I have a warehouse with a roof 20 feet above. The designer has branch lines hanging under the ceiling joists. He has 10 foot drops of 1-1/2" sched 40 to an ACT ceiling over office spaces. We are in a "D" seismic design category building. I am unable to find any requirements for vertical restraint in the NFPA 13 or ASCE 7-10. Can anyone direct me?
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8/23/2019 10:22:22 am
NFPA 2016 22.214.171.124 Drops and arm-overs shall not require restraint
8/23/2019 10:34:13 am
New code NFPA 2019 126.96.36.199 (Restraint of Branch Lines)
8/23/2019 10:36:14 am
below is what I found from NFPA 13, 2016 edition
8/23/2019 10:47:32 am
Thank you Jonathan. I fail to understand the reasoning behind this. A 4' vertical sprig requires lateral restraint but a drop of any length with a vertical sidewall head doesn't. Hmmmm...I'll have to chew on this some more.
8/23/2019 11:15:34 am
Yeah it's strange but I'm assuming they think since the head will be in ceiling tile there will be little to no lateral movement. I don't see grids handling to well during an earthquake. Depends on how bad the earthquake will be I guess.
8/23/2019 10:54:03 am
Normally they have one feed main pipe drop down to just above the office (which is seismically braced with four way brace) and use long hangers that use connector nuts to extend the all thread rod to make it reach the structure. They will have end of line restraints on the horizontal branch piping. I've seen seismic cable used in a lot of spaces for the mains. If you locate the main 8" above ACT they'll have normal sized drops. Also make sure they have retaining straps and surge clips.
8/23/2019 11:32:39 am
You never want to brace drops to a single sprinkler. Drops are supposed to have flexibility so that the differential movement is absorbed. Springs are restrained so they do not fall over and twist through lever action on the fitting below. You can not equate the two.
8/23/2019 03:45:20 pm
The long 15'-0" drop does have a flexible hose connection at the ACT ceiling. Would it be deemed acceptable to brace the drop then?
8/26/2019 08:25:05 am
Acceptable, but not code-required.
8/26/2019 08:37:02 am
Good discussions. In our area the local AHJ's have all amended NFPA 13 188.8.131.52 to state any drops and arm-overs over 10' shall be restrained.
3/5/2021 12:49:08 pm
@DTC That's great your AHJ has a clear definition!
4/5/2021 10:13:54 am
I would counter that with: Arm-overs that are more than 2' long (cumulative length of horizontal pipe) are required to be supported (steel pipe).
5/8/2022 04:12:06 am
This is a little late I realize but better late than never. What I figured when interpreting this matter is simple physics. You have to brace a sprig over 4’ because gravity is working against you so that if it were to go off the pressure along with the force of gravity would pull the sprig down affecting the operation of the sprinklers ability to do what it’s supposed to do. Where as a drop on the other hand would be reversed and gravity would be the very force holding it in place therefore it wouldn’t need to be braced because no matter how long if the drop were to go off it wouldn’t affect its ability to operate properly. Of course this is just speculation or interpretation of my own but I am also dealing with this issue and peoples opinions on the matter vary. I hope this helps clear up some confusion on the matter but the rule on drops and bracing seems nonexistent because it is. I assume there’s nothing on the matter because you wouldn’t right an explanation as to why there isn’t a rule.
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