Shells and Heads

The tests have been able to display the stresses distribution on the vessel surface (shell and heads) as well as characterize the most relevant zones for structural controls (weldings and so on). 

The experimental activity was carried out on a cylindrical pressure vessel whose capacity is 50 litres and made from steel 3 mm thick. Fig. 2 shows the layout of the pressure vessel considered. The pressure vessel was connected to an oil hydraulics apparatus providing a cyclical pressure change of arbitrary amplitude and frequency (fig.3). Furthermore the vessel was equipped with a pressure transducer and some rosetta strain gauges to measure the stresses on the shell and heads. A layout of the rosetta strain gauges locations is shown in fig.4. 

Openings are always required in pressure-vessel shells and heads. Stress intensification is created by the existence of a hole in an other-... 

Figure 14-81 provides early 1990 cost data for the shell and heads, and Fig. 14-82 provides 1990 cost data for connections. For very approximate estimates of complete columns, including internals, Fig. 14-83 may be used. As for Figs. 14-81 and 14-82, the cost index is 904. 

Often, a slightly higher MAWP than that calculated from Tabl possible at almost no additional cost. Once a preliminary MAWP is cted from Table 12-1, it is necessary to calculate a wall thicl r shell and heads of the pressure vessel. The procedure for doii s... 

The weight of nozzles and internals can be estimated at 5 to 10% of the sum of the shell and head weights. The weight of a skirt can be estimated as the same weight per foot as the shell with a length given by Equation 12-8 for an ellipsoidal head and Equation 12-9 for a conical head. 

Openings are always required in pressure-vessel shells and heads. Stress intensification is created by the existence of a hole in an otherwise symmetrical section. The code compensates for this by an area-replacement method. It takes a cross section through the opening, and it measures the area of the metal of the required shell that is removed and replaces it in the cross section by additional material (shell wall, nozzle wall, reinforcing plate, or weld) within certain distances of the opening centerline. These rules and formulas for calculation are included in Subsec. A. 

Also such factors as allowable tensile strengths, weld efficiencies, and possible inaccuracies of formulas used to calculate shell and head thicknesses may be pertinent. 

Figure 8.11. Tubular Exchanger Manufacturers Association classification and terminology for heat exchangers, (a) TEMA terminology for shells and heads of heat exchangers, (b) Terminology for parts of a TEMA type AES heat exchanger. The three letters A, E, and S come from part (a).

Horizontal tanks. Above ground they are limited to 35,000 gal. Normally they are supported on steel structures or concrete saddles at elevations of 6 to 10 ft. The minimum thickness of shell and heads is 3/16 in. in diameters of 48-72 in. and 1/4 in. in diameters of 73-132 in. 

Allowable tensile stresses are one-fourth the ultimate tensile strength of the material of construction. Values at different temperatures are given in Table 18.4 for some steels of which shells and heads are made. Welded joint efficiencies vary from 100% for double-welded butt joints that are fully radiographed to 60% for... 

The mechanical design of the column incorporates three main stages. The first specification is for the materials of construction. Second, the shell and head thickness must be chosen in order to withstand the operating conditions and also extraneous forces. Finally, consideration of the construction and assembly. The design was performed according to the relevent Australian Standard, AS1 210 SAA Unfired Pressure Vessels Code (Ref. Al 0). 

The shell and head design was in accordance with the design... 

Select the shell and head weld efficiencies, Es and Eh, from Table 6.1. 

Also such factors as allowable tensile strengths, weld efficiencies, and possible inaccuracies of formulas used to calculate shell and head thicknesses may be pertinent—that is, the relative uncertainty or error in the function is related hnearly to the fractional uncertainties of the independent variables. For example, take the case of a steam-heated thermosyphon reboiler on a distillation column for which the heat transfer equation is... 

In addition to the shell and heads, contributions to the weight of a vessel include nozzles, manways, any needed internals, and... 

---