A new purpose for gas carriers

As the LNG market has grown, the number of gas carriers providing LNG transportation and distribution has risen in parallel. However, recent years have seen increased numbers of laid-up ships, leading owners to repurpose their vessels and extend their lifecycle by converting them to FSRUs and FSUs.

Unique challenges for FSRU and FSU conversion

Regulatory questions at both flag state and class levels are a major consideration for FSRU/FSU conversions. Depending on the intended modifications, project specifications and conversion work, different systems may be decommissioned, removed, modified or added. Project developers must account for all statutory and classification concerns, including regulations like SOLAS, MARPOL and the IGC Code, which ensure that units comply with safety and environmental requirements. Coastal state and local port authorities may also need to be consulted, and their requirements taken into consideration.

Technical challenges also abound. Gas carriers may have their power generation systems (e.g. boilers, generators), power distribution, propulsion, LNG cargo tanks, cargo handling system, cargo control system, mooring system, handling cranes and more modified. Owners looking to remove certain systems need to evaluate how to do so safely, and under what conditions. From reviewing structural elements, to upgrading cargo containment systems, to adding new equipment, the list of technical challenges is considerable for FSRUs and FSUs.

Another key question is how to keep a vessel on location for an extended period of time, potentially exceeding the typical 5-year dry-docking regime. Project developers frequently seek a “no-dry dock” approach, which has implications for conversion work on hull structure and equipment.

Finally, there is the question of cost, as owners seek to limit the price of on-site maintenance and minimize OPEX for their vessel’s extended lifecycle. 

Where class societies come in

Classification societies can perform a range of analyses for gas carrier hull structures, cargo tanks, machinery, mooring systems and more. Evaluation of hydrodynamics, design loads and scantling data, as well as structural assessments, offer owners a clear picture of their vessel’s condition, and allow class societies to assist in developing a full inspection program.

Bureau Veritas has long-standing experience in FSRU and FSU conversion, providing dedicated Guidelines for LNG Conversion to FSRU/FSUs (NI 655). Our guidance note addresses the scope of survey for conversion work, and includes the development of an in-service inspection program. Bureau Veritas’ regulatory and technical experts can address the class and design elements of FSRU and FSU conversion, keeping the process safe and ensuring a compliant asset.