INSTALLATION OF EVAPORATORS

Many details must be considered when installing heat transfer equipment. Some of these may seem of minor importance but it is precisely these small details that often lead to poor performance, operational difficulties, and increased maintenance. 

Vertical steam-heated exchangers must also be vented to remove carbon dioxide and other gases which can accumulate under the top tubesheet. Corrosion of the shell, tubes, and tubesheet, especially in the area just opposite the steam inlet nozzle, may result if adequate venting is not provided. Sometimes a continuous steam purge or intermittent venting is recommended. 

Generally, U-bend exchangers should not be installed in a vertical position. Vertical U-bends are difficult to vent or drain on the tube side because connections cannot be provided at the U-bend end. Multi-pass exchangers are relatively high and provisions are made to ensure that the tubes operate completely flooded. 

The manner in which a heat exchanger is piped up can influence its performance. Horizontal units should have inlet and outlet nozzles on the top and bottom of the shell or channel. Nozzles should not be on the horizontal centerline of the unit. In general, fluids should enter the bottom of the exchanger and exit at the top, except when condensation occurs. Units are almost always designed to be counterflow and the piping must reflect this. When cocurrent flow has been specified, it is equally important that it be piped to suit. 

If the equipment will be used in corrosive service and if the components will have a short life expectancy, the design engineer should select units that are easy to repair. Removable bundle units may be required. In addition, the plant equipment layout should be arranged to facilitate removal and repair. 

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