Calculating Duct Resistance
Figure 37
Duct
Dia.
Approximate
Static Pressure
Loss Per Foot of
Rigid Pipe
Approximate
Static Pressure
Loss Per Foot
of Flex Pipe
Fitting
Dia.
90˚
Elbow
45˚
Elbow
45˚
Wye(Y)
90˚
Wye(Y)
Figure 37.
Additional Factors Static Pressure
To calculate the static pressure of any given
line in the system, follow these steps:
1.
Figure 37
2.
Figure 37
3. Figure 38
Figure 38.
4.
Figure 39
Note: Always account for a seasoned filter,
so you don't end up with a system that only
works right when the filter is clean.
Figure 39.
Main Line
6" Rigid Pipe (0.037) at 20' ................ 0.740
Branch Line
4" Rigid Pipe (0.075) at 10' ................ 0.750
4" Flex Pipe (0.28) at 5' ........................ 1.400
Elbows/Branches
6" 45˚ Y-Branch ................................ 0.329
4" 45˚ Elbow ........................................ 0.225
Additional Factors
Seasoned Filter ................................ 1.000
Total Static Pressure Loss ................ 4.444