Assuming only sprinkler piping is supported, the point loads at the hangers attached to the building structure would need to be accumulatively added for all pipes hanging from that location, depending on the spacing of the hangers, plus 250 lbs. These cumulative loads then need be verified supportable from the structure per NFPA 13 (2022) Sections 17.1.2(1 & 2). If both pipes are running parallel to supporting structural members, this could push you into trapezing a pipe that would normally not need trapeze. Coordination with the building structure/structural engineer on where/how to hang the pipe is always recommended.
If you are supporting other non-system components, then you are in Section 17.1.4 shared support territory and the 5x plus 250 lbs requirement that entails. Either way, ATR diameter needs to be sufficient both for the pipe it is hanging, and for the cumulative sizes it is supporting which may be larger than the minimum required. You may find yourself having issues with rod nut sizes in rings if trying to mix and match sizing from typical ring offerings. Irregardless, detailed calculations may be required by the AHJ to prove these point loads can be supported and that assembly component load limits from bottom ring to the structural attachment, are not exceeded per NFPA 13 (2022) Section 17.1.2(5). If the pipes are perpendicular to each other, it is possible you may encounter a situation where the upper pipe is a trapeze member for the lower pipe. In this case, the trapeze requirements of Section 17.3 would apply, as would the considerations indicated above regarding building structural load points. You may ultimately need a structural engineer to sign off on the detail...if determined necessary by the AHJ. Hope this helps, Ryan L. Hinson, PE*, SET** \ Burns & McDonnell Associate Fire Protection Engineer \ Upper Midwest Region O 612-900-3755 \ M 763-688-4045 \ F 952-229-2923 rhin...@burnsmcd.com<mailto:rhin...@burnsmcd.com> \ burnsmcd.com<http://www.burnsmcd.com/> 8201 Norman Center Drive, Suite 500 \ Bloomington, MN 55437 *Registered in: AK, LA, MD, MN, PA, TX, & UT **NICET IV - Water-Based Systems Layout From: Brian Harris <bhar...@bvssystemsinc.com> Sent: Tuesday, July 23, 2024 1:19 PM To: sprinklerforum@lists.firesprinkler.org Subject: [Sprinklerforum] Ring to Ring Trapeze Any thoughts on "ring to ring" instead of using Unistrut? Meaning, hanging lower smaller pipe from larger pipe at the deck. Thank you, Brian Harris, CET BVS Systems Inc. bvssystemsinc.com<http://bvssystemsinc.com/> Phone: 704.896.9989 Fax: 704.896.1935
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