Process Equipment and Plant Design
A cylindrical storage tank can have a self supported conical roof,

If the thickness of the roof is more than that of the cylindrical shell
Irrespective of its diameter
If its diameter is more than 50 meters
If its diameter is less than 15-20metres

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Process Equipment and Plant Design
In a shell and tube heat exchanger for a given heat transfer surface area, smaller diameter tubes are favoured as compared to larger diameter ones ; because the smaller diameter tubes

Are easier to clean
Are less prone to fouling
Can be fitted into a smaller shell diameter hence the cost of the heat exchanger would be less
None of these

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