This document discusses replacement analysis for existing assets. It defines key terms like defender, which refers to the existing asset, and challenger, which refers to potential replacement options. Reasons for replacing an existing asset include reduced performance over time, changing requirements, and obsolescence due to new technologies. The document provides details on how to evaluate the existing asset versus replacement options, including factors to consider like maintenance costs, reliability, and budget constraints. The goal of replacement analysis is to determine when an existing asset should be replaced and with what alternative.