Upload
abdul-rhovick
View
41
Download
2
Tags:
Embed Size (px)
DESCRIPTION
Pompa sentrifugal
Citation preview
5/22/2018 Bahan Kuliah Pompa Centrifugal
1/60
Pompa Centrifugal
5/22/2018 Bahan Kuliah Pompa Centrifugal
2/60
DynamicPositive
Displacement
Centrifugal Special effect Rotary Reciprocating
Internalgear
Externalgear
Lobe Slidevane
Others (e.g.Impulse, Buoyancy)
Pumps
DynamicPositive
Displacement
Centrifugal Special effect Rotary Reciprocating
Internalgear
Externalgear
Lobe Slidevane
Others (e.g.Impulse, Buoyancy)
Pumps
5/22/2018 Bahan Kuliah Pompa Centrifugal
3/60
Types of Pumps
Positive displacement pumps
Rotary (gear, screw, etc.)
Reciprocating (piston, diaphragm, etc.)
Used as injection and sprayer pumps, butnot for irrigation water
Centrifugal pumps
Rotating impeller converts mechanicalenergy into hydraulic energy (showexamples and transparency)
5/22/2018 Bahan Kuliah Pompa Centrifugal
4/60
Rotating Impeller Converts Mechanical
Energy to Hydraulic Energy
5/22/2018 Bahan Kuliah Pompa Centrifugal
5/60
Centrifugal Pump Impellers
Enclosed Impeller Semi-Open Impeller
5/22/2018 Bahan Kuliah Pompa Centrifugal
6/60
Centrifugal Pumps
Horizontal
Drive shaft is horizontal
Often used when pumping from a surfacesource (pond, lake, stream, etc.), Or forboosting the pressure in an irrigation pipeline(booster pump)
Usually sold as completely assembled units
5/22/2018 Bahan Kuliah Pompa Centrifugal
7/60
Typical Horizontal Centrifugal Pump Installation
5/22/2018 Bahan Kuliah Pompa Centrifugal
8/60
Horizontal
Centrifugal Pumps
5/22/2018 Bahan Kuliah Pompa Centrifugal
9/60
Centrifugal Pumps, Contd...
Vertical Turbine
drive shaft is vertical
used when pumping from a well
normally custom built from components(with multiple stages)
submersible: electric motor below the
lowest stage
5/22/2018 Bahan Kuliah Pompa Centrifugal
10/60
Vertical Turbine Pump
5/22/2018 Bahan Kuliah Pompa Centrifugal
11/60
Single-Stage Vertical Turbine Pump
Water Flow Path
Through a One-Stage
Vertical Turbine Pump
5/22/2018 Bahan Kuliah Pompa Centrifugal
12/60
Two-Stage Vertical Turbine Pump
Water Flow PathThrough a Two-Stage
Vertical Turbine Pump
5/22/2018 Bahan Kuliah Pompa Centrifugal
13/60
Gearhead for
engine drive
Holloshaft electric
motor
(Discharge Heads)
5/22/2018 Bahan Kuliah Pompa Centrifugal
14/60
Submersible Water Pumps
-Same as vertical turbine
pump design
-Driven from below by
electric motor
-Good for deep wells
-High efficiency
-Wells as small as 4 diameter
5/22/2018 Bahan Kuliah Pompa Centrifugal
15/60
Head Capacity Curve
5/22/2018 Bahan Kuliah Pompa Centrifugal
16/60
Pump Characteristics
Head vs. discharge
discharge (or capacity): volume of waterpumped per unit of time (gpm)
head (or total head or total dynamic head):
energy added to the water by the pump
units of feet (energy per unit weight of water
5/22/2018 Bahan Kuliah Pompa Centrifugal
17/60
Pump Characteristics Contd
Pump Efficiency vs. Discharge
Power = energy/time; 1 HP = 33,000 ft-lb/min
- Q in gpm; TDH in ft, whp in horsepower
-whp = power added to the water by the pump
Eoutput power (or energy)
input power (or energy)
water HP
brake HP
whp
bhpp
whp =(Q)(TDH)
3960
5/22/2018 Bahan Kuliah Pompa Centrifugal
18/60
Pump Characteristics Contd
Brake horsepower vs. Discharge
where: Q, (gpm); TDH, (ft); bhp & whp, (HP)
Combined characteristic curves Horizontal centrifugal pump
Vertical turbine pump
bhp =whp
E
(Q)(TDH)
(3960)(Ep p
)
5/22/2018 Bahan Kuliah Pompa Centrifugal
19/60
Vertical Turbine Pump Performance Curve
5/22/2018 Bahan Kuliah Pompa Centrifugal
20/60
Horizontal Centrifugal Pump Performance Curve
5/22/2018 Bahan Kuliah Pompa Centrifugal
21/60
Affinity Laws
Speed
Law applies to virtually all irrigation pumps
Epmay be affected a little, but not as predictable
Ways of changing speeds:pulleys, gear ratios, throttle, change motor
RPMRPM
TDHTDH
RPMRPM
bhpbhp
RPMRPM
2
1
2
1
2
1
2
1
2
1
2
1
2 3
5/22/2018 Bahan Kuliah Pompa Centrifugal
22/60
Affinity Law Example
A pump operating at 1800 RPM delivers 200 gpm at a TDH of 150 feet
and requires 10 HP to operate. What will be its Q, TDH and BHP
conditions if it is sped up to 2000 RPM?
RPM1=1800 RPM2= 2000 RPM2/RPM1=1.11
Q2/Q1= RPM2/RPM1 Q2= Q1x RPM2/RPM1= 200 x 1.11= 222 gpm
TDH2/TDH1=[RPM2/RPM1]2 TDH2
= TDH1 x [RPM2/RPM1]2
TDH2= 150 x [1.11]2= 185 feet
BHP2/BHP1= =[RPM2/RPM1]
3 BHP2= BHP1 x [RPM2/RPM1]
3
BHP2= 10x [1.11]
3 = 13.7 HP
5/22/2018 Bahan Kuliah Pompa Centrifugal
23/60
Affinity Laws Contd
Impeller diameter Law strictly applies only to horizontal centrifugal
pumps, but good approximation for vertical turbinepumps
Epmay change a little Diameter is changed by trimming the impeller
(law holds up to about 10-20% trim)
3
1
2
1
2
2
1
2
1
2
1
2
1
2
D
D
bhp
bhp
D
D
TDH
TDH
D
D
Q
Q
5/22/2018 Bahan Kuliah Pompa Centrifugal
24/60
Pumps in Series
Booster pump
Multi-stage turbine pump
Q1= Q2
TDHtot= TDH1+ TDH2(add heads at the same discharge)
bhptot= bhp1+ bhp2
tot
tot
pbhp
TDHQ
E 3960)(
Pumps in Series Contd
5/22/2018 Bahan Kuliah Pompa Centrifugal
25/60
Pumps in Series Cont d
P i P ll l
5/22/2018 Bahan Kuliah Pompa Centrifugal
26/60
Pumps in Parallel
5/22/2018 Bahan Kuliah Pompa Centrifugal
27/60
Pumps in Parallel Contd
Qtot= Q1+ Q2(add discharges at the same head)
bhptot
= bhp1
+ bhp2
E
Q H
bhpp
tot
tot
( )
3960
5/22/2018 Bahan Kuliah Pompa Centrifugal
28/60
Pumps in Parallel Contd
5/22/2018 Bahan Kuliah Pompa Centrifugal
29/60
Pump Selection
System Head
Definition:
Total head imposed on a pump by the irrigation
system also called TDH (Total Dynamic Head),total pumping head, etc.
Components
Static Head (Elevation Head): elevation
difference between water level on the inlet sideand the water delivery point
5/22/2018 Bahan Kuliah Pompa Centrifugal
30/60
Components Contd
Pressure Head: difference in water pressuresbetween the source and the delivery point
Friction Head: total friction loss between the source
and the delivery point Velocity Head: V2/(2g) (usually considered negligible)
System Head =Static + Pressure + Friction (units of feet)
5/22/2018 Bahan Kuliah Pompa Centrifugal
31/60
Components of Total System Head
(or Total Dynamic Head, Total Pumping Head)
5/22/2018 Bahan Kuliah Pompa Centrifugal
32/60
System Head Curve
H increases with increasing Qbecause of:
drawdown (wells)
friction
pressure at nozzles
System head can also vary withtime:
water table fluctuations
changes in the irrigation system
pipe aging
S t H d C
5/22/2018 Bahan Kuliah Pompa Centrifugal
33/60
System Head Curve
5/22/2018 Bahan Kuliah Pompa Centrifugal
34/60
Pump Operating Point
As indicated by its TDH-Q curve, a
pump can operate at many possiblepoints
A pump will operate at a Q and TDH
determined by the point where thepump curve and the system headcurve cross
The same pump is likely to operate attwo different TDH-Q combinationswhen placed in two different
irrigation systems
P O ti P i t i S t
5/22/2018 Bahan Kuliah Pompa Centrifugal
35/60
Pump Operating Point in a System
Diff t P i th S S t
5/22/2018 Bahan Kuliah Pompa Centrifugal
36/60
Different Pumps in the Same System
5/22/2018 Bahan Kuliah Pompa Centrifugal
37/60
Matching a Pump to theSystem
General
buyer specifies desired Q and TDH(usually not the entire system head curve)
supplier specifies operating characteristics(including pump curves)
obviously want a high Ep
can fine tune a match by adjusting speedand/or trimming the impeller
5/22/2018 Bahan Kuliah Pompa Centrifugal
38/60
Matching a Pump to the SystemContd
Horizontal Centrifugal Pumps provide correct Q and TDH at a high Ep
usually buy off-the-shelf unit
Vertical Turbine Pumps choose a bowl and impeller to provide the
desired Q at a high Ep
determine the number of bowls required toprovide the desired TDH (pumps in series)
5/22/2018 Bahan Kuliah Pompa Centrifugal
39/60
A vertical turbine pump is needed to deliver 400 gpm from a well
that will have a static pumping lift of 237 feet, plus an operating
pressure of 55 psi at the pump head. Is the WLR 10JKH pump
below a good choice? If so, how many stages are required?
TDH= 237+(55psi*2.31 ft/psi)=364 ft
@ Q=400 gpm:
TDH=52 ft/stage for 7.7 & Ep=79.5%
TDH=41 ft/stage for 7.13 & Ep=77.5%
TDH=30 ft/stage for 6.56 & Ep=72%
364 ft/52 ft/stage=7 stages
The best choice is the 7.7 diameterimpeller at 52 ft/stage, because it not
only requires the fewest stages (low
initial cost), but has the best efficiency
(low operating cost) near 80%.
5/22/2018 Bahan Kuliah Pompa Centrifugal
40/60
A vertical turbine pump is needed to deliver 400 gpm from a well
that will have a static pumping lift of 237 feet, plus an operating
pressure of 60 psi at the pump head. Is the WLR 10JKH pump
below a good choice? If so, how many stages are required?
TDH= 237+(55psi*2.31 ft/psi)=364 ft
@ Q=400 gpm:
TDH=52 ft/stage for 7.7 & Ep
=79.5%
TDH=41 ft/stage for 7.13 & Ep=77.5%
TDH=30 ft/stage for 6.56 & Ep=72%
364 ft/52 ft/stage=7 stages
The best choice is the 7.7 diameterimpeller at 52 ft/stage, because it not
only requires the fewest stages (low
initial cost), but has the best efficiency
(low operating cost) near 80%.
5/22/2018 Bahan Kuliah Pompa Centrifugal
41/60
Net Positive Suction Head
Suction lift and cavitation Handout
Pump does not "suck" or "pull" water
Impeller causes partial vacuum
Atmospheric pressure forces water upto the impeller
Theoretical vs. practical lift
Describe cavitation
S h ti F NPSHA V At h i P
5/22/2018 Bahan Kuliah Pompa Centrifugal
42/60
Schematic For NPSHA Versus Atmospheric Pressure
5/22/2018 Bahan Kuliah Pompa Centrifugal
43/60
NPSHa
NPSHa= AP - SL - FL - VP
AP = atmospheric pressure
SL = suction lift (vertical distance)
FL = friction loss on suction side
VP = vapor pressure
all have units of feet
Atmospheric Pressure at Various Altitudes
5/22/2018 Bahan Kuliah Pompa Centrifugal
44/60
Atmospheric Pressure at Various AltitudesAltitude (feet) Absolute Pressure(psi) Absolute Pressure(ft)
0
500
1000
1500
2000
2500
3000
3500
4000
5000
60007000
8000
9000
10,000
14.7
14.4
14.2
13.9
13.7
13.4
13.2
12.9
12.7
12.2
11.811.3
10.9
10.5
10.1
34.0
33.3
32.8
32.2
31.6
31.0
30.5
29.8
29.4
28.2
27.326.2
25.2
24.3
23.4
Vapor Pressure at Various Temperatures
5/22/2018 Bahan Kuliah Pompa Centrifugal
45/60
Vapor Pressure at Various Temperatures
Temperature 0F Vapor Pressure (Feet)
5060
70
80
90
100
110
130150
170
190
210
0.40.6
0.8
1.2
1.6
2.2
3.0
5.28.7
14.2
22.3
34.0
5/22/2018 Bahan Kuliah Pompa Centrifugal
46/60
NPSHr
NPSHris a pump characteristic
(increases as Q increases) If NPSHa> NPSHr:Design is OK
If NPSHa< NPSHr:
Cavitation will be a problem(good idea to have a factor of safety)
5/22/2018 Bahan Kuliah Pompa Centrifugal
47/60
Power Units
Electric motors
direct coupled High Efficiency drive (Edrive=100%), but Fixed Speed
belt drive Variable Speed, but Lower Efficiency drive (Edrive= 90%)
rated by output HP
Em's
90% are common Emdoesn't vary much with load
(unless it's significantly under-loaded)
Epower or energy out (shaft)
power or energy in (electricity)m
5/22/2018 Bahan Kuliah Pompa Centrifugal
48/60
Internal Combustion Engines
Fuels Natural gas
Diesel fuel
Propane Gasoline
Right-angle Gear Drives Convert power in horizontal engine shaft to
power in vertical pump line shaft
Edrive95% (5% loss through the gear drive)
5/22/2018 Bahan Kuliah Pompa Centrifugal
49/60
Internal Combustion Engines Contd
Eevaries with engine speed and with theload on the engine
Ee's rarely exceed 30%
Epower or energy out (shaft)
power or energy in fuel usede
5/22/2018 Bahan Kuliah Pompa Centrifugal
50/60
Pumping Costs
Fixed Costs vs. Operating Costs
Fixed: pump, motor/engine, well, other equipment (total cost is the same regardless of use)
Operating: energy, maintenance, repairs, labor(total cost increases with increasing use)
Overall Pumping Plant
5/22/2018 Bahan Kuliah Pompa Centrifugal
51/60
Overall Pumping PlantPerformance
Overall pumping plant efficiency, (Eo):
Electric Motor Driven
Eo= Epx Emx Edrive
Internal Combustion Engine Driven Eo= Epx Eex Edrive
Efficiencies are expressed in decimal for this calculation, (%/100)
Eoutput power or energy (supplied to water)
input power or energy (electricity or fuel)o
Typical Values of Overall Efficiency for Representative
5/22/2018 Bahan Kuliah Pompa Centrifugal
52/60
Typical Values of Overall Efficiency for Representative
Pumping Plants Expressed as Percent
Power
Source
Maximum
Theoretical
Recommended as
Acceptable
Avg Values from
Field Tests
Electric 72-77 65 4555
Diesel 2025 18 1315
Natural
Gas
1824 1518 913
Butane,Propane
1824 1518 913
Gasoline 1823 1416 912
5/22/2018 Bahan Kuliah Pompa Centrifugal
53/60
Annual Pumping Energy CostElectric Powered Pumping Plant
V = volume of water pumped per year, acre-feet
TDH = total system head, feet
Eo= overall pumping plant efficiency = %
Ce= electricity price, $/kilowatt-hour
$/yrkwh
$Cx
HP-hr
kwh.x
TDH ftx
%)/( E
V ac-ftx
ac-ft ft
HP-hr. e
o
7460
100
3731
Annual Pumping Energy Cost
5/22/2018 Bahan Kuliah Pompa Centrifugal
54/60
Annual Pumping Energy Cost
Natural Gas Engine DrivenPumping Plant
V= volume of water pumped per year, acre-feet
TDH = total system head, feet
Eo= overall pumping plant efficiency, %
Cg= natural gas price = $/1000 cubic feet of gas
$/yrft
$Cx
HP-hr
BTUx
BTU
ftx
TDH ftx
%)/(E
V ac-ftx
ac-ft ft
HP-hr. g
o
3
3
1000
2545
1000100
3731
Annual Pumping Energy Cost
5/22/2018 Bahan Kuliah Pompa Centrifugal
55/60
Annual Pumping Energy CostSimplified Equations
Total Seasonal Energy Costs Unit Energy Costs
Nat. Gas: Energy Cost, $/yr = Vx TDHx Cg Energy Cost, $/ac-in = TDH x Cg
2.862 x Eo 34.691 x Eo
Propane: Energy Cost, $/yr = 3.698 x V x TDH x Cp Energy Cost, $/ac-in = TDH x Cp
Eo 3.278 x Eo
Diesel: Energy Cost, $/yr = 2.496 x V x TDH x Cd Energy Cost, $/ac-in = TDH x CdEo 4.856 x Eo
Electric: Energy Cost, $/yr = 102.4 x V x TDH x Ce Energy Cost, $/ac-in = 8.448 x TDH x Ce
Eo Eo
Cg= cost of natural gas, $/Mcf
Cp= cost of propane, $/gal V = volume of water pumped, acre-feetCd= cost of diesel, $/gal TDH = total pumping head, ft
Ce= cost of electricity, $/kWh Eo= overall pumping plant efficiency, %
Nebraska P mping Plant
5/22/2018 Bahan Kuliah Pompa Centrifugal
56/60
Nebraska Pumping PlantPerformance Criteria
Target" for a system that is well designedand operated (can be exceeded)
Calculated based on reasonable values for
Ep, Em, Ee, Edrive, energy content of fuel, etc.
PC
energy output
energy input
water horsepower - hours
energy unit
5/22/2018 Bahan Kuliah Pompa Centrifugal
57/60
Nebraska Pumping Plant
Performance Criteria Contd energy unit" :
kilowatt-hour (electricity)
gallon (diesel, propane, gasoline) 1000 cubic feet (mcf) (natural gas)
performance rating = PR = (actual
performance) / (performance criteria)
Nebraska Performance
5/22/2018 Bahan Kuliah Pompa Centrifugal
58/60
Nebraska PerformanceCriteria
Q = 800 gpm
TDH = 218 feet
diesel fuel consumption = 4 gallons per hour
performance rating? -- Equation 7.12 gallons of fuel per acre-inch of water
pumped? -- Equation 7.14
(800 gpm)(216 ft)44 whp
3960
Nebraska Performance Criteria
5/22/2018 Bahan Kuliah Pompa Centrifugal
59/60
Nebraska Performance CriteriaContd
performance = (44 whp) / (4 gal/hr) = 11whp-hr/gal
performance criteria = PC = 12.5 whp-
hr/gal performance rating = PR = 11 / 12.5 =
0.88
E =
TDH
(8.75)(PC)(PR) =
218
(8.75)(12.5)(0.88) = 2.26 gal / ac - in
Head Capacity Curve for Centrifugal Pump With Various Pump Speeds
5/22/2018 Bahan Kuliah Pompa Centrifugal
60/60