A study on flow characteristics and discharge coefficients of safety valve used in LNG/LNG-FPSO ships

The safety valves used in liquefied natural gas — floating production storage and offloading (LNG-FPSO) ships play an important role in maintaining a fixed pressure by controlling the release of liquefied natural gas (LNG) from pipes in an LNG piping system. Therefore, the discharge coefficient is regarded as the most important parameter influencing the valve performance. In order to satisfy the ship’s classification criteria, the discharge coefficient of the safety valve must usually be over 0.8. Despite the importance of a good understanding of the flow phenomena inside the safety valve for the improvement of the discharge coefficient, the successful design of valves depends on experience and experiments in an industrial field. In this study, a computational fluid dynamics (CFD) investigation was carried out with ANSYS-CFX software to observe the flow phenomena inside the valve and to determine the discharge coefficients from changes in the valve lift, which is the distance between the exit of the nozzle and the lower part of the disc plate. The discharge coefficients obtained were also verified through comparison with available experimental data.