Grizzly G0508 owner manual Calculating Duct Resistance

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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 many sharp turns (90˚ elbows), it will take a lot more effort for you to travel from one end to the other than if your path had been smooth and straight.

The purpose of calculating this resistance is to determine if it is low enough from the machine to the dust collector to meet the given requirement for the machine. Use the charts in Figure 29 to calculate the resistance of duct work.

Duct

Approximate

Approximate

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

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

1.Make a list of each size duct in the line, including the length, and multiply those num- bers by the static pressure loss value given in Figure 29.

2.List each type of elbow or branch and multiply the quantity (if more than one) by the static pressure loss given in Figure 29.

3.Add the additional factors from Figure 30 to your list.

Additional Factors Static Pressure Loss

Seasoned (well used)

Dia.

Static Pressure

Static Pressure

 

Loss Per Foot of

Loss Per Foot

Dust Collection Filter

Entry Loss at Large

1

Rigid Pipe

of Flex Pipe

Main

Branch

Main

Branch

Machine Hood

2

 

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 29. Static pressure loss charts.

-22-

Figure 30. Additional factors affecting static

pressure loss.

4.Total your list as shown in the example in Figure 31 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.

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Figure 31. Example list for totaling SP loss. G0508 10 HP Industrial Dust Collector

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Contents Model G0508 HP Industrial Dust Collector Page Table of Contents Introduction ForewordContact Info Machine Data Sheet Impeller Information Identification G0508 10 HP Industrial Dust Collector Safety Instructions for Machinery Additional Safety for Dust Collectors 220/440V 3-Phase Grounding Rewiring toCircuit Requirements SET UP Set Up SafetyItems Needed for Setup UnpackingContents Figure Qty InventoryAssembly Placement LocationSite Considerations Floor LoadPage Page Lower collection bag secured to Collector Test Run To test run the dust collectorDesigning System GeneralDuct Material Metal DuctFlexible Duct Plastic DuctSystem Design Decide Who Will DesignSketch Your Shop Layout Sketch a Basic Duct LayoutDetermine Required CFM of Each Machine Machine ApproximateMachine Determining Main Line Duct Size Determining Branch Line Duct SizeTotal CFM Branch Line Size Calculating Duct Resistance System Grounding Blast Gate Accessories Metal Duct Starter KitMetal Elbows Metal BranchesReducers & Adapters G6252-4 Floor Sweep G7341-5 Floor Sweep G7342-6 Floor SweepDust collection pipe clamps H2443-Universal AdapterOperations Maintenance Lubrication Bag CleaningSchedule Daily CheckService About ServiceTroubleshooting Motor & Machine OperationDust Collection Operation Designing the System on Page 17 for moreG0508 220V switch Electrical ComponentsWiring Diagram Parts Breakdown Parts List DescriptionLabel Placement Warranty and Returns Page Page Page