Baffles spacer

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 tube bundle is the most important part of a tubular heat exchanger. The tubes generally constitute the most expensive component of the exchanger and are the one most hkely to corrode. Tube sheets, baffles, or support plates, tie rods, and usually spacers complete the bundle. 

Tie Rods and Spacers Tie rods are used to hold the baffles in place with spacers, wmich are pieces of tubing or pipe placed on the rods to locate the baffles. Occasionally baffles are welded to the tie rods, and spacers are ehminated. Properly located tie rods and spacers serve both to hold the bundle together and to reduce bypassing of the tubes. 

Tie rods with spacers. These hold the baffles in place but can be located to prevent bypassing. 

Dummy tubes or tie rods with spacers may be located within the pass partition lanes (and between the baffle cuts) in order to ensure maximum bundle penetration by the shell-side fluid. 

Essentially, a shell and tube exchanger consists of a bundle of tubes enclosed in a cylindrical shell. The ends of the tubes are fitted into tube sheets, which separate the shell-side and tube-side fluids. Baffles are provided in the shell to direct the fluid flow and support the tubes. The assembly of baffles and tubes is held together by support rods and spacers, Figure 12.2. 

The baffles and support plate are held together with tie rods and spacers. The number of rods required will depend on the shell diameter, and will range from 4, 16 mm diameter rods, for exchangers under 380 mm diameter to 8, 12.5 mm rods, for exchangers of 1 m diameter. The recommended number for a particular diameter can be found in the standards. 

Baffles or support plates > - Tie rods and spacers Packing box, x)x... 

The endcap contains two hard rubber baffles, a spacer end a retaining washer which Is staked In place Ths undersized holes In the baffles become enlarged and Ineffective after several hundred rounds The unit Is then removed by hand and a fresh replacement Is Installed. The worn caps can be discarded or may be returned to an arsenal for rebuilding. 

Tie Rods and Spacers Tie rods are used to hold the baffles in... 

The breath-actuated MDI Autohaler, is cocked with a lever to load the dose of medication, a baffle is opened by inspiratory pressure, and the dose is expelled from the canister metering chamber. " While the need for hand-lung coordination for proper actuation is reduced significantly with breath-actuated MDIs, these devices do not allow the use of a spacer device. 

After the exchanger size is set, the shell must be filled with the maximum number of tubes in accordance with the process and mechanical requirements. Figure 2-5 shows the tube bundle which, except for the stationary tubesheet (E), is inserted in the shell. The exchanger consists of the two tubesheets D and E), tubes (F) and baffles (G). Tube ends are roller-expanded into each tubesheet. The baffle is held in place by means of tie rods (H) and spacers (M). 

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