I had worked on Delayed Coker Plant of IOCL, Panipat. There I had seen that the supporting arrangement of the coker drum is from the bittom and the bottom portion is not allowed to move as the telescopic chute gets connected to that for the handling purpose. I agree with Mankotia, for this case, you have to consider only the displacement, not the thermal expansion of the drum.
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Engineer.
GE India Technology Centre Pvt. Ltd.