Q. Heat exchangers for plant design?
All exchangers shall be arranged to be readily dismantled for cleaning and maintenance. Cooling and heating streams generally flow against each other (counter flow), to maximize heat transfer. Elevations of exchangers shall be kept to a minimum unless stipulated for process requirements, but should be of sufficient height to allow minimum clearance under bottom outlets and drains. Also, exchangers containing hydrocarbons operating above 260 °C (AIT) should not have process equipment located directly above them.
Heat exchangers are generally positioned in process flow sequence, or grouped together for convenient interconnection, and spaced on the plot to allow sufficient operational access between them. Space should be allocated to one side of exchangers for piping valves and manifolds. Where piping requirements are the deciding factor, drains from exchanger piping must be allowed for. Horizontal thermo-syphon reboilers require a specific elevation relative to the distillation column vapour return; this should be defined on P&ID's and is a critical dimension.