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Types of Liquefied Gas Carriers

MEO Class 4
2nd Mate
Chief Mate
UK Management
MEO Class 2

times asked: 19; times asked
questions: 7; questions
last asked: 2026; last asked

The slides, written out

AI-drawn illustration. Simplified to explain the idea, not to scale.

Slide 1 · TYPES OF

TYPES OF LIQUEFIED GAS CARRIERS Understanding LPG, LNG and Specialized Gas Carrier Designs 5 MAIN CATEGORIES EXPLAINED FULLY PRESSURISED LPG CARRIER MOSS SPHERICAL LNG TANK MEMBRANE LNG CARRIER

Slide 2 · 5 TYPES OF

5 TYPES OF LIQUEFIED GAS CARRIERS Based on cargo type, carriage conditions and containment systems 1 FULLY PRESSURISED (FP) LPG CARRIERS Cargo: LPG, anhydrous ammonia, VCM Type C tanks, 15–22 bar No refrigeration required Small volumes, short-haul trades CYLINDRICAL TANKS PROTRUDING ABOVE DECK 2 SEMI-PRESSURISED / SEMI-REFRIGERATED (SR) LPG / MULTI-GAS CARRIERS Cargo: Propane, butane, ethylene, ethane, ammonia Type C tanks, 4.5–8 bar Temperatures down to −104 °C Medium volumes, port-to-port flexibility INSULATED PRESSURE TANKS FOR MULTI-GAS CARGOES 3 FULLY REFRIGERATED (FR) LPG CARRIERS Cargo: LPG, ammonia Type A prismatic tanks Atmospheric pressure, ~−42 °C Large volumes, long-haul trades PRISMATIC TANKS, FLAT WEATHER DECK 4 LNG CARRIERS Cargo: Methane (natural gas) Fully cryogenic, ~−162 °C Containment: Membrane / Moss Spherical / Type B (SPB) tanks Large volumes: 145,000 to 266,000 m³ (modern range) FULLY CRYOGENIC LNG CARRIAGE & BOG MANAGEMENT 5 CNG CARRIERS (COMPRESSED NATURAL GAS) Cargo: Methane High-pressure storage, typically several hundred bar Niche trade, very limited deployment HIGH-PRESSURE CYLINDERS CARRIED ON DECK

Slide 3 · LNG CONTAINMENT SYSTEMS

LNG CONTAINMENT SYSTEMS COMPARING THE THREE MAIN LNG CARGO TANK TECHNOLOGIES 1 MOSS SPHERICAL TANKS (TYPE B) 2 MEMBRANE TANKS (TYPE B) 3 TYPE B SPB TANKS (PRISMATIC) Independent spherical tanks self-supporting (Type B) Thin membrane supported by insulation and secondary barrier, not self-supporting Self-supporting prismatic tanks made of 9% Ni steel or Aluminium ADVANTAGES Proven design with long operational history Easy access to tank dome for inspection Robust independent Type B containment Simple structural behaviour and well understood ADVANTAGES Best space utilisation – maximises cargo capacity Higher cargo volume for a given hull size Lower centre of gravity – improves stability Flat weather deck – easier operations and cargo handling Excellent thermal performance with multi-layer insulation Industry standard – most widely adopted system ADVANTAGES Flat weather deck Excellent resistance to sloshing pressures Robust self-supporting Type B containment Good operational experience in specific fleets LIMITATIONS Lower cargo efficiency – wasted space around equator Higher centre of gravity compared to membrane More steel weight for same cargo volume Larger deck footprint LIMITATIONS More complex construction and installation Requires high-quality insulation and precise workmanship Dependence on ship's double hull for support LIMITATIONS Higher construction cost than membrane Heavier compared to membrane systems Limited adoption – niche application KEY TAKEAWAY All three systems provide safe and reliable LNG containment. However, membrane tanks are the preferred choice for modern LNG carriers due to superior cargo capacity, lower centre of gravity and operational efficiency.

Slide 4 · WHY MODERN LNG SHIPS PREFER MEMBRANE TANKS

WHY MODERN LNG SHIPS PREFER MEMBRANE TANKS ENGINEERED FOR MAXIMUM EFFICIENCY. BUILT FOR THE FUTURE. MAXIMUM CARGO CAPACITY Conforms to hull shape, eliminating wasted space and delivering the highest cargo capacity for a given hull size. BETTER HULL UTILISATION Membrane tanks fit within the hull envelope, optimising deadweight and revenue potential. LOWER CENTRE OF GRAVITY Cargo is carried lower within the hull, enhancing stability and reducing roll motions. ENHANCED THERMAL PERFORMANCE Multi-layer insulation with advanced materials ensures minimal heat ingress and lower boil-off rates. PROVEN TECHNOLOGY Over 50 years of continuous development and operational experience across thousands of LNG voyages. DOMINANT MODERN NEWBUILD SOLUTION Membrane containment systems (GTT Mark III & NO96) are the industry standard for modern LNG carriers worldwide. THE BOTTOM LINE Membrane containment systems dominate modern LNG carrier construction because they maximise cargo capacity while delivering excellent thermal efficiency, structural performance and operational reliability. More Cargo Better Efficiency Greater Stability Proven Reliability

In exams

Asked 19 times across 7 different questions, most recently in 2026. Asked most in MEO Class 4 (6), 2nd Mate (5), Chief Mate (3), UK Management (3).

Drafted by SailR from our daily lessons. AI-drawn illustration. Simplified to explain the idea, not to scale. Last updated 19 Oct 2026.

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