Buried Pipe Design (B31.3 & DOT) - API 1102 vs ASCE 2

[gfdoug]

As far as I am aware, there are two different codes that can be used for buried pipe design underneath a road crossing: API RP 1102 for Steel Pipelines Crossing Railroads and Highways AND ASCE Guidelines for the Design of Buried Steel Pipe.

I am having trouble coming up with any major difference that would cause me to choose on over the other. It seems that API 1102 might be more conservative in most cases; but since it defines highways as any roadway that is traversed by a propelled vehicular traffic, it would cover all crossings that ASCE covers.

API 1102 does not ever reference the ASCE code, but ASCE references the API code in regards to pipe ovality (less than 3%) and in fatigue.

Do any of the ASME B31 codes call out API 1102 in particular as the code of choice for design? I have not been able to find anything. DOT 195 only says that "The pipe at each railroad or highway crossing must be installed so as to adequately withstand the dynamic forces exerted by anticipated traffic loads." So that's no help.

My main question is, if I am designing a process pipe (to B31.3 & DOT regulations) that is stainless steel going under an HS-20 designed roadway at a plant -- why would I choose one design standard over the other?

For what it's worth, I have already done the design in the example and just ended up following the guidelines for both codes per the specified pipeline. It passed under both design standards, I am merely asking for future reference of why one vs. the other.

Thanks,

-G

 

[BigInch]

First, neither API RP 1102 nor ASCE are codes. They are practices. API 1102 is referenced in ASME B31.4 & B31.8 because those are the pipeline design codes for liquid and gas pipelines respectively. In the USA they are somewhat irrelevant as DOT 192 and 195 are the governing legal requirements. B31.3 is not a pipeline code, so there are no public road or highway crossings in that one, although crossing under a "plant road" might make you think so. Plant roads (controlled access to owner's property with absolutely no public access allowed) are totally under the control by the owner, hence any adequate design practice ,or ASME codes (you might have a look at the underground design provisions of B31.1), can be used, as neither CFR 192 & 195 apply. I do not like ASCE crossing methods because of their poor method of considering soil interaction. I use a combination of 1102 and Corp of Engineers EM 1110-2-2902 is far better for soil friction lock up which is based on more than 200 years of experience.

http://www.eng-tips.com/viewthread.cfm?qid=358829

http://www.publications.usace.army.mil/USACE-Publications/Engineer-Manuals/u43544q/70697065/

So... you must first determine if you simply are designing some kind of underground process pipe on private land, or if you will be covered by the legal provisions of CFR 195. CFR 195 references ASME B31.4, which in turn references API 1102. If the pipeline crosses roads with public right of way or the crossing area can otherwise be accessed by the public, CFR is likely to apply so use API 1102. If that is true, you may be faced with becoming a regulated, or non regulated pipeline company, with all the data reporting and compliance issues that go along with it. My recommendation is, if you are not a pipeline company already, stay on your own land with the pipe works and control access with fences and locked gates (company personal only).

 

[Duwe6]

B31.3 is not appropriate for underground piping. Period.

As evidence, look at the hydro testing requirements. Each weld has to be 'felt up' during the hydro; kinda tough to do after backfill. Switch to B31.8 for this crossing, or put in a culvert [using a coated Sch40 pipe 2 sizes larger than the fluid-carrying line] and cross the road that way. Now your process line is not underground, and is inspectable & repairable.

 

[BigInch]

However underground B31.1 and B31.3 piping are both quite common. Burying after hydrotesting on short lengths of pipe is also quite common.