Lloyd’s Register (LR), Carnival UK and Carnival Cruise Line have successfully completed Europe’s first major LNG dry-dock projects for large passenger vessels, marking a key milestone in the cruise sector’s transition toward lower-carbon propulsion and setting new operational benchmarks for LNG-powered ships.
As LNG-fuelled cruise vessels mature, early adopters are now entering a critical lifecycle phase. Specifically, they must complete renewal surveys and dry-docking campaigns that involve systems far more complex than those found on conventionally fuelled ships. Against this backdrop, the renewal surveys and dry-docks of Iona and Mardi Gras represent a significant step forward for LNG operations in passenger shipping.
A new phase for LNG cruise vessels
The projects marked the first major LNG dry-docks for large passenger ships in Europe. Early and continuous involvement from LR’s Cruise Ship Centre of Expertise played a central role, ensuring technical alignment, structured planning and coordinated surveys across multiple locations.
Moreover, the work followed more than a year of joint preparation, combining technical reviews, risk assessments and operational planning. As a result, the experience has already begun to shape future thinking around alternative-fuel ship design, maintenance planning and survey execution.
Why LNG dry-docking is different
Dry-docking an LNG-powered cruise ship presents distinct challenges. Cruise vessels typically spend limited time out of service, which significantly narrows the window available for LNG system maintenance. Consequently, planning must begin far earlier than for conventional refits.
To address this, teams aligned survey schedules, secured specialist availability well in advance and planned spare parts procurement with lead times extending up to a year for critical components such as LNG pumps. In parallel, LNG systems had to be prepared for immediate post-drydock bunkering, adding further complexity.
Extensive collaboration supported this effort. Ship visits, workshops and technical sessions across several locations helped build a shared understanding of system conditions, survey scope and operational constraints.
Managing complex LNG systems
Both vessels feature three LNG fuel tanks, dual fuel trains and fully redundant systems supported by advanced control logic and extensive cryogenic piping. Managing inspection, testing and recommissioning within tight schedules required close coordination between shipboard crews, technical teams and attending surveyors.
Detailed inspection and test plans were developed well ahead of the dry-docks. These plans covered every component, down to individual valves, ensuring no task was left to chance once the vessels entered dock.
Vessel-specific operational challenges
Each ship introduced unique constraints that shaped the survey strategy. For Iona, regular operations in Norwegian fjords meant continuous LNG availability was essential to maintain emissions compliance, leaving little room for extended system downtime.
Meanwhile, Mardi Gras faced a different challenge. Its transit from Cape Canaveral to Marseille exceeded the vessel’s Safe Return to Port radius, which required one LNG tank and propulsion line to remain fully operational throughout the voyage. Survey activities therefore had to follow a staged and carefully isolated sequence.
Surveys conducted during passenger operations
Not all inspections could wait for dry-dock. LNG tank inspections and fuel system tests also took place while the ships were in service and carrying passengers. These operations demanded precise coordination, detailed isolation and venting procedures, and strict safety controls.
Across multiple voyages, dry-docks and commissioning runs, inspections were completed safely and on schedule. Support from survey teams across several regions proved critical to maintaining continuity and consistency.
Shaping future alternative-fuel practices
Beyond meeting regulatory requirements, these renewal surveys helped refine LNG maintenance strategies across the fleet. Structured planning reduced disruption and established a more predictable framework for future dry-docking cycles.
Importantly, the experience is already influencing broader industry practices. Early risk modelling, long-lead spare planning, multi-location survey coordination and in-service inspections are likely to become standard features as fleets expand and adopt fuels such as methanol, biofuels and future synthetics.
What comes next
The dry-docks of Iona and Mardi Gras demonstrate the value of early collaboration, data-driven planning and integrated expertise. They also highlight how complex alternative-fuel vessels can be maintained safely without compromising operational demands.
As LNG-powered cruise fleets continue to grow and age, these projects provide a practical blueprint for future maintenance, survey and assurance strategies across the global cruise industry.
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Source: Lloyd’s Register
