MODELLING OF CLADDED PIPE

I am working on a sysytem where the line size 42" and this line is cladded with alloy steel( 1/8 " thk. )
My approach is - changing the density of the material ( Average of C.S. & alloy material )and using the thickness of the C.S. material( THickness of the cladding material not considered )

Iwant to know my approach is correct or not.
Secondly as I am not considering the cladded thickness whether the nozzle load I will be getting is correct or not.

You're right in not considering the cladding for stiffness purposes. Its effects will be minimal.

However, the weight of the cladding must be properly considered. You do not want to average the densities of the carbon steel pipe and the alloy cladding. Instead, you want to compute an equivalent density for the pipe material such that the unit weight computed by the software is equal to the sum of the unit weights of the pipe plus cladding.

As to the issue of whether or not the cladding will add additional load on your nozzle, I don't think so. You're considering the proper weight (via the equivalent density), and any other system loads encountered (through system displacement) will affect the nozzle regardless of the presence of the cladding.

Perhaps others have additional insight into this problem?

Hello Ashish,

Your clad pipe system may not closely resemble "most other" clad pipe systems. Yours is a relatively large diameter pipe with a significant cladding thickness.

Clad pipe is stiffer than common or "unclad" pipe. How much stiffer is open to debate. IF (and this is a big IF) the cladding is bonded to the pipe ID continuously it might have the effect of simply adding (in your case 1/8 inch) to the total wall thickness. If this were the case the effect would be predictable (we could calculate the resulting pipe section modulus "Z").

If the cladding is not tightly bonded to the pipe ID but is attached to the pipe only at the butt welds the pipe would be stiffer by "some amount". The "pipe-within-a-pipe" effect might be similar to "double containment" systems or "jacketed" systems. The section modulus, "Z", will be still be increased, but by how much.

The stiffer the pipe is the more load will be transferred from the piping system to the vessel nozzles. If you effectively have greater wall thickness, or if you have "composite" construction ("pipe-within-a-pipe") I think the pipe streses would be lessened.

As Rich says, you will have to "account" for the total weight of the piping material (and all the support hardware, etc.) in the analyses.

I have asked Rich to put an ExCel spreadsheet template on the COADE site for the use of anyone who would find it useful. The spreadsheet is offered with NO IMPLIED GUARANTEES OF ITS ACCURACY. Like all such tools the user is cautioned to check out the resulting calculated values - it is your responsibility as an engineer to check your answers. The spreadsheet may prove useful for those who would like to quickly check the stiffnesses ("Z") of piping of standard and non-standard wall thickness.

Best regards, John.

The Excel spreadsheet mentioned above in John's post can be acquired by clicking here .

Dear Richard Ay,
Could you please re-upload again the Excel file...
Thanks

Regards

Tengku Syahdilan

Dear Richard,
With respect Could you please re-upload the excel file...

Thanks
TS

I don't have this file, it was on the old website and must have been lost during the (web site) migration.