Exchangers nozzle orientation

Figure 12 shows the plan and elevation views of a process unit piping (9). A dmm is supported off the piperack. Heat exchangers are located far enough back from the support columns so that they are accessible and their shell covers can be removed. Pumps are located underneath the piperack, but sufficient room is provided for maintenance equipment to access the motors and to remove the pump if necessary. The motor is always oriented away from the process equipment and located on that side of the piperack. Instmment valve drops are shown supported from the columns. The instmment trays themselves mn on the outside of the support columns. Flat turns are only made from the outside position of the piperack. Nozzle-to-nozzle pipe mns are made whenever possible. Larger lines are located on the outside of the piperack. Connections to nozzles above the rack are made from the top... 

Orientation of aU nozzles for incoming and outgoing gas/liquid, e.g. gas inlet and outlet nozzles on HGF, heat exchanger (air preheater) ... 

Disc- and doughnut-type heat exchangers for gases have lesser pressure drops and do not have idle gas pockets (which may occur in conventional shell- and tube-type heat exchangers with segmental baffles), and the orientations of inlet and exit nozzles for the process streams can he made to suit the ducts (routes of gas duct can also be shortened which is helpful to reduce the pressure drops) without generally affecting plant performance. 

Orientation of inlet and outlet nozzles should be veiy carefully decided, especially on the shell side. The possibility of short-circuiting (when inlet and outlet nozzles ate on the same side of the axis of a single-pass heat exchanger) is always there. In the case of multiple-pass heat exchangers (on shell side), there is a possibility of idle pockets at comers of baffles. 

In the case of disc-and-donut-type heat exchangers, the baffles are in the shape of a disc-and-donut. Because of the shape of the baffles, gas distribution is almost uniform on the shell side in spite of any orientation of gas inlet and outlet nozzles (not very critical unlike segmental baffle-type heat exchangers). 

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