A custom yacht under construction turned to commercial company Circor to eliminate unwanted heeling during crane operations. The customer was looking for a system providing dynamic counterweights – an anti-heeling system. Such a system must be designed to automatically shift ballast water from one side to the other in a continuous, dynamic operation.
Onboard this superyacht, low levels of noise and vibration were important for passenger comfort, so an anti-heeling system that was quiet and didn’t generate much residual vibration or structure-borne noise was needed. In addition, the superyacht had limited installation space available.
The shipyard reached out to Allweiler with their requirements, and Allweiler designed a system accordingly — an Allweiler Anti-Heeling system based on a centrifugal pump.
Allweiler transferred technology from other marine markets, such as Navy and research vessels where low levels of noise and vibration are crucial, and merchant marine markets where the level of accuracy is generally higher than for pleasure yachts.
The pump operates at ultra-low speed and is controlled by a variable speed drive with prolonged ramp-up time. Operating a centrifugal pump at lower than normal speed prevents wear on rotating parts such as impellers and bearings and enables the pump to operate with less noise and less vibration. Slower pump speed also creates better suction capabilities. This is achieved as water speed inside the pump casing is reduced. With reduced water speed, the risk of water hammering in the ship’s piping (leading to noise, vibration and possibly damaging piping and valves) is reduced. The low pump speed also removes any risk of cavitation, another source of noise and vibration.
The pump, drive and valves in the yacht’s anti-heeling system are all controlled by the CIRCOR control system, which is also connected to an inclinometer that monitors the yacht’s inclination with accuracy down to 0,04°. The system may be manually or automatically operated.
For maximum safety, the system has a fail-safe arrangement including automatic shut-down and complies with DNV-GL class rules and regulations.