Re: [PipingDesign] Wall thickness calculation for pipeline branches

From: <Sajit>
Date: Wed Jul 20 2005 - 07:55:00 EDT

There isn't a separate consideration for the calculation of the branch pipe thickness. The pipeline code usually results in lesser thickness, than the B31.3, due to the higher allowable and the difference in the formulae used. The code breaks between the pipeline and the on-plot piping generaly occurs after the launcher / receiver.


Almost all companies developes piping specifications for various line services (gas, water drains, produced water, oil, etc.). Sch. 80 for 2" pipe and sch. 160 for 1-1/2" and smaller is very common. The heavy wall is not to meet the hoop stress, but for strength, corrosion allowance, thread allowance, and rigidity.

2" STD branch on 20" STD Pipe: It is more likely that the 2" will accidentally be knocked off or develop a leak than the 20" pipe.

Also most companies require the use of corrosion allowance 0.625" to 0.125". Try to calculate the min. wall thickness for 2" pipe to meet 50 bar + 1/16" corrosion allowance + depth of thread if threaded.


ILIAS VITALIS <> wrote: Greetings Everyone,

As a young part of an engineering department I have a rather naive question to you all and it has to do with piping branches and their schedule. If there is no customer specification directing you to the necessary thickness of the branches (i.e stub-ins, weldolets e.t.c),
is there any " rule of thumb" concerning the above matter. For example in a recent project where the customer did not stipulate the " branching" matter we proceeded with the XS scedule for the 2" piping & schedule 160 for 1" piping even though the main pipeline is 10 " STD. The operating conditions where 40 deg. Celsius & design pressure of 50Barg (medium natural gas).If someone uses the ASME B 31.8 for the piping wall thickness calculation like we did, do we have to do the same for the branches? If so, the calculated thickness is leading us to a smaller thickness.Could somebody direct me to this matter? Is there any particular paragraph or section of the ASME B 31.8 spec. that handles this issue? If not I sure need the advise from an experienced engineer or somebody who has faced this problem & troubled his/her mind.

Thanks in advance,

Elias Vitalis

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