Effective Ship Design and Issues That Must Be Considered - Essay Example

DESIGN PROCESS THAT WOULD BE UNDERTAKEN FOR EFFECTIVE SHIP DESIGN AND ISSUES THAT MUST BE CONSIDERED By Table of Contents Fully Cellular Containership 5 Summary 9 Design Process That Would Be Undertaken For Effective Ship Design and Issues That Must Be Considered Introduction There are different designs of ships for the passenger and cargo ships. The ships vary in their developmental processes in terms of vessel equipment, engine, security and safety and hull. The essay will feature the Roll-on/Roll-off vessels and Fully Cellular Containership. The essay will explore how the ships differ and resemble in design by considering different aspects such as safety and security, hull and the vessel’s equipment. Roll On / Roll Off Passenger Ferry (RO-PAX) Roll-on/Roll-off vessels are primarily ships in which the cargo is wheeled or rather it is loaded on board by use of vehicles or platforms that are equipped with wheels. The pioneer roll-on/roll-off vessel was the ferry; it was equipped, with railroads to allow for the transportation of rail carriages across river sections that were too broad to facilitate the construction of bridges. The first ferry ship was built in 1861 in Scotland, and it was known as Forfarshire. The Second World War facilitated the development of this kind of vessels since they were ideal for the transportation and dispatch of military paraphernalia. Since many of the army equipment were bulky and often occupied irregular spaces this kind of vessels were recommended to ensure easier movement (Papanikolaou, 2014). Additionally, the fact that they accommodated movable cargo made them even more efficient since cargo like military tanks and war planes would be easily dispatched to their required destinations with a lot of ease. However, the utilisation of the Roll-on/Roll-off technology in merchant ships started in the late 1940s primarily in short-sea routes to facilitate the movement of movable cargo as well as transportation of passengers between channels in the sea where bridges were not feasible (Papanikolaou et al., 2004). There are several types of roll-on/roll-off vessels based on the kind of cargo that they transport. Some of the notable roll-on/roll-off ships include; freight, ferry, Ro-Pax just to name but a few. A ferry mainly carries both passengers and vehicles with each type of cargo having its compartments. The freight is specialised RO/RO vessels that exclusively transport wheeled cargo. On the other hand, RO-PAX combines the roles of the other two as it can carry passengers, vehicles as well as wheeled cargo at a go since its design can accommodate all these items. The basic design of a typical ferry includes some specifications that ought to be fulfilled to ensure safety and efficiency of the vessel while on transit (Molland, 2008). The access ways of the ferry are normally 2.90-3.0 metres wide with some allowance to accommodate extraordinary cargo (Wu, Cui, & Zhou, 2001). The external access ramps should be inclined to an angle less than twelve degrees to ensure the wheeled cargo and vehicles easily access the vessel with ease. Internal ramps should assume a slope that is between six and eight level. The width should be carefully selected depending on the type of cargo that is to be stowed on the upper deck. In larger ferries, a diameter of about 7-12 meters is used to the surfaces being anti-skid to avoid incidences of slipping over while boarding. Elaborate sketch and details of the access ways are provided in Appendix 1 (Barrass, 2004). The deck configuration mainly depends on the size of the ferry in general. Ideally, the number of decks will increase with the size of the vessels that is a smaller ferry will tend to have fewer decks as compared to a larger ferry. Ferries that measure up to 150000 +dw are recommended to have two decks any vessel greater than that will have three permanent layers. Often, movable car decks are fitted in between the permanent floors. RO/RO vessels require a broad range of access equipment to facilitate the loading and offloading of cargo and passengers some of these include; stern door, stern ramp, side ramp, ramp cover, hostable ramp, shell door just to name but a few (Schneekluth and Bertram, 1998). A detailed description of all these equipment in the ferry is presented in Appendix 2. Typically, the inclination angle for internal ramps should be kept at seven degrees while all interior doors should be watertight designed to enhance perfect subdivision of the cargo spaces with minimum interference. Movable car decks are normally intermediate floors made up of light weight construction that are installed in between the permanent layers to allow for the storage of cars away from the heavy vehicles. They come in two types namely; hostable and lift-table car decks. The hostable decks are integrated with a lifting device either hydraulic or electrical while the lift-table decks are not integrated with any device but move by means of lifts that are arranged in a scissor fashion (Janić, 2014). The construction design of the RO/RO should be in agreement with IMO guidelines on maritime security. The recommended vehicles that ought to be carried by these vessels should be approximately between 3.5- 40 tonnes including their cargo. In the ferry, the deck has some secure points with a longitudinal space of less than 2.5 metres, traverse space of between 2-3 meters while the minimum strength with permanent dysfunction should be 20KN. Lashing should consist of a chain or any other device that is made up of steel; however, an equivalent material will similar characteristic can also be used. The power of the lash utilised should not be less than 120KN (Wijnolst et al., 2009). At the same time, lashings should only be attached to the secure points that are designated in the vessel. Typically, the lashing angle is kept between thirty and sixty degrees. The closed deck of the wheeled cargo should have a class A boundary with the ventilation system for the load space being entirely segregated from the rest of the vessel’s ventilation system (Parsaei and Sullivan, 1993). Fully Cellular Containership The primary principle in the design of a container ship is the shore-based lift-on/lift-off equipment and, in particular, the gantry cranes. These are the machines that are utilised for loading and unloading of cargo to and from the container ships. The first commercial container ship was built in 1970, and it was gearless meaning it had no shipboard cranes. Since then the number of vessels being built without on-board cranes has been drastically dropping with only 10% of the containerships being equipped with shipboard cranes by 2010. The introduction of shore side cranes revolutionised the shipping industry and, in particular, the container ships (Lane, 2001). The pioneer shore-side crane that was specially designed to handle containers was built in 1959 at the Port of Alameda in California. It was capable of moving containers on a three-minute cycle and equivalent to four hundred tonnes per hour. With the growing demand for sea transport and in particular the use of container ship; organisations are coming up with bigger and more sophisticated containerships to meet the market demand as well as enhance efficiency through the utilisation of less fuel and having the least environmental impact (Langevin and Riopel, 2005). For instance, in 2011 Emma Maersk was the largest container vessel in the word with a capacity of 15,000 TEU, later in 2012 CMA CGM Marco Polo became the biggest container ship with a load capacity of 16,020 TEU. In 2013, Maersk Shipping line unleashed Maersk Triple E class of container vessels that had the capacity of 18,270 TEU making them the current largest containerships on earth (Eyres, 2007). There are various categories of containerships depending on their sizes. The ultra large container vessel (ULCV) has a capacity of 14, 501 TEU with dimensions of 366m, 49m, 15.2m for length, breadth and draft respectively. The new Panamax has a capacity of between 10,000 and 14,400 TEU with its dimensions being 366m, 49m, 15.2m for length, breadth and draft measurements respectively. Other smaller container ships include the Panamax, post-Panamax and feeder vessels that have a relatively lesser capacity (International Conference on Machine Design Departments and Ševčík, 2014). Efficiency is the primary in the design of containership. A crucial concept of containership specialisation is the hatches. These are openings from the main deck to the cargo holds (Hocker and Ward, 2004). Conversely, on top of the hatch coamings are the hatch covers (Ham and Rijsenbrij, 2012). Traditionally, hatch covers were made up of wooden boards and tarpaulins that were held down by battens. With the advancement of technology modern hatch covers are secured by metal sheets that are made up of ground steel plates. The hatch covers are lifted on and off the ship by cranes, or use of an articulated mechanism is implemented whereby they are opened and closed by powerful hydraulic racks (Sweeney, 2010). Similarly, the use of cell guides is an essential component in the containership. It is the distinguishing factor between dedicated container ships and other conventional vessels. Cell guides are a very high vertical structural construction of metals that are installed in the cargo of the vessel haul. Their purpose to guide the containers into well-defined rows during loading and ta the same time provide support for the vessels while on transit as the vessel rolls at sea. Cargo guides are a fundamental component of modern container ships as the United Nations Conference on Trade and Development utilises them to distinguish between dedicated fully cellular containerships and break-bulk cargo ships (Jacobsson, Borgström, & Williams, 1976). The typical characteristics of an ideal fully cellular containership include the following; a maximum tonnage of approximately 35,881 GT, Deadweight of about 44, 850 tonnes, length of O.A of 220 metres, B.P about 210 metres. The moulded breadth should measure around 32.24 metres while the depth of the main deck should be nearly 18.70 metres. Its free board draught should measure approximately 12.15 metres, and its engine propulsion speed should be around 22.30KN (Rapo, 1982). There are some factors that influence the ship hull structure topology to be implemented in any particular containership. The type of securing device that are utilised in that vessel, for instance, the use of cell guides will determine the kind of topology to be implemented. In a situation whereby cell guides are used the topological structure of that particular ship has to be fashioned in a manner that accommodates those guides (Vassalos, 2000). Similarly, the type of cargo handling equipment that are used for loading and unloading of the container ship is yet another critical factor to be considered to determine the kind of hull topology to be selected (Okumoto, 2009). The topology chosen should make it convenient for the cranes to load and unload cargo from the container ship with ease to enhance efficiency (Greenway, 2011). In the structural topology, a longitudinal framing system is implemented with the longitudinal frame spacing being equivalent to 790mm see Appendix 3 for more illustration. The transverse bulkhead structure should be designed in a manner that each bulkhead is extended over two frames. The spacing between each bulkhead should be equal to the size of a single 40ft container (Helvacioğlu, 2001). The bottom of the hull should assume a double layer structure with a side longitudinal girder while the floors are designed to provide a rigid support level for the containers to firmly fit intact. The side structure should be made up of a longitudinal stringer and a web of frames to form a rigid support for the ship between the transverse bulkheads. The structural illustrations are elaborated in Appendix 4, 5 and 6 (Biran and Pulido, 2013). The typical mass of the steel that is utilised for the construction of the ship’s hull is typically estimated to be around 3453 tonnes that represent approximately 7% of the total displacement of the container vessel. Higher tensile steel is appropriate for the construction of the flanges and the lower web plans of the vertical beam that provides the overall support of the ship. Relatively, standard steel is adopted for the bulkheads plates and the other parts of the bulkheads since they are required to be lighter to balance the weight of the ship (Papanikolaou and Soares, 2009). There are several systems that are put, in place to ensure the security of the cargo that is on board. Stowage instruments provide the containers are secure by use of container guides, anti-rack spaces and locating cones to ensure the cargo is intact in its right place and thus secure while on board. The lashing system provides a mechanism whereby the containers are secured against the ship by use of wire ropes or chains. The effectiveness of the mechanism is enhanced by securing the containers to one another by stacking twist-locks between them before being lashed to the ship’s safe point. A comprehensive illustration of the central parts of the design of the fully cellular containership is elaborated in Appendix 7 (Cudahy, 2006). Summary It is evident the Roll-on/Roll-off vessels and Fully Cellular Containership differ in design in terms of their developmental processes such as vessel equipment, engine, security and safety and hull. For instance, whereas the primary principle in the design of a container ship is the shore-based lift-on/lift-off equipment and, in particular, the gantry cranes, the design of Roll-on/Roll-off vessels is not based on such as aspect. Ultimately, it clear the Roll-on/Roll-off vessels and Fully Cellular Containership vary in their designs based on a number of the aforementioned factors. References Barrass, C. B., 2004. Ship design and performance for masters and mates. Oxford, Elsevier Butterworth-Heinemann. Biran, A., & Pulido, R. L., 2013. Ship Hydrostatics and Stability. Burlington, Elsevier Science. Cudahy, B. J., 2006. Box boats: how container ships changed the world. New York, Fordham Univ. Press. Eyres, D. J., 2007. Ship Construction. Burlington, Elsevier. Greenway, A., 2011. Cargo liners: an illustrated history. Barnsley, Sea Forth Pub. Ham, J. C. V., & Rijsenbrij, J., 2012. Development of containerization: success through vision, drive and technology. Amsterdam, IOS Press. Helvacioglu, S., 2001. Utilisation of expert systems in container ship design: accommodation layout design expert system (ALDES). PhD theses, Department of Naval Architecture, Istanbul Technology University, Istanbul. Hocker, F. 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Oxford, Butterworth-Heinemann. Sweeney, P., 2010. Liffey ships & shipbuilding. Cork, Mercier. Vassalos, D., 2000. Contemporary ideas on ship stability. Amsterdam, Elsevier. Wijnolst, N., Wergeland, T., & Levander, K., 2009. Shipping innovation. Amsterdam, IOS Press. Wu, Y.-S., Cui, W.-C., & Zhou, G.-J., 2001. The practical design of vessels and other floating structures proceedings of the Eighth International Symposium on Practical Design of Ships and Other Floating Structures, 16-21 September, 2001, Shanghai, China. Amsterdam, Elsevier. Available at: http://www.engineeringvillage.com/controller/servlet/OpenURL?genre=book&isbn=0080439500. [Accessed on 28 May 2015]. Appendices Appendix 1 Appendix 2 Appendix 3 Appendix 4 Transverse bulkhead structure Double bottom structure Appendix 5 Mid ship section sketch Appendix 6 Cargo hold analysis Read More