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Air Velocity in a Pipe
Using the equation and typical values of V, D and L explained to the right approximate values of P are computed as follows:
V = air velocity in feet per second
D = pipe inside diameter in inches
L = length of pipe in feet
P = pressure loss due to air friction in ounces/square inch
V = 25,000 DP
L
v
Air Volume Discharged from Pipe
CFM = air volume in cubic feet per minute
V = air velocity in feet per second as determined in the
equation at the top of this page
A = cross section area of pipe in square feet
CFM = 60VA
Boyle's Law
If temperature is kept constant, the volume of a given mass of
gas is inversely proportional to the pressure which is exerted
upon it.
Initial Pressure
Final Pressure
Final Volume
Initial Volume
=
Velocity
Ft / Sec
Pipe Diameter in Inches, 10' long
1
2
4
6
10
1
.0004 .0002 .0001 .00007 .00004
2
.0016 .0008 .0004 .00030 .00016
5
.0100 .0050 .0025 .00170 .0010
10
.0400 .0200 .0100 .00670 .0040
15
.0900 .0450 .0225 .01500 .0090
20
.1600 0080 .0400 .02700 .0160
25
.2500 .1250 .0625 .04170 .0250
30
.3600 .1800 .0900 .06000 .0360
Air
Air Supply Requirements (operating pressure: 90 PSI)
Tool
Class
Typical Air Consumption (CFM)
Hose Size (inches)
0 - 10 ft.
10 - 50 ft.
50 - 200 ft.
Paving breakers
25 lb.
35 lb.
60 lb.
80 lb.
45
50
65
80
1/2"
1/2"
1/2"
3/4"
1/2"
3/4"
3/4"
3/4"
3/4"
3/4"
1"
1"
Clay diggers
45
1/2"
1/2"
3/4"
Hand drills
8 lb.
15 lb.
20
32
3/8"
3/8"
3/8"
1/2"
1/2"
1/2"
Rock (sinker) drills
45 lb.
55 lb.
105
130
3/4"
3/4"
3/4"
1"
1"
1"
Tampers
5" butt
6" butt
20
30
3/8"
1/2"
1/2"
1/2"
1/2"
3/4"
Sump pump
Sludge pump
3 HP
Ejector
100
90
3/4"
1"
3/4"
1"
1"
1"
Vibrators
2-1/2"
3"
60
60
1"
1"
1"
1"
1"
1"
Chipping hammers
25
3/8"
1/2"
1/2"
Impact wrenches
3/8" sq. dr.
1/2"
3/4"
1"
10
15
25
50
5/16"
5/16"
3/8"
1/2"
3/8"
3/8"
1/2"
3/4"
3/8"
1/2"
1/2"
3/4"
Drills
1/4" - 1/2"
22
3/8"
3/8"
1/2"
Grinders
die / burr
small angle
3 HP vertical
20
20
75
3/8"
3/8"
1/2"
3/8"
3/8"
3/4"
1/2"
1/2"
1"