Pressure vessels hemispherical

For high-pressure vessels, hemispherical heads are usually the most economical. 

As the size or the pressure goes up, curvature on all surfaces becomes necessary. Tariks in this category, up to and including a pressure of 103.4 kPa (15 Ibf/in"), can be built according to API Standard 620. Shapes used are spheres, ellipsoids, toroidal structures, and circular cylinders with torispherical, elhpsoidal, or hemispherical heads. The ASME Pressure Vessel Code (Sec. TII of the ASME Boiler and Pressure Vessel Code), although not required below 103.4 kPa (15 Ibf/in"), is also useful for designing such tanks. 

Figure 16.1 shows part of a steel tank which came from a road tank vehicle. The tank consisted of a cylindrical shell about 6 m long. A hemispherical cap was welded to each end of the shell with a circumferential weld. The tank was used to transport liquid ammonia. In order to contain the liquid ammonia the pressure had to be equal to the saturation pressure (the pressure at which a mixture of liquid and vapour is in equilibrium). The saturation pressure increases rapidly with temperature at 20°C the absolute pressure is 8.57 bar at 50°C it is 20.33 bar. The gauge pressure at 50°C is 19.33 bar, or 1.9MN m . Because of this the tank had to function as a pressure vessel. The maximum operating pressure was 2.07 MN m" gauge. This allowed the tank to be used safely to 50°C, above the maximum temperature expected in even a hot climate. 

Gupta, J. P. Fundamentals of Heat Exchanger and Pressure Vessel Technology (Hemisphere, 1986). 

Moss, D. R. Pressure Vessel Design Manual (Hemisphere, 1987). 

The pressure vessels are hollow cylinders, of 100- to 10,000-liter capacity, having a flange onto which the cover is fastened by means of bolts and nuts. The bottom of die vessel is usually hemispherical for greater strength. Autoclaves are almost always made of iron, either cast steel or cast iron, the former being safer to use at high pressures. Sheet iron is also used, in wall thicknesses up to 40 mm., in either riveted or welded construction. The reluctance in many dye plants to use welded autoclaves is entirely unjustified and has arisen simply because in the early days of the industry welding processes had not been perfected. 

These supports will not make a rectangular or square vessel suitable for pressure or vacuum service. If such a vessel is to receive a masonry lining, it must be designed as a cylinder with dished or hemispherical heads, both top and bottom or as a sphere. (Reference 8, p 80). Such vessel must also be designed in accordance with the ASME Code For Unfired Pressure Vessels, Section VIII. 

The computer program PROG43 determines the vessel weight of the pressure vessel with hemispherical, elliptical, and torispherical heads. Table 4-7 gives input data and computer output for 2 ft 6 in.-diameter vessel. The output gives the shell and head thicknesses, the weights of the shell and head, and the total weight of the vessel with hemispherical, elliptical and torispherical heads. 

Vacuum/pressure vessel with hemisphere bottom. 

Reddy, T.Y., Wen, H.M., Reid, S.R., and Soden, P.D. (1998) Penetration and perforation of composite sandwich panels by hemispherical and conical projectiles. ASME Journal of Pressure Vessel Technology, 120, 186-194. 

This is why most high pressure vessels do not use typical pressure vessel heads such as hemispherical or semi ellipsoidal. These heads are impractical in high pressure applications. So the economics and mechanical limits of the materials will determine the ultimate shape of the vessel. 

The Reactor Pressure Vessel (RPV) is of cylindrical shape with hemispherical heads. The main openings of the Reactor Vessel are the water/steam nozzles and the two connections to the... 

The Pressurizer is a pressure vessel of slim cylindrical shape with hemispherical heads. The pressure control function is carried out in the upper part, which is externally insulated to limit heat losses from the steam and hot water plena. 

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