LEG carrier
File:Neptun werft.jpg in 2009]]
Liquefied ethylene gas (LEG) carriers are a type of gas carrier, a ship designed to transport ethylene at sea.{{cite web | title=Ethylene carriers – second to none | website=Riviera | url=https://www.rivieramm.com/news-content-hub/news-content-hub/ethylene-carriers--second-to-none-52328#:~:text=Liquefied%20ethylene%20gas%20carriers%20(LEGCs,with%20pressure%20vessel%20cargo%20tanks. | language=br | access-date=2025-05-26}}{{cite book | title=UK P&I Club, Carefully to Carry, 2023 | publisher=Witherby Publishing Group |date=2023 | isbn=978-1-914993-12-1 | page=247-258}} Most LEG ships are considered small compared to other gas carriers (typically {{cvt|2000|to|15000|m3|disp=comma}}) although there are larger LEG ships that have the hybrid capability of carrying liquid natural gas (LNG) and/or liquefied petroleum gas (LPG) as well.{{cite book | last=Stopford | first=Martin | title=Maritime Economics | publisher=Routledge | date=2013-04-15 | isbn=978-1-134-74266-0 | page=}}
History
Gas carriage
LEG carriers are build with a cargo containment system to handle ethylene with a boiling point of {{cvt|-104|C|F}}. Ethylene is transported at sea for industrial purposes as it is one of the main feedstocks for the petrochemical industry. The low temperature requires fully refrigerated ships with the cargo at atmospheric pressure or semi-pressurised/fully refrigerated (semi-ref) ships with pressure vessel cargo tanks. Semi-refrigerated LEG carriers use special alloyed steels to allow the carriage of ethylene at -104°C.{{cite web | title=Gas carrier types | website=Wartsila.com | date=2016-03-07 | url=https://www.wartsila.com/encyclopedia/term/gas-carrier-types | access-date=2025-05-26}} Tanks must be kept in clean and well maintained condition as product purity is important in carriage onboard.{{cite book | last=House | first=David | title=Cargo Work | publisher=Routledge | date=2006-08-11 | isbn=978-1-136-42286-7 | page=176}} Cargo operations on these ships are carried out with a view to avoiding impurities affecting the cargo and in ensuring cargoes are carried at atmospheric pressure.
Design and equipment
The design and construction of LEG carriers operating internationally is regulated by the International Maritime Organization through the International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk.{{cite book | title=LNG shipping knowledge: underpinning Knowledge to the SIGTTO Standards | publisher=Witherby Publishing Group | publication-place=Livingston | date=2020 | isbn=978-1-85609-903-5 | page=15}} LEG ships are fitted with a re-liquefaction plant for ethylene.{{cite web | author=Trade press release | title=Two LEG Carriers built by Sinopacific with Wärtsilä solutions onboard are named | website=Wartsila.com | date=2018-03-28 | url=https://www.wartsila.com/media/news/28-03-2018-two-leg-carriers-built-by-sinopacific-with-wartsila-solutions-onboard-are-named-2147818 | access-date=2025-05-26}} Some ships also have the capability for ethane, and LPG, as well as for various petrochemical cargoes. A pressure swing adsorption (PSA) plant is sometimes used to separate some gases from a mixture of gases under pressure on LEG carriers.{{cite web | title=ECO STAR 36K Liquefied Ethylene Gas Carrier | website=Ship Technology | date=2017-07-06 | url=https://www.ship-technology.com/projects/eco-star-36k-liquefied-ethylene-gas-carrier/ | access-date=2025-05-26}} Most ships utilise a number of compressors onboard.
Some new LEG carriers are being built with dual fuel capability, including the use of LNG alongside existing marine gas oil (MGO) to reduce carbon dioxide emissions.{{cite web | last=Bahtić | first=Fatima | title=Hartmann welcomes new LNG-powered LEG carrier (Gallery) | website=Offshore Energy | date=2024-07-22 | url=https://www.offshore-energy.biz/hartmann-welcomes-new-lng-powered-leg-carrier-gallery/ | access-date=2025-05-26}}{{cite web | last=Maritime | first=Baird | title=Hartmann Group Receives Final Ethylene Carrier from CIMC SOE | website=Baird Maritime / Work Boat World | date=2024-09-23 | url=https://www.bairdmaritime.com/shipping/gas/hartmann-takes-delivery-of-third-ethylene-carrier-in-series | access-date=2025-05-26}}