The anti heeling system is part of the ballast system which has been explained in one of my previous posts and can be found if follow thins link.
The anti-heeling tanks are located on the port and starboard sides of the ship and are filled and emptied by means of the ballast system.
A reversible propeller pump is used in the heeling system. This pump is attached to a pipeline that connects the two heeling tanks.
Depending on the control position that has been preset, the pump can be started and stopped either from the anti-heeling system control panel located in the SCC or from the integrated control and monitoring system (ICMS) screen displays, located either in the SCC or on the bridge. On board, the use of the control panel for the anti-heeling system is the option that is most highly recommended because it enables full access to the system through a menu-driven operator display.
When heeling operations are being performed, there will be a lowest level at which the pump will automatically shut off, same as a maximum level that can be reached in any tank.
Floats for the highest level are installed in each tank. These are wired up and attached to the monitoring and alarm system. Each tank is equipped with a low level transmitter, which will turn off the pump when the predetermined level is reached. When the pump is running, the system will turn off automatically if the ship’s heel is greater than 8 degrees.
During cargo loading and discharge activities, the vessel will be able to stay within acceptable heeling limits thanks to the anti-heeling system. On container vessels, the vessel should not be listed more than 0.5 degree to either side of upright in order to guarantee that containers move freely in the cell guides. However, the loading and unloading of containers can cause the ship to list beyond these limitations. The list can be corrected by moving a quantity of water from the port anti-heeling tank to the starboard anti-heeling tank, or vice versa.
The operating modes of the system are as follow:
- AUTO: starting and stopping is decided by heel measurement to keep the vessel at a predetermined heel
- MANUAL: starting and stopping is controlled by the operator
- GOTO: the operator keys in a desired heel and the pump will run until that heel value is obtained
- VALVE: the tank valves only are opened to gravitate water between tanks achieving the desired heel correction without starting the pump
- LOCAL/COMP: operation of the heeling pumps remotely from the ICMS screen display in the SCC or the bridge.
It is important to note that only authorized personnel with a knowledge of the system and an understanding of ship stability make any adjustment to the anti-heeling system. Errors in adjustment can have serious implications on the vessel’s stability and operational performance.
Make sure that the anti-heeling tanks are filled with sea water to the correct level before beginning any mode of operation. This means that the combined total of both tanks should be less than 95% of the capacity of one tank.
Check to see that the pump, the control panel for the anti-heeling system, and any other system equipment all have access to electrical power.
The operation on AUTO mode of the anti-heeling system is only permitted in harbor. Here below I will exemplify, the operating mode based on above illustrated control panel:
On anti-heeling system control panel, key in MAIN to begin at the main menu, select RUN, then select AUTO. It is not possible to select RUN if the system is blocked for any reason. In this window the operator has two choices, START and SET. Firstly select SET; this will open a new window, AUTO SETTINGS. The operator must now verify that the settings are as required, as follows:
- WORKING POINT: this is the reference value, normally set at 0 degrees. However, if another value is required, key in that required value. Positive values (+) refer to STARBOARD and negative (-) values refer to PORT
- START AT: the pump will start when the heel angle from the working point exceeds this value. The factory setting is 1°
- STOP AT: the pump will stop when the heel angle is less than this selected value. Typical heel would normally be when the vessel is upright or 0 degrees. The STOP setting must be at least 0.5 degrees less than the START setting to prevent the pump from operating too many stops and starts and so avoid overheating the pump motor
- START DELAY: a time delay can be keyed in to start the pump only after the completion of the time delay, measured in seconds. Normal setting would be 0 seconds.
When all operating values have been selected and set return to the previous window by pressing the PREV key. The current heel value of the vessel will be displayed. If the text NOT READY is shown above the field START, make sure that the system is not in alarm and also make sure that the system is not in SEAMODE. If READY is displayed the START pushbutton can be operated; an LED light will illuminate to indicate that the system is now in auto. Two LED lights will illuminate to indicate when the pump is pumping to port or starboard.
To select MANUAL on the control panel key in MAIN to reach the main menu, then select RUN and then MANUAL. It will not be possible to select RUN if the system is blocked for any reason. In this mode there are three choices: PORT, STBD and TIMER. If the text NOT READY is shown above the field PORT or STBD, make sure that the system is not in alarm and make sure that the mode is not blocked. Pressing the pushbutton PORT or STBD will open the heeling tank valve and start the pump in the desired direction. When the desired heel correction has been achieved press key to stop the pump. Two LED lights will illuminate to indicate when the pump is pumping to port or starboard. A countdown timer will stop the pump when zero is reached. The preset value of this timer can be set by the operator, within certain limits. If the timer approaches zero when the pump is still required to run press the TIMER key. The timer will then start over again for the preset value.
To select GOTO control return to the main menu by keying in MAIN, select RUN, and then select GOTO. Once again RUN cannot be selected if the system is blocked. In this mode there is one selection: START. If the text NOT READY is shown above the field START, check out the alarms and make sure that the mode is not blocked or that SEAMODE has not been selected. NOT READY will also be shown if the current value is the same as the set value. Key in the desired heel value in the input field SET VALUE, positive (+) value indicates starboard and negative (-) value indicates port. Pressing the START pushbutton will open the heeling tank valve and start the pump in the desired direction.
The pump will stop automatically when the pre-selected heel value has been reached. Pressing the Key F8 STOP will interrupt the process. Two LED lights will illuminate to indicate when the pump is pumping to port or starboard.
To select VALVE control, return to the main menu by keying in MAIN. Select RUN and then VALVE. It is not possible to select RUN if the system is blocked. In this window there are two choices, OPEN and TIMER. If the text NOT READY is shown above the field OPEN, check out the alarms to make sure that the mode is not blocked or in SEAMODE. Pressing the OPEN pushbutton will open the anti-heeling tank valves while pressing Key F8 STOP will interrupt the process. Valve position is indicated by the text showing CLOSED, OPEN, CLOSING and OPENING. A countdown timer will close the tank valves when the desired heel correction has been achieved; the preset value of this sequence can be set by the operator within certain limits. If the timer approaches the desired heel correction position but the operator wishes to continue ballast transfer, press the TIMER key and ballast transfer will continue up to the preset value again.
The anti-heeling pump may be operated locally in manual mode for maintenance
purposes. Pushbuttons allow the pump to be started locally, in either the port or
starboard flow direction.
As specified, the above instruction is for exemplification purpose only, as every vessel has its own designed system which may be close or similar with the above.
Some vessels are equipped with anti-rolling tank which is fitted to provide a roll damping system to control the rolling of the vessel at sea and is a passive free surface open channel type anti-roll tank. The system is capable of adapting to changes in load and operation conditions by a change in the liquid level, the natural response period of the tank can be adjusted to the roll period of the ship. The system includes a liquid level and roll period indicating system and a phase sensing system to monitor the movement and control the anti-roll tank to assist the crew in achieving the most effective roll stabilization.
The operation of this type of anti-rolling tank consist of the following:
- Calculate the solid transverse metacentric height (GMs) without any free surface reduction of any tanks for the anti-rolling tank filled at the maximum operating liquid level.
- Check whether the calculated GMs is equal or higher than 3.0 meters. If this is the case, continue with 4.
- If the GMs is less than 3.0 meters, refer to the figure to obtain the correct operational liquid level. Recalculate GMs with the obtained liquid level. Refer again to the figure whether GMs is within the indicated range of GMs. If the GMs should fall on the dividing line between two operational liquid levels, use the higher level.
- Check whether the corrected GM including the free surface correction of all tanks (including the anti-rolling tank filled to the corresponding operating level) is above all minimum stability requirements. If operating parameters are acceptable fill or adjust the anti-rolling tank to the correct liquid level.
- The tank liquid level/roll period indication system constantly monitors the operational conditions and will automatically alarm to alert the crew if any adjustment of the system is required.
- In case of emergency, vessel’s stability must be considered carefully. If necessary the tank can be emptied by operating the quick discharge dump valves from the control panel.
- The tank should be emptied if the GMs is below or above certain values.
- If the roll period of the vessel is shorter than 16.0 seconds the range of design efficiency is reached. The tank should be operated at the maximum designed operational liquid level.
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Source and Bibliography:
- Youtube channels: Marine Online and Hoppe Marine