TEMA stands for “Tubular Exchangers Manufacturers Association” and is a set of standards that were developed by leading shell and tube manufacturers. These standards define the style of heat exchanger and the machining and assembly tolerances.
Fixed Tube sheet BEM, AEM, NEN
Advantages
Provides for single and multiple tube passes to assure proper velocity.
Less costly than removable bundle designs.
Disadvantages
Shell side / out side of the tubes are inaccessible for mechanical cleaning.
No provision to allow for differential thermal expansion developed between the tube and
the shell side. This can be taken care by providing expansion joint on the shell side.
Floating head AEW, BEW, BEP, AEP, AES, BES
Advantages
Floating tube sheet allows for differential thermal expansion between the shell and the tube bundle.
Both the tube bundle and the shell side can be inspected and cleaned mechanically.
Disadvantages
To provide the floating-head cover it is necessary to bolt it to the tube sheet. The bolt circle requires the use of space where it would be possible to place a large number of tubes.
Tubes cannot expand independently so that huge thermal shock applications should be avoided.
U-tube BEU, AEU
Advantages
U-tube design allows for differential thermal expansion between the shell and the tube bundle as well as for individual tubes.
Both the tube bundle and the shell side can be inspected and cleaned mechanically.
Less costly than floating head or packed floating head designs.
Disadvantages
Because of U-bend some tubes are omitted at the centre of the tube bundle.
Because of U-bend, tubes can be cleaned only by chemical methods.
Due to U-tube nesting, individual tube is difficult to replace.
No single tube pass or true countercurrent flow is possible.
Tube wall thickness at the U-bend is thinner than at straight portion of the tubes.
Draining of tube circuit is difficult when positioned with the vertical position with the head side upward.
Comments