Craig, I don’t know of any requirement for the length of drops, especially in building that don’t require seismic restraint. Drops to a single sprinkler are excluded. The only requirement I know of is for sprigs and not drops, and in the commentary it specifies that it is not required on drops. A.9.3.2.3 (5) Within 24 in. (610 mm) of the top of drops exceeding 15 ft (4.6 m) in length to portions of systems supplying more than one sprinkler, regardless of pipe size Drops to a single sprinkler are not required to be equipped with a flexible coupling because of the concern regarding the difficulty of sprinkler installation and replacement [see 9.3.2.3(6)]. The rotation inherent in a flexible coupling can prevent the development of the torque necessary to properly install the sprinkler. 9.3.6.6* Sprigs 4 ft (1.2 m) or longer shall be restrained against lateral movement. Sprig-ups are addressed in 9.3.6.6. A vertical sprig, or a sprig-up, is considered the opposite of a pipe drop. A vertical sprig is a pipe rising from the branch line to serve an individual upright sprinkler. They are susceptible to rotation during relatively minor seismic events. The requirement for restraint of sprigs was originally instituted for sprigs more than 8 ft (2.4 m) in length but was changed in the 1996 edition of NFPA 13 to apply to sprigs exceeding 4 ft (1.2 m) in length. The change was based on observations of rotated sprigs following the Northridge, CA, earthquake. The additional stability gained from this requirement results in time and money saved, because sprigs do not have to be manually repositioned after the event. The restraint provisions of 9.3.6.6 do not apply to drops to individual sprinklers, because gravity acts to pull them back to center.
Hope this helps. Mike Stossel SET [400dpiLogoCropped] 36 Barren Road East Stroudsburg, PA 18302 Office: 973-670-2627 m...@knssprinkler.com<mailto:m...@knssprinkler.com> From: Sprinklerforum [mailto:sprinklerforum-boun...@lists.firesprinkler.org] On Behalf Of craig.pr...@ch2m.com Sent: Monday, November 14, 2016 12:01 PM To: sprinklerforum@lists.firesprinkler.org Subject: Bracing on vertical sprinkler drops - 15 ft long I’ve been hunting the answer to this question and so far have come up short. I have a case where there are drops off the bottom of 2” branch lines down to sprinklers in a ceiling 15 feet below. They are hard piped to within 2-3 ft of the ceiling with a flex drop from that point to the ceiling. This is seismic design cat. B, so no EQ bracing required. I’ve been trying to find rules on bracing of vertical drops but find only info on unsupported armovers, which this is not. Also the pump rated pressure is 150 psi so the system will see pressures over 100 psi. Any help on locating that elusive one line or paragraph on bracing requirements for vertical drops would be appreciated. Craig L. Prahl Fire Protection Group Lead/SME CH2M 200 Verdae Blvd. Greenville, SC 29607 Direct - 864.920.7540 Fax - 864.920.7129 CH2MHILL Extension 77540 craig.pr...@ch2m.com<mailto:craig.pr...@ch2m.com>
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