Jacketed vessels thickness

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. 

A jacketed vessel is to be used as a reactor. The vessel has an internal diameter of 2 m and is fitted with a jacket over a straight section 1.5 m long. Both the vessel and jacket walls are 25 mm thick. The spacing between the vessel and jacket is 75 mm. 

Radius of toroidal section of closure, in Reynolds number Critical Reynolds number Inside radius of vessel, in Inside radius of jacket, in Outside radius of vessel, in ASME Code allowable stress, tension, PSI Thickness of closure bar, in Thickness of Jacket, in Thickness required, jacket, in Thickness required, closure bar, in Thickness of vessel shell, in Heat transfer coefficient, BTU/Hr/Ft /°F Velocity of media, FPS or FPH Rate of flow in jacket, Lbs/Hr Weld sizes, in Density of fluid, PCF Pressure drop, PSI Straight fine pressure drop, PSI Dynamic viscosity, cP... 

Typically, modern, vertical boilers are of tubeless design. They contain a suspended, dry-back, two- or four-pass, circular water jacket, of pressure vessel construction, about 5/16th inch (7.94 mm) in thickness. The inner tube of the water jacket is in reality the furnace tube, whereas the outer tube is the boiler shell. 

A simple jacketed pan or kettle is very commonly used in the processing industries as a reaction vessel. In many cases, such as in nitration or sulphonation reactions, heat has to be removed or added to the mixture in order either to control the rate of reaction or to bring it to completion. The addition or removal of heat is conveniently arranged by passing steam or water through a jacket fitted to the outside of the vessel or through a helical coil fitted inside the vessel. In either case some form of agitator is used to obtain even distribution in the vessel. This may be of the anchor type for very thick pastes or a propeller or turbine if the contents are not too viscous. 

BROWN et al.i95) have given data on the performance of 1.5 m diameter sulphonators and nitrators of 3.4 m3 capacity as used in the dyestuffs industry. The sulphonators were of cast iron and had a wall thickness of 25.4 mm the annular space in the jacket being also 25.4 mm. The agitator of the sulphonator was of the anchor type with a 127 mm clearance at the walls and was driven at 0.67 Hz. The nitrators were fitted with four-bladed propellers of 0.61 m diameter driven at 2 Hz. For cooling, the film coefficient hb for the inside of the vessel was given by ... 

A jacketed reaction vessel containing 0.25 nv1 of liquid of specific gravity 0.9 and specific heat 3.3 kJ/kg K is heated by means of steam fed to a jacket on the walls. The contents of the tank are agitated by a stirrer rotating at 3 Hz. The heat transfer area is 2.5 nr ami the steam temperature is 380 K. The outside film heat transfer coefficient is 1.7 kW/m2 K and the 10 mm thick wall of the tank has a thermal conductivity of 6.0 W/m K... 

The vessel and jacket are made of carbon steel. The vessel will operate at atmospheric pressure and the jacket will be supplied with steam at 20 bar. Check if the thickness of the vessel and jacket is adequate for this duty. 

FF = fouling factor, inside vessel, m2oC/W xw = wall thickness of vessel or coil, mm k = thermal conductivity, W/m°C FFj = fouling factor, inside jacket, m2oC/W hj = coefficient on inside surface of jacket, W/m2oC... 

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