Wall thickness stress analysis: Subsea pipeline with cladding 2

[OtherCart]

Hi there,

I’m looking at a pipeline with wall thickness of 20mm and a 5mm corrosion-resistant alloy cladding. In terms of stress analysis and calculations, are there any guidelines or codes that state whether or not the 5mm cladding can be considered as part of the pipe wall thickness?

Thanks

 

[MJCronin]

ASME B31.1 "Power Piping Code" Under Section 124 - Limitations of Materials

Section 124.8

(E) the thickness of the cladding is not credited for structural strength in the piping design.

I do understand that B31.1 does not apply to subsea piping ..... but these codes are all written by the same people

MJCronin
Sr. Process Engineer

 

[SJones]

DNVGL-ST-F101

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[LittleInch]

Well cladding, presumably internal, at 5mm thick sounds like a lot - often it is 2-3mm.

Generally it is accepted that the cladding is not regarded in an analysis due to the very uncertain strength of the bond between the cladding and the mother pipe.

Also "clad pipe" can be many things, - weld overlay, explosive compression, loose fit, tight fit, cold expansion, you name it. Makes for a very difficult analysis when using two different materials and basically most people can't be bothered to find out how it actually works , err on the side of caution and just ignore the clad material apart from the weight.

Internally clad pipe is still uncommon and hence not many codes or procedures address it.



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[OtherCart]

Thanks MJCronin, SJones, LittleInch.

DNVGL – ST – F101, section 5.3.2.6 states

Possible beneficial strengthening effect of cladding on steel pipe shall not be taken into account in the characteristic resistance, unless the strengthening effect is documented.

However, if the bond between CRA alloy cladding and outer pipe was better understood, would it be beneficial to model the layers of the pipe and perform FEA?

Thanks

 

[LittleInch]

At a normal thickness of 2-3mm of cladding - not worth it unless the analysis is free.

Think it would need quite a lot of actual physical testing to prove the analysis before anyone will accept it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.