Hybrid System for Large Marine Applications

Hybrid System for Large Marine Applications

The most powerful and one of the most efficient prime-movers in the world today (2008) is the Wartsila-Sulzer 14 cylinder turbo charged two-stroke diesel engine, designed for powering very large container ships.

The cylinder bore is 960 mm (38 inches) and the stroke is 2500 mm (98 inches) providing a capacity of 25,337 litres (1,546,165 cu ins) and a continuous output power of 80,080 kW (108,920 bhp) or 4.27 bhp/litre at 102 rpm with an overall efficiency of around 52%. The engine is 27.3 m long and 13.5 m high with an overall weight of 2300 tonnes.

The engine's main output shaft drives the ship's propellers and exhaust gases from the engine pass through a heat exchanger to generate steam for a turbine-driven electricity generator. The turbo generator set also includes an exhaust-gas powered turbine driven by a portion of the exhaust gases diverted from the main flow through the engine's turbochargers. The power output from the generator is 9,860 KWe, about 12% of the main engine power. A portion of the steam from the exhaust economiser is also utilised in shipboard heating services.

Corrosion in marine Environments

Seawater systems are used by many industries such as shipping, offshore oil and gas production, power plants and coastal industrial plants. The main use of seawater is for cooling purposes but it is also used for fire fighting, oil field water injection and for desalination plants. The corrosion problems in these systems have been well studied over many years, but despite published information on materials behavior in seawater, failures still occur.

Most of the elements that can be found on earth are present in seawater, at least in trace amounts. However, eleven of the constituents alone account for 99.95% of the total solutes, chloride ions being by far the largest constituent. The concentration of dissolved materials in the sea varies greatly with location and time because rivers dilute seawater, rain, or melting ice, or is concentrated by evaporation. The most important properties of seawater are:

• The ratios of the concentrations of the major constituents are remarkably constant worldwide
• High salt concentration, mainly sodium chloride;
• High electrical conductivity
• Relatively high and constant pH
• Buffering capacity
• Solubility for gases, of which oxygen and carbon dioxide in particular are of importance in the context of corrosion
• The presence of a myriad of organic compounds
• The existence of biological life either as microfouling (e.g. bacteria, slime) or macrofouling (e.g. seaweed, mussels, barnacles and many kinds of animals or fish).

The U.S. flag fleet can be divided into several categories as follows: the Great Lakes with 737 vessels at 62 billion ton-miles, inland with 33,668 vessels at 294 billion ton-miles, ocean with 7,014 vessels at 350 billion ton-miles, recreational with 12.3 million boats, and cruise ship with 122 boats serving North American ports (5.4 million passengers). The total annual direct cost of corrosion to the U.S. shipping industry is estimated at $2.7 billion. This cost is divided into costs associated with new construction ($1.1 billion), with maintenance and repairs ($0.8 billion), and with corrosion-related downtime ($0.8 billion). (Internet reference)

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Information Module

• Anti-fouling coatings
• DO in seawater
• Fouling
• FPSO
• Ions in seawater
• Marine systems
• Monel Corrosion
• Seawater scaling
• Type 316L (UNS S31603) in in the Arabian Gulf

What are Very Large Crude Carrier (VLCC) and Ultra Large Crude Carrier (ULCC)?

What are Very Large Crude Carrier (VLCC) and Ultra Large Crude Carrier (ULCC)?

A Very large crude carrier and an ultra large crude carrier are two examples of the different types of oil tankers. These oil tankers are extremely important in the shipping industry for they help to transport huge quantities of crude oil across the oceans and seas.

Dead Weight Tonnage (DWT) is the measure of weight when it comes to tankers. In terms of oil tankers like a very large crude carrier or an ultra large crude carrier, the DWT represent the maximum quantity of DWT that can be carried. The terms ‘very large’ and ‘ultra large’ are in fact categorisations of the oil tankers which are included in the category of being ‘large.’

It has to be noted that tankers are basically divided into two types: the product tanker and the crude tanker. The product tanker is designed to ferry cargo like petroleum and other refined products that are produced from crude oil, from the industrial plants to the final markets for selling.

This being the case, product tankers are generally smaller and compact as compared to the crude tankers which are bulkier and huger. The bulk and the hugeness of a crude tanker help to carry more containers and barrels of crude oil. However it has to be noted that there are six main classifications of crude tankers:

• Tankers that are classified as being under General Range
• Tankers that are classified as being under Medium Range
• Tankers that are classified as being under Large Range 1
• Large Range 2 Tankers
• Very Large Crude Carrier
• Ultra Large Crude Carrier

A very large crude carrier (VLCC) has a dead weight tonnage or cargo carrying capacity ranking up to 2,50,000 tons. On the other hand, an ultra large crude carrier (ULCC) has a DWT of anything between 2, 50,000 to 5, 00,000 tons. In simple terms, it can be said that these two types of oil tankers ferry about two billion oil containers and barrels.

Carrying such a heavy weight would not only ensure that many oil containers are being transported, but it would also ensure that limited number of trips are taken to ferry a specified number of containers. A very large crude carrier and an ultra large crude carrier are also known as ‘supertankers’ because of their mammoth weight carrying capacity.

The Shell Oil Company first designed the weighing system that brought into use the terminology of ‘very large crude carrier’ and ‘ultra large crude carrier.’ As per the Average Freight Rate Assessment system, the denominations of oil tankers were based on the concept of DWT and the above listed oil tankers classification was introduced. The method adopted was very successful as tankers could be specified more easily on the basis of their cargo-carrying capacity and thereby reduce accidents that could be caused due to excessive cargo.

Tankers and more specifically oil tankers are built for a very important purpose. With the help of oil tankers like a very large crude carrier or an ultra large crude carrier, the role and scope of oil tankers becomes far more feasible. Development is a major factor in today’s times. In order to facilitate better development of the human civilization, it is relevant that very large crude carriers and ultra large crude carriers are used appropriately and successfully.

Reference:

businessdictionary/vlcc

businessdictionary/ulcc

Image Credits:

stenabulk

nauticexpo

Related posts:

1. American Bureau of Shipping (ABS) Proposes New Rules for Ultra Large Container Ships
2. What are Gas Carrier Ships?
3. Panamax and Aframax Tankers: Oil Tankers with a Difference
4. The TI Class Super Tankers: The Fantastic Four
5. Distinctive Ships of 2010 : Dry Bulk Carrier E.R. Brandenburg

Tags: big ship, classification of oil tanker, crude oil carrier, large vessel. oil carrier, Oil tanker ship, oil tankers, product tanker, supertankers, Tankers, types of oil tanker ship, ULCC, ULCC tankers, ultra large crude carrier, Very large crude carrier, VLCC, VLCC tankers
Adapted from http://www.marineinsight.com/marine/types-of-ships-marine/what-are-very-large-crude-carrier-vlcc-and-ultra-large-crude-carrier-ulcc/

1. Carrying liquefied natural gases by various type LNG ships
   
   
   ( We have extracted gas carrier images and information from the publication ‘LNG Shipping Knowledge’ by Witherby Seamanship )
   
   Liquefied Natural Gas (LNG) Carriers
   
   LNG carriers in service are fitted with independent cargo tanks and with membrane tanks. LNG carriers are generally specialised ships transporting LNG at its atmospheric pressure boiling point of approximately -162 degree C, depending on the cargo grade. These ships are usually dedicated vessels, but some smaller examples may also carry basic LPG cargoes. If an LNG ship is capable of carrying basic LPG cargoes, a reliquefaction plant is installed to handle the boil-off LPG cargo vapours.
   
   

   
   
   LNG carriers were typically in the range 80-135,000 m3 up until 2006. In 2006 the first LNG ships of over 200 and 250,000 m3 were being constructed for the new LNG trains being constructed in Qatar.
   
   Temperature control 
   
   LNG is liquefied by refrigeration to -162°C and this process is carried out ashore, before the cargo is loaded onto the ship.
   
   LNG carriers are fully insulated because it is not cost effective to liquefy methane onboard (2006, though the first vessels with reliquifaction plants may appear in the next few years). As the ship has no reliquifaction plant any boil-off vapours are burned as fuel gas in the the engine room.
   
   
   Fig:Various type LNG carrier
   Construction
   
   The cargo containment systems will generally be either: LNG Carriers - Membrane systems (Gaz Transport / Technigaz) previously described. (A full secondary barrier with inerted spaces is required for the membrane system) This system has a primary and secondary barrier that is constructed of a thin material and an insulation layer. - Type B (Moss Rosenberg) (The Type B spherical tank requires only a partial secondary barrier) A full double-bottom and side tank ballast system is fitted to all LNG ships.
   
   
   Fig:LNG carrier membrane gaz transport
   Membrane (Gaz Transport or Tecnigaz)
   
   There are two membrane systems in use. In both cases the insulation is fitted directly into the inner hull and the primary barrier consists of a thin metal membrane less than one millimetre thick.
   
   The Gaz Transport system uses two such membranes constructed of ‘Invar’ (36% nickel-iron low expansion alloy). One acts as the primary barrier and the other the secondary barrier and they are separated by plywood boxes of perlite insulation. Similar boxes are fitted between the secondary barrier and the inner hull. Loading is transmitted through the insulation to the ship structure. No centreline division is possible in this type of tank. The other system, developed by Technigaz, has a stainless steel membrane as the primary barrier while the secondary barrier is included in the insulation, which consists of load bearing balsa and mineral woods.
   
   
   Fig:LNG carrier moss tanks
   Moss Tanks
   
   Spherical tanks are generally produced in aluminium or 9% nickel steel. The sphere is welded to a steel skirt that is connected to the hull of the ship and is then free to expand and contract as necessary.
   
   Insulation is fitted to the outside shell of the sphere but no secondary barrier is regarded as necessary across the upper part of the sphere. However, below the sphere, an aluminium drip tray, together with splash plates, provides secondary protection for the hull.
   Fig:LNG carrier moss tanks cross section
   
   
   
   
   
   
   
   Related Information:
   

   1. Carrying liquefied gases by fully pressurized ships
   2. Transport of bulk liquefied gases by semi pressurized ships
   3. Fully refrigerated ships for carrying liquefied gases
   4. Use of ethylene carriers
   5. LNG spill risk during marine transportation and hazards associated
   6. Increased Cargo Capacity for LNG ships & Advantages of the dual fuel diesel electric propulsion

   
   External links :
   

   1. IMO publications

GAS Carrier

Gas carriers are ships that are specially designed to transport gas. This ship type is considered to be more technically advanced than Bulker and Tankers. Most ships of this type are built at yards in Korea or Japan as they have the experience and proven track record.
Oil price and the resent environmental debate has increased demand for LNG. Not only as source of energy for land based installation but also as fuel for ships due its environmental advantages. However there are still some challenges in infrastructure around LNG.

LNG CarrierIs a ship that designed to transport Liquefied Natural Gas (LNG). In order to keep the natural gas liquefied the gas has to be cooled held in the tanks at -162°C. The liquefied gas is in some designs kept in sphere shaped tanks that are carefully insulated to avoid heating up and “boil-off” of the LNG. It also gives the ship a very characteristic look. No insulation is perfect and according to WGI (World Gas Intelligence), on a typical voyage an estimate of 0.1% – 0.25% of the cargo converts to gas each day, depending on the efficiency of the insulation and the roughness of the voyage. Some LNG carriers are designed to use the “boil-off” from the cargo tanks as fuel for propulsion and are equipped with dual fuel engines.

LPG CarrierThis ship type is specially designed to transport petroleum gas like propane,butane, propylene and butylene.

CNG Carrier
Is a ship that is designed to transport Compressed Natural Gas. A CNG carrier is at the time of writing still only a concept ship and no ship has been built yet. More information could be found here.

Adapted from http://www.shippipedia.com/ships/ship-types/tanker/gas-carrier/