Ballast and de-ballast operations on the ship must be performed by an experienced and responsible officer because they directly affect the ship’s stability.
A ballast system may differ from ship to ship, but the basics of all ballast systems remain the same: filling, removing, and transferring water from one tank to another to provide a ship with the necessary stability.
Getting Familiar with the System
All Pres Vac valves in the ballast system are normally hydraulically operated from the ship’s control center or the ECR, either manually or automatically.
The ballast pump suction and discharge valves, as well as other valves, have a fail-safe in the OPEN position, so that even if a valve malfunctions or becomes stuck, the ballast operation can continue.
The fail-safe position for overboard discharge valves is fail-stay.
Different Forms of Ballasting and De-ballasting
Ballasting or de-ballasting can be accomplished in five ways:
- Using gravity to transfer water between tanks.
- Gravity is used to ballast or de-ballast tanks from the sea.
- The tanks are ballasted using the ballast pump/pumps.
- Using the ballast pump/pumps, de-ballast the tanks.
- Using the stripping ejectors, de-ballast the tanks.
It should be noted that double bottom tanks should always be filled by gravity.
Important Points to Consider while Operating Ship’s Ballast System
A ballast system, like any other critical component in the vessel, such as boilers, Pres Vac valves, IGS, and burners, must be well-maintained to ensure that the tank is not overfilled, as this will damage the tanks because the pressure vacuum valves have a lower capacity than the pump. When the tanks reach their pre-set set point level, the filling valves will automatically close.
It is also important not to run the pump dry or with the discharge valves closed. This can be handled by an automated system that prevents the pump from starting until all necessary valves are opened.
Valves can be set to close automatically once the ballast tank has been filled with the required amount of water or when the setpoint is reached.
The port and starboard sides are considered separate systems, each with its own automatic ballast/de-ballasting sequence.
When using ballast pumps to fill ballast tanks, ensure that the motors are not overloaded (check current in ammeter). If this happens, the number of open ballast tank valves must be immediately reduced (closed) until the current is within the allowable limit. A ballast pump motor overload alarm is provided for the ballast pump’s safety.
Occasionally, during a sea voyage, an alarm on the ballast pumps suction pressure high will sound. Simply open the suction valve to the sea chest and close it when the pressure drops.
The water level in the heeling tanks should always be half full. However, if necessary, the heeling tanks can be used as ballast tanks. The heeling tank is emptied or filled using the ballast pump.
In some ports, port authorities may also request a sample of the ballast carried by the ship. The sample must be taken from the sounding pipe connection in this case. The locations of all sounding pipes are shown on the ship’s ballast system plan.