LNG Custody Transfer - Marine

The practice of transferring LNG between marine vessels is growing rapidly, even more so than traditional transfers between LNG carriers and land-based terminals. The use of Floating Storage Regasification Units (FSRUs) in place of traditional LNG to natural gas conversion onshore is increasing. In addition to the increased prevalence of FSRUs is the growing demand for LNG bunkering vessels, which provide LNG fuel to a ship for its own consumption.


The growth in ship-to-ship LNG transfers brings great demand for accurate LNG sampling and highlights significant challenges including:

  • The use of flexible hoses creates a low-pressure environment when transferring LNG between vessels, so the sampling system must be able to sample LNG at these low pressures without causing LNG fractionation. This is a common problem affecting older LNG sampling solutions that are specialised only for land-based applications
  • It is imperative that methane and natural gas do not escape to the atmosphere during the sampling process
  • Sampling systems must be built to comply with demanding marine vessel structural requirements
  • With space at a premium, the sampling system must be of a small form factor
  • The system must withstand highly corrosive environments
  • Full remote access and support and diagnostics must be available, regardless of the vessel’s location


Synertec’s Custody Transfer System (CTS) is one of the only systems in the world that can sample LNG at the low pressures that are commonly found in ship-to-ship transfer. Our unique design ensures that LNG fractionation does not occur, even in LNG that is not sub-cooled. Our system can achieve this without the loss of any gas during the process, which is vitally important.


All our systems are built bespoke for our customers. This ensures that the vessel’s structural integrity is preserved, the CTS footprint is minimised, compliance with hazardous area requirements is achieved, interfaces to ship services such as air and power are considered, and the system complies with lifting agreements in place.


Synertec’s CTS can be monitored and controlled as a standalone system or can be fully integrated into the ship’s Integrated Automation System (IAS).


Our best-in-class LNG CTS achieves the highest accuracy possible in marine-based LNG transfer and we provide a broad range of LNG sampling services.


Our systems can be built for all LNG transfer applications including:

  • LNG Export Terminals
  • LNG Import Terminals
  • Floating Storage Regasification Units (FSRUs)
  • Floating Storage Units (FSUs)
  • Floating Liquefied Natural Gas (FLNG) facilities
  • LNG Bunkering Vessels
  • LNG Truck Loading


Our designs and builds are certified to CE European Standard requirements, and all major ship classifications including Det Norske Veritas (DNV), American Bureau of Shipping (ABS), Bureau Veritas (BV) and Lloyd’s Register (LR).