Secure Your Building: Ducts

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Disclaimer: The effects, descriptions, recommendations, and suggestions included in this web site are intended to improve earthquake preparedness; however, they do not guarantee the safety of an individual or a structure. The Earthquake Country Alliance (ECA) takes responsibility for the inclusion of materials from various sources on these pages. The State of California, the Seismic Safety Commission, the ECA and all contributors to this document do not assume liability for any injury, death, property damage, loss of revenue, or any other effect of an earthquake.

Ducts

Larger imageDuct Bracing

Source: Noson, Perbix, SSD

Purpose

To brace ducts.

Recommendation

Provide transverse and longitudinal bracing in accordance with the SMACNA Seismic Restraint Manual Guidelines for Mechanical Systems.

Supplies Required

Steel angles—size varies with ducts
Machine bolts—1/2" diameter
Sheet metal screws—No. 10

Installation

Provide angle braces sized in accordance with the SMACNA guidelines. Attach together with machine bolts. Maximum spacing is 40' for transverse bracing and 80' for longitudinal bracing.
Provide screws at 18" on center maximum from the bracing to the duct.
Attach bracing to the structure above in accordance with the SMACNA guidelines.

Note

Bracing is required at ducts exceeding 6 square feet in cross-sectional areas, and for round ducts exceeding 28" in diameter.
No bracing is required if the top of the duct is 12" or less from the support above. See SMACNA guidelines for hanger requirements.
Walls, through which ducts pass, can be substituted for transverse braces. Provide blocking around the duct.

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Created in the SCEC

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Last modified: May 24 2007 10:44

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