Head blank diameter

The total weight excludes the nozzles, attachments, and vessel internals. Table 4-3 shows the head blank diameter factor for different types of head. 

BD = head blank diameter, inch c = corrosion allowance, inch D = inside diameter of shell or head, inch E = joint efficiency H.Fac = head blank diameter factor OD = outside diameter of head, inch P = internal design pressure, psig R = inside radius, inch R = crown radius of torispherical head, inch S = allowable stress, Ib/in ... 

The weight of material may be calculated from the blank diameter, gage thickness, and density of steel (490 lb per cu ft). The cost of the st I may be obtained ftom Appen-0x C. Table 5.9 gives the cost of ftiiniing per head for heads having an outside diameter of up to 48 in. Figure... 

For eost-eslimating purposes the procedure presented in the previous section for code flanged and dished heads is followed Fig. 5.12 is used for the blank diameter and Table 5.12 and Fig. 5.13 are used for the cost of forming per head for two to four heads. Table 5.10 may be used for determining other quantity diflerentials. 

BD = Blank diameter, in ID = Inside diameter of head, in T = Thickness of head wall, in... 

TABLE 10-67 Factors for Estimating Diameters of Blanks for Formed Heads... 

Using ASME flanged and disbed heads (F D) from Appendix Tables of Blanks, the circle size is 152 in. for a 12-ft diameter tank. Then add 3-in. straight flange which becomes 158 in. which is 158/12 = 13.166 ft diameter. Area of this diam,eter for surface area of head = 136.14 sq ft equivalent surface area of one head. For a horizontal vessel there are two heads possibly exposed to fire. 

Pumps shall be capable of at least a 5% head increase at rated conditions by replacement of the impeller(s) with one(s) of larger diameter or different hydraulic design, variable-speed capability or use of a blank stage. 

D, = diameter of circular blank from which head is shaped (D, will depend on the type of head). 

End caps (heads) of pressure vessels have a variety of shapes which are chosen based on cost or availability for a given chamber diameter and working pressure. Factors affecting that choice are size of flat blank needed, ease and cost of fabrication, need for welded nozzles in the cap, retained fluid volume, etc. The choice of type of end cap should be left to the supplier of the enclosed cleaning machine as it has no bearing on cleaning operations. For completeness, various types of end caps are briefly described below. 

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