Abstract: Open rack vaporizer (ORV) is a popular model widely used in LNG receiving terminals and highly regardedfor its advantages. In order to make full use of ORV, three factors related to the max ORV operating load are analyzed, i.e. sea water flow rate, sea water temperature and operating pressure. Based on their performance curves and mechanical constraints, a mathematical model for max operating load estimation is established with 1stOpt, a non-linear curve fittingtool, which is proved to be accurate and practical through correlation and error analysis. Results show that the model canbe used to rapidly estimate the maximum operating load under existing operating conditions, which could be used as atheoretical and mathematical reference for uses in ORV application.