Conical sections, pressure vessels

A formed section would normally be used for the transition between a cylindrical section and conical section except for vessels operating at low pressures, or under hydrostatic pressure only. The transition section would be made thicker than the conical or cylindrical section and formed with a knuckle radius to reduce the stress concentration at the transition, Figure 13.11. The thickness at the knuckle can be calculated using equation 13.46, and that for the conical section away from the transition from equation 13.45. 

The fluidised bed reactor is a vertical pressure vessel with a total height of up to 40 m. A fluidised bed of polymer particles in gaseous ethylene is maintained by a recycle compressor. The ethylene recycling gas enters the reactor through a distributor plate at the bottom to achieve an even gas flow over the entire cross-section and to hold the particles when the gas flow is turned off. In the characteristically conical upper part of the reactor, the gas velocity decreases with the increasing diameter of the reactor to keep the particles in the fluidised bed. The gas leaves the reactor at the top. It is cleaned from entrained particles by a eyelone, the reaction heat is removed by a recycle gas cooler and the gas is then routed back to the bottom reactor inlet. 

Fig. 13.9. Large head openings—reverse-curve and conical shell-reducer sections. (Extracted from the 1956 edition of the ASME Boiler and Pressure Vessel Code, Unfired Pressure Vessels, with permission of the publisher, the American Society of Mechanical Engineers [11].)...

It is a requirement of the food laws that areas of the pressure vessel in contact with the product during the extraction of natural substances for human consumption must be made of stainless steel. This necessitates the use of austenitic steel. As a special feature, the pressure vessel shown in Figure 8.5 is equipped with a lined conical bottom constructed of a special steel which retains its strength at low temperatures. This precaution was considered necessary since it is possible to produce very low temperatures when depressurising the vessel at the end of the extraction (see section 8.4.3). 

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