Carlon Determining the Number of Innerducts Contained in Outerducts - Manual (Page 3)

Determining the Number of Innerducts Contained in Outerducts
Outerducts enclosing a given number of innerducts based on complexity of run.
The volume fill is the amount of volume the innerduct occupies inside the outerduct. To
calculate the volume fill of an innerduct use the below equation:
(# of innerducts * cross sectional area of pulled innerducts)/(cross sectional area of outerduct)
♦ cross sectional area of innerducts is calculated as follows (use OD of innerduct):
(3.14*OD^2)/4
♦ cross sectional area of outerduct is calculated as follows (use ID of outerduct):
(3.14*ID^2)/4
The volume fill is called the “Run Factor.” The more difficult the run, the lower the run factor.
Typical run factors:
♦ Run factor = .7 maximum value recommended
♦ Run factor = .5 for shorter and straighter runs
♦ Run factor = .3 for longer and more complex runs
Adjust value as needed per experience.
To estimate the number of innerducts that can be pulled through an outerduct use the following
formula:
No. of innerducts that can be pulled through an outerduct = (Run factor x cross sectional area of
outerduct) / (cross sectional area of pulled innerducts).
The Excel Spreadsheet uses the above equation to automatically calculate the number of
innerducts that can be pulled through an outerduct.
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