The next generation of LNG bunkering ships

Representing just 1.5% of the global LNG carrier fleet, bunkering ships are a still-maturing segment. However, demand for LNG-fueled ships – which have more than doubled in number since 2012 – has brought into focus the growing need for corresponding bunkering ships.

With the delivery of MOL’s Gas Agility, the maritime industry is getting a first look at a potential future for bunkering ships. This includes new containment systems, improved onboard technology and greater cargo capacity than previously seen.

A one-of-a-kind LNG bunkering ship

Measuring 135 meters long and with 18,600 m³ storage capacity, the Gas Agility is the world’s largest LNG bunkering ship. It more than doubles its forerunners’ capacity (5-8,000 m³), enabling less frequent refilling. The Gas Agility shows how future bunkering ships could prioritize vessel and tank size, providing LNG to greater numbers of ships, while taking fewer reloading trips to import or export terminals.

The Gas Agility is equipped with GTT’s Mark III Flex membrane containment system to keep LNG at atmospheric pressure. Pressure for a standard bunkering ship with an atmospheric tank cannot rise above 0.7 Pa without the need to release vapors (this being against international regulations).

However, the Gas Agility’s membrane technology, combined with boil-off gas management and LNG subcooling system, ensures that optimal levels of temperature and pressure are maintained. This allows the ship to deliver a maximum amount of cargo at the lowest possible temperature.

The Gas Agility is further equipped with a dual-fuel diesel-electric propulsion system, a first for LNG bunkering ships. The dual-fuel generator sets burn boil-off gas from the LNG tanks to produce electricity. This is sent to the ship’s distribution switchboard and feeds the electrical motors connected to the propellers, enabling the ship to limit fuel consumption and emissions. In addition, the azimuthal propellers are designed to enhance ship maneuverability for port operations.

Finally, the transfer systems and cargo pumps installed onboard are designed for maximum efficiency, delivering cargo in less than 12 hours. This is a major benefit for vessels, especially large vessels that would otherwise have to remain in port for longer periods to undergo refueling. As the Gas Agility will supply LNG to CMA CGM’s nine 23,000 TEU containerships, efficient transfer and cargo handling is a key aspect of the bunkering ship’s design.

A complete classification journey

Bureau Veritas accompanied the stakeholders throughout the development of the Gas Agility, providing regulatory and classification expertise from the earliest stages of the project. Our longstanding experience with LNG bunkering ships and gas carriers enabled us to provide guidance for cargo handling, reliquefaction and cooling systems, propulsion and more.

Bureau Veritas provided design approval, survey at yard, and vessel classification, managed statutory certification for SOLAS and MARPOL requirements, and provided an IGC fitness certificate. Notably, in order to de-risk the project, HAZID and HAZOP analysis were conducted for the LNG transfer system, defining safety zones in port areas where transfer operations can occur.

As LNG bunkering ships evolve to encompass a wider variety of designs and operations, classification societies will need to continue upping their expertise. No particular model of bunkering ships has yet emerged as the next evolution, but the Gas Agility shows the kinds of changes the maritime industry should prepare for.