Dear L. Narayana,
Genarally, column downcomer lines have to travel a lot to get down to the working levels of the plant. Just imagine a hot line falling straight by some 20 metres. Later it has to travel short distance flat horizontally to the condenser / heat exchanger as the case may be.
This set-up will call for an expansion loop to compensate for the thermal expansion of the column upwards. Next point is, where shall be the anchor at top? The column outlet nozzle has to bear some load / moment / stress on account of the pipe's contribution. The effect can be minimised if the anchor and the pipe move in unison. Obviously the top tangent line is the neutral level where the node as well as the support move in phase. The operating temperature, material of construction also will be more or less the same for the line as well as the top shell of the tower. That means no differential thermal expansion. It means / concludes that, at this level there is perfect harmony. I hope you get my point.
For more details refer any stress analysis guide book.
Good luck!!!
C. V. Gangadharan
--- Varanasi_L_Narayana@ril.com wrote:
> Generally column over head vapour line first rest
> support is given as close
> to top tangent line of column as possible. Can any
> body give the reason
> behind that .
>
> Regards
>
> Lakshmi narayana V
>
>
>
>
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