Dear All,
Please introduce that I am new member here.
I have to study of pipe stress on buried flow line which made from API 5L-X52 with 2 mm inconel 825 internal clad.
I have to know how to input material properties of API 5L-X52 with 2 mm inconel 825 internal clad. The difficulty is the material is cladded, so we have to combine 2 material into one material which input to Caesar model. Does someone have experience about it

As we know that for buried pipe, intensification stress will happen on bend section. Our simulation result with simplify pipe material to AP 5L-X52 (without cladd), buried bends overstresses due to thermal expansion, and one solution is make expansion loops with UNBURIED bends. But, the cost for install it is expensive and big work.

Someone maybe has experience with other idea. Sharing your knowledge is very appreciated.

Thanks,
Agung C

Hello Agung

I really don’t know what to do about the 2 mm inconel clad, I would said that can be disregarded if it does not represent a big portion of the cross section of the pipe (How much is big, depends on you). As far as I know, cladding is to protect the piping against wearing or corrosion so should not be a problem to disregard this material for stress calculations. You can always calculate an equivalent thickness of the pipe as input data for CAESAR II, if you want to do so. However for the remaining issues as expansion and allowables, I think you can contact the vendor he would probably have a material data sheet that can be useful.
Regarding with buried bends, I would say that you should avoid turns, as you would do above ground. This implies that every turn must be made with a big radius of gyration (These can range from 5 diameters and up).

Regards,

Pedro Massabié

I would be hesitant to change the cross section of the pipe, as this will affect the area and inertia, both of which are used to form the stiffness matrix. If the cladding serves no structural purpose, then it can be ignored from a stiffness point of view. The only thing you need to worry about is the weight of the cladding, on the unburied sections. This can be included by specifing the cladding as refractory. Alternatively, you could just adjust the density of the pipe to obtain the same unit weight.

There could be other issues to evaluate, such as the differential expansion of the pipe relative to the cladding. However, this is beyond the scope of the 3D Beam element, and therefore CAESAR II can not address this issue.