Dear All,

What is the difference between cladding and lining? Can these two terms be used interchangeably?

Appendix 3 of the Code (ASME VIII-1) defines a “clad vessel” and a “lined vessel”. To me, it appears that the differences between these two terms is based only on whether the corrosion resistant material is integral/continuous (in case a clad vessel) or whether it is intermittent (in case a lined vessel). Is my interpretation correct?

Your opinions on this subject will be highly appreciated.

Regards,

jehan

The wording and referenced standards of part UCL will clarify the meanings.  In summary - clad is (100%) metallurgically bonded either during plate manufacture or by deposition of weld overlay; lined is simply 'stuck on' by attachment welds.

Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/

Steve,

Thanks for your reply. But now I have some other questions.

Based on your below reply, would it be ok to interpret that a lining is in a way a "mechanicaly inferior cladding" since it is attached by plug welds?

When is lining prefererred over cladding? What are the merits of lining over cladding?

Is cladding applicable for metals only and does lining include both metallic and non-metallic (example- plastic lined, FRP lined, etc) lining?

-Jehan

If you are intending to adopt UCL-23 (c), then yes, one would argue that lining is a mechanically inferior cladding.

The choice of whether to go for lining or cladding is a function of all the usual input parameters in materials selection: cost, availability, schedule, fitness for service etc etc.

As to the last question, you really should study the wording of UCL-1 and not get confused with painting and coating terminology that ASME VIII does not address.

Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/

I would not say that lining, ie stip lining or sleeve lining is inferior to clad in all applications.  While clad is widely used in many applications, weld overlayed lining is preferred in reactors where higher temperatures and vacuumn may occur.  Strip lining can be used where there are not wide deviations in temperatures and external pressure is not a concern and in alloys where clad is not readily available and time and monetary constraints are important.  Recently the use of a solid alloy constuction for vessels that are relatively thin and austenetic stainless steel is much more economically feasible than a clad vessel of say 516-70 base with 304 or 316 ss cladding.

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:
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
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

roca,

a star for you for clearly out"lining " the differces (!?!) between the two.

-jehan

The difference has been rightly outlined by Roca.

I wish to share my experience with a cladded & lined vessel. If any one wishes to measure the thickness of shell using Ultrasonic method, on a cladded vessel & a lined vessel, the results would be as under:-

Cladded Vessel : Will get thickness of Shell + Clad
Lined Vessel   : Will get Thickness of outer shell only.

This may sound simple but sometimes the info may be very useful.  

One reason why lining might be preferable is that the lead times for bare carbon steel and bare alloy are usually significantly less than the lead time for clad material.

Another reason is that cladding usually has to be stipped back prior to welding the carbon steel portion to ensure good weld quality. Lining is added afterward so this is not an issue.

-Christine