Research On Ballastin System Of Steady For Semi-submersible Vessel

Steady state of the ship control system is mainly realized by the ballast system.Through ballasting and excavating the sea water from the water tank, the floating status of vessel can be controled. At the same time, the bank angle of vessel can also be checked. So that the sailors can kown well about the steady state of hull.Self-propelled semi-submersible vessel is a kind of multi-functional multi-purpose driving force of ship, which is used for sea transport or oil drilling platform and other large steel structure equipment or ship. In the process of working, the vessel's up and down status is controled by how many water in the hull's tank, then the structure which should be transported can be pull onto the deck of vessel. The most importan is that the steady state of vessle itself should be controled in a safe scope which is the important performance measure. Following the size of water tank, adjusting the sea water in the tank can keepthe vessel's balance. When the vessel is working, ballast water should be taken in and out by drive control.From the perspective of safety and improve work efficiency on vessel, through operating the level gauging and valve control system, the sailor can monitor the change of ballast water during the process of loading and unloading, further to control the transverse and longitudinal tilt angle. At the whole process of semi-submersible vessel, the security is insured. One of methods is to measure the ship's lower level directly, also we can use the actual data to find out the realationship between the former and the liquid level sensor date. At the same time, the date from ship's auxiliary equipment can alse correct the information. Every measurement method has its own advantages an disadvantages. The paper analyzes the level telemetry and valve remote control system of the ship, the ship loading computer at work, and the mathematical model of optimization operation. From the level of telemetry system of water tank, oil tank liquid level input data, through the calculation of mathematical model, the output instructions to valve remote control system, it is concluded that the heel and trim of the ship angle, to control the dynamic stability when ship is loading.From the valve remote control system, escpacially the ballast tank piping system, the mathematical model has been optimized, and the traffic and valve's pressure can be calculated from the system of linear qurations. Also the optimize has been done through the mathematical model for the vessel's loading working status. The floating working condition of semi-submersible vessel has been shown, just like the semi-submersible vessel consign the semi-submersible drilling platfor the professional software can calculate the date of vessel on two diffrernt floating status. And at the same time analys the dynamic stbility of the working vessel. Based on the research of the ship loading conditon, we can simulate different aspects based on the weight of bending moment distribution curve. When we control the ship of stability, make sure that the shear stress of the fusion point is near the center of the vessel, or in the center of gravity position as a symmetric distribution. So that when the semi-submersible vessel is up,the heel and trim which is controled by the ballast system is in a relatively simple variation, making within the prescribed scope of angle in the design, and do not produce moments of uphearal. The vessel can keep balance during a short time with ballast.