This exercise takes place during the final stages of the LNG loading operation. The user is given a starting point that is close to the completion of the loading process. The objective is to reduce the flow rate from the shore, a process known as ramp-down. The flow rate is reduced in steps of 1,000 m³ per hour until the total flow decreases from 10,000 m³ per hour to 0.
During the loading operation, the following instructions must be implemented or taken into account:
The loading of LNG cargo must be carried out in a sequence to satisfy the following:
- The cargo tanks are filled simultaneously at a uniform rate. Each tank filling valve should be adjusted to maintain even distribution;
- The cargo tanks are to be topped off at the fill heights given by the loading tables as much close to (99.2%) full by volume, measured after necessary adjustments to the temperature of the cargo have been completed. Attention should be given to the last tank to complete. Sufficient space shall be provided to allow drain of lines/ arms to the tank. Space/ quantity required shall be provided from the terminal;
- During topping off, the ship should be kept on an even keel;
- During loading, the ship may be trimmed in accordance with the terminal’s maximum draught, in order to assist in emptying the ballast tanks;
- The structural loading and stability, as determined by the loading computer, must remain within safe limits.
Normally when loading the cargo, vapour is returned to the terminal by means of the HD compressors or shore compressor. The pressure in the ship’s vapor header is maintained by adjusting the compressor flow;
The cargo tanks must be maintained in conjunction with the vapor header on deck, with the vapor valve on each tank dome open.
Exercise Overview:
- Key Objectives:
- The user must maintain the staggered filling of the tanks and complete each tank one by one, achieving the required levels specified in the exercise.
- Throughout the process, the user is required to correctly operate the loading valves to ensure that the tanks are filled in a staggered manner.
- The user must monitor and verify that there is no excess buildup in the loading line and that the tank pressures are maintained within the required range.
- Assessment Process:
- The assessment begins as soon as the exercise starts, with the user reducing the flow rate step by step.
- As the flow rate is ramped down, the user must maintain proper staggering between the tanks and ensure that each tank reaches the required level.
- The user should also ensure that no alarms are triggered, and that tank pressures remain within the specified range.
- Completion Criteria:
- The exercise is considered complete when the flow rate reaches 0, and all tanks have been correctly topped off without triggering any alarms.
- The user is evaluated based on their ability to correctly manage the flow rate, maintain staggered filling, and respond to any issues that arise during the exercise.
- Evaluation:
- The final assessment is based on the user’s ability to handle the operation smoothly and respond to various remarks, Cautions, and alarms during the course of the exercise.
