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:

1. 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.

2. 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.

3. 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.

4. 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.

Participants will be able to effectively demonstrate the process of topping off cargo tanks on LNG ships, understanding the necessary safety protocols, operational procedures, and the significance of accurate loading to prevent overfilling and ensure safe operations.

Key Components:

Understanding Topping Off:

• Explain the purpose of topping off cargo tanks and its role in achieving optimal loading levels.
• Identify the importance of monitoring liquid levels to prevent overfilling and ensure safety.

Operational Procedures:
Detail the step-by-step process for topping off cargo tanks, including:

• Assessing the current liquid level in the cargo tanks.
• Carefully controlling the flow rate and monitoring liquid levels throughout the process.

Explain the significance of maintaining vapor space and pressure balance during topping off.

Monitoring and Verification:

• Demonstrate the use of level gauges and monitoring systems to accurately track liquid levels during topping off.
• Describe how to confirm that the tanks are filled to the correct levels without exceeding capacity.

Practical Demonstration:

• Simulate the topping-off process in a controlled environment or through hands-on training exercises.
• Role-play scenarios to address potential challenges or deviations from the procedure.

Assessment Criteria:
• Ability to articulate the significance of the topping-off process for LNG cargo tanks.
• Accurate execution of the topping-off procedure and effective monitoring.

By achieving this objective, participants will gain the knowledge and skills necessary for safely and efficiently topping off cargo tanks on LNG ships, ensuring successful and secure LNG operations.

Loading Ramp down and Topping off- Operational Assessment

Milestones:

• Assessment Phase – Operational flow and Assessment:

1. All Tank Levels Achieved
   • 1.A Tank 1 required level achieved.
   • 1.B Tank 2 required level achieved.
   • 1.C Tank 3 required level achieved.
   • 1.D Tank 4 required level achieved.
2. Loading Completed
3. Double Shut Valves on Liquid Lines Closed
4. ESD Set to Blocking Mode
5. Line Draining Completed
6. Closing Custody Transfer Print-Out for Official Tank Gauging

Required Valves and Criteria:

• No Need to Open Any Valves during this exercise.

Actions During Exercise:

Deviation from Exercise:

After starting or resuming the loading, the user should not open any non-required valves or close any required valves. If this happens, a caution message will appear, instructing the user to undo the previous action. If the user fails to correct the action, the exercise will be terminated.

High Crossover Pressure:

• If the crossover pressure reaches 4.5 bar, the user will be warned to increase the filling valve openings.
• If the pressure reaches 5 bar, the exercise will be terminated.

High Pressure in Manifolds:

• If the instantaneous rate of a tank reaches 4000 m³/h, the user will be warned to increase the filling valve openings.
• If the instantaneous rate reaches 5000 m³/h, the exercise will be terminated.

Alarms & Remarks

Step By Step Procedure

• Assessment Phase – Operational flow and Assessment:

Starting Ramp Down:

• • The exercise starts with a ship rate of 10,000 m³/h and a total tank volume of 168,447.2 m³. When the total volume reaches 173,347 m³, ramp-down will commence, and different loading rates will become available to the user.

Tank Levels (CT1 – CT4)

CT1 Tank Levels:

• • 95% of Max Volume (25,543.8 m³): Low-priority alarm indicating the tank is nearing high volume.
  • 98% of Max Volume (26,350.5 m³): Low-priority alarm indicating the tank is nearing high-high volume.
  • 99.2% – 500 m³ (26,673.2 m³): High-priority alarm prompting the user to adjust the filling valve.
  • 99.2% – 50 m³ (26623.2m³) or higher: Required level achieved.

CT2 Tank Levels:

• • 95% of Max Volume (48,574.9 m³): Low-priority alarm indicating the tank is nearing high volume.
  • 98% of Max Volume (50,108.8 m³): Low-priority alarm indicating the tank is nearing high-high volume.
  • 99.2% – 500 m³ (50,222.4 m³): High-priority alarm prompting the user to adjust the filling valve.
  • 99.2% – 50 m³ (50672.4 m³) or higher: Required level achieved.

CT3 Tank Levels:

• • 95% of Max Volume (48,580.2 m³): Low-priority alarm indicating the tank is nearing high volume.
  • 98% of Max Volume (50,114.3 m³): Low-priority alarm indicating the tank is nearing high-high volume.
  • 99.2% – 500 m³ (50,227.9 m³): High-priority alarm prompting the user to adjust the filling valve.
  • 99.2% – 110 m³ (50617.9 m³) or higher: Required level achieved.

CT4 Tank Levels:

• • 95% of Max Volume (48,576.3 m³): Low-priority alarm indicating the tank is nearing high volume.
  • 98% of Max Volume (50,110.3 m³): Low-priority alarm indicating the tank is nearing high-high volume.
  • 99.2% – 500 m³ (50,223.9 m³): High-priority alarm prompting the user to adjust the filling valve.
  • 99.2% – 50 m³ (50673.9m³) or higher: Required level achieved.

Stop Loading Process:

• • When the current ship rate is 1000 m³/h, the “Stop Loading” button will become available. The user can stop the loading process by clicking this button once the required tank levels are achieved.

Closing Double Shut Valves:

• • After stopping the loading, the user must close the double shut valves.

ESD Set to Blocking Mode:

• • After closing the double shut valves, the user must set the ESD system to blocking mode. Navigate to the ESD Systems page under the ESD tab to do this.

Line Draining:

• • After setting the ESD to blocking mode, the user will be prompted to open the return valve of Cargo Tank 3. Once opened, 60 m³ of cargo will drain into Cargo Tank 3.

Closing Custody Transfer Print-Out:

• • After line draining is complete, the user can close the CTS Report and Setup by navigating to the CTS Main page. This will complete the exercise.