Anti-Heeling System (AHS)
The Anti-Heeling System (AHS) can either be provided as a stand-alone system or as a sub-system integrated in the ballast control. The AHS provides manual or automatic heel correction to keep the ship on ?even keel? during cargo operation. The heel angle is measured by an inclinometer which generates a signal for the control system initiating the necessary actions to keep the vessel in a horizontal position. In automatic mode, the system operator can pre-select a heel angle of up to three degrees starboard or portside which is kept by the system automatically. The prevailing heel angle is indicated on the panel. However, all operations are interrupted when the heel exceeds five degrees, or when one of the limiting tank level sensors has indicated low or high water level. The AHS usually operates a pair (or multiple pairs) of anti-heeling tanks (portside and starboard) which are connected via cross-pipes. The nominal transfer rate of ballast water from one ballast tank to the other on the opposite side depends on the cross-duct diameter, tank height (max. water-head amplitude) and the capacity of the ballast pump. A stability test system is available as an optional feature, which is considered useful to specify and report the actual stability of the vessel, after discharging and/or loading operations.