scope:

This recommended practice provides guidelines fir the selection and/or evaluation of air preheat systems applied to process heaters. Details of fired heater design are considered only where they interact with the air preheat system design. This recommended practice does not provide rules for design but indicates areas that need attention and offers calculation methods to check the suitability of systems or equipment.

The systems discussed in detail are those currently in common use in the industry and it is not intended to imply that other systems are not recommended. Many of the individual features dealt with in these guidelines will be applicable to any type of air preheat systems