This standard API STD 660:2015(R2025) outlines the necessary specifications and recommendations regarding the mechanical design, material choices, fabrication, inspection, testing, and shipping preparations for shell-and-tube heat exchangers used in the petroleum, petrochemical, and natural gas sectors.

It applies to various types of shell-and-tube heat exchangers, including heaters, condensers, coolers, and reboilers. However, it does not cover vacuum-operated steam surface condensers or feed-water heaters.