HD Hyundai Heavy Industries – Engine Machinery Division (HHI-EMD) has received type approval from Lloyd’s Register (LR) for a new ammonia dual-fuel marine engine intended for commercial operation, marking a notable milestone in the development of ammonia propulsion at a multi-megawatt scale.

The approval follows a full type approval test campaign conducted in Korea in September and applies to the H32CDF-LA engine, which delivers a maximum output of 5.4MW. According to LR, this is the first time an ammonia-fuelled engine of this size, designed for real-world maritime use, has successfully completed a classification approval programme.

Moving from research to commercial application

The H32CDF-LA builds on HHI-EMD’s earlier ammonia engine development under its HiMSEN programme. Previous work focused on smaller research engines, including the H22CDF-LA model, which operated in the 1.4–2.2MW range. By contrast, the new engine more than doubles that output, signalling a shift from experimental development toward practical deployment.

Seonghun Lee, Head of Engine Development at HHI-EMD, said: "The H32CDF-LA is an ammonia dual-fuel engine based on the proven H32C diesel platform and equipped with the world's first high-pressure direct-injection ammonia technology introduced in 2024."

The engine operates at 720 rpm and is suitable for both main propulsion and auxiliary generation. Its dual-fuel capability also allows operation on conventional marine fuels, including heavy fuel oil (HFO), providing flexibility while ammonia bunkering infrastructure continues to develop.

Testing and performance verification

Type approval testing was conducted at HHI-EMD’s Ulsan facility under LR supervision and included several days of full-load operation, fuel changeover trials and safety demonstrations. During the campaign, the engine was operated at close to 4,000kW on the testbed, a level LR described as unprecedented for ammonia at this scale.

The test programme aimed to verify not only performance, but also the robustness of fuel containment and safety systems under representative operating conditions.

Safety focus during approval

Given ammonia’s toxicity and corrosive properties, safety assessments formed a central part of the approval process. LR specialists reviewed the ammonia supply system, emergency preparedness measures and personal protective equipment ahead of testing, with particular attention paid to potential leakage points and material compatibility.

LR’s Global Gas Technology Director, Jose Navarro, attended the testing alongside local surveyors and technical specialists. He said the results demonstrated effective containment throughout the programme, "Across three days of continuous testing, we observed no detectable ammonia concentrations, not even inside the annular spaces of the fuel piping systems. This was an outstanding outcome given ammonia's strong odour threshold and the sensitivity of detection equipment in use."

The test site was equipped with emergency showers, eye-wash stations, chemical suits and respiratory protection, and material compatibility assessments were carried out to address ammonia’s interaction with elastomers and certain metals.

Regulatory context and remaining challenges

The type approval confirms that the engine concept meets LR’s current safety and technical requirements for ammonia-fuelled machinery. However, LR noted that broader regulatory frameworks for ammonia propulsion continue to evolve, particularly in areas such as crew training, operational procedures and bunkering infrastructure.

Navarro said wider adoption would depend on continued progress beyond engine technology, "Regulatory adoption and standardisation must continue to evolve. Crew training and operator confidence will require significant investment and the development of dedicated training programmes adapted from ammonia cargo handling expertise."

He added that the availability of green ammonia supply and bunkering networks would be critical, drawing comparisons with the early development of LNG infrastructure.

Positioning ammonia in a multi-fuel future

Fuel choice in shipping is expected to vary by vessel type, trade route and regional availability, rather than converging on a single solution. In that context, ammonia is viewed as one of the few scalable options capable of delivering significant greenhouse gas reductions, provided low-carbon production pathways are available.

While challenges remain, the successful type approval of the H32CDF-LA provides tangible evidence that ammonia engines at commercially relevant power levels can be designed, tested and certified within existing classification frameworks.

Lee said HHI-EMD plans to build on this milestone, "HD Hyundai Heavy Industries will continue to expand its ammonia DF engine portfolio in cooperation with LR, leading the global maritime sector's decarbonisation efforts and driving the transition toward a more sustainable marine environment."