Heat Exchanger Unit at Central Gathering Station 5 (CGS 5) Chevron Pacific Indonesia Ltd. is an industry component to exchange heat of production fluid into CGS. CGS facility consists of Oil Treatment Plant (OTP) and Water Treatment Plant (WTP). Production Fluid (gas-oil-water-sand mixture) from field and test station entering OTP facility first is separated in HEX to control the temperature up to 180 - 200Â°F. Chemical requirement on oil and water is at temperature 120 - 150Â°F. Therefore, the heat exchanger in CGS 5 has been installed as much as 20 heat exchangers (HEX). The performance of this instrument is very important because if its performance decreases, it can increase the production cost due to increasing steam flowed into the heat exchanger. The performance of the heat exchanger can be determined from several parameters, i.e. the overall heat transfer coefficient (U), the extent of area (A), and Pressure Drop (P). One of the components to increase the value of heat transfer is baffle. The HEX type used in the HEX CGS 5 unit is Shell and Tube Heat Exchanger with segmental baffles. The redesign is a solution to increase heat transfer by replacing baffle type into helical baffle. Based on the analysis data that has been done on helical baffle, it shows that the design of helical baffle on heat exchanger can improve the heat exchanger coefficient of 164.5658 W/m 2 .Â°C and reduce pressure drop of 12.0607 kPa in area of 454.1232 m 2 . In redesigning heat exchanger, it must determine the optimum design parameters and optimization methods. The design parameters for helical baffles are tube diameter and helical angle. The optimization method used in this research is Genetic Algorithm optimization method. The optimum result for tube diameter design is 19.063 mm with helical angle 35.014Â°.