Text 7 Developing Environmentally Friendly Ships

Ships in operation produce a range of different types of waste – solid, liquid and gas – which used to be discharged into the environment and which include rubbish, grey water from sinks, washbasins, dishwashers and washing machines, black water from toilets, bilge water containing or free from hydrocarbons, water from vessel cleaning, exhaust fumes and emissions from tank and hold ventilation systems. But times have changed. Environmental concerns have been translated into increasingly restrictive norms and regulations, supported in particular by the International Maritime Organization. “Clean shipping” has today become a statutory obligation for those working in merchant and naval shipbuilding and repair. For ship owners, possessing an environmentally friendly fleet is a question of image and represents a commercial advantage, enabling them to approach their markets differently and to operate in all maritime zones.

Existing ships are currently equipped with various types of waste storage and treatment systems. Equipment add-ons, which vary depending on the type of transportation, do not allow a global overview of emissions for each ship, and often result in cumbersome and even inappropriate systems being installed in what are necessarily confined spaces.

NACRE offers a global environmental approach, comprising both diagnostic and technological solutions. It involves initial measurement of the overall environmental footprint of different types of ships in operation, taking account of all their emissions, as well as their specific operational conditions. NACRE then puts forward economically viable technical solutions to suit the space available and the operational methods of different types of vessels: compact format, low energy consumption and compatibility with platform movements. The equipment will go beyond existing waste norms in anticipation of changes to the regulations. Tested in real-life situations on merchant and naval ships, this innovative equipment will be incorporated into existing ships and, more particularly, into ships under construction.

Between now and 2020, the 45 000 merchant ships which make up the commercial shipping fleet worldwide will have to be brought into line with regulations. As with CONVENAV, HYCARE and PAINTCLEAN, the NACRE project is a response to environmental and economic challenges shaping the future globally of maritime transport and ship repair and maintenance. The involvement of major stakeholders in this project is evidence of their desire to anticipate changes in evolving markets and in services and equipment manufacture relating to environmentally friendly maritime transport.

TEXTS TO UNIT III

Text 8

The construction of large vessels which travel over seas, lakes, or rivers. Many different approaches have been used in the construction of ships. Sometimes a ship must be custom-built to suit the particular requirements of a low-volume trade route with unique cargo characteristics. On the other hand, there are many instances where a significant number of similar ships are constructed, providing an opportunity to employ procedures which take advantage of repetitive processes.

The building of a ship can be divided into seven phases: design, construction planning, work prior to keel laying, ship erection, launching, final outfitting, and sea trials.

The construction planning process establishes the construction techniques to be used and the schedules which all of the shipbuilding activities must follow. Construction planners generally start with an erection diagram on which the ship is shown broken down into erection zones and units. To facilitate the fabrication of steel, insofar as possible, the erection units are designed to be identical. The size (or weight) of the erection units selected is usually limited by the amount of crane capacity available. Once the construction planners have established the manner in which the ship is to be erected and the sequence of construction, the schedules for construction can be developed. Working backward from the time an erection unit is required in the dock, with allowances made for the many processes involved, a schedule of working plans and for procurement of purchased equipment is prepared.

Before the keel of a ship is laid (or when the first erection unit is placed in position) a great deal of work must have been accomplished for work to proceed efficiently. The working drawings prepared by ship designers completely define a ship, but often not in a manner that can be used by the construction trades people. Structural drawings prescribe the geometry of the steel plates used in construction, but they cannot be used, in the form prepared, to cut steel plates. Instead, the detailed structural drawings must be translated into cutting sketches, or numerical-control cutting tapes, which are used to fabricate steel. Several organizations have developed sophisticated computer programs which readily translate detailed structural drawings into machine-sensible tapes which can be used to drive cutting torches.

If all of the preceding work has been accomplished properly and on schedule, the erection of a ship can proceed rapidly; however, problem areas invariably arise. When erecting a ship one plate at a time, there are no serious fitting problems; but when 900-metric-ton erection units do not fit (or align) properly, there are serious problems which tend to offset some of the advantages for this practice.

A ship is launched as soon as the hull structure is sufficiently complete to withstand the strain. Ships may be launched endwise, sidewise, or by in-place flotation (for example, graving docks). The use of a graving dock requires a greater investment in facilities than either of the other two methods, but in some cases there may be an overall advantage due to the improved access to the ship and the simplified launch procedure.

The final outfitting of a ship is the construction phase during which checks are made to ensure that all of the previous work has been accomplished in a satisfactory manner; and last-minute details, such as deck coverings and the top coat of paint, are completed. It is considered good practice to subject as much of the ship as possible to an intensive series of tests while at the dock, where corrections and final adjustments are more easily made than when at sea. As a part of this test program, the main propulsion machinery is subjected to a dock trial, during which the ship is secured to the dock and the main propulsion machinery is operated up to the highest power level permissible.

When a comprehensive program of dockside tests have been completed, the only capabilities which have not been demonstrated are the operation of the steering gear during rated-power conditions and the operation of the main propulsion machinery at rated power; these capabilities must be demonstrated during trials at sea.