vember 1983
Circular 583
Pump Characteristics
And Power Consumption
COMPUTER SERIES
F. S. Zazueta, D. S. Harrison, and A. G. Smajstria
Florida Cooprative Extenion Service / Intitute of Food and Agriultural Solenms / Univerity of Florida / John T. Woes, Dean
Trade names are used liberally in this documentation. Their
mention is for illustrative purposes only and does not reflect
any preference, support or relationship by or to the authors, The
University of Florida, and The Cooperative Extension Service, in
any explicit or implicit manner.
FLORIDA COOPERATIVE EXTENSION SERVICE
INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES
Department of Agricultural Engineering
University of Florida
PUMP CHARACTERISTICS AND POWER CONSUMPTION
(c) IFAS, University of Florida, 1983
SECTION III
PUMP CHARACTERISTICS AND POWER CONSUMPTION
by
Fedro S. Zazueta, Dalton S. Harrison, and Allen G. Smajstrla\l
INTRODUCTION
This program is executed by typing PUMP.
This is an interactive program for the computation of 1) the
pump characteristics and, 2) the power requirements of a trickle
irrigation system. The final selection of the pump and the power
unit must be made by finding the commercially available units
that best match the specifications given by this program.
INPUT DATA
The required input data are as follows:
1) Pump discharge (gpm). This is the required flow
through the pump given in gallons per minute.
2) Discharge pressure (psi). This is the pressure deli
vered by the pump at the ground level where water
enters the trickle irrigation system. For centrifugal
pumps this is usually the pressure at the pump outlet.
For impeller or submerged pumps this is usually the
pressure at the top of the well. This value should be
given in pounds per square inch.
3) Dynamic pumping depth (feet). This is the vertical
distance from the point at which the discharge pressure
is measured to.the dynamic water level in the well.
The dynamic pumping depth is the sum of the static
depth of the water table and the steady state drawdown
due to pumping.
4) Pump efficiency. This is the ratio of the work done by
the pump to the energy input to the pump, expressed in
percent. Typical values of pump efficiency for well
maintained irrigation pumps are greater than 75%.
\1 Visiting Assistant Professor, Professor and Associate
Professor, IFAS, Department of Agricultural Engineering,
University of Florida, Gainesville, FL 32611, respectively.
5) Drive efficiency. This is the ratio of the work done
by the drive to the energy input to the drive,
expressed in percent. Drive efficiencies will depend
on the type of drive and how well it is maintained.
Typical values of drive efficiencies are shown in Table
31.
TABLE 31
Typical Drive Efficiencies
for Properly Designed Drives
Direct 100%
Flat belt 80%97%, 90% typical
V belt 99%
Gear 95%
6) . If an electric motor is to be used as a power unit:
a) The cost of electricity in cents/KWh. Notice
that standby charges are not considered,
unless you include them by increasing the
cost per KWh.
b) The efficiency of the electric motor in percent.
(88% is normally assumed).
. If an internal combustion engine is used:
a) The fuel consumption in brake HPhour per
gallon. This can be obtained from the
manufacturer's specifications using the
continuous operation performance curve.
Typical values are as follows:
Fuel Type hphr/gal
Gasoline 11.54
Propane 9.2
Diesel 14.58
b) Cost of fuel in cents per gallon.
7) . If a centrifugal pump is used:
a) Internal diameter of the suction pipe in
inches.
b) Length of the suction pipe in feet.
32
c) HazenWilliams constant of the suction pipe.
Some typical values are given in Table 32.
TABLE 32
Typical Values for the
HazenWilliams Constant
Pipe Material CH
Cast iron (new) 110
Cast iron (old) 90
Galvanized iron 125
Polyethylene 140
PVC 150
If a turbine (submersible or deep well) pump is used.
a) The standard column size in inches for deep
wells (see table 32) or, the internal diame
ter of the column for submersible pumps.
b) Length of well's suction column in feet.
c) HazenWilliams constant of well column. The
values of these constants are shown in Table
32 for open or enclosed line shaft in
standard pipe column. For submersible pumps
use values in Table 32.
OUTPUT
This program generates the following output:
1) The discharge in gallons per minute and total pumping
head in feet. These two values should be used to
select a commercially available pump from the manufac
turer's catalog of characteristic curves.
2) Water horsepower. This is the horse power which the
pump must supply to the water to operate the irrigation
system.
3) Brake horse power. This is the continuous horsepower
required at the shaft of the pump. It is greater than
the water horse power because of pump efficiency. It
is also the continuous horse power rating required of
the power unit to operate the pump.
4) Hourly pumping cost. This cost is given in dollars per
hour of operation. To obtain the yearly cost multiply
by the estimated number of operating hours in one year.
5) NPSH. This is the AVAILABLE net positive suction head
at the entry of the pump. This value should be greater
than or equal to the NPSH required specified in the
manufacturer's characteristic curves.
The available NPSH can be increased for submersible
and impeller pumps by placing the impellers or the pump
at a greater depth below the dynamic pumping level. To
determine the required minimum depth of placement of a
turbine pump in a well, substract the NPSH available to
the NPSH required. The difference is the depth that
the pump must be placed below the dynamic pumping
depth.
For centrifugal pumps the suction line must be made
shorter or a larger diameter must be used to reduce
head losses and increase the NPSH available. Moreover,
in centrifugal pumps the practical limit of syphon lift
is about 20 feet. For further discussion on this term
see Smajstrla and Harrison (1982).
CRTs 31 through 34 show a sample session with this program.
34
1) Pump discharge (
2) Discharge press
3) Dynamic pumping
4) Pump efficiency
Drive efficiency
5) Is an electric m
Cost of electric
Efficiency of e
gpm) :
re (psi) :
depth (feet):
(%) :
(%) :
500
25
20
75
100
otor used as a power unit? yes
city (cents/kwh): 8
electric motor (%): 88
6) Is a centrifugal pump used? yes
Internal diameter of suction pipe (in): 6
Length of suction pipe (ft): 25
HazenWilliams constant of suction pipe: 130
Any corrections? no
Enter "P and
Enter to s
PAUSE
.n> to send results to th
send results to the scree
e printer.
n.
CRT 31
 35
_112111
7 Head L
Friction velo
.52 .
Discharge Total
gpm fe
I00 0a 7
losses (feet)
:ity elbow
50 .50
Head
et
9.77
WATER HORSE POWER
BRAKE HORSE POWER
HOURLY PUMPING COST
/
screen
.50
Energy cost
cents/Kwh
8.
10.07 HP
13.43 HP
$ .91
Motor e
%
ff. Pump eff.
%
88. 75.
NET POSITIVE SUCTION HEAD AVAILABLE
*This value should be larger
than the minimum NPSH required
which should be shown on your
pump characteristic curves.
10.78 feet.*
CRT 32
1
.
.
1) Pump discharge (g
2) Discharge pressuz
S 3) Dynamic pumping c
4) Pump efficiency
I Drive efficiency
5) Is an electric me
Fuel consumption
Cost of fuel in
Data out of bounds,
no
Cost of fuel in
pm) :
*e (psi) :
lepth (feet) :
%) :
(%):
500
25
50
75
95
~t~r t~das o~ i
iit? no
in hphour/gallon: 115411.54
cents per gallon: 8
is the value correct?
cents per gallon:
120
6) Is a centrifugal pump used? no
Internal diameter of well column (in): 6
Length of well column (ft): 55
HazenWilliams constant of well column: 120
Any corrections? no
Enter ^P and to send results to the printer.
Enter to send results to the screen.
PAUSE
CRT 33
I
i

Head Los
friction veloci
1.33 .50
Discharge Total H
gpm feet
500.00 110.
WATER HORSE POWER
BRAKE HORSE POWER
HOURLY PUMPING COST
ses (feet)
ty elbow
.50
ead
58
screen
.50
Fuel use
hphour/gal
11.54
13.96 HP
19.60 HP
$ 2.04
Fuel Cost Pump eff.
cents/gal %
120. 75.
NET POSITIVE SUCTION HEAD AVAILABLE
36.80 feet.*
The lowest impeller of the pump should be
submerged below the dynamic pumping level
in the well to produce an available NPSH
greater than or equal to the value of the
NPSH obtained from the manufacturer's
characteristic curves.
CRT 34
38
I
i
TABLE 33
Hazen Williams Constant for Open or Enclosed Line Shaft Standard Pipe Column
FOR ENCLOSED LINESHAFT, use the FOR OPEN LINESHAFT, use the friction
friction loss under the appropriate loss under the appropriate shaft.
tube size. size.
3" tube takes 111/16" and 115/16" shaft
5" tube takes 211/16", 115/16", 33/16" and 317/16" shaft.
6" tube takes 311/16" and 315/16" shaft.
Column Size 2 1/2" ID 3" STD 4" STD
Tube Size N/A N/A N/A 1/4" 1 1/2 2"
Shaft Size /4 3/4" 3/4" 1" 1 /6
CH 40 45 45 70 60 40
Column Size 5" STD
Tube Size 1 1/4" 1/2" 2" 2 1/21
Shaft Size 3/4" 1" 1 3/16" 1 1/2
CH 85 80 65 55
Column Size 6" STD
Tube Size 1 1/2" 2" 2 1/2" 31
Shaft Size 1" 1 3/16" 1 1/211 [1]
CH 90 80 65 50
39
TABLE 33 continued
8" STD
Column Size
Tube Size
Shaft Size
CH
1 1/2
1"
125
2"
1 316"
95
2 1/2
3"
I 
1 1/2"
85
[1]
70
Column Size
Tube Size
Shaft Size
CH
Column Size
Tube Size.
Shaft Size
CH
2"
11
1 3/16"
110
2"
1 3/16"
110
2 1/2
1 1/2"
100
2 1/2"
1 1/2"
105
C[1
3"
[I]
10" STD
3 1/2" i
2 3/16
80
12" STD
3 1/211
2 3/16"
90
Pipe Size
Tube Size
Shaft Size
CH
2 1/2"
1 1/2"
100
3"
[11
14" OD
3 1/2"
2 3/16" 2
90
4"
7/ 16
85
[2] [3]
310
4"
2 7/16"
70
[2]
4"
2 7/16"
80
[2]
6"
[360
60
TABLE 33 continued
Pipe Size
Tube Size
Shaft Size
CH
2 1/2"
1 1/2"
100
[1]
16" 00
3 1/2"
2 3/16" 2
90
4"
7/16"
85
[2] [3]
Pipe Size
Tube Size
Shaft Size
CH
Pipe Size
Tube Size
Shaft Size
CH
Pipe Size
Tube Size
Shaft Size
CH
18" OD
3 /2"
2 3/16"
100
4"
2 /16"
95
[21
6"
[3]
70
20" OD
[2]
6"
[3)
75
3 1/2
2 3/16"
100
3 1/2"
2 /1600
100
4"
2 7/16"
95
24" OD
4" "
2 /16
100
[2]
6"
[3]
80
311
TECHNICAL NOTES
The equations used in the computations in this program are
as follows:
1) Total dynamic head:
Ht = Dd +
Hf + Vh
+ HKe + HKs
Where:
Ht
Dd
Hf
Vh
HKd
HKs
All of
equation
Total dynamic head.
Dynamic pumping water depth.
Friction losses in suction pipe or column.
Dynamic head.
Head loss for a 90 degree elbow.
Head loss for a screen.
the above are given in feet. Notice that in the above
allowance is made for one elbow and a screen.
2) Water horse power:
Q Ht
WHP =
3960
Where:
WHP Water horsepower in HP.
Q Pump discharge in gallons per minute.
Ht Total head in feet.
3) Brake horse power:
WHP
BHP =
Epump Edrive
312
Where:
BHP is the brake horse power in HP.
Epump is the pump's efficiency as a decimal fraction.
Edrive is the right angle or gear drive efficiency as a
decimal fraction.
4) Hourly pumping costs (Harrison and Choate, 1968):
For an electric motor driven pump.
Ht Ce
Cost =
5310 Em Ep Ed (100)
Where:
Cost is the cost of operation in dollars per hour.
Q is the discharge in gallons per minute.
Ht is the total dynamic head in feet.
Ce is the cost of electricity in cents per Kwhr.
Em is the efficiency of the motor as a fraction.
Ep is the efficiency of the pump as a fraction.
For a internal combustion engine driven pump:
Q Ht Cf
Cost =
3960 Ep Fc Ed (100)
Where:
Cost is the cost of operation in dollars per hour.
Ht is the total dynamic head in feet.
Cf is the cost of fuel in cents per gallon.
Ep is the efficiency of the pump as a decimal fraction.
Fc is the fuel consumption rate in gallons per brake
HPhr.
313
5) Net Positive Suction Head Available:
For a centrifugal pump:
NPSH =
Ha Dd Hfk
Where:
NPSH is the net positive suction head available in
feet.
Ha is the atmospheric pressure expressed in
value of 32.8 ft is used here.
Dd is the dynamic pumping depth in feet.
Hfk is the head loss in the suction pipe
friction, one screen, one elbow and the
change in kinetic energy of the water .
For an impeller or submersible pump:
NPSH = Ha + Lc Dd Hk
Where:
Lc is the length of the pump column in feet.
Hk is the head loss due to one screen,
in the suction pipe and
of kinetic energy of the water.
feet. A
in feet due
friction loss
the change
6) Local head losses:
These are head losses that occur due to changes in geometry
of the pipe, such as, elbows, tees, valves or sudden enlargements
or contractions in pipe diameter. Local losses are computed
using the following equation:
Hk = K
2g
Where:
Hk is a local head loss in feet.
314
K is the local head loss coefficient. The values
used in this program are as follows:
Cause K
screen 1
elbow 1
V is the average velocity of water after the change
in geometry that causes the local head loss in
feet.
g is the acceleration of gravity in feet per second
squared
7) Friction losses in straight pipe:
These are computed using the HazenWilliams equation.
1.852
H = 10.533 L ) D
\CH
Where:
H is the head loss in feet.
L is the length of the pipe in feet.
Q is the flow through the pipe in gallons per
minute.
CH is the HazenWilliams constant. It depends only
on the pipe material and periodic obstruction to
flow in the pipe. It applies only to flow of
water in straight pipes.
D is the internal pipe diameter in inches.
315
REFERENCES
Harrison D.S. and R.E. Choate
1968 Selection of pumps and power units for irrigation
systems in Florida. Circular 330. Agricultural
Extension Service, IFAS, Department of
Agricultural Engineering, University of Florida.
Smajstrla A.G.
1982
and D.S. Harrison
Net positive suction head (NPSH) required and pump
installation. Extension Mimeo Report 827. IFAS,
Department of Agricultural Engineering, University
of Florida.
316
COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL
SCIENCES, K. R. Tefertiller, director, in cooperation with the United States Department of Agriculture, publishesthis Infor
mation to further the purpose of the May 8 and June 30, 1914 Acts of Congress and Is authorized to provide research. educa
tlonal Information and other services only to Individuals and Institutions that function without regard to race, color, sex or U
national origin. Single copies of Extension publications (excluding 4H and Youth publications) are available free to Florida
residents from County Extension Offices. Information on bulk rates or copies for outofstate purchasers Is available from
C. M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainewille, Florida 32611. Before publicizing this
publication, editors should contact this address to determine availability.
