Validation and verification of simulation model for initial subcooled LPG filling into LFSS pipelines and fuel gas skid on LPG dual-fuel carrier

Abstract

At the initial start-up of low-flash point fuel gas supply system (LFSS), commissioning engineers place considerable emphasis on manually flowing liquefied petroleum gas (LPG) into the pipelines and fuel gas skid of the LFSS. For this purpose, they consider the vaporization of the LPG in relation to the pressure and temperature conditions within the LFSS. To alleviate the burden of manual operation for commissioning engineers and minimize system misoperation during the initial start-up, a stepped sequence for initially filling LPG into the pipelines and package was developed and simulated using Aspen HYSYS. This sequence entails confirming the system line-up, following a step-by-step procedure for LPG line pressurization and pump operation, and incorporating an alert system that detects any deviations from the preset values at each step. Each sequential step has an expected LPG condition, and guidelines with threshold values are displayed in both the simulation and monitoring systems of the vessel. All simulated data, parameters, and logic were validated and verified during the commissioning period of the gas trial on an LPG dual-fuel (DF) carrier. The simulated sequence, as well as the validation and verification during the gas trial, demonstrated that the initial LPG filling sequence can be a reliable tool for the commissioning of the LFSS. Further, the sequence will potentially reduce the risk of system misoperation by commissioning engineers and seafarers after the delivery of the ships.