Calculating Duct Resistance

Adding duct work, elbows, branches and any other components to a duct line increases airflow resistance (static pressure loss). This resistance can be minimized by using rigid (smooth) pipe and gradual curves, as opposed to flexible pipe and 90˚ elbows.

To help you think about this resistance, imagine riding a bicycle in a tunnel that is an exact replica of your duct work. If the inside of the tunnel is very bumpy (flexible pipe) and has a lot of sharp turns (90˚ elbows), it will take a lot more effort to travel from one end to the other.

The purpose of calculating the resistance is to determine if it is low enough from the machine to the dust collector to meet the given CFM require- ment for the machine. Use the charts in Figure 41 to calculate the resistance of duct work.

Duct

Approximate

Approximate

Dia.

Static Pressure

Static Pressure

 

Loss Per Foot of

Loss Per Foot

 

Rigid Pipe

of Flex Pipe

 

Main

Branch

Main

Branch

 

Lines

Lines

Lines

Lines

 

at 3500

at 4000

at 3500

at 4000

 

FPM

FPM

FPM

FPM

 

 

 

 

 

2"

0.091

0.122

0.35

0.453

 

 

 

 

 

2.5"

0.08

0.107

0.306

0.397

 

 

 

 

 

3"

0.071

0.094

0.271

0.352

 

 

 

 

 

4"

0.057

0.075

0.215

0.28

 

 

 

 

 

5"

0.046

0.059

0.172

0.225

 

 

 

 

 

6"

0.037

0.047

0.136

0.18

7"

0.029

0.036

0.106

0.141

8"

0.023

0.027

0.08

0.108

9"

0.017

0.019

0.057

0.079

 

 

 

 

 

Fitting

90˚

45˚

45˚

90˚

Dia.

Elbow

Elbow

Wye(Y)

Wye(Y)

 

 

 

 

 

3"

0.47

0.235

0.282

0.188

 

 

 

 

 

4"

0.45

0.225

0.375

0.225

 

 

 

 

 

5"

0.531

0.266

0.354

0.236

 

 

 

 

 

6"

0.564

0.282

0.329

0.235

 

 

 

 

 

7"

0.468

0.234

0.324

0.216

 

 

 

 

 

8"

0.405

0.203

0.297

0.189

 

 

 

 

 

Figure 41. Static pressure loss charts.

Model G0562Z/ZP, G1030Z2/Z2P (Mfg. 11/11+)

In most small/medium shops it is only necessary to calculate the line with the longest duct length or the most fittings (operating under the assumption that if the line with the highest resistance works, the others will be fine).

To calculate the static pressure of any given line in the system, follow these steps:

1.Make a list of each size duct in the line, includ- ing the length, and multiply those numbers by the static pressure value given in Figure 41.

2.List each type of elbow or branch and multiply the quantity (if more than one) by the static pressure loss given in Figure 41.

3.Add the additional factors from Figure 42 to your list.

Additional Factors

Static Pressure

 

 

Seasoned (well used)

1"

Dust Collection Filter

 

 

 

Entry Loss at Large

2"

Machine Hood

 

 

 

Figure 42. Additional factors affecting static

pressure.

4.Total your list as shown in the example in Figure 43 to come up with your overall static pressure loss number for that line.

Note: Always account for a seasoned filter, so you don't end up with a system that only works right when the filter is clean.

Main Line

+G^\^YE^eZ%#%(,Vi'% ################ %#,)%

Branch Line

)G^\^YE^eZ%#%,*Vi&% ################ %#,*% );aZmE^eZ%#'-Vi* ######################## &#)%%

Elbows/Branches

+)*ßN"7gVcX] ################################ %#('. ))*ß:aWdl ######################################## %#''*

Additional Factors

HZVhdcZY;^aiZg ################################ &#%%%

Total Static Pressure Loss

4.444

Figure 43. Totaling static pressure numbers.

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Grizzly G0562Z Calculating Duct Resistance, Duct Approximate Dia, Loss Per Foot, Fitting 90˚ 45˚ Dia Elbow WyeY
Page 26 Page 28

G0562Z specifications

The Grizzly G1030Z2 and G0562Z are two remarkable dust collection systems designed for woodworkers and craftsmen who prioritize maintaining a clean and efficient working environment. These machines are pivotal in minimizing airborne dust and debris, contributing not only to a tidier workspace but also to improved health and safety standards.

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