Jurong Shipyard Private Limited (JSPL) is a wholly owned subsidiary of the Sembcorp Marine Ltd and its services include the following: Ship repair, Ship building, Ship Conversion, Rig building and Offshore engineering. Given its diverse range of services offered, the corporate profile of JSPL sees a total of 8 departments under its organisational structure. The 8 departments ranges from, commercial, offshore, production, project management, quality assurance and quality control, safety, project development to engineering.
1b) What the product/system/process is for the study?
Heave is considered to be the principal motion to affect drilling rigs. The movement is for the ship to consider the hydrostatic stability of a floating offshore structure for its influence on its payload performance and on its dynamic reaction in waves. The study of hydrodynamic forces on platforms became very important, and is worthwhile to discuss their behavior in waves so to prevent large motions which could affect the entire operation of semi-submersibles. When the preliminary design has been determined the following information shall be studied in greater details:
Propulsive characteristics and hull form.
Tentative general arrangement.
Principal structural details.
Hull characteristic (coefficient / non-dimensional coefficients)
Stability (stable equilibrium, unstable equilibrium, neutral equilibrium)
Equation of heave motion.
Type of water resistance.
Concept of Metacentric ( GM = KB+BM-KG)
GM : Metacentric height.
KB : Z-coordinate of centre of buoyancy from hydrostatic calculations.
BM : Metacentric radius and discussed next.
KG : Z-coordinate of the centre of gravity from weight calculations.
What are the characteristics of the product/system/process:
Combining the technologies which are currently practiced by shipbuilding industry can be used to fabricate the hull structures. However, the design of all joints, the structural and material characteristic of the metal-elastomer composite must be taken into account. Besides that, water density, steel density and instrument mass are used to predict the weight of the ship body. Consequently, we must centralize on the following vital item :
Propulsive characteristic and hull form.
Stability of the ship.
Principal structural details.
The centre of gravity(G).
What are the current problems:
One of the main problems arising in the course of the project is the practicality of the ship designs. This problem surfaces due to a conflict of interest between the naval architect and the ship owner with regard to the ship design.
On one hand, the naval architect faces a complex array of organizational problems regarding the structure of the shipâ€™s building designs in his quest to fulfill the obligations of the ship owner to obligations such as his commercial objectives.
As with all rational business economics for competitive firms, the objectives is to achieve productive efficiency at the lowest possible cost, with a set amount of resources and requirements, legal obligations, as guidelines.
However, with shipbuilding, these guidelines are dynamic and ever changing. For example, given the complex shipbuilding process- the complicated structures parts, intricate machinery systems processes, the ship as a transportation system, all these have complicated and diverse methods of execution due to varying resource allocation.
Given the unpredictability of the nature of problems as a result, the above cases can be differentiated into categories of problems, usually solved by the induction of mathematical formulae. However, in certain cases, a compromise by forcibly relaxing the initial constraints on objectives is unavoidable due to the inability to accommodate all conditions, ceteris paribus.
What the exact focus of the project is (i.e. the need to have this project)
The objective for my proposal is to redesign the heave motion on shipbuilding and shipping whereby the drilling can done efficiently and effectively. This is because having a balance in the heave motion is important as too much motion will waste drilling time and increased of operation cost while too few will caused ineffective in drilling. With the increasing demand for energy, newer versions of semi-submersibles have been developed to operate in further and deeper environment with much harsher conditions. The idea for the project was formed due to the need for creating a better semi-submersible to compete in the competitive marine industry. This project will calculate and analyze the heave motions of semisubmersibles.
The project demonstrates that redesigning the heave motion of the ship can result in varying degrees of changes in ship performance. Therefore, optimizing the motion response of the ship is important. Therefore, a ship can be in stable equilibrium if the ship, when inclined and return to the initial position. In order to make it possible, the centre of gravity must be below the metacentre and the ship must have positive initial metacentre height.
It is important to show the hydrostatic stability of a floating offshore structure to illustrate its impact on its payload performance and on its dynamic response in waves. Therefore, to prove that the body floating freely on the surface is in equilibrium stable with regards to its draught.
Contributions to refine the shipbuilding process that this project has offered are:
Entry of the sea water has been prevented.
The shape of space has been maintained.
Security has been provided against forces and movement.
Stability of ship and dry dock combination.
Longitudinal stability can effect transverse stability of the ship turned through 90. Instead of trim being measured in degrees it is measure as the difference between the drafts forward and after. If forward draft is greater than after draft, the vessel is trimming by the bow. If after draft is greater than the forward draft, the vessel is trimming by the stern. Consider a ship floating at rest on the sea, the centre of gravity and the centre of buoyancy will be in the same vertical line and the ship will thus displace her own weight of water.
How to assess the effectiveness of this project?
The sea water is incompressible.
Viscosity plays no role.
Surface tension plays no role.
The sea water surface is plane.
Source of Information and Key Words
A project was designed to calculate and analyze the heave motions of semisubmersibles. The following are the information needed for successful completion of the project:
Conditions of equilibrium
Concept of metacentre
Below sources are used to find the relevant information:
A list of key words for my project:
Stability + Buoyancy
Hull structure + panel
Powering + capacity
I intend to conduct my investigation and try to provide as much evidence, i.e. facts and figures, as possible that Iâ€™ve collected. I will also divide my projects into various chapters to make the project flows well from one chapter to another chapter.
An Example Reference
*P.W.Penny.M.Sc, CEng, Associate Member, Preliminary Design of Semi-Submersibles, 8th Octorber 1984. University of Newcastle.R.M.RIISER, B.Sc, M.Sv, Associate Member, VO offshore Ltd.