The heavy fuel oil of ship has increasingly been replaced by LNG in accordance with the eco-friendly trend at the world market in ship. Natural gas of cryogenic liquid condition stored in fuel tank has to be evaporated in order to supply natural gas to engine.
The high pressure vaporizer is an equipment to vaporize LNG. The inlet of HP vaporizer is cryogenic and high pressure condition, the outlet is high temperature and pressure condition. Assessment of structural integrity of HP vaporizer in these conditions was performed due to evaluate structural damage.
In this study, we had performed structure analysis of vaporizer on high pressure condition and we determined structural integrity after comparing analysis result with allowable stress values on ASME code section VIII Division 2.
The HP vaporizer consists of channel cover, tubesheet, shell near the supports, the shell-nozzle intersection, rear cover and supports. Finite element analysis models are constructed for each analysis. Three-dimensional isoparametric solid elements are used.
Material properties with temperature are based on ASME Section II Part D.
This was done by two methods. The first is code calculation for pressure parts by showing compliance with all of the applicable requirements of the ASME Code Section VIII Div.1 & 2. The HP vaporizer is designed to the requirements of the ASME Code Section VIII Division 1 for shell side and Division 2 for tube side respectively.
The second is analysis, which is performed by calculating stress for the discontinuity parts, stress concentrated area and structures due to the weight and nozzle loads including pressure loads and then comparing these stress to the allowable stress limits.
Finally, we confirmed that the calculated stress don't exceed allowable stress, thus it is proved that structural integrity can be maintained.