Module 5 : Ship Types Flashcards
Ship types
- Design depends on intended use, task to accomplish, need for specialized equipment, area of operation, commercial requirement, specialized crew requirement, etc.
Cargo Ship development: Flush deck ship
No raised structures on the deck.
Machinery spaces at amidships and long shaft tunnel to the aft spaces. Done for weight distribution as propulsion was coal fired steam.
Only short coaming and engine room skylights protected the machinery spaces -> there was too much water coming in
Cargo Ship Development: Three Island Type Ship
Features 3 raised areas: the superstructure to protect the machinery space at amidships, forecastle, and poop structure to reduce water on deck and provide visibility.
Still steam engines
Double bottom introduced
Cargo Ship Development : Combined poop and bridge type ship
Long bridge ships provided a continuous deck from the start of the superstructure to the aft end of the ship.
Machinery space still amidships
Still have a forecastle
Cargo Ship Development : Raised Quarter deck type ship
Machinery is completely aft.
Trim by the bow when full and trim by the stern when empty. The main deck was discontinued after the holds (and raised half the height of a normal deck) to provide more capacity in the machinery space and correct the forward trim when loaded.
The breaks in the deck poses significant strength issues.
Diesel age
Cargo Ship Development : All aft cargo type ship
A completely aft positioned superstructure has become the standard. Machinery space is located under the superstructure and provides short runs of shafting and a more centralized location for most machinery.
No cargo in forepeak.
When cargo holds wear out, could cut before machinery space and reuse engine room and superstructure with new cargo holds.
Bulk Carriers
Transportation of a wide range is material in bulk quantities, e.g. ore, coal, salt, grain, sugar, etc.
Specialized bulk carriers are designed to provide extreme flexibility in cargo carrying.
Some vessels may have self-unloading devices or this equipment could be located at the shoreside facility.
The construction of a bulk carrier depends on the density of the cargo being carried. The space outboard of the cargo area are often used for side ballast tanks, passageways, fuel tanks, etc. Higher double bottom will raise the center of gravity, making the ship more comfortable and giving better seagoing characteristics.
Bulk carriers are often fitted with sloped sections (hoppers) within the cargo hold to facilitate discharge and provide area for tanks or passageways.
Smaller coastal bulk carriers are called colliers
Bulk Carriers : lower mid body section construction
Double bottom, peak areas, deep tanks.
The inside of the cargo hold is reasonably free from obstructions and hatches are wide to facilitate unloaded.
Transverse framing in cargo area and in high load areas (e.g. engine room) while the double bottom and the deck are longitudinally framed.
Bulk Carriers : Upper Mid Body Section Construction
Slide 15
Bulk Carriers: Growth in design
Handysize = colliers : 20k-40k DWT
Handymax = 40k-50k DWT
Supramax = 50k-60k DWT
Panamax = 60k-80k DWT
Post-Panamax = Baby capers : up to 125k DWT
Capesize = 125-220k DWT
VLOC (very large ore carrier) = above 220k DWT
Self-unloading bulk carriers
Fitted with a conveyor belt system to transport cargo from the hold ashore. Corrugated type bulkheads for cargo to run down. Angled bottom with stools to facilitate the direction towards the hopper conduits.
By comparison, other vessels rely completely on shore facilities to discharge cargo. These vessels have strict routes where the ports of call have the necessary equipment.
Self-Unloaded Bulk Carrier drawings
Slides 26- 28
Shore-based loading
All bulk carriers are generally loaded by the shore-based equipment. This is generally done via gravity with hopper belts or via grabs.
Shore-based unloading
Some vessels rely completely on shore facilities to discharge cargo. These vessels have strict routes where the ports of call have the necessary equipment.
Unloading can be done in various ways depending on the port facilities, type of cargo and the hold construction.
Generally see a vacuum system, a screw type system or mechanical grab system.
Great Lakes Bulk Carriers
Size of the vessels are limited to the size of locks and depth of water in the area of operation. Plumb bow and transom stern to reduce length and maximize cargo carrying space.
Container Ships
Use of containers to facilitate loading and unloading, shorter turn around time = more profit.
Standard container size is 20 feet called TEU. Made of corton steel, alloys added for corrosion resistance and strength.
Container units are stacked in holds and on deck and secured to the vessel to avoid loss or shifting while at sea. Stacking capacity will depend on quality of container. Containers must be lashed together.
Cargo handling is rarely done by shipboard equipment.
Vessel size is measure by how many TEU can be loaded.
Container Ship Construction
Superstructure is generally fully or slightly forward of completely aft, allowing for some cargo space behind the superstructure. Usually very high and thin longitudinally. Stern may be square shaped to provide more area for container placement.
Hatch openings are made in consideration of the container size: either very wide or 2 abreast. This results in a large loss of deck material and loss of longitudinal and transverse strength. Box girders or torsion girders are found at the ship’s sides to regain some strength. These are extensively reinforced internally to reduce deformation of the hull due to static and dynamic stresses. Prevent racking and twisting. Gives a passageway or space for ballast without cutting into the space for containers. Located in the shearstrake area.
Double hull, double bottom. Guides may be fitted in the cargo holds to assist with stowage and securing of the containers. Most use a system of longitudinal framing in the cargo area with transverse framing at the fore and aft ends.
General Cargo Vessels
“Tramp” is a cargo vessel with no particular cargo or port of call.
Feature heavy cargo handling masks and derricks as well as wide hatchways.
Increase versatility, smaller in size.
General Cargo Ship - Construction
Engine room and bridge are either completely aft or slightly forward of aft. The double bottom tank tops are covered with a ceiling (protective coating that can be replaced when worn down) or made with thicker steel to withstand the weight and movement of the cargo and cargo-handling equipment. A tween deck can be used to provide more flexibility in cargo loading and unloading, better cargo segregation and better stability.
Vessels under 120 m will be transversely framed, whereas larger will be longitudinal or combined. Modern ships may use longitudinal bulkheads near the ship’s sides with stiffening on the outboard of the bulkheads to provide smooth, easily cleaned holds.
Tankers
Some are designed to only carry 1 type of liquid where others can vary the cargo and others still are compartmentalized to allow the transport of multiple liquids at the same time.
Chemicals and other products may require special construction arrangements to protect the environment, reduce corrosion and deal with toxicity.
Pump room or pump house contain cargo handling pumps and associated equipment.
Explosion and fire hazards are always a factor on these ships and are dealt with by suitable standing orders and training, proper ventilation, inert gas smothering systems and the fitting of void spaces and cofferdams.
