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Does NFPA 13 require pipe hangers and supports (that are not UL/FM listed) to account for pressure thrust forces and any other forces beyond NFPA 13-2019 Section 17.1.2 for five times the weight of the water-filled pipe plus 250 lb at each point of piping support?
We have a 6-inch dry standpipe and we calculated a downward force of around 2,000 lbs to satisfy NFPA 13-2019 Section 17.1.2. However, taking thrust into account at a specific location with a 90 degree elbow, the calculated thrust force is around 6,000 lbs. This appears very high and wondered whether any other fire protection professionals can weigh in on whether thrust force should be accounted for in the calculation. I do not see any NFPA 13 requirements to satisfy thrust forces for aboveground piping. Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
4 Comments
Pete H
6/16/2022 06:27:39 am
On hangers and supports that are not UL/FM listed, make sure they're compliant with 17.1.6 (NFPA 13 2019 ed.) which states that components of hanger assemblies that directly attach to pipe, building structure, or racking structure, must be listed. The exceptions outlined in 17.1.6.2 and 17.1.6.2 are for mild steel hanger rods, hangers formed from mild steel roods, and fasteners. But all other parts of hanger assemblies that touch pipe need to be listed.
Anthony
6/16/2022 07:01:35 am
I think its reasonable to think you have a 4250lb safety margin given that hanger should be able withstand 10250lbs with a 2000lb static load, in that axial direction. If the thrust is in an other direction then add a pipe stand or a riser clamp.
James Phifer
6/16/2022 08:20:10 am
I've seen 6" pipe hangers rip away from the structure on a dry system at the elbow when the system tripped and the fire pump kicked on. For this reason, we install sway bracing at the elbows on a dry system to account for thrust.
Barry
6/16/2022 09:56:03 am
Above ground piping is generally restrained against the thrust of the water pressure inside the pipe by the joints themselves. Grooved couplings are an example of this. For example, an 8" cap has roughly 10,000 pounds of total force on the cap at an internal pressure of 200 PSI. This force is restrained by the grooved coupling and is distributed over the circumference of the groove. Leave a Reply. |
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