February 29, 2016 Longitudinal Bracing on Branch Lines "Is longitudinal bracing required on branch lines or only on feed mains and cross mains?" We have reviewed NFPA 13, 2013 edition that you indicated as the applicable standard. Our informal interpretation is that longitudinal bracing is not required on branch lines unless the riser is too long. Section 9.3.5.6.1 states, "Longitudinal sway bracing spaced at a maximum of 80 ft on center shall be provided for feed and cross mains." There is no mention of branch lines. The cross main carries the longitudinal loads from branch lines by resisting the forces parallel with the branch lines. Lateral bracing is required on branch lines is when the diameter is 2 1/2 in. and larger, but not longitudinal bracing. If the riser nipple to the branch line is greater than 4 ft, a further evaluation is needed. Riser nipples 4 ft or less can effectively handle loads from branch lines without harming the riser nipple pipe or its connections. It is possible to overstress the pipe and cause damage when the riser nipple is greater than 4 ft and the load is significant from the branch line. The riser nipple should be evaluated per the guidance and formula provided in Section 9.3.5.9.6.1. As stated in 9.3.5.9.6.2: "If the calculated value is equal to or greater than the yield strength of the riser nipple, the longitudinal seismic load of each line shall be evaluated individually and branch lines shall be provided with longitudinal sway bracing per Section 9.3.5.6."
Technical Update is prepared by the Technical Services Dept. of the AFSA: Vice President of Engineering and Technical Services Roland Huggins, a PE registered in fire protection engineering; Phill Brown, a NICET IV certified automatic sprinkler technician and NFPA Certified Fire Protection Specialist (CFPS) and Tom Wellen, a PE registered in fire protection engineering. This is provided with the understanding that the AFSA assumes no liability for this opinion or actions taken on it and they are not to be considered the official position of the NFPA or its technical committees. Copyright 2016, American Fire Sprinkler Association. All Rights Reserved Training Calendar AFSA Beginning Fire Sprinkler System Planning School 2016 Schedule April 4 - 15, 2016 May 16 - 27, 2016 July 18 - 29, 2016 Oct. 3 - 14, 2016 For more info, call: 214-349-5965 ext. 132 American Fire Sprinkler Association | 12750 Merit Drive, Suite 350 | Dallas | TX | 75251
