Hello!

Cladded pipe is jacketed pipe?
In that case I suggest to model both traces - technological pipes and jacket pipes and connect one to the other with CNODE facility in their connecting points (supports, welds, etc.).
I am not sure if you have to analyze a jacketed piping system or a traced piping system (because of the big difference between the two diameters). In the case of traced piping system, at big difference of diameters between the technological pipe and the tracing pipe, you can take to account only about the weight of tracing pipe, its fluid, clamps for support, etc for adding it to the pipe weight. I usual calculate a thickness for insulation for including the weight of tracing pipe and fluid in insulation weight.

Of course the kind of modeling the ensemble depends from one case to other. There are cases when we have to model both technological and tracing pipes.
To obtain more information, please tell us more about your situation.

I hope this helps,
Dragos Aron