The anti heeling system is designed to maintain the stability of the ship during loading and unloading conditions. The idea was first introduced by Marc Girard of the United States in 1991. Further on the system was developed by China followed by Germany and Russia from 2009 to 2011. Finally, the system was implemented in 2013 this system is used mostly on container ships some of the leading companies providing the anti heeling systems are TKT tanktech, Wartsila, Hoppe, VEGA.
1) Heel – A vessel is said to be heeling when there is a temporary inclination of the ship due to the movements caused by the outside forces such as winds waves or when the ship undergoes a sharp turn.
2) List – The vessel is said to be listing if there is a permanent inclination of the ship caused by off-center weight or negative metacentric height or combination of off-center weight and negative metacentric height.
The ships are always designed and operated to maintain a positive metacentric height but sometimes the CG shifts upwards due to the empty double bottom and ballast tanks or when there is a very heavy cargo on the deck as a result the metacentric height becomes negative. But chances of occurring are very rare hence the main cause of listing is the off-center weight. This is caused when there is an uneven loading or discharge of cargo. Now Assume that the ship is undergoing a loading operation on the port side with the help of a port facility (crane). The ship will get inclined to the port side due to the moment produced by the cargo loaded. To make the ship upright again, the operator has to load equal weight on the starboard side. This increases the downtime during the during loading and the same condition is applicable during the unloading operation as well. Thus the anti heeling system deals with the correction of the listing helping the ship to remain upright. Let’s not get confused with the name anti heeling the system does not correct the heel but it corrects the list of the ship..
Concept of Anti heeling system
As we know, the anti heeling system corrects the list and makes the ship upright. This is achieved by pumping the ballast water into heeling tanks. The heeling tanks and nothing but a few of the wing tanks interconnected to each other. Both the port and the starboard side tanks are connected with the help of a pipeline. If the ship lists towards the port side the system transfers water from the port side tanks to the starboard side thanks hence make the ship upright. Refer to the figure below to observe the water in the last picture.
Main components of the anti heeling system
A simplified diagram of the anti heeling system is shown below main components of the system include
- Main control panel – This panel consists of a digital display of the transfer process, working pressures, etc. The anti heeling system can be operated from the control panel. It is located in the cargo control room.
- Pump starter panel – The anti heeling pump can be started or stopped from the pump starter panel. The panel is located in the engine control room.
- Anti heeling pump – It is a reversible pump it can be inside a type (inside the piping) or outside type (conventional pump attached to a bevel gear) some models use unidirectional pump too.
- Pneumatic valves – Usually butterfly valves are used in this system.
Working of anti heeling system
The system can be operated in manual as well as automatic mode. In auto mode, the inclination of the ship is measured by an inclinometer and is fed to the controller the controller controls both the valves and the and dealing pump if any inclination is sensed. The controller opens the valves and turns on the pump to start the transfer of water in order to correct the inclination.
In manual operation, the valve and the motor have to be operated from the main control panel. The inclination of the ship is displayed on the monitor. The user manually starts the transfer to the desired side during manual operation. The operator needs to be careful to open the valves and then start the transfer; if the valves are not open the pump will run dry and burn out.
The reasons for providing two modes of operation in the anti heeling system are as follows:
Sometimes the food facility takes a long time to load-unload the cargo the time period can go up to two days it is not possible for the operator to operate the anti heeling system continuously for two days due to human physical limitations hence auto mode is used. The control circuit of the and dealing pump consists of many wires and complex codes to attend the automatic operation if any of this fails, the anti heeling system would not be able to operate on its own therefore at such times manual mode is used.
Some models eliminate the use of the pump. They transfer water by using high-pressure compressed air. The air is induced in the top of the tank from where the water needs to be transferred. The air pushes the water out of the tank and thus it enters the tank on the opposite side.
Advantages of Anti heeling system
- Reduction of downtime during loading and unloading operations.
- The safety of the ship and seafarers is ensured.