User Manual

8
Field Pipe Pressure Drop Calculation Example:
Wall mount panel installed with 30 feet of ¾” linear pipe between panel and hood. (2) 90 degree elbows
are installed in the pipe run and the pipe run has a vertical rise of 5 feet. Length of end-to-end hood
system is 32 feet.
Hood System = 32 feet. Flow rate = 32 feet * 0.7 gpm = 23 gpm
Pressure required at hood = 37 psi
Pressure at panel gauge = 50 psi
Allowable pressure drop between panel and hoods: 50 psi – 37 psi = 13 psi
Equivalennt length of pipe = 30 + 2 * 2.10 = 34.20 feet
Friction Pressure Drop through pipe = 34.20 * 0.556 = 19.01 psi
Gravitational Pressure = 0.43 psi/ft * 5 feet = 2.15 psi
Total Pressure Drop in Field Pipe between panel and hood = 19.01 psi + 2.15 psi = 21.16 psi
Allowable pressure drop = 13 psi
This system will not work correctly because calculated pressure drop is greater then allowable
pressure drop. Pipe size will need to be change to 1inch diameter.
Re-calculate with 1 inch pipe instead of 3/4” pipe:
Equivalennt length of pipe = 30 + 2 * 2.60 = 35.20 feet
Friction Pressure Drop through pipe = 35.20 * 0.159 = 5.59 psi
Gravitational Pressure = 0.43 psi/ft * 5 feet = 2.15 psi
Total Pressure Drop in Field Pipe between panel and hood = 5.59 psi + 2.15 psi = 7.74 psi
Allowable pressure drop = 13 psi
This system will work correctly because calculated pressure drop is less then allowable pressure
drop.
Pressure Loss Through Typical Water Pipe Chart
0.01
0.1
1
10
1 10 100 1000
Pressure Loss (PSI/Ft)
FLOW (GPM)
Pressure Loss Water Flow
3/4" pipe
1" Pipe
1 1/2" Pipe
2" Pipe