Buried process piping, is it permitted?

[jcme7212]

Dear coleagues.

I am in doubt, is there any code that does not permit to install process piping buried, inside a gathering & separation natural gas station?, what about in the case of a petroleum processing plant, liquid and gas piping?.
I will apreciate a lot your helping.

jcme7212

 

[bvi]

It is permitted to have ASME B31.3 piping buried. Not becuse that is specifically stated in the Code, but because it is not prohibited. And in fact people do have buried B31.3 lines. However, the rules in B31.3 do not provide specific requirements relative to soil/live load on the pipe, or on how to deal with thermal expansion of buried piping. B31.1 has a good appendix dealing with the latter.

 

[bulkhandling]

It is reminded that the Code pipe test requirement does not apply to a buried pipe. An acceptable procedure for pipe test shall be established before the installation. For example, the pipe examination and pressure test should be done before the pipe is buried.
Bulk

 

[jsummerfield]

Piping from storage tanks to refinery units are sometimes buried for part of the distance. Product pipelines are buried. Different piping standards apply to pipelines.


John

 

[bvi]

You can run the piping from the tank farm to the refinery as a pipline, B31.4, rather than piping, B31.3, but the question was in the process unit. bulkhandling brings up a good point, which is that during leak testing, all the joints must be exposed and observable during the test. As a result, in buried installations, the pipe must be tested prior to burial (at least before burying the joints). Sometimes the pipe is buried except for the joints. Note you can test portions of the piping system, and then bury them, prior to testing the entire installation.

 

[1969grad]

Just a note on buried joints. Never bury flange, socket weld or screwed joints. All buried joints should be butt welded including valves. If you follow the above, I don't see the point of leaving the pipe exposed during testing assuming the welders have all been qualified to API 1104 or ASME Section 9. Consider cross country pipelines which are buried during hydro testing except for the ends.

Burying large diameter pipe has advantages. You get better access to equipment and the pipe will have better support in general if you backfill correctly. However, I generally put a rest pier under the pipe where it comes above ground into equipment and under any buried valves.

As for thermal growth, the soil will over some resistance to movement.

Just make sure that you have 3 feet or 1 meter of cover.

 

[MJCronin]

acme7212,

I think you have to consider a system-by-system review....

Some of the fire protection codes prohibit buried piping. I would review ASME B31.3 about buried piping use on toxic or flammable systems

NFPA-50A or B, I believe, probibits buried piping use in hydrogen systems

I suspect oxygen systems have similar restrictions

MJC

"There comes a time in the affairs of man when he must take the bull by the tail and face the situation." W.C. Fields

 

[bvi]

1969grad: Visual examination of all weld joints during hydrotest is a ASME B31.3 requirement.

Note that folks have been tending to avoid underground lines in process units, or replacing them with overhead for a while, because of the potential consequences of undetected leakage.