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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.