Thursday, May 6, 2010

Container ship design and Her Propulsion Performance

Container ship whether it is for international or national market is always related to the  transport cargoes that are stored in metal boxes (called containers)  from the consignors to the consignees.  In shipping business, cargoes are transported from the seaports where manufacturers  or producers are located to the seaports where the products and agricultural produces are needed or demanded. Please, read my other article Shipping and Container Ship.

There are three components involved in shipping system:
  1. Ports or container terminals with their cargo or container handling equipment;
  2. Marine transport vehicles such as container ships, general cargo ships and barges;
  3. Managerial systems that control the flow of ships, cargoes, trucks or lorries, port infrastructure for the efficient, effective and fast movement of cargoes from areas of supply to areas of demand.
Container ship plays a very important role in shipping industry. In theory, modern container ship is designed to carry thousands of containers in a fast, efficient and safe way. To carry a lot of containers, the ship has to be big. A typical container ships have deadweight: 10,000 - 72,000 metric ton; LBP: 200-300 meters; Breadth moulded: 30-45 meters; Block Coefficient: 0.56-0.60; and speed: 20 to 28 knots (Captain D.R. Derrett and Dr. C.B. Barras 2001).
The above range of block coefficients for container ships are lower than the Cb of supertankers that are between 0.85 to 0.82. Reading this number, you might ask, "Why big container ships do not have block coefficients that are the same as the Cb of oil tankers?"
To answer this question, we have to see the above Point 3 of shipping system. It explains that containers have to be moved to the area of demand in a fast, effective and efficient way. To be able to move at the speeds of 20 to 28 knots at sea water, container ships need to have streamlined hulls that have medium sized block coefficients. If the Cb is too high, it will definitely need high rate driving power, usually marine diesel engine. When container ships are installed with high engine ratings, they will consume huge amount of fuel. High consumption of fuel will automatically raise the cost of transportation and finally the freight rate. When this condition happens to a container ship, it will not be attractive to shippers anymore.
Therefore, the design of container ships have to be optimized to meet the demand of a fast, effective and efficient shipping lines. Highly optimized container ships and cargo handling equipment will continue to be the backbone of shipping industry for years to come. by Charles Roring

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