LNG as a fuel is now used by a wide range of vessels, but this growth requires standardisation across the LNG bunker vessel industry
Since 2017, the global fleet of LNG bunker vessels has more than tripled in size to meet the demand for LNG as a marine fuel, growing to 31 vessels in operation globally and another 20 under construction. While the availability of LNG as fuel no longer suffers from the “chicken and egg” dilemma, safety, standards and regulation for bunkering different types of vessels need to continue to evolve as the LNG-fuelled fleet continues to grow.
Following the implementation of the IMO 2020 0.50% sulphur cap, there are 199 LNG-fuelled vessels operating and another 295 on order at shipyards – driven most recently by a strong uptake in the last two years in the container ship and crude oil tanker sectors. This is a distinct difference from the first movers in the LNG as fuel market, which was dominated by passenger car ferries and offshore support vessels (OSVs). Large, oceangoing ships offer different refuelling challenges and complexity, requiring a different breed of LNG bunkering vessel.
Speaking at Riviera Maritime Media’s LNG bunker vessels: safety, standards and regulation webinar held in April, TGE Marine LNG-to-power and bunker vessels specialist Johannes Dziuba said the LNG bunkering market has evolved since its earliest days, with initial operations being conducted using tanker trucks, small-scale LNG carriers and converted vessels. A pioneer in the LNG bunkering sector and sponsor of the webinar, TGE Marine designs and produces cargo-handling systems and cargo tanks for gas carriers and offshore units.
One of the earliest bunker vessels (pre-2017) was Seagas – converted from an existing small ferry – to serve the bunkering needs of Viking Line’s LNG-fuelled cruise ferry Viking Grace.
By contrast, post-2017, a new generation of purpose-built LNG bunker vessels has emerged, growing in sophistication and capacity, positioned in “bunkering hotspots” in Europe, Singapore, China, Japan and the US, pointed out Mr Dziuba. Among these are 6,500-m3 Cardissa and 5,800-m3 Coralius, both stationed in Europe and fitted with cargo-handling, cargo tanks and LNG fuel supply systems from TGE Marine.
Singapore’s first LNG bunkering vessel, the 7,500-m3 FueLNG Bellina, has a transfer rate of between 100 and 1,000 m3 of LNG per hour, and can reach bunker manifolds 23 m above the water level, allowing it to serve a wide range of LNG-fuelled vessels in port.
In his presentation Mr Dziuba highlighted how the type of LNG-fuelled vessel impacts bunkering operations, including the LNG volumes and the rate of refuelling. Bunkering rates vary widely based on vessel size and fuel tank type – IMO Type C or membrane containment systems, for example. “This means that the pressure you are bunkering at will be different, the operation time will be different, and the manifold size, arrangement and location may be different,” he said.
“Standardisation will bring us closer to a very simple bunker vessel”
Mr Dziuba gave various examples of LNG volumes, tank types, bunker times, bunker rates, bunker connections, bunker manifold heights and bunker station locations that could be encountered during a ship-to-ship transfer (STS) operations.
Bunker rates, for example, could be 25 to 200 m3/hr for a coastal vessel, but as high as 1,500 m3/hr for an ultra-large container ship (ULCS). Bunker manifold heights could be about 4 m above the waterline for the smaller vessel, to 8 m above the waterline for the large box ship. Bunker station locations can vary widely, too, positioned about 50 m from the stern to midships to a quarter of a ship’s length.
“This is what the industry has struggled a little bit with,” noted Mr Dziuba. “To get the rules and standards [in line] for these different equipment and interfaces – such as ESD links, custody transfer systems, manifold arrangements, and transfer systems from different suppliers. We see that this alignment is taking place, but it still needs some modification,” he said. “And now we see also different kinds of fuels, or alternative fuels, entering the market. And this might change the whole picture again if we talk, for example, about ammonia or hydrogen.”
With years of lessons learned and thousands of STS transfers performed, Mr Dziuba believes the industry’s valuable operational experience needs to be incorporated into standards and rules. “Standardisation will bring us closer to a very simple bunker vessel which is cheaper to build and easier to operate, to enhance this movement of alternative fuels,” he said.
A poll conducted during the webinar suggested that the industry’s preferred alternative fuel choice in 30 years would be LNG. Results showed 42% of respondents chose LNG as the alternative fuel of choice, followed by ammonia (26%), hydrogen (24%), scrubbers (5%) and other (5%).
ESD links and safety
Since Methane Princess set sail in 1964, safety has always been a key concern when transporting and transferring LNG. This is no different in LNG bunkering. A vital component in the safe control of the LNG transfer process is the use of linked emergency shutdown (ESD) systems. These systems provide safe, timely and mutual shutdown of both the ship and shore transfer processes; in order to do this, these two processes must be interlinked, explained Trelleborg Marine Systems UK technical director Andrew Stafford, who joined Mr Dziuba on the panel.
Mr Stafford said that in 2019, the Society for Gas as a Marine Fuel (SGMF) published the ESD guidance document, detailing the monitoring and control of ESD systems. It covers SSL in large scale, and now bunker safety link (BSL) in bunkering. The guidance takes into account the requirements of the IGF code, and ISO 20519, as well as best practices for the three main types of links, based on their capabilities.
Type 1 BSL is a pneumatic link, with ESD only; Type 2 BSL is electric (SIGTTO link) with ESD only; and Type 3 BSL has fibre optic ESD, telecoms, and data.
Mr Stafford said Type 2 systems were “perfectly suited” for bunkering applications because they provide “fast and reliable ESD signaling.” However, he said connecting different ships or different terminals can prove troublesome: “It’s very difficult to set up an ESD to trip within a suitable time frame.”
ESD-only electric and pneumatic links – as in the case of Type 1 and Type 2 BSL links – are satisfactory for many users, while others might prefer the advantages offered by Type 3 BSL. These advantages include a digital fibre-optic link to carry telecommunications and process data to help inform operators on both ship and shore sides of the status of the bunkering operation.
“It is especially important for ship-to-ship transfer that the master relay is available on at least one side of the link,” said Mr Stafford. “Traditionally the master is the shore system. In new transfer markets, it is recommended that at least the LNG bunkering source has the capability to perform master functions,” he added.
Concluded Mr Stafford: “Not all operators will choose to install the full features of a Type 3 system. It is more important that they fully consider the safety of their assets, than solely the systems appropriate for their application. We’re all doing what we can to ensure this industry develops … as safely as possible.”