EXTERNAL PRESSURE DESIGN (Acc. to B31.3)

[tolga11]

I have a question about external pressure design according to Asme B31.3.

There is a pipe line D=48 inch, t=17.5 mm, and length of line is 4000 meters.

I want to calculate max allowable external working pressure for this line.

31.3 refers to BPV code section VIII Div.1 UG-28 to UG-30. For the calculations I need to use a L (design length.)

I dont have stiffening rings or tubesheets. The line is a straight line.

How can I determine this Length.?

Thanks in advance

best regards.

 

[prex]

Simply L=[∞](infinite)

prex

http://www.xcalcs.com

Online tools for structural design

 

[mylexicon]

tolga11
This pipe is awfully long! Is this an underground pipeline, you have there? Are you dealing with a buried pipe or an offshore line? I don't know much about designing offshore (underwater) pipelines but if it is a buried pipe and you're worried about soil pressure acting as the external pressure on your pipe wall, "Guidelines for the Design of Buried Steel Pipe" by ASCE might help you. You may find it at

http://www.americanlifelinesalliance.org

. It is a fast way to get familiar with this topic.
if you were simply asking about design of pipes at full or partial vaccum you had the right reference to start with. If I recall correctly, you can solve for length "L" or the maximum spacing between stiffening rings.
good luck

 

[vpl]

tolga11:

Besides pres's infinite suggestion, you can also use L=4000 m (as that is the length you give). Or you could solve the problem in terms of "unit length" where L=1.

I'd also like to know what application calls for a 4000 m pipe without stiffening rings. And why the heck is your pipe diameter in inches when your thickness and length are metric?

Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[DSB123]

vpl,
If you solve for unit length then that's silly as the longer the pipe the lower is the allowable external pressure. so you are saying that to solve for L=1 will give a valid answer!! I don't think so somehow. Also what's the problem with calling off pipe in imperial with the thickness and length in metric? The units are given and that's all that is needed.

 

[odem]

tolga11,

4000 meters sounds to me like a pipeline. Pipelines aren't typically designed to B31.3. Most pipeline systems are designed to B31.4 or B31.8. B31.3 is typically a process piping spec.