November 1
November 1983
Circular 582
Utilities for Main Line
And Submain Line Design
COMPUTER SERIES
F. S. Zazueta, D. S. Harrison, and A. G. Smajstrla
'Ifmm
Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / John T. Woeste, Deah
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
. UTILITIES FOR MAIN LINE AND SUBMAIN LINE DESIGN
(c) IFAS, University of Florida, 1982,1983
SECTION II
UTILITIES FOR MAIN LINE AND SUBMAIN LINE DESIGN
by
Fedro S. Zazueta, Dalton S. Harrison and Allen G. Smajstrla \1
Two utilities are included in this package that are useful in
the sizing of main and submain lines in trickle irrigation sys
tems. The first is a HazenWilliams equation calculator for any
of the variables in the equation in a section of straight pipe.
The second computes head losses in pipeline systems including
friction and local losses.
HazenWilliams Calculator
Introduction
This program is executed by typing HAZEN.
This is an interactive program that allows any one of the
variables in the HazenWilliams equation to be computed as a
function of the remaining variables. All variables in the equa
tion are kept in a buffer area* with one of the variables being
dependent on the value of all the other variables. If any one of
the independent variables is changed, the machine will recompute
the value of the selected dependent variable and update the
display.
This program has two levels of interaction. When the program
starts executing it enters the first level, or main menu. At
this level the machine expects: 1) the first set of values of the
independent variables to beentered and, 2) the selection of the
dependent variable. After all requested data on the first level
are entered, the machine will enter a second level in which the
program will continuously update the value of the dependent
variable if one of the independent variables is changed.
Redefinition of the dependent variable can be made at the second
level.
* A buffer is an area in memory reserved for storage.
\1 Visiting Assistant Professor, Professor and Associate
Professor, IFAS, Agricultural Engineering Department, University
of Florida.
21
Input Data
The input data necessary to run this program are as follows:
1) Q, the flow rate through the pipe in gallons per minute.
2) CH, the HazenWilliams constant for the pipe used.
3) L, the total length of the pipe in feet.
4) HF, the head loss due to friction in feet.
5) D, the internal diameter of the pipe in inches.
One and only one of the above may be the dependent variable.
To specify the dependent variable a carriage return is entered
when the computer requests the value of that variable. Notice
that only one data item may be undefined. If more than one data
item is undefined the last one will be taken as the dependent
variable and a value of zero will be assigned to the others.
This might produce an error: for example, a zero diameter will
cause the head loss to be infinite regardless of the values of
the other variables. The computer will warn the user if he has
attempted to redefine the dependent variable at the first level.
Output
The program will display results only on the second level.
These results include:
1) The variable selected as the dependent variable.
2) The current values in the data buffer of the
independent varibles.
3) Flow rate in cubic feet per second in addition to
gallons per minute.
4) Velocity of water in the pipe in feet per second.
5) Friction loss expressed in pounds per square inch in
addition to feet.
At this level, a menu will be displayed that allows the user
to: 1) change any of the values of the independent variables,
2) exit to the first level (main menu) and, 3) exit to the
operating system. The dependent variable cannot be changed at
the second level. To change the dependent variable the user must
return to the main menu and enter the data required at 'that
level.
Example Calculations
CRTs 21, 22 and 23 show an example of the use of this
program. The screen shown in CRT 21 is the first level. Notice
that a value has been entered for each of the variables, except
head loss. When a carriage return was entered for the head loss,
this variable was defined as the dependent variable. When the
last data item was entered at level 1, the machine computed the
22
value bf the dependent variable (head loss), performed a few
conversions and displayed the screen shown in CRT 22. To change
the value of one of the independent variables a selection is made
from the menu. In CRT 22 selection 5 was made indicating that
a new diameter is to be used. After entry of the new diameter
the machine recomputes the head loss and redisplays the current
values of all variables.
To change the dependent variable the user must hit a car
riage return and enter the number corresponding to the desired
new dependent variable.
Notice that although they are shown at the same level, FLOW
RATE AND VELOCITY ARE NOT EQUIVALENT. Flow rate is the volume per
unit time passing through the pipe and velocity is the average
speed at which water moves within the pipe.
23
CRT 21
24
CRT 22
2 5
CRT 23
26
Technical Notes
The equation used in the computation of the selected
dependent variable is the HazenWilliams equation:
1.852
( Q \4.866
H = 10.536 L  D
(_CH
Where:
H is the head loss in feet.
Q is the pipe flow in gallons per minute.
L is the length of the pipe in feet.
CH is the HazenWilliams constant.
D is the internal pipe diameter in inches.
The above equation is used to express each of the variables
as a function of the others. All constants in the equation are
kept at least to four significant digits.
27
Head Loss Computations in Pipeline Systems
Introduction
This program is executed by typing PIPELINE.
This program computes the total head losses in a single pipe
line system, including friction and local losses due to changes
in pipe diameter and "tees". The program computes losses in main
and submain lines of trickle irrigation systems. THIS PROGRAM IS
NOT AN OPEN PIPE NETWORK ANALYSIS. The program assumes that the
flows trough each pipe are prescribed, and can be used only to
compute the head losses through a given path in a pipe network.
Pipe data are input to the program starting at the downstream
end.
Input Data
The program requests the following information for each of
the pipe sections:
1) Q, the flow rate in gallons per minute in the current
pipe section.
2) L, the lenght of the current pipe section in feet.
3) D, the internal pipe diameter of the current
pipe section in inches.
4) CH, the HazenWilliams constant for the current pipe
section.
5) Is the next connection a tee? If the answer to this
question is no, the program assumes a change in
pipe diameter, which may be an expansion or a
reduction.
Output
The PIPELINE program produces two tables. The first table
consists of the input data. The second table consists of: 1)
the friction loss in feet for each section of pipe, 2) the local
loss due to a change in pipe diameter and, 3) the cumulative head
loss. Values of head losses are given in feet of water.
Example Head Loss Computations
Consider the trickle irrigation system shown in Figure 21.
The head losses to any subunit in the system are assumed to be
identical regardless of which path is followed to the water
source because all subunits are identical and there is no field
slope. In this case, the pipeline system to be analyzed consists
of a single submain and a main line. CRT 24 shows the data input
for the example shown in Figure 21. CRT 25 shows the computed
loss due to friction, the computed loss due to the connection,
and the cumulative head losses from the distant end of the
submain pipe.
28
100 GPM
400'
PUMP
I
U
F LATERALS
100 GPM
400'
FIGURE 21:
FLOW DISTRIBUTION IN THE MAIN AND SUBMAIN
LINES OF A TRICKLE IRRIGATION SYSTEM
~j..
I
rLTRL
SECTION:
r
SECTION: 2
1) Q(gal/min): 200
2) L(ft) : 400
3) D(in) : 5.133
4) CH(i) : 140
5) Is next connection a "T"? no
Any items to correct? no
Finished entering data? yes
CRT 24
210
1) Q(gal/min) : 100
2) L(ft) : 100400
3) D(in) : 3.23
4) CH(i) : 150
5) Is next connection a "T"? yes
Any items to correct? yes
Which item? 4
Enter new value: 140
More correction? no
Finished entering data? no
_,'
CRT 25
211
Technical Notes
Head losses due to friction are computed using the Hazen
Williams equation:
1.852
(Q \4.866
H = 10.536 L  D
\CH
Where:
H is the head loss in feet.
Q is the pipe flow in gallons per minute.
L is the length of the pipe in feet.
CH is the HazenWilliams constant.
D is the internal pipe diameter in inches.
Local head losses are computed using the equation:
2
V
H = K
2g
Where:
H is the head loss in feet.
K is the local head loss coefficient.
V is the average water velocity in the pipe down
stream from the connection in feet per second.
g is the acceleration of gravity in feet per second
squared (32.2 ft/sec**2)
The local head loss coefficient is given as follows:
For a pipe diameter reduction:
2
K = (1/Mu 1)
Where the coefficient Mu depends on the ratio of the inter
nal area of the downstream pipe A2, and the internal area of the
upstream pipe Al as follows:
212
A2/A1 Mu
0.1 0.63
0.2 0.64
0.3 0.65
0.4 0.67
0.5 0.69
0.6 0.72
0.7 0.77
0.8 0.85
0.9 0.92
1.0 1.00
For pipe diameter expansion the value of K is given by the Borda
Carnot equation:
2
K = (A2/Al 1)
where Al and A2 are as previously defined.
Since local head losses are dependent on the geometry of the
fittings, and these may vary from manufacturer to manufacturer it
follows that the above equations for local head losses are ap
proximate. However, since local losses are normally only a small
percentage of the total losses in the main and submain lines,
exact values for the constant K are not necessary.
213
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, publishes this Infor
mation to further the purpose of the May 8 and June 30, 1914 Acts of Congress; and Is authorized to provide research, educa IfAS
tional Information and other services only to Individuals and Institutions that function without regard to race, color, sex or
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, Gainesville, Florida 32611. Before publicizing this
publication, editors should contact this address to determine availability.
