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Can black steel be used for trapeze support? We have a project where the contractor has hung the sprinkler pipe with trapeze hangers from a piece of black steel pipe, anchored to the deck instead of directly to a piece of Unistrut or angle iron. Looking at NFPA 13 Chapter 17 (17.1.2, 17.4.1.3.1), it seems like this method is not allowed. Can you provide some insight as to whether this is allowed, or the pipe needs to be Unistrut, angle iron, or something else? Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe 
11 Comments
Jesse
8/29/2025 08:09:29 am
That's a lot of extra work. They should have cut a T in where the hanger currently is, then extended the pipe with a nipple & cap, then hung off the beam. Unless they are leaving room for future duct work, I don't understand the logic here.
Chad
8/29/2025 08:32:02 am
Weird…. There has to be a reason they did all that extra work… and it’s compliant despite being extra 8/29/2025 08:10:27 am
NFPA 13 (2022) 17.3.1 has the requirements for trapeze hangers, it even has a pictures of trapeze using pipe. Before unistrut was invented, this was the only way to hang the pipe. Yes, sch 40 steel pipe is good for a trapeze. There are specific design standards of the hangers that need to be followed and should have been detailed on the approved plans, that should be on-site.
C Denholm
8/29/2025 08:17:10 am
Yes, black steel pipe can be used for trapeze hangers.
Chad
8/29/2025 08:33:32 am
If you look in the back of the picture, they did it in every beam pocket!?
Dan Wilder
8/29/2025 08:48:04 am
Yes, compliant. hanger rings are sized for the pipe they are supporting, assumption that the trapeze pipe support is sized correctly, the only technical item I can point out it the trapeze pipe does not look to have a means to prevent the ring from slipping off (a cap, welded ATR, a top beam clamp attached to the end, or even a through the pipe ATR/washer/nut after the ring).
Jack G
8/29/2025 08:54:45 am
Pipe is probably the oldest trapeze hanger.
Jesse
8/29/2025 08:59:29 am
Compliant, yes. But sure seems like a lort of extra effort
Glenn Berger
8/29/2025 09:14:59 am
Compliant installation. The AHJ may require some calcs to be performed to ensure compliance with NFPA 13 for all the hanging provisions. In NFPA 13 Chapter 17, Section 17.3 references Trapeze Hangers, there are also Tables for "Section Modulus" (17.3.1 (a), (b) for Schedule 10 steel, schedule 40 steel and Angle Iron. The Modulus is a number associated with the type of pipe being hung, then used on Table 17.3.1 (c) to show what size pipe to use as the hanger. So to answer the question, yes steel pipe can be used but you need to know, the span, pipe size and schedule.
Jeff
9/7/2025 09:44:41 am
Looks like the sprinkler fitters were the first trade to hang. The designer specifies hanger stock, he’s using trapeze to stay in his hanging lane. If the installer or contractor changes the hanger locations, they may end up doing the work twice. Put it in according to the working prints provided. Good job. Leave a Reply. |
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