This operation is carried out onboard an LNG carrier after the cargo tanks have been successfully cooled to the required -130°C. During this operation, liquid LNG is supplied from the shore and directed from the spray lines to the main cargo line (liquid header). The objective is to achieve the required temperature of -100°C in the liquid lines so that the loading operation can commence.
The purpose of cooling down cargo lines is to avoid thermal shock on the piping and associated valves which would occur if no gradual cooling was employed. Therefore, prior to loading LNG into the cargo tanks, the cargo liquid lines, crossovers and cargo filling lines must be cooled down to cryogenic temperatures and this can be undertaken with LNG supplied from the vessel’s cargo tanks.
Exercise Overview:
- Initial Setup:
- The exercise begins with the necessary preparations, including:
- Opening the required valves.
- Connecting the manifold arms.
- Lining up the correct valves to direct the LNG into the liquid header.
- Assessment Process:
- The assessment begins once the lineup is complete, and the LNG liquid is started from the shore.
- During the assessment, the user must continuously monitor:
- The drop in temperature of the liquid lines.
- The rise in pressure within the cargo lines.
- The user must open and close the valves correctly throughout the process while ensuring safety is maintained at all times.
- Completion Criteria:
- The exercise is considered complete when the liquid header temperature reaches -120°C.
- At this point, the user must operate certain valves to complete the procedure.
- Evaluation:
- The user is assessed based on their ability to respond to various remarks, alarms, and cautions during the course of the exercise.
