Coating System Selection on Offshore Flare Bridge Structure Using Maximum Temperature Estimation from Flare Radiation Simulation

Abstract

Offshore structures are highly susceptible to general corrosion which can lead to damage and lower the mechanical strength of the structure. Flare bridge structure are more susceptible to corrosion, due to experience combined effects of the corrosive marine environment and thermal radiation from flare. It is important to select a suitable coating system by considering the affected temperature. This paper will discuss about a brief case that describes how coating system selection is implemented in PHE ONWJ using a flare radiation simulation to estimate a maximum temperature. This study was started by reviewing previous Flare Heat Radiation and Dispersion Study in ‘U’ flow station to focus on flaring scenario, flare design data, and flare heat radiation contour. The next step is calculating the flare bridge temperature due to flare heat radiation exposure. This work combines four steps: (1) Collect flare bridge data, (2) Define maximum heat radiation based on flare contour, (3) Calculate the heat radiation received by flare bridge, (4) Calculate the flare bridge temperature. Lastly, select the coating system which considers the estimate of the flare bridge surface temperature and corrosion resistance to marine environment. The flare bridge temperature is estimated to be 136°C based on conservative calculation as affected by emergency flaring scenario that last(s) approximately 15 minutes of maximum flare relief duration. After the emergency flaring is over, the fluid service temperature slowly drops to the ambient temperature (approximately 28 to 30°C). This scenario is considered as the conservative approach due to the highest flow rate and maximum thermal radiation applied. Hence, apart from considerations to select an appropriate coating system such as: Minimum area average roughness, Sa 3; Prime coat functions as corrosion resistance in cyclic temperature; it should be considered that the coating temperature resistance > 136°C. Referring to the company's coating specification, we select BM 4-1 for coating the flare bridge structure. This practical approach aims to achieve as low as reasonably practicable coating system on the offshore flare bridge structure. Coating refurbishment using the selected coating system is expected to be highly suitable and can stand last for a long time.