Restraint of Branch Lines

[firesprinklergirl]

Regarding NFPA 13 2010, 9.3.6 Restraint of Branch Lines. I have a few questions.

If you are working with branch lines attached at both ends by a main (grid) which is restrained laterally and longitudinally by sway bracing in accordance with the code, do you have to restrain the branch lines within the grid according to 9.3.6?

 

[firepe]

It depends. You may not dismiss branchline restraint just because the mains attached are braced.

What size are the branchlines? How long is the run between the mains? How are the branchlines hung, ie, how long is the hanger assembly?



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[firesprinklergirl]

The branch lines are 2" the mains are 3" and 4"

The length of the branch lines between the mains is approximately 200'-0"

The branch lines are hung 21" below the deck with a top beam clamp, 3/8" A.T.R. and a hanger strap.

 

[firepe]

Based on this information, YES, you must provide branchline restraint for the 2-in. branchlines.

Fire Sprinklers Save Lives.
Can You Live Without Them?

 

[firesprinklergirl]

Thank you. I just spoke with the local AHJ and he is in agreement. I appreciate your time.

Amanda

 

[TravisMack]

Don't forget to verify that your rods meet the l/r requirement of not exceeding 400. 3/8" atr with a vertical dimension of 21" installed on a 45° angle will just barely be under 400 for the l/r value. If you increase that length at all, you are going to have to go to 1/2" atr.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[firepe]

Wire is another option.

Fire Sprinklers Save Lives.
Can You Live Without Them?

 

[firesprinklergirl]

We use the wire option... It seems to work the best at the cheapest cost material/labor.

 

[firesprinklergirl]

When laying out the branch line restraints along branch lines that are part of a grid, do you space the restraints from one head onward, or do you consider the connection to the main at both ends the end of a line and both heads at the "end" need to be restrained?