Jacketed vessels external pressure

Two types of process vessel are likely to be subjected to external pressure those operated under vacuum, where the maximum pressure will be 1 bar (atm) and jacketed vessels, where the inner vessel will be under the jacket pressure. For jacketed vessels, the maximum pressure difference should be taken as the full jacket pressure, as a situation may arise in which the pressure in the inner vessel is lost. Thin-walled vessels subject to external pressure are liable to failure through elastic instability (buckling) and it is this mode of failure that determines the wall thickness required. 

Figure 13.15. Effective length, vessel under external pressure (a) Plain vessel (b) With stiffeners (use smaller of 1J and Ls) (c) I — section stiffening rings (d) Jacketed vessel...

Hydrogenation reactions are frequently run in fed-batch reactors. The chemical component to be hydrogenated is charged to the reactor vessel. The hydrogen is then fed into the vessel on pressure control. The temperature of the reactor is controlled by manipulating the flowrate of coolant to the jacket, coil, or external heat exchanger. Thus this system has two manipulated variables (the flowrate of hydrogen and the flowrate of coolant) and two controlled variables (pressure and temperature). 

External chambers, such as welded jackets, can provide a means for both heating and cooling from external sources such as steam generators or circulating baths. These jackets are themselves pressure vessels and have the same design considerations as the inner vessel. 

External pressure can also be created when x essels are jacketed or when components are within multichainbered vessels. Often these conditions can be many times greater than atmospheric pressure. 

External jackets are used to heat or cool the contents of a vessel. In effect, this turns the pressure vessel into a heat exchanger. Jacketing is an optimum means to accomplish this in terms of control, efficiency and product quality. The advantages are as follows ... 

---