Floating head

Provision for differential expansion Expansion joint in shell Individual tubes free to expand floating head Floating head I loating head Floating head... 

For odd niimher of tube side passes, floating head requires packed joint or expansion joint. 

Among the topics of the TEMA Standards are nomenclature, fabrication tolerances, inspeclion, guarantees, tubes, shells, baffles and support plates, floating heads, gaskets, tube sheets, channels, nozzles, end flanges and bolting, materi specifications, and fouhng resistances. 

FIG. 11-36 Heat-exchanger-component nomenclature, (a) Internal-floating-head exchanger (with floating-head hacking device). Type AES. (h) Fixed-tiihe-sheet exchanger. Type BEM. (Standard of Tiihiilar Exchanger Manufacturers Association, 6th ed., 1978. )... 

The floating-head cover is usually a circular disk. With an odd number of tube-side passes, an axial nozzle can be installed in such a floating-head cover. If a side nozzle is required, the circular disk is replaced by either a dished head or a channel barrel (similar to Fig. 11-36/) bolted between floating-head cover and floating-tube-sheet sldrt. 

Interna] Floating-Head Exchanger (Fig, 11-36a) The internal floating-head design is used extensively in petroleum-refinery service, but in recent years there has been a dechne in usage. 

With an even number of tube-side passes the floating-head cover serves as return cover for the tube-side fluid. With an odd number of passes a nozzle pipe must extend from the floating-head cover through the shell cover. Provision for both differential expansion and tube-bundle removal must be made. 

Tube-Side Passes Most exchangers have an even number of tube-side passes. The fixed-tube-sheet exchanger (which has no shell cover) usually has a return cover without any flow nozzles as shown in Fig. 11-35M Types L and N are also used. All removable-bundle designs (except for the U tube) have a floating-head cover directing the flow of tube-side fluid at the floating tube eet. 

When points for 20-ft-long tubes do not appear in Fig. 11-41, use 0.95 times the cost of the equivalent 16-ft-Iong exchanger. Length variation of steel heat exchangers affects costs by approximately 1 per square foot. Shell diameters for a given surface are approximately equal for U-tube and floating-head construc tion. 

For an exchanger AAith alloy parts and a design pressure of 150 Ibf/im, the alloy extras are added. For shell and shell cover the combined alloy-pressure extra is the alloy extra times the shell-side pressure extra/100. For channel and floating-head cover the combined alloy-pressure extra is the alloy extra times the tube-side pressure extra/100. For tube sheets and baffles the combined alloy-pressure extra is the alloy extra times the higher-pressure extra times 0.9/100. (The 0.9 factor is included since baffle thickness does not increase because of pressure.)... 

Stationary Head—Bonnet 21. Floating Head Cover—... 

Gasket materials Metal jacketed or solid metal for (a) internal floating head cover. (b) 300 psi and up. (c) all hydrocarbons. Metal jacketed or solid metal (a) internal floating head. (b) 300 psi and up. Asbestos permitted for 300 psi and lower pressures. (same as TEMA C)... 

Type of Design U Tube Fixed Tubesheet Floating Head Outside Packed Floating Head Split Backing Ring Floating Head Pull-Through Bundle... 

Removable-Bundle, Externally Sealed, Floating-Head Exchanger... 

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