(2) roca (Mechanical)
22 Aug 07 3:04
ASME VIII Div 1, Appendix 3, para 3-2 defines exactly what clad and lined means
However in my experience the two terms are sometimes interchanged and can cause some confusion as some people call clad, “lining” – which I suppose is correct too.
I define it as:
Clad steel is a base carbon steel material (which takes the pressure and loads) covered with a corrosion resistant alloy (CRA) material.
The CRA can be either integrally bonded (i.e. explosive or hot roll bonded to the base carbon steel material) or applied by weld overlay deposit.
Although UCL-23c allows you take account of the claddings strength, I have never done this and most clients don’t allow it either. The cladding is just assumed as a corrosion allowance and no credit is taken for its strength in the pressure calculations.
The CRA material can also be applied as strip lining or as loose sleeves in pipes. However there is still welding involved here back to the base CS material. Strip or sleeve lining is not used as stated above in high temperature services or where there is vacuum pressure. Additionally sleeve lining is used in situations where CRA material cannot be or is difficult to integrally bond to the base CS.
Lining are loose non metallic linings (e.g. rubber, PTFE) or painted / sprayed coatings or glass linings. The glass or painted / sprayed coatings may also need to be cured at temperature.
The loose non-metallic linings are bonded to the base CS
Loose and coated / sprayed and glass linings will required attention to vessel internal surfaces, welds and nozzle corners which need to be of a smooth profile and radiused in accordance with the lining manufacturers or clients requirements,
Hope this helps