The inerting of cargo tanks is carried out once the LNG vapor inside the tanks has been warmed up. The process involves replacing the LNG vapor with inert gas, preparing the vessel for the upcoming dry dock. The primary goal is to remove the flammable LNG vapor from the tanks and make them safe for entry and inspection.

The exercise uses the inert gas generator onboard both vessels. The inert gas, being heavier, is introduced into the tanks from the bottom, while the lighter LNG vapor is extracted from the top. This process is known as the displacement of LNG vapor with inert gas.

Exercise Overview:

1. Initial Setup:

• The initial steps involve setting up the equipment, installing the required school pieces, and opening the necessary valves for the correct lineup.
• The ballast pump is used, and the inert gas generator is prepared for operation.

2. Assessment Process:

• The assessment begins when the inert gas generator system is activated, and gas is delivered to the tanks.
• The user must carefully monitor the tank atmosphere and check the samples from the sampling points.
• The objective is to reduce the methane content inside the tanks to less than 2% by volume.

3. Completion Criteria:

• The exercise is complete when all cargo tanks are inerted, and the gas meters indicate the presence of inert gas, with the methane content reduced to the required level.

4. Evaluation:

• The final evaluation is based on the user’s response to various remarks, cautions, and alarms during the exercise, as well as their ability to navigate the procedure efficiently and safely.

Participants will be able to effectively demonstrate the process of inerting cargo tanks on LNG ships using inert gas, understanding safety protocols, operational procedures, and the importance of preventing explosive atmospheres.

Key Components:

1. Understanding Inerting:
   • Explain the purpose of inerting cargo tanks to eliminate the risk of flammable gas mixtures.
   • Identify the dangers associated with the presence of oxygen in cargo tanks and the necessity of maintaining an inert atmosphere.
2. Operational Procedures:
   • Detail the step-by-step process for inerting cargo tanks, including:
     • Preparation and inspection of inert gas supply systems.
     • Connection of hoses and fittings to the cargo tanks.
     • Control of flow rates and pressure during the inerting operation.
3. Monitoring and Verification:
   • Demonstrate the use of oxygen analyzers and pressure gauges to monitor inerting effectiveness.
   • Describe the target oxygen concentration levels and how to confirm they have been achieved.
4. Practical Demonstration:
   • Simulate the inerting 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 inerting cargo tanks.
• Accurate execution of the inerting procedure and effective monitoring.

By achieving this objective, participants will gain the necessary knowledge and skills to safely and efficiently inert cargo tanks on LNG ships, enhancing overall safety and operational integrity.

Inerting pre dry dock-intro and line up

Inerting preparation and starting of IGG in inert gas mode-Pre Dry dock

Inerting pre dry dock- Operation and Assessment

Milestones:

• Learning and Training Phase – Pre-Requisites for the start of operation:

1. Start The Portable Multi Gas Detector And Dew Point Meter.
2. Install The Spool Piece To Connect Inert Gas Line To Liquid Line.
3. Set Cargo Tank Vapour Valves.
4. Set Cargo Tank Liquid Valves.
5. Set The Vapour Line To No. 1 Vent Mast Regulating Valve.
6. Set The Inert Gas Line Valve.
7. Prepare And Start Ballast Pump 2.
8. Prepare Inert Gas Generator In Inert Gas Mode.

• Assessment Phase – Operational flow and Assessment:

9. Start Inert Gas Generator In Inert Gas Mode.
10. Methane Content < 2% By Volume.
11. Maintain Cargo Tanks Pressure Between 5 kPa And 7 kPa.
12. Check The Sampling Point On Vapour Line In All Cargo Tanks.
13. When All Of The Cargo Tanks And Piping Are Inerted, Stop The Supply Of Inert Gas.

Actions During Exercise:

1. Deviation From Exercise:
   • After starting gassing up, the user must not open non-required valves or close required ones. If this occurs, a caution message will appear, instructing the user to undo the action. Failure to correct it will terminate the exercise.
2. Not Maintaining IGG Outlet Flow:
   • During inerting, maintain IGG outlet flow and flow to the atmosphere between 15,500 kg/h and 16,500 kg/h. Failure to do so will trigger a high-priority alarm. If the flow is not corrected within 1 minute, the exercise will terminate.

Alarms & Remarks

Step By Step Procedure

• Learning and Training Phase – Pre-Requisites for the start of operation:

1. Start The Portable Multi Gas Detector And Dew Point Meter

Steps:

• • Navigate to the “MISCELLANEOUS EQUIPMENT” page.
  • Press and hold the power button on the Portable Multi Gas Detector and Dew Point Meter for 5 seconds to start the instruments.
  • Verify both devices are operational to complete this milestone.

2. Install The Spool Piece

• • Connect the spool piece above valve CL701, linking the IGG outlet to the cargo tank’s liquid lines.

3. Set Cargo Tank Vapour Valves

Once these valves are set, the milestone is complete.

4. Set Cargo Tank Liquid Valves

5. Set Vapour Line To No. 1 Vent Mast Regulating Valve

6. Set Inert Gas Line Valve

7. Prepare And Start Ballast Pump 2

Steps:

• • Navigate to the Ballast System or Ballast Water Treatment System page.
  • Ensure at least two generators are operational:
    • Navigate to the “PMS” page and activate another generator.
  • Configure the ballast pump:
    • Open BA010F (15%)
    • Open BA006F
    • Close BA005F (if open)
    • Open BA026F
  • Start the ballast pump to complete this milestone.

8. Prepare Inert Gas Generator In Inert Gas Mode

Steps:

• • Set Generator Mode to “Inert Gas”.
  • Adjust Operating Percentage to “100%”.
  • Turn Fuel Pump to “On”.
  • Activate IG Chiller Unit.

• Assessment Phase – Operational flow and Assessment:

9. Start Inert Gas Generator In Inert Gas Mode

Steps:

• • Wait for the IG chiller outlet temperature to drop to 3°C or below.
  • Click “Start” on the IGG system to initiate inert gas production.
  • Ensure the oxygen analyzer shows <2% oxygen before starting delivery.

10. Cargo Tank Dew Point < -40°C

• • Use the Dew Point Meter to confirm the dew point is below -40°C.

11. Cargo Tank Methane Content < 2%

• • Use the Portable Multi Gas Detector to confirm methane content is <2% by volume.

12. Maintain Cargo Tanks Pressure Between 5 kPa And 7 kPa

• • Regulate the vent mast valves to maintain pressure within the specified range.

13. Check Sampling Points

• • Verify vapor line sampling points for the following:
    • CH₄: 0% LEL
    • O₂: 1% vol
    • CO: 100 ppm
    • CO₂: 14% vol
    • Dew Point: -45°C

14. Stop Inert Gas Supply

• • Once all tanks achieve a dew point of -45°C, stop the IGG delivery.
  • Close CG702 to finalize the operation.
  • A confirmation remark will indicate completion.

Proper line up for inerting: