Surge protection via the installation of an anti-surge control valve is indispensable in cen-trifugal compression systems, and the designs of such valves are often specified in the early design phase of centrifugal compression systems. However, additional recycle valve piping, such as hot or cold gas bypass valves, could be required in the case of emergency shutdowns. Furthermore, design verification via dynamic simulations is crucial in the engineering workflow. Because of the unavailability of design guidelines in the early design phase, only late verification is possible, necessitating system redesign when dynamic simulation results evidence the need for additional protection. This study presents a compressor surge distribution map by analyzing sensitivity parameters and establishing a new dimensionless number called the "surge number" (Ns). The surge distribution map is used to classify the safe and unsafe areas for surge protection using numerical threshold values. The map is to be used as a preliminary guideline for surge protection for engineers to quickly review the system and take additional protection measures in the early phase of design. (c) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.