Uni-strut and clamps used as fire sprinkler pipe hangers 1

[seehorn]

WE are seeing more and more cases of unistrut type systems fastening sprinkler piping to building structure. If oriented so that piping is not hanging down against the clamp, the shear or slip load limits are small enough so that the piping does not meet the 5X weight of water-filled pipe + 250 pounds from each point of attachment per NFPA 13. Anyone else seen this? Would appreciate an AHJ point of view also.

 

[SprinklerDesigner2]

I hate seeing this sort of thing. Not your question but uni-strut clamps on sprinkler systems.

I can't find uni-strut clamps anywhere in the FM Approval Guide or UL Listing for fire sprinklers. If they are not there you can't use them unless you can get a PE to sign off.

From a personal standpoint I'd go with using a uni-strut clamp to secure a 1" inspector's test drop to a wall, I've never met anyone that would object to that yet, but hanging mains is a different story.

 

[MGXFP]

Unistrut is strictly forbidden here.

 

[firepe]

"Unistrut is strictly forbidden here."

Please explain you lost me here. Forbidden?

 

[MGXFP]

Simply put, if a local fire marshal were to see sprinkler pipe hung from unistrut, he would not allow occupancy in the building.

This is just my local AHJ's stance on unistrut.

 

[stookeyfpe]

It appears that Unistrut obtained FM approval for fire protection service:

http://www.unistrut.com/DB/PDF1/SWIFT-GRIP_flyer.pdf

I would need to research the listing but on the surface it looks as if this system can specified for hanging fire protection piping.

 

[PEDARRIN2]

Looking at the pdf - it looks like it is the clamp (looks like a modified beam clamp) not the unistrut structural members that have received the FM approval.

 

[seehorn]

Thank you for the input.
I should have been clearer on the type of clamp I was referring to...it is one that actually rides in the strut. The answers confirm what we have maintained, that typical unistrut and pipe clamps are not listed for fire sprinkler piping use.

 

[ContractorDave]

There's a whole chapter devoted to hangers. If the only criteria were listings, this wouldn't be the case. 9.1.1.6.1 and .2 address the trapeze hanger that I believe seehorn would be referring to? If the pipe is laid upon the strut and the clamp is merely used to secure it I don't see a problem. If the clamp is actually used to support the weight of the pipe, then 9.1.1.2 applies and you require an engineer to sign off on it.

Regards
Dave

 

[SprinklerDesigner2]

I think everyone has seen this but here goes anyway.

http://www.powerstrut.com/psjan2005/fibergl182.jpg

Remember this is for solid unistrut and not slotted.

Most of the time we see PS200 Uused (oftentimes slotted which makes it worse) and given the literature it can't much be used for anything other than branch lines and very short spans.