Ship-to-ship ammonia transfer pilot in the Pilbara

To showcase lightering and simulate bunkering operations before ammonia-fuelled vessels are available

• Conduct feasibility, risk and consequence assessment

• Establish emergency response protocols with operators and regulators

• Mobilise assets and conduct trials

• Publish report on methodology and learnings

The findings across all four study areas confirmed that ship-to-ship ammonia transfer at anchorage can be both safe and practicable, provided that recommended safeguards and operational controls are implemented.

Key highlights from the safety studies include:

• Response motions analysis using historical metocean data from August to November 2023 revealed a critical roll motion threshold of four degrees to prevent bridge wing collisions for this particular pair of handysize and midsize gas carriers, when the wave limit was set at 0.88 m and the wave period was between 9 and 11 s.

• Mooring analysis indicated a maximum wind speed of 20 knots and a maximum swell height of 0.3 m for safe operations. Mooring loads were capped at 50% of line mean breaking load (MBL), around 211–265 kiloNewtons (kN) and 3,015 kN for fender systems.

• Risk assessments, including hazard identification (HAZID) and hazard and operability study (HAZOP), revealed no high-level risks. HAZID identified 15 medium and eight low risks, while HAZOP identified eight medium and three low risks. By implementing existing safety measures and introducing additional controls—such as the use of Vessel Separation Detection (VSD) devices, Emergency Release Couplings (ERC), avoiding simultaneous operations (SIMOPS), scheduling fire and spill drills closer to the operation date, and stationing a standby incident response vessel—the probability of medium-level risks was further reduced.

• Computational Fluid Dynamics (CFD) plume dispersion modelling simulated a release of 33 m³ of ammonia, corresponding to four times the volume of the most credible worst-case scenario, under winds from the bow and transverse directions of the vessels. The resulting Acute Exposure Guideline Level 3 (AEGL-3), representing an ammonia concentration of 1,600 parts per million (ppm), showed plume distances ranging from 750 to 1,300 m at variable wind speeds of 1, 5, and 10 metres per second (m/s). These distances remained within the dedicated anchorage boundaries of 1 NM in diameter.

• Emergency response measures were guided by onboard operational procedures and insights from dispersion modelling. The plan included communication protocols with local authorities, a personal protective equipment (PPE) matrix for each operational stage, the appointment of a key incident handler, and verification of onboard spill kits and firefighting systems.