Cargo Ship Types and Classifications
Container Ships
Container Design and Construction
Open design for double bottom square shape to hold ballast tanks and pumps. Features advanced hydrodynamic hull shapes. Capacity is expressed in TEU’s.
Classification
By Generation:
- 1st Generation: <1000 TEUs
- 2nd Generation: <2000 TEUs
- 3rd Generation: <3000 TEUs
- 4th Generation: <6000 TEUs
- 5th Generation: <8000 TEUs
- 6th Generation: >8000 TEUs
By Service:
- Feeder: <500 TEUs (Short Sea)
- Feedermax: <1000 TEUs (Coastal)
- Handy: <2000 TEUs (Intra-regional)
- Sub-Panamax: <3000 TEUs (Long Haul)
- Panamax: <4000 TEUs (80% Sea)
- Post-Panamax: >4000 TEUs
Tankers
Overview
Transport liquefied gases. High cost due to technical excellence, technology, and design. Carry petroleum derivatives and natural chemicals. Design, construction, and equipment are covered by the IMO Code, most recently the IGC code.
Classification
By Danger:
- Maximum 1G
- 2G and 2PG (Half)
- 3G
By Cargo Tanks:
- Independent Tanks: Self-sustaining, not part of the ship’s structure.
- Type A: Pressurized, chilled, 0.25 kg/cm2, LPG
- Type B: Pressurized and chilled, 0.35 kg/cm2, LNG and ethylene
- Type C: Fully or semi-pressurized, 0.7 kg/cm2, LPG
- Membrane Tanks: Supported by the ship’s hull, withstand thermal contractions and expansions, transport LNG at -163°C.
- Semi-Membrane Tanks: Supported by the ship’s hull at the corners, designed for thermal contractions and expansions.
- Integral Tanks: Part of the ship’s structure, subject to the same stress as the hull, prohibited below -10°C, transport butane.
By Transport Conditions:
- Pressurized: Type C, up to 3500m3.
- Semi-Pressurized and Semi-Cooled: Up to 5000m3 at -10°C and 8.5 kg/cm2, up to 15000m3 at -48°C and 5.8 kg/cm2.
- Refrigerated: Suitable for long voyages due to large capacity and better space utilization.
Bulk Carriers
Overview
Transport solid bulk raw materials, comprise 40% of the world fleet.
Features
- Single deck with access hatch to wing holds.
- Engine and machinery room aft.
Classification
By Size:
- Handysize: 10,000-35,000 DWT (34%)
- Handymax: 35,000-55,000 DWT (37%)
- Panamax: 60,000-80,000 DWT (19%)
- Capesize: >80,000 DWT (10%)
By Structure:
According to load size. Vessels with soft cargo have slow stability and balance, while vessels with hard cargo have fast stability and balance.
Special Types
- Conbulkers: Bulk containers
- OBO: Bulk and petroleum ore carriers, open access, easy self-discharge
- Chip Carriers: Sawdust and wood chips
- Loggers: Logs
Bulk Chemical Carriers
Overview
Transport chemicals in bulk (corrosive, flammable, toxic, reactive, animal and vegetable oils), typically smaller vessels (5000-40,000 DWT).
Features
- Large number of tanks with segregated piping circuits for simultaneous transport of different chemicals.
- Tanks are coated with special paint or stainless steel, coating determines the product to carry.
- Tank washing is essential to prevent reactions.
Regulations
Due to product hazards, design and construction are governed by MARPOL, SOLAS, IBC, and IMDG codes.
Classification (According to IBC Code)
- Specialized Chemical Carriers: Maximum safety measures, harmful products, small vessels transporting a single product, maximum tank size 1250m3, distance between side shell and tank 0.5m, distance between bottom shell and tank 1.5m.
- Complex Chemical Parcel Tankers: Low hazard products, up to 40,000 DWT, 54 stainless steel cargo tanks, each with its own pump and pipes, up to 3000m3, 760mm side shell depth, 1.5m distance between bottom shell and tank.
- Product/Chemical Tankers: Low hazard, no location or size restrictions, lined tanks.
General Cargo Ships
Overview
Transport solid bulk, containers, palletized goods, etc. Characterized by flexibility rather than efficiency.
Features
- Size: 15,000-22,000 DWT
- 4-5 cargo holds
- Length: 100-150m
- Speed: 18 knots
- Some have tween decks
- Own loading/unloading means
Function
Carriage of goods by weight or size that will not fit in containers.
Refrigerated Cargo Ships (Reefers)
Overview
Transport perishable cargo at controlled temperatures (chilled or frozen). Typically operate in tramp trade between hemispheres.
Classification
- Reefers: Refrigerated cargo spaces throughout the vessel.
- Partial Reefers: Only part of the vessel is refrigerated.
Types
- Side door vessels with side and deck hatches.
- Traditional vessels with hatches and loading/unloading means.
- Refrigerated container ships.
Space Loss
- Refrigerated: 25%
- Frozen: 35%
Features
- Painted white
- Large number of separate cargo spaces
- Several tween decks
- Palletized goods
- Conveyor belts and bulldozers for moving cargo
- Essential cleaning and temperature control
- Powerful generators for cooling plant and refrigerated containers
Roll-on/Roll-off Vessels (RoRo)
Overview
Cargo is rolled on and off via ramps.
Classification
- RoPax: Passenger and RoRo
- ConRo: Container and RoRo
- StoRo: General cargo and RoRo
- RoLo: RoRo and general cargo on deck
- PCC: Pure Car Carrier
- PCTC: Pure Car and Truck Carrier
Capacity
Measured in CEUs (Car Equivalent Units).
Features
- Speed: 20 knots
- Length: 50-300m
- Cargo holds divided into several high decks and covered in lashing points
- High ballast capacity
- Ventilation system in cargo holds
- Two ramps at similar height for simultaneous use
Advantages
- Fast loading and unloading
- Easy and cheap loading and unloading
- Suitable for small and underdeveloped ports
- Integration with other transport modes
- Large reserve buoyancy
Disadvantages
- Inefficient cargo space and high fuel consumption
- High freeboard (problems with depression, lowering lifeboats)
- Internal partitioning (easy spread of fire and flooding, loss of stability due to free surface effect)