Minggu, 23 Januari 2011



Ballast water is carried in ships to provide stability and trim. A ship’s ability to take on and discharge ballast water is fundamental to its safe operation. As a ship loads or unloads cargo or takes on or consumes fuel, the ship must accommodate changes to its displacement and trim by taking on or discharging ballast water. Ballast water is taken on through openings near or on the bottom of a ship’s hull and is pumped in or out of a ship through piping connected to ballast pumps which are located in the ship’s lower machinery space. Without these ballast water operations, ships cannot be operated safely: ballast water intake and discharge provides proper stability and trim, minimizes hull stress, aids or allows maneuvering, and reduces ship motions of roll and pitch. The water pumped into a ship’s ballast tanks must inevitably be pumped out when the ship takes on cargo. Ballast uptake and discharge most often occurs in port during cargo operations, but may also occur while the ship is in transit on the open lake or through connecting waterways to maintain proper trim and stability.
               ship can take some animal (plankton) from one port to other port in different country by ballast system

Ballast water is fresh or saltwater held in the ballast tanks and cargo holds of ships. It is used to provide stability and maneuverability during a voyage when ships are not carrying cargo, not carrying heavy enough cargo, or when more stability is required due to rough seas. Ballast water may also be used to add weight so that a ship sinks low enough in the water to pass under bridges and other structures.

Usually ballast water is pumped into ballast tanks when a ship has delivered cargo to a port and is departing with less cargo or no cargo. Ballast water is then transported and released at the next port-of-call where the ship picks up more cargo. If a ship is receiving or delivering cargo to a number of ports, it may release or take on a portion of ballast water at each port. In such cases, the ship’s ballast water contains a mix of waters from multiple ports.

A ballast tank is a compartment within a boat or ship that holds water. A vessel may have a single ballast tank near its center or multiple ballast tanks typically on either side. A large vessel typically will have several ballast tanks including double bottom tanks, wing tanks as well as forepeak and aftpeak tanks. Adding ballast to a vessel lowers its center of gravity, and increases the draft of the vessel. Increase draft may be required for proper propeller immersion.
A ballast tank can be filled or emptied in order to adjust the amount of ballast force. Ships designed for carrying large amounts of cargo must take on ballast water for proper stability when travelling with light loads and discharge water when heavily laden with cargo. Small sailboats designed to be light weight for being pulled behind automobiles on trailers are often designed with ballast tanks that can be emptied when the boat is removed from the water.
All bulk carriers are to have ballast tanks of sufficient capacity and so disposed to at least fulfill the following requirements. There are 2 ballast conditions.
Normal ballast condition is a ballast (no cargo) condition where:
  • the ballast tanks may be full, partially full or empty. Where ballast tanks are partially full, must be calculated according to the class.
  • any cargo hold or holds adapted for the carriage of water ballast at sea are to be empty
  • the propeller is to be fully immersed, and
  • the trim is to be by the stern and is not to exceed 0.015 ship length
In the assessment of the propeller immersion and trim, the draughts at the forward and after perpendiculars may be used.
Heavy ballast condition is a ballast (no cargo) condition where:
  • at least one cargo hold adapted for carriage of water ballast at sea is to be full
  • the propeller immersion I/D is to be at least 60 %, where:
    = Distance from propeller centerline to the waterline
    = Propeller diameter
  • the trim is to be by the stern and is not to exceed 0.015L
  • the moulded forward draught in the heavy ballast condition is not to be less than the smaller of 0.03 ship’s length or 8 m.

Another important component in ship is bilge system, It is as water place of exile if there is leakage in ship, the spesifict function is as cleanshing system if :
3.  leakage in connection welds
bilge system component:
type of bilge system are:
1. bilge system in space loes
2. bilge system at cargo tanker tank ship
3. bilge system in engine space

Because of bilge system is very susceptible, it have some requirements such is it should be could pumped  in every condition, it have relation with safety in the ship. Because of late to dischard leak water is very dangerous for many people in ship. The other requirement are pump location as low as may be above tank top, and then bilge system is fitted in portside and starboard of ship, except to ship end enough one pump

The requirement of suction well are minimal found two pieces that is beside starboard and portside, except to ship end , for long ship more than 30 m so found at least 3 pumps, minimal volume is determined class that is minimal 0.57 m3 and depth minimal 0.5 depth

The arrangement of bilge system according to rules All the distribution boxes, valves and cocks in connection with the bilge pumping arrangements are to be so arranged that, in the event of flooding, one of the bilge pumps may be operative in any compartment. If there is only one system of pipes common to all pumps, the necessary valves or cocks for controlling the bilge suctions must be capable of being operated from above the bulkhead deck. Where, in addition to the main bilge pumping system, an emergency bilge pumping system is provided, it is to be independent of the main system and so arranged that a pump is capable of operating on any compartment under flooding conditions; in this case, only the valves and cocks necessary for the operation of the emergency system need be capable of being operated from above the bulkhead deck.
while in bilge system, water that appear leakage consequence in ship will be sucked by suction well then be channelled to pass pump aims overboard

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