bridge standpipe
bridge standpipe
(OP)
I have a 6,000 foot bridge that is 300 feet above grade. I have been tasked with specifying the dry pipe fire standpipe system on this bridge. An acutal fire engineering firm will do the design build of the system but I want to make sure I am specifying it correctly. Can anyone shed some insight as to what the specs should be for material, flanges, expansion joints etc? I am thinking galvanized steel, but is ductile iron used ever, I can only seem to find restrained mechanical joints with ductile iron pipe? It looks like most standpipes have restrained joints with expansion joints in the system and the pipe is supported on roller hangers. I'm probably looking at 600 psi flanges correct due to the height, length and movement of the bridge? Any help is appreciated! Thanks.





RE: bridge standpipe
You won't need any flanges unless the system will have an underground portion.
Rolled groove galvanized steel piping, with grooved fittings, per NFPA 14 requirements. Use multiple flexible couplings where necessary for thermal expansion or seismic. Contractor to submit complete material specifications prior to design or construction activities.
Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.
RE: bridge standpipe
RE: bridge standpipe
Flexible couplings is the option. Any motion and vibration from the bridge itself will be absorbed by the hanging components of the bridge and the flexibility of the structure itself. Bridge standpipes are self contained and dry. Never connected to any underground. At least I have never seen one and I travel the country a lot. 600 psi flanges would be an overkilled.
RE: bridge standpipe
No offense swoosh, but you are advising the advisor? It's ok I do the same thing, it's part of being a good engineer to question why.
Restraint is needed to counteract the axial aka longitudinal forces due to the water pressure. Think of the end cap on your 6" standpipe. It will have a force of 175 psig * pi/4 * ID^2. Where ID is the inner diameter.
This force is held back by the wall of the pipe. As it goes across a flexible coupling the axial force is still transmitted but the pipe is allowed to rotate (a small amount but enough to account for wind, thermal expansion, structural deflection, and seismic deflection of the supporting structures). If you put two or more flexible couplings together it allows upstream and downstream piping to move relative to each other. The way the flexible couplings should be arranged depends on the movements that would apply.
The rest of the couplings would be rigid couplings, which do NOt rotate. The engineer you hire will know this, so basically if you specify to follow NFPA 14 you should be fine..,
Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.
RE: bridge standpipe
RE: bridge standpipe
RE: bridge standpipe
I assumed the FDC was on the same level as the bridge. You never mentioned that and it is key info.. Now I get why you mentioned 600 lb flanges.
Just a side bar if you want to learn something else; from my days as a pipe stress engineer; I believe you will find that 300 lb flanges are good for up to about 400+ psig or so at water temps.. The 300 designation is roughly the pressure rating when the metal is at a temp of 300 psig saturated steam. Eg 150 lb flange good for ~150 psig at a temp of 366 F. At room temps, the allowable design pressure goes up. It is easy to google up the actual allowables.
But to stay on subject, the solution here is to change the FDC location to be on the same level as the bridge.
There is no brand of flexible coupling required. Every company that makes grooved fittings makes a flexible coupling. Victaulic is one example.
BTW If you are a "hatched plan mechanical engineer" as I call them, and really want to learn about fire protection buy the SFPE Study Guide for the Fire Protection Professional Engineering Exam. It would help you fill in knowledge gaps regarding standpipes, sprinklers, passive features, life safety plans, fire dynamics. I have a strong hunch you don't know everything you should know about sprinklers, water supply, or pumps to keep yourself out of trouble in the work you already do regularly. I am a reformed mechanical engineer myself (BSME) and it takes one to know one.
Best of luck on your project. I'll bow out of this thread now.
Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.
RE: bridge standpipe
This is why internet based engineering is dangerous.
RE: bridge standpipe