Determining main line duct size, Determining branch line duct size – Grizzly G0638 User Manual

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G0637/G0638 Cyclone Dust Collector

Determining Main Line Duct Size

The general rule of thumb for a main line duct is
that the velocity of the airflow must not fall below
3500 FPM.

For small/medium sized shops, using the inlet
size of the dust collector as the main line duct size
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.

For the Model G0637/G0638 this is 10". Mark your
drawing as in

Figure 52.

Figure 52. Main line size labeled on sketch.

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Determining Branch Line Duct Size

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 appli-
cations. 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 53.

Figure 53. Branch line sizes labeled on sketch.

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A few frequently asked questions when deter-

mining branch line sizes:

What size of branch line do I use if the machine

has two dust ports?
Simply add the total CFM given for each size from

Figure 49 and refer to that CFM number in Figure

54. Then, split the branch line just before the dust
ports with matching duct sizes.

How do I manage two machines on the same

branch line?
You have two options:

1. If both machines will be running at the same

time, add the total CFM given for each size
from

Figure 49 and match the branch line

given in

Figure 54.

2. If both the machines will never be run at the

same time, reference the machine with big-
gest dust port in

Figure 54 and add blast

gates after the Y-branch to open/close the
line to each machine.

Total CFM

Branch Line Size

600

700

800

1000

1200

1400

1600

Figure 54. Branch line sizing chart by total CFM

(for use when multiple machines share line).