Tube bundle removal

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. 

Kettle 10-lF Tube bundle removable as Boiling fluid on shell side, as For horizontal installation. 1.2-1.4... 

Figure 7-70. This plan view shows provision for tube bundle removal with minimum removal of piping.

Compressors and their related equipment are usually located in one area for conunon operation and servicing adjacent to the main pipe radk and the auxiliary road. The suaion drum for the machine should be positioned for flexibility in the piping and to accommodate orifice run requirements. If the compressor is driven by a condensing turbine, a surface condenser and condensate pumps are required. If servicing one machine, the condenser may be located beneath the turbine. If it services two or more, the condenser must be located ac acent to the machines it services. In both cases, space must be provided for condaaser tube bundle removal. 

The two columns and the 3 reactors should all be aligned with suitable spacing and all the exchangers should have clearance for tube bundle removal. 

Spacing should be sufficient to permit safe bUnding and tube bundle removal without damage to or removal of adjacent piping or valves. 

Tube bundle Removable on all sizes if required. Standard design of size "A and B units may not have a removable tube bundle. TUbes are normally 1 in (25.4 mm)... 

The other space-saving approach is to use the Kobe (Kobe Steel) type of channel enclosure, which does not have all the external head bolts of typical TEMA Type B or Type C head enclosures. These exchangers require special tools to remove the tube bundles and trained maintenance personnel to do the work. These exchangers should never be located in stmctures because of the need to be able to access the channel from grade as it is difficult to remove the channel cover plate by using special equipment. 

Circulating fluidized-beds do not contain any in-bed tube bundle heating surface. The furnace enclosure and internal division wall-type surfaces provide the required heat removal. This is possible because of the large quantity of soflds that are recycled internally and externally around the furnace. The bed temperature remains uniform, because the mass flow rate of the recycled soflds is many times the mass flow rate of the combustion gas. Operating temperatures for circulating beds are in the range of 816 to 871°C. Superficial gas velocities in some commercially available beds are about 6 m/s at full loads. The size of the soflds in the bed is usually smaller than 590 p.m, with the mean particle size in the 150—200 p.m range (81). 

U-Tube Heat Excbajiger (Fig. 11-36J) The tube bundle consists of a stationaiy tube sheet, U tubes (or hairpin tubes), baffles or support plates, and appropriate tie rods and spacers. The tube bundle can be removed from the heat-exchanger shell. A tube-side header (stationary head) and a shell with integr shell cover, which is welded to the shell, are provided. Each tube is free to expand or contract without any limitation being placed upon it by the other tubes. 

The U-tube bundle has the advantage of providing minimum clearance between the outer tube hmit and the inside of the shell for any of the removable-tube-bundle constructions. Clearances are of the same magnitude as for fixed-tube-sheet heat exchangers. 

The tube bundle is removable, and the floating tube sheet moves (or floats) to accommodate differential expansion between shell and tubes. The outer tube hmit approaches the inside diameter of the gasket at the floating tube sheet. Clearances (between shell and OTL) are 29 mm (IV in) for pipe shells and 37 mm (I ifi in) for moderate-diameter plate shells. 

Longitudinal fins are commonly used in double-pipe exchangers upon the outside of the inner tube. U-tube and conventional removable tube bundles are also made from such tubing. The ratio of external to internal surface generally is about 10 or 15 1. 

Tube-Bundle Bypassing Shell-side heat-transfer rates are maximized when bypassing of the tube bundle is at a minimum. The most significant bypass stream is generally between the outer tube limit and the inside of the shell. The clearance between tubes and shell is at a minimum for fixed-tube-sheet construc tion and is greatest for straight-tube removable bundles. 

Air cooled heat exchangers are used to transfer heat from a process fluid to ambient air. The process fluid is contained within heat eonducting tubes. Atmospherie air, whieh serves as the eoolant, is caused to flow perpendicularly across the tubes in order to remove heat. In a typical air cooled heat exchanger, the ambient air is either forced or induced by a fan or fans to flow vertically across a horizontal section of tubes. For condensing applications, the bundle may be sloped or vertical. Similarly, for relatively small air cooled heat exchangers, the air flow may be horizontal across vertical tube bundles. 

Because there are neither flanges, nor packed or gasketed joints inside the shell, potential leak points are eliminated, making the design suitable for higher-pressure or potentially lethal/toxic service. However, because the tube bundle carmot be removed, the shellside of the exchanger (outside the tubes) can only be cleaned by chemical means. 

Just inside the shell of the tube bundle is a cylindrical baffle F that extends nearly to the top of the heating element. The steam rises between this baffle and the wall of the healing element and then flows downward around the tubes. This displaces non-condensed gases to the bottom, where they are removed at G. Condensate is removed from the bottom of the heating element at H. This evaporator is especially suited for foamy liquids, for viscous liquids, and for those liquids which tend to deposit scale or crystals on the heating surfaces. Vessel J is a salt separator. 

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