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Friction Loss occurs when water is pumped through a hose or pipe.
Distance, diameter, and the GPM all affect friction loss. As water passes
through the fire hose, friction develops between the moving water and the inside
surface of the hose. This turbulance reduces the PSI at the other end of the
hose. The friction loss formula calculates the friction loss for hoses between
3/4" & 6" diameter.
Use the following formula to determine friction loss. You can use a scientific
calculator or if you are good with math, write out the equation by hand to solve
for friction loss. Create your own friction loss problems, like the problem
below, and solve for the answer. Use the online
Friction Loss Calculator
to verify your answer.
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Fire Hose Friction Loss
Formula
FL = C * (Q / 100) ^2 * L / 100
FL = Friction loss in PSI
C = Friction loss Coefficient (Table 1)
Q = Flow rate in GPM
L = Hose length
Example:
Determine the friction loss for a 100 foot section of 1 inch hose with 60 GPM of
flow.
FL = C * (Q / 100) ^2 * L / 100
54.0 = 150 * (60 / 100) ^2 * 100 / 100
Coefficient (C) for 1" hose is 150
GPM (Q) = 60 GPM
Length (L) = 100 feet
Answer: There is 54.0 PSI of friction loss for a 100 foot section of 1
inch hose with 60 GPM of water passing through it. |
Table 1
Friction Loss Coefficient
|
|
Diameter
|
Coefficient
|
|
0.75 inch hose |
1100
|
|
1 inch hose |
150
|
|
1 ¼ inch hose |
80
|
|
1 ½ inch hose |
24
|
|
1 ¾ inch hose |
15.5 |
|
2 inch hose |
8 |
|
2 ½ inch hose |
2 |
|
3 inch hose |
0.677 |
|
3 ½ inch hose |
0.34 |
|
4 inch hose |
0.2 |
|
4 ½ inch hose |
0.1 |
|
5 inch hose |
0.08 |
|
6 inch hose |
0.05 |
|
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Methods to determining friction loss calculations:
- The
Friction Loss Formula
calculates friction loss for fire hose between 3/4" & 6" and is the most
accurate method. But, determining friction loss with this method is the most
time intensive, has a high probablity for human error, and is not very practical in the field or for learning hydraulics
theory.
- The
Friction Loss Calculator will calculate Friction loss for
any size fire hose between 3/4" & 6". This method uses the friction loss
formula to perform calculations and is just as accurate.
- The Friction Loss Slide Rule can provide calculations for a wide variety of
hose sizes and is faster than the friction loss formula, but it has a higher
probability for human error, and the slide rule is the least accurate of the
three methods.
- The Friction Loss Chart
(by FireEngineAcademy.com) provides a friction loss chart for each size
of hose between 3/4" & 6". The Friction Loss Grid
is a little more bulky, but is the easiest, fastest, and a very accurate method of
determining friction loss.
- Information about Hardware Friction
Loss.
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