

DIFFERENCE BETWEEN PUMPING SYSTEM’S DISCHARGE AND SUCTION HEADS.

CALCULATING HEAD REQUIREMENTS• FORMULAS• COMPUTER PROGRAMS (FEP, PEGASYS)

FORMULAS

head (ft) = (pressure x 2.31 / specific gravity

hs = hss + hps - hfs (all units expressed in ft.)

where:

hs = total suction head

hss = suction static head

hps = suction surface pressure (gauge)

hfs = suction friction head

hd = hsd + hpf + hfd (all units expressed in ft.)

where:

hd = total discharge head

hsd = discharge static head

hpd = discharge surface pressure (gauge)

hfd = discharge friction head

TDH (ft) = hd-hs

PIPE & FITTINGS PRESSURE DROP FORMULAS

Pipe

hf = f LV^2/(D*2g)

Fittingshf = KV^2/(2g)

where: hf = frictional head loss, ft. f = pipe friction factor, dimensionless (see crane manual)K = fittings friction factor, dimensionless (see crane manual)L = pipe length, ft.D = pipe diameter, ft.V = fluid velocity, ft./sec.g = acceleration of gravity, 32.17 ft./sec.

30 psig

Given:

Oil S.G. = 0.87

Pipe = 4" sch. 40

Flowrate = 250 gpm

EXAMPLE PROBLEM

Determine· TDH

800 psig

35’15’

15’

10’

Pump

Calculate - Total Dynamic Head

TDH = hd - hs

hs = hss + hps - hfs

hss = 35’

hps = 30 (2.31) = 79.66’.87

hfs = 5.31’ from crane manual (fluid flow & friction loses) (takes into account piping length & diameter, fitting)

hs = 35 + 79.66 - 5.31’ = 109.35’

hd = hsd + hpd + hfd

hsd = 0’

hpd = 800 (2.31) = 2124.14’

.87

hfs = 2.65’ from Crane Manual (fluid flow & friction losses)

hd = 0 + 2124.14 + 2.65 = 2126.79’

TDH = 2126.79’ - 109.35’ = 2017.44’

EXXON COMPANY, U.S.A.PRODUCTION DEPARTMENT – TECHNOLOGY SECTION

FACILITY ENGINEERING PROGRAMS VERSION 3.7.1 –

KINETIC PUMP REQUIREMENTS

Date:Project Name: Total Dynamic Head CalculationTag Number:

INPUT PARAMETERS

Flow Rate (gpm) ……………………………..: 250.0Pump Efficiency Factor (fraction)……………: 0.50

Motor Efficiency Factor (fraction)…………...: 0.84

Atmospheric Pressure (psia)………………….: 14.65

Liquid Vapor Pressure (psia)…………………: 44.65

Specific Gravity (water = one)………………: 0.87

***FROM SUCTION SOURCE TO PUMP INLET***Suction Source Operating Pressure (psig)……………...: 30.00Height of Fluid Above Pump Reference (ft)…………...: 35.00Frictional Losses (psi)………………………………….: 2.00

***FROM PUMP OUTLET TO DISCHARGE POINT***Discharge Point Operating Pressure (psig)……………...: 800.00Discharge Point Above Pump Reference (ft)…………...: 0.00Frictional Losses (psi)…………………………………..: 1.00Flow Control Valve Losses (psi) ………………………: 0.00

RESULTS

Suction Head, feet………… 109.34Discharge Head, feet ………. 2126.79Total Dynamic Head, feet … 2017.45

TYPES OF PUMPS MOST COMMONLY USED AT EXXON

• CENTRIFUGAL – SINGLE IMPELLER

– MULTISTAGE

• RECIPROCAL– PLUNGER (DUPLEX, TRIPLES,

QUINTUPLEX)

CENTRIFUGAL PUMPS

CENTRIFUGAL PUMPS CONSIST OF A ROTATING

IMPELLER AND A STATIONARY HOUSING. THE

FLUID CONTAINED IN THE PUMP CASING IS

FORCED OUT OF THE HOUSING THROUGH THE

DISCHARGE OUTLET; THE CREATED VACUUM

PULLS IN MORE FLUID THROUGH THE SUCTION

INLET. THE IMPELLER IS ROTATED BY A SHAFT.

CENTRIFUGAL PUMPSCENTRIFUGAL PUMPS

THE FLUID MOVES IN THE DIRECTION OF

ROTATION AND RADIALLY OUTWARD THROUGH

THE VOLUTE (A CURVE THAT WINDS AROUND

AND CONSTANTLY RECEDES FROM A CENTER

POINT) AND TO THE DISCHARGE OUTLET.

CONTROLLING PUMP PERFORMANCECONTROLLING PUMP PERFORMANCE

• BACKPRESSURE VALVES

• RECYCLE FLOW VALVE

• VARIABLE SPEED CONTROLLER

CHANGING PUMP PERFORMANCE

• CHANGE PUMP SPEED

• CHANGING IMPELLER DIAMETER

GPM2 = GPM1 ((D2/D1) x (N2/N1))

TDH2 = TDH1 ((D2/D1) x (N2/N1))^2

BHp2 = BHp1 ((D2/D1) x (N2/N1))^3

Pegasys Pump Rating

Data Describing Existing PumpPump Catalog No. H – 6 x 13 VPManufacturer UNITED

------------------------------Curve Data----------------------------------------------------

Flow 200.0 400.0 570.0 700.0 800.0 US gpm

Head 178.0 174.0 163.0 150.0 138 ftEff’y 46.0 67.0 75.0 77.0 75.0 %NPSH Reqd 4.8 4.9 5.0 6.5 7.5 ft

------------Basis of Curve------------Speed 1780 rpmDiameter 12.56 inNo. of impellers 1Viscosity 0.75 cpSuction Press 10.0 psig

Rating Point Input | Calculated PerformanceData Required for All Cases: | Suction Pressure 10 psig | Calculated Mode: At given Flow Specific Gravity 0.88 | Viscosity 0.75 cp | Flow 570.0 US gpm Impeller Diameter 13.5 in | Head 192.0 ft Speed 1780 rpm | Disch Press 83.3 psig Number of stages 1 | Power 32.4 hpData Dependent on Calc Mode: | Percent BEP flow 82.7 %Flow 570.0 US gpm | Effeciency 75.0 %--or- | NPSH Reqd 5.0 ftDischarge Press - psig | Ns, Sp Speed 949-or- | Nss, Suct Sp Sp 11653System Resistance Curve: |Flow - - US gpm |Pressure - - psig |

PEGASYS

SUCTION PIPING

• Flooded Suction/Vapor Free• Minimal Turbulence• Head Loss < 1 ft/100 equivalent feet• No Vapor Traps/Constant Slope• Short and Direct/Free of Turns• Long Radius bends• Straight pipe ahead of pump• Eccentric (FSU) reducers

DISCHARGE PIPING

• Velocity ~ 7 fps• Head Loss ~ 1 #/100 equivalent feet• Recycle/Bypass Line• Straight pipe downstream of pump• Concentric reducers• Backpressure valve (if required)• Relief Valve• Check Valve• Block Valve

CENTRIFUGAL PUMP TYPES AND SELECTION CRITERIA

Centrifugal pumps haven been well accepted in production operations. Compared to other pump types, centrifugal pump advantages are numerous:

• high rotational speeds (900, 1200, 1800, 3600)• smooth, non-pulsating discharge• small space requirements• low investment cost• low operating costs• direct coupling to drivers (no gear box)• quietness of operation• reduced weight

Several different types of pumps have been developed to fill both general and specialized needs. The following discussion examines each pump type and explores their limitations.

RECIPROCATING PUMPS

Reciprocating pumps consist of piston or plunger moving back and forth within a fixed volume cylinder. As the piston or plunger moves backward, the reduced cylinder pressure opens the suction valve. As the piston or plunger moves forward, the increased cylinder pressure opens the discharge valve.

The alternating or reciprocating action results in flow and pressure variation in the pump suction, within the pump, and in the pump discharge. The flow is thus said to be pulsating.

RECIPROCATING PUMPS

RECIPROCATING PUMPS SERVE IN A LARGE NUMBER OF APPLICATIONS. THEY ARE LOW SPEED MACHINES COMPARED TO CENTRIFUGALS; HOWEVER, RECIPROCATING PUMPS DO HAVE SIGNIFICANTLY HIGHER EFFICIENCIES, GENERALLY 85 TO 95 PERCENT. THIS MEANS LOWER HORSEPOWER REQUIREMENTS. RECIPROCATING PUMPS ARE BEST SUITEDFOR HIGH PRESSURE, LOW VOLUME APPLICATIONS

PD PUMP CALCULATION

Quintuplex Pump - (5) PlungersPlunger diameter = 3.75” Stroke = 4.25”Speed = 276 rpm V.E. = 90%Maximum load (F) = 10,000 lbs.

Capacity = Speed x Displacement x V.E.

Displacement = (# of plungers) x stroke x (plunger area)

Displacement = (5) x (4.25/12) x ((3.14/4)x(3.75/12)^2)Displacement = 0.1358 cuft/rev x 7.48 gal/cuftDisplacement = 1.0159 gal/rev

Capacity = 276 rev/min x 1.0159 gal/rev x 0.90Capacity = 252.3 gal/min x 34.28Capacity = 8650 BPD

Maximum discharge pressure (Pmax) = load/areaPmax = 10000 lbs./11.044 sq inchPmax = 905 psi

____ ________________________ __________ ________ _________ __________ _________ _________ _________ _________ ________ | | EXXON MECHANICAL DESIGN PROGRAM PDPUMP, Version 1.1 ROTATING EQUIPMENT |___ ________________________ __________ ________ _________ __________ _________ _________ _________ _________ ________ | | Program: Reciprocating Pumps | Formula Source(s): API 14E, Gaso Design Info, Pump Module, Greer Catalog | Description: Calculates hydraulic and power requirements for a PD pump, including | acceleration head. Calculates pulsation dampener sizing. |___ ________________________ __________ ________ _________ __________ _________ _________ _________ _________ ________ | | Project Name: ? | Item Description/ Tag: ? | Service: ? | Case Description: ? | Prepared by: ? | Date: 24-Sep-02 Revision: 0 | | Checked/ Approved by: __________ ________ _________ __________ _________ _________ _________ _________ ________ |___ ________________________ __________ ________ _________ __________ _________ _________ _________ _________ ________

INPUTS OUTPUTS COMMENTS--------- --------- ---------

Type of Pump (T for Triplex, Q for Quintuplex): QStroke, inches: 4.25Exxon Max RPM ===> 340Plunger Diameter, inches: 3.750Volumetric Efficency, % : 90 <-- Typically 95 to 90 percentPump RPM: 276Percent of max RPM ===> 81%Gallons per Revolution ===> 1.0160Rate, BPD ===> 8,657 ( = 252 GPM)Max discharge Pressure, psig: 905 <--- PSV setting typically usedPlunger Load required, lbs ===> 9,995Suction Pressure, psig: 30Mechanical Efficency, % 84 <-- Typically 87% to 82%, 85% is normalHorsepower required ===> 153Horsepower at: 90 % VE, & 800 psig ===>> 135 ( = 8657 BPD rate)

Suction Piping ID, inches: 4.026 Velocity should be less than:Liquid Velocity, ft/sec ---> 6.36 <-- 1.5 ft/sec per 14ESuction Piping Length (actual), ft: 40 2 ft/sec per Exxon specLiquid Factor: 2 <-- 1.5 for water, glycol, amineEmpirical Constant for pump type ---> 0.040 2.0 for most hydrocarbonsAcceleration Head, ft ===> 43.6 2.5 for compressible fluidsAcc Head w/ 100% VE: Suction Velocity --> 7.07 1.4 for incompressible fluids Acc Head, ft ===> 48.5Pulsation Dampener sizing: Pulsation allowed in system, % : 2 % <-- Must enter 1, 2, 3, 4 or 5 Minimum Pulsation Dampener Size, gallons ===> 0.9 2 % is typical Suction Stabilizer, gallons ===> 10.2 <-- Based on 10 times displacement/rev

____ ________________________ __________ ________ _________ __________ _________ _________ _________ _________ ________

SUCTION PIPING

• Flooded Suction/Vapor Free• Minimal Turbulence• Velocity ~ 2 fps• Head Loss < 1 ft/100 equivalent feet• No Vapor Traps/Constant Slope• Short and Direct/Free of Turns• Long Radius bends• Straight pipe ahead of pump• Eccentric (FSU) reducers• Pulsation dampener

DISCHARGE PIPING

• Velocity ~ 7 fps• Head Loss ~ 1 #/100 equivalent feet• Recycle/Bypass Line• Straight pipe downstream of pump• Concentric reducers• Pulsation dampener• Relief Valve• Check Valve• Block Valve

Reciprocating Pumping System

NPSH

CAVITATIONCAVITATION IS VAPORIZATION WITHIN A PUMP. IT CAN REDUCE A PUMP’S PERFORMANCE AND MAY DAMAGE THE PUMP.

TO UNDERSTAND THE OCCURRENCE OF CAVITATION IT IS IMPORTANT TO REMEMBER THAT A LIQUID WILL VAPORIZE AT A COMPARATIVELY LOW TEMPERATURE IF ITS PRESSURE IS REDUCED SIGNIFICANTLY. WATER, FOR INSTANCE, WILL VAPORIZE AT 100 DEG F IF IT IS EXPOSED TO A VACUUM OF 28 INCHES OF MERCURY. THE PRESSURE AT WHICH A LIQUID WILL VAPORIZE IS CALLED IT’S “VAPOR PRESSURE”.

EACH PUMP DESIGN HAS A REQUIRED NET POSITIVE SUCTION HEAD (NPSH). THE REQUIRED NPSH IS DEFINED AS “THE REDUCTION IN TOTAL HEAD AS THE LIQUID ENTERS THE PUMP”. THIS NUMBER IS SPECIFIED BY THE MANUFACTURER.

THE AVAILABLE NPSH IS “THE DIFFERENCE BETWEEN THE TOTAL SUCTION HEAD AND THE VAPOR PRESSURE OF THE LIQUID”.

WHEN THE AVAILABLE NPSH IS EQUAL TO OR GREATER THAN THE REQUIRED NPSH, THE PUMP WILL NOT CAVITATE. (NPSHA>NPSHR)

CALCULATING THE AVAILABLE NPSH OF A PIPING SYSTEM

FORMULAS

NPSHA = hpsa+hss-hps-hvpa

where:NPSHA = available net positive suction head in feethpsa = suction surface pressure in absolute feet of liquidhss = static suction head in feet of liquidhfs = friction head loss in feet of liquidhvpa = vapor pressure in absolute feet of liquid

NPSH EXAMPLE PROBLEM(Centrifugal Pump)

477 gpm of preheated boiler feedwater must be supplied to the plant boilers to produce 450 psig steam. How high must the water level be above the pump suction in order to prevent cavitation? The boiler feedwater vessel (flash tank) operates at 5 psig and 228 deg F.

Given:From pump design data: NPSHR = 16 feet S.G. = 0.95Fluid vapor pressure = 47.9 feet (see attached chart)hfs = 2 psi or 4.86 feet

5 psig

hss

pump

NPSHA > NPSHR > 16 feet (to prevent cavitation)NPSHA = hpsa + hss - hfs -hvpaSolve for hsshss = 16 + hvpa +hfs - hpsahss = 16 + 47.9 + 4.86 - 47.9 = 20.86 feet

PROPERTIES OF WATER

Temperature Vapor PressureDegrees F. Specific Gravity Feet of Water, Absolute 40 1.001 0.3 50 1.001 0.4 60 1.000 0.6 70 0.999 0.8 80 0.998 1.2 90 0.996 1.6 100 0.994 2.2 110 0.992 3.0 120 0.990 4.0 130 0.987 5.2 140 0.985 6.8 150 0.982 8.8 160 0.979 11.2 170 0.975 14.2 180 0.972 17.9 190 0.968 22.3 200 0.965 27.6 210 0.961 34.0 212 0.959 35.4 220 0.957 41.5 230 0.953 50.4




Date:Project Name: NPSHA CalculationTag Number:

INPUT PARAMETERS

Flow Rate (gpm) ……………………………..: 477.0Pump Efficiency Factor (fraction)……………: 0.78Motor Efficiency Factor (fraction)…………...: 0.80Atmospheric Pressure (psia)………………….: 14.65Liquid Vapor Pressure (psia)…………………: 19.65Specific Gravity (water = one)………………: 0.95

***FROM SUCTION SOURCE TO PUMP INLET***Suction Source Operating Pressure (psig)……………...: 5.00Height of Fluid Above Pump Reference (ft)…………...: 20.86 trial & errorFrictional Losses (psi)………………………………….: 2.00


RESULTS

Suction Head, feet………… 28.15Discharge Head, feet ………. 1119.07Total Dynamic Head, feet … 1090.92NPSHA, feet……………… 16.00

CALCULATING HORSEPOWER

FORMULAS

CENTRIFUGAL PUMPBHP = (GPM x TDH x S.G.)/(3960 x e) e = 0.5

RECIPROCAL PUMPBHP = (GPM x DELTAP)/(1714 x e) e = 0.9

CENTRIFUGAL PUMPBHP = (250 x 2017.45 x 0.87)/(3960 x 0.5)BHP = 221.6 hp

RECIPROCAL PUMPBHP = (250 x 759.8)/(1714 x 0.9)BHP = 123.1 hp

SAMPLE CALCULATION




Date:Project Name: Brake Horsepower CalculationTag Number:

INPUT PARAMETERS

Flow Rate (gpm) ……………………………..: 250.0Pump Efficiency Factor (fraction)……………: 0.50

Motor Efficiency Factor (fraction)…………...: 0.84

Atmospheric Pressure (psia)………………….: 14.65

Liquid Vapor Pressure (psia)…………………: 44.65

Specific Gravity (water = one)………………: 0.87



RESULTS

Suction Head, feet………… 109.34Discharge Head, feet ………. 2126.79Total Dynamic Head, feet … 2017.45NPSHA, feet……………… 29.69Brake Horsepower………… 221.6



POSITIVE DISPLACEMENT PUMP REQUIREMENTS

Date:Project Name: Brake Horsepower CalculationTag Number:

INPUT PARAMETERS

Flow Rate (gpm) ……………………………..: 250.0Pump Efficiency Factor (fraction)……………: 0.90Motor Efficiency Factor (fraction)…………...: 0.84Atmospheric Pressure (psia)………………….: 14.65Liquid Vapor Pressure (psia)…………………: 44.65Specific Gravity (water = one)………………: 0.87


***FROM PUMP OUTLET TO DISCHARGE POINT***Discharge Point Operating Pressure (psig)……………...: 800.00Discharge Point Above Pump Reference (ft)…………...: 0.00Frictional Losses (psi)…………………………………..: 1.00

RESULTS

Suction Head, feet………… 109.34Discharge Head, feet ………. 2126.79Total Dynamic Head, feet … 2017.45Brake Horsepower………… 123.12

DRIVERS MOST COMMONLY USED BY EXXONMOBIL

ELECTRIC MOTOR•SINGLE SPEED•DUAL SPEED•VARIABLE SPEED

GAS TURBINE•VARIABLE SPEED

STEAM TURBINE•VARIABLE SPEED

ELECTRIC MOTORS

STANDARD RATINGS

The following are standard motor ratings for voltage, horsepower, and speed. Other ratings may be availableupon special request.

Voltage RatingVoltage Typical Horsepower460 or 575 1/2 to 6002300 200 to 40004000 or 4600 200 to 70006600 1000 to 1200013200 3500 to 25000

Horsepower Ratings1/2 7-1/2 50 300 800 2250 6000 13000 200003/4 10 60 350 900 3000 7000 14000 225001 15 75 400 1000 3500 8000 15000 250001-1/2 20 100 450 1250 4000 9000 160002 25 125 500 1500 4500 10000 170003 30 200 600 1750 5000 11000 180005 40 250 700 2000 5500 12000 19000

Typical Speeds (rpm)600, 900, 1200, 1800, 3600

Pump Information

General- What is the make / model / serial # of the pump frame?- How fast is the pump operating (rpm)?- What is the operating speed of the pump? (current, min. / max. operating speed)

Positive Displacement Pump (Plunger)- How many plungers are installed in pump?- What is the diameter of the plungers?- What is the pump stroke?- What is the pump’s net positive suction head required (NPSHR)?- What type of pump valves are being used- What are the sizes of the pulsation dampeners- What type of packing is used in the fluid end- What type of lubrication system is being used on the power end?

Centrifugal Pump- Where are the pump curves for this pump?- How many stages is this pump?- What is the pump’s impeller size?- What is the maximum and minimum impeller sizes for this pump?- What is the pump’s net positive suction head required (NPSHR)?- What seal plan is being utilized?- What type seal flush is being utilized?

PUMP SURVEILLANCE QUESTIONS

The list of questions below are provided to:· Initially evaluate whether opportunities may exist. (Some questions will not apply depending on

the actual equipment installed.)· Develop the fluid process flow through the pumping system and understand the basic pump

setup.

Pumping Process- What is the facility’s / pump’s throughput forecast over the next 5-7 years?- How much is the facility’s / pump’s throughput now?- How many pumps are designated as full-time operating units?- What type of driver is on each pump? (e.g. engine, motor, gas turbine)- What is the driver rated BHP?- How many pumps are designated as “back-up” units?- Are the pumps in series are parallel?- What are the flow rates of each pump?- What is the specific gravity and viscosity of the fluid being pumped?- What are the suction and discharge pressures of the fluid being pumped?- What are the current suction temperatures of the fluid being pumped?- How do the suction temperatures fluctuate (from summer to winter)?- How is the pump’s volume controlled? Recycle valve, backpressure valve,

on/off, variable speed control, etc.?- If fluid is being recycled, how much?- Where does the recycle line feed back into the suction system ? Upstream of

the pump suction, upstream separator, etc.?- What is the system’s net positive suction head available (NPSHA)?

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