551
OF ENGINEERING FORMULÆ.
Pneumatic Transmission—continued.
Formula for the Velocity.
S = Velocity of carrier In tube, feet per second.
I z=. L<‘ngih of tube in feet.
d = Diameter of tube in feet.
P = Pressure in tube in lbs. per square Inch.
k -- Coefficient of work.
t = l ime in seconds required for a carrier to go through
the tube. , _
/d 1 \/13
t- -000482—— V
p. lbs. per square inch. Values of k with different pressures. Horse-power required for each cubic foot of air per minute.
Pressure working Vacuum working
Con- tinuous. Inter- mittent. Con- tinuous. Inter- mittent. Pressure. Vacuum.
3 3520 3570 3770 3690 •014 •012
4 4000 4080 4420 4310 •019 •016
5 4420 4550 5030 4850 •024 ■018
6 4810 49-0 5620 5380 •029 •022
7 5150 5350 6170 5850 •035 •024
8 5460 5680 6760 6370 •040 •025
9 5750 6020 7350 6850 •046 •026
10 6020 6330 8000 7350 •052 •028
11 6250 6580 8700 7870 •058 •028
12 6490 6850 9430 8400 •064 •026
5U per cent, additional tngine power should be provided In
excess of the power necessary to compress or rarefy the air.
10 lbs. per square inch and pipes of 21 inches diameter are
most convenient for general purposes.
To maintain equal velocities in different lengths of tubing
of the same diameter, the pressure must be varied so that
kJ I : kJl\ : :k: k\.
To maintain equal velocities in tubes of the same length
but different diameters; /Jd : kJ'1x k '.k\.
To maintain equal velocities when both lengths and
. /T . /I7
diameters are different; V - : v — :: k : k-i.
’ d d, 1