Four week retrofit for feeder container vessel to sail on ammonia

Lloyd’s Register, Seaspan, and Technolog outline conversion pathway for ammonia-ready vessel design

Click to learn more about the feeder vessel design, which can be converted from LNG to ammonia fuel use in four weeks of dry dock. Source: Lloyd’s Register.

The next-generation “feeder” vessel developed by Seaspan and Technolog is designed for a capacity of 3,370 TEU, powered by a two-stroke, dual-fuel LNG engine able to be converted to run on ammonia fuel. The LNG version of the feeder vessel was granted AiP in early 2024, followed by AiP for the ammonia-fueled version in September 2024. Seaspan and Technolog had modified the LNG design, allowing for a “transition to ammonia during its operational life cycle”. A new case study published by Lloyd’s Register now outlines the conversion pathway for the vessel, comprising four weeks in dry dock.

Container vessels in the “feeder” size play an important role in global trade networks, particularly as ocean-going container vessels increase in capacity – and are not able to be accommodated at all ports. Most of the current feeder fleet that connects large container hubs with smaller ports is well through its lifespan, with obvious emissions considerations and limited dry-dock availability for maintenance and retrofits.

New vessels need to have a degree of flexibility in their designs, be future-proofed, and be able to operate in a variety of locations. Designs also need to incorporate a baseline level of energy efficiency and optimized propulsion capabilities, not unique to the use of ammonia fuel. Seaspan and Technolog’s design aims to meet these challenges, operating on LNG to begin with, but able to be quickly retrofitted once ammonia fuel becomes available:

Its ammonia-prepared configuration enables conversion during a four-week dry-docking period. The containment system can be adapted through specialised tank coating or materials suited to both LNG and ammonia. Double-walled piping installed at build supports both fuels with limited modification, and the two-stroke dual-fuel LNG engine forms the basis for later conversion.

The design also reflects operating conditions common to regional feeder routes. A forward wheelhouse improves visibility and creates additional cargo capacity, while the aft deckhouse supports compact machinery integration. Power management is strengthened through a 1 MW battery used for peak shaving and bow-thruster support. Propulsion efficiency comes from the gate-rudder arrangement, with further gains available from an optional telescopic Flettner rotor sail. PTO, PTI and PTH functions support lower fuel use and reduced maintenance exposure across coastal and variable-load operations.

LNG-to-ammonia operations onboard the feeder vessel design, from “Next-Generation Feeder Development: A Future-Ready Design Pathway” (Lloyd’s Register, Apr 2026)

Fuel arrangements onboard the vessel provide for an approximate range of 5,000 nautical miles on heavy fuel oil or ammonia, and around 9,000 nautical miles on LNG.