Determining main line duct diameter, Determining branch line duct diameter – Woodstock SHOP FOX W1816 User Manual
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W1816 Owner's Manual (Mfg. Since 10/09)
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Determining Main Line Duct Diameter
The general rule of thumb for a main line duct is that the
velocity of the airflow must not fall below 3500 FPM.
Use the inlet size of the dust collector as a starting point
for the main line. Neck the main line down 1" for every
10' of length. This will usually keep the air velocity above
3500 FPM and, depending on your system, will allow you
to keep multiple branches open at one time.
Mark your drawing as in
Figure 43, but using the inlet size
for your dust collector as the main line.
Determining Branch Line Duct Diameter
The general rule of thumb for a branch line duct is that
the velocity of the airflow must not fall below 4000 FPM.
For small/medium sized shops, using the dust port size
from the machine as the branch line duct size will achieve
the correct velocity in most applications. However, if the
dust port on the machine is smaller than 4", make the
branch line 4" and neck the line down right before the
dust port.
Note: Systems with powerful dust collectors work better
if multiple blast gates are left open. This also allows you
to run two machines at once. Experiment with different
combinations of blast gates open/closed to find the best
results for your system.
Write your determined branch line sizes on your drawing,
as shown in
Figure 44.
395
395
614
790
395
220
98
8"
8"
Figure 43. Sketch example with the main
line duct diameter labeled.
395
395
614
790
395
220
98
8"
8"
4"
4"
4"
6"
4"
4"
5"
Figure 44. Sketch example with branch
line diameters labeled.