bridge pipe crossing 1

[swoosh172]

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.

 

[SlideRuleEra]

Ductile Iron Pipe is often used for fire protection systems. Here is some general guidance on bridge crossing with DIP from the Ductile Iron Pipe Research Institute (DIPRA):

http://www.dipra.org/pdf/bridgeCrossings.pdf

Check the DIPRA website for other information that may be helpful.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[MiketheEngineer]

Your state DOT may have some suggestions

 

[Tekki]

Hi there - I have a new project that involves an elevated bridge and am working on the project specifications and scope for a horizontal standpipe system. At this time our design team is looking into the piping materials, including corrosion protection, thermal protection, pipe support, thermal expansion, seismic movement and methods to cross a vertical draw bridge. I saw these recent posts and wanted to see if anyone could shed some light on DIP versus carbon steel pipe?

Thanks much.

 

[rconner]

You have gotten some good guidance. Both steel and ductile iron piping are of course widely used for exposed piping, including aboveground crossings such as bridge crossings. I believe general success of both forms the basis of current specifications of many very large and notable utilities with considerable experience (that could be observed with a quick web search, e.g. see

http://www.amwater.com/files/33 05 29.13 - Bridge Crossing.pdf

). While I don’t profess to know all the reasons for this, when bridge crossings (most of which are small diameter) are actually built, and even when the project is replacing older steel lines that are for whatever reasons being replaced, it appears cement mortar lined ductile iron piping is most often used. Along with joining systens that offer performance and ready constructability in virtually all environments, another reason for this may be that this piping may be more readily available in these small diameter sizes and with the proven quite durable cement mortar lining (than perhaps are small steel pipes).

 

[swoosh172]

Hi Tekki, I can give you some information on what i've found in my research to date. I plan on using galvanized steel pipe with rolled grooved joints and victaulic fittings. The pipe will be an empty "dry" fire standpipe so expansion/contraction really comes into play. Victaulic has some good articles on their website regarding their expansion fittings. I figure I will need 1 expansion fitting every 200 feet or so over my 6,000 foot bridge based on a 0 to 100 degree ambient temperature difference. Hangers should be roller hangers on the top bottom and sides of the pipe. Anchors should be located at the expansion joints. Good luck, I'd be interested to know what information you have found that may help me.

 

[Tekki]

Hi rconner and swoosh172,

You have both provided some good information and it is very much appreciated.

rconner - the weblink was very helpful, thank you for this link. It seems from that information and additional information that there are two main piping methodologies that can be used as you point out. For black carbon steel pipe if used, it appears that for above-ground exposure to the elements and for locations near bodies of brackish or salty water some sort of coating must be provided. Galvanized pipe could also be used with or without an exterior coating The question then is if internal protection of the piping is in order through the use of galvanized pipe or some sort of internal lining.

swoosk172 - the piping approach you provided is similar to what I have found that was used on other similar projects. As outlined to rconner above, you may want to verify if some sort of exterior coating is in order in addition to the galvanized pipe. One source offers fusion-bonded epoxy (FBE) and recommends an outer covering of a UV protective coating. But all this material does add cost. I have also found after discussing the issues of pipe vibration, expansion, water hammer, etc. that there are engineering firms that handle piping designs all the time, which includes methods like you describe. For fire protection, a good resource is NFPA 502 (2011) that I was told is a recommended standard but one not necessarily adopted by the AHJ or local codes.

 

[rconner]

I saw the reference in the original inquiry to "600 psi flanges" (implying to me that some quite high pressures could conceivably be involved). For whatever it is worth, I know some manufacturers and joints of ductile iron piping have over the years demonstrated very high pressure capabilities/strength. E.g. with a free sign-up and log-in to "FM Global" Approval listings at

http://www.approvalguide.com/CC_host/pages/public/custom/FM/login.cfm

one can see that a manufacturer has available certification/approval ductile iron piping systems in sizes up to 16" for up to 350 psi FM "rated pressure" (signifying they have passed a battery of witnessed tests, including a strength test at actually 4X that rated pressure). I'm not sure about capabilities of "rolled steel joints" etc. mentioned in another post.

 

[CPENG78]

Hello Everyone,
I'm a bit late from the dates on your posts. But I wanted to share a little input.

swoosh172
In your original post, it was stated "An actual fire engineering firm will do the design build of the system but I want to make sure I am specifying it correctly". My question is, as to why would you need to specify something that someone else is carrying out as a "design-build"? In other words, you would want to carry out preliminary hydraulic calcs in order to size the pipe but that is as far as I would take it. My plans would then show an "X inch" line to be "built by others" or "by separate submittal".

Those preliminary hydraulic calculations with any applicable code would then determine the expected pressure in the pipe and thereby choosing a pipe material. Again, however I would only specify the material if I was responsible for the design. That would also include any anchorage, fittings, etc.

Now in previous fire system applications, I have seen vitaulic materials used for "indoor" applications such as piping inside a parking structure or not exposed to the elements. In fact, in one of my previous projects I spoke to a vitaulic rep and he did not recommend such materials for an outside application. In my case, it involve dry stand piping to be attached to the outer face of a hospital building.

Like rconner's recommendation, I would use steel or dip for this application, including an outer coating to protect against exposure. There are flexible expansion joints or expansion-contraction joints that you could call out to address pipe movement due to seismic or any other loading producing movement. EBBA Iron is one manufacturer but there are others. I would also check into NFPA requirements for additional guidelines.

In short, its just a heads up on taking liabilities on a pipeline that is be designed and bult by others.