Pressure vessels torispherical

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 18.17. Types of heads for cylindrical pressure vessels, (a) Flat flanged KR = knuckle radius, SF= straight flange, (b) Torispherical (dished), (c) Ellipsoidal, (d) Spherical, (c) Conical, without knuckle, (f) Conical, with knuckle, (g) Nonstandard, one of many possible types in use.

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. 

A pressure vessel designer generally has flexibility in selecting head geometry. Most common is of course the torispherical head, which is characterized by inside diameter, crown radius, and knuckle radius. The designer selects a head configuration that minimizes the total cost of the plate material and its formation. 

Shield, R, T., and D. C. Drucker, Design of Thin-Walled Torispherical and Toriconical Pressure-Vessel Heads in Pressure Vessels and Piping Design and Analysis—A Decade of Progress, American Society of Mechanical Engineers, 1972,... 

Standard torispherical heads (dished ends) are the most commonly used end closure for vessels up to operating pressures of 15 bar. They can be used for higher pressures, but above 10 bar their cost should be compared with that of an equivalent ellipsoidal head. Above 15 bar an ellipsoidal head will usually prove to be the most economical closure to use. 

Select a vessel head. If the internal pressure is 150 psig (10.3 barg) or less, select a torispherical head. If the internal pressure is above 150 psig (10.3 barg), select a 2 1 ellipsoidal head. 

Process conditions in the CPI often change, and a tower that is initially designed for vacuum operation may at a later stage be employed at pressure greater than atmospheric. Therefore, thin-walled vessels are often rated for both pressure and vacuum conditions. If the vessel is thick-walled and designed for high pressure service, no vacuum rating will be required. Tall vessels have one of a number of closures such as hemispherical, ellipsoidal, torispherical, conical, or flat ends. 

In tall vessels subjected to internal pressure, the shell is almost always cylindrical with a top closure that may have a hemispherical, ellipsoidal, torispherical, toriconical, conical or flat shape. Figure 4-3 shows some of the closure shapes available. 

U he real ntwl for the use of formed clt)sures on cylindrical vessels artwe with the development of the power steam b< iler early in the nineteenth century. As a result of the frequent occurrence of boiler explosions, the British House of Commons in 1817 made the recommendation that the heads of cylindrical boilers be hemispherical (12). Since then a wide variety of formed closures termed heads have been developed, standardised, and extensively used in the fabrication of prowss pressure ve sls. The develppment of the thermal cracking process in the petroleum industry during the period from 1915 to 1930 resulted in the construction of thousands of prewure vessels with formed heads operating in the range of from 100 to 400 psi. The heads of t he rly vessels usually were of the torispherical-dish type with a small knuckle radius. 

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