This document specifies requirements and gives recommendations for the mechanical design, material selection, fabrication, inspection, testing and preparation for shipment of shell-and-tube heat exchangers for the petroleum, petrochemical and natural gas industries.This document supplements API Std 660, 9th edition (2015), the requirements of which are applicable with the exceptions specified in this document.This document is applicable to the following types of shell-and-tube heat exchangers: heaters, condensers, coolers and reboilers.This document is not applicable to vacuum-operated steam surface condensers and feed-water heaters.