MGH Completes Ship Handling and Mooring Simulations

MGH Completes Ship Handling and Mooring Simulations

Over the past year, the Murchison Green Hydrogen (MGH) Project has completed a series of detailed ship handling and mooring simulations at the Fremantle Marine Simulation Centre (FMSC).

Using real vessel models, local wind and wave conditions, and expert input from pilots and tug masters, these simulations tested how ships would safely approach and connect to the Project’s marine offshore infrastructure. The work assessed different offshore distances and sea states to understand how vessels behave during normal operations and in emergency scenarios.

The results confirmed the importance of placing the CALM buoy far enough offshore to provide safe manoeuvring room, reliable tug access, and sufficient time for intervention during challenging weather and emergency situations. This simulation program has been essential in selecting a location that protects both vessel safety and the local coastline, ensuring that ship movements can be carried out confidently under a wide range of real-world conditions.

Ship Handling and Mooring Simulations

The ship handling and mooring simulations took place at the FMSC in consultation with the Mid West Port Authority’s (MWPA) marine team and MGH’s Technical Director.

What is the Fremantle Marine Simulation Centre?

The FMSC is a cutting-edge facility dedicated to maritime training for pilots, tug masters and ships’ masters. It utilises advanced technology, Simflex Navigator Ship Simulation Software, to recreate realistic ship manoeuvring simulations. This technology produces detailed maritime models and scenarios to reflect real-world conditions.

FMSC’s simulation facilities and services are used across numerous sectors and for various purposes such as port development, maritime training and the development of safety management systems in line with the International Maritime Organisation standards.

You can find out more information about the Centre by visiting the FMSC website.

What was the objective of the simulation?

The simulation was aimed at rigorously testing the approach and mooring of offtake ships, Very Large Ammonia Carriers, at the proposed CALM buoy site. The simulation was run under a range of realistic sea conditions to assess the site’s viability and determine the optimal location of the CALM buoy, and performance requirements of supporting tugs. The program included both routine operations and emergency scenarios.

Each simulation accounted for a variety of sea states and wind directions to provide an accurate understanding of ship and tug handling capabilities in varied conditions.

What is a CALM buoy?

CALM stands for Catenary Anchor Leg Mooring and is an offshore mooring system that is used to load ships in open water. The CALM buoy is a mature, established mooring technology with a long track record of safe use worldwide, and is favoured in lieu of extensive port infrastructure, to minimise construction risk and environmental impacts.

CALM buoys float on the surface of the sea and are held in place by multiple chains and anchors on the seabed. Using this anchoring system a ship can weathervane around the buoy and in so doing, reduce the forces exerted by the ocean and weather conditions on the vessel. CALM buoys commonly facilitate floating hoses which are used for the loading of product onto ships.

What is a Very Large Ammonia Carrier?

Very Large Ammonia Carriers (VLACs) are specialised vessels designed to transport large quantities of ammonia and will be used as the marine offtake ships for the Murchison Green Hydrogen project.

When a VLAC arrives offshore, ammonia will be delivered through an underwater pipeline to a seabed connection point called the Pipeline End Manifold (PLEM). From here, it will flow up through flexible risers to the CALM buoy, and then through strong floating hoses that link the pipeline system to the ship. Once on the vessel, the ammonia will be pumped into large, refrigerated tanks that keep it chilled, allowing it to remain in a stable, liquid state. This cooling process ensures the ammonia is safe to store and transport over long distances to our offtake markets.

How does the simulation work?

The SimFlex software uses advanced algorithms to replicate ship behaviour and environmental conditions in maritime simulations. The simulation process involves a progression from physical scale models to advanced mainframe simulations and then ultimately to a computer-based ship simulation suite such as the one at FMSC.

Custom software is used to evaluate the mooring forces and motions of the marine vessels. These programs provide detailed data on important factors such as fender forces or line tensions. (Fender force refers to the impact that occurs when a vessel collides with another structure, making contact with its fender. Line tension refers to the force exerted on mooring lines, ropes and/or cables securing the marine vessel to a structure.)

A numerical navigator controls the marine vessel in fast-time mode allowing for multiple situational simulations to be run under various scenarios. The software also uses human error as a variable as well so that diverse and realistic simulations can be statistically analysed for informed decision-making and planning.

What was reviewed during the simulation?

During the workshop, participants explored simulated VLAC manoeuvres under a range of swell and wind conditions typical of the marine area. The conditions were chosen carefully to reflect the environmental factors that VLACs might encounter at the proposed site.

1. Simulations under normal conditions

Simulations were conducted to assess normal mooring activities. This included testing the ability of VLACs to approach and moor successfully to the CALM buoy within the navigable area.

2. Simulations under abnormal conditions

Simulations were also conducted to assess activities in abnormal event scenarios, e.g. a rudder malfunction or a loss of vessel power. The simulations in these conditions are designed to evaluate the tug’s capacity to recover the situation and ensure the safety of the vessel and the surrounding environment.

Simulation Outcomes

The outcomes of the simulations are integral for ensuring the safety and operational efficiency of the offshore facilities. On conclusion of the simulations:

• The VLACs successfully completed manoeuvres within the navigable area available at the proposed location under all conditions; and
• The tug boats successfully managed emergencies and moved the VLACs to safety under both normal and abnormal scenarios.

Previous Wave Climate Research

In addition to the ship mooring simulations, the Project has conducted extensive studies to evaluate the local wave climate and determine feasibility of green ammonia export.
The wave height data off the Murchison coast in the area of the proposed offtake facility location was collected in three separate campaigns:

1. Acoustic Wave And Current Profiler (AWAC) measurements of current and wave height from 7 May 2022 to 18 July 2022.
2. AWAC measurements of current and wave height from 7 August 2022 to 20 October 2022.
3. Waverider buoy measurements of wave height and current from 3 December 2023 to 12 December 2024.

Additionally, historical data from the regional hindcast (Centre for Australian Weather and Climate Research, [CAWCR], 1979 to present) and global hindcast (European Centre for Medium-Range Weather Forecasts [ECMWF] fifth generation  [ERA5], 1950 to present) has been statistically analysed against the measured data to ensure alignment in calculations.

What Comes Next

After the successful completion of the mooring simulations, MGH is working with the Mid West Port Authority to finalise the CALM buoy’s location.

More Information

For more information regarding the CALM buoy and the rest of the Project’s Marine Export Facility, read our Offshore Facilities Fact Sheet available on the informational resources page of our website and sign up for our newsletters for regular Project updates.