U–Tank Roll Damping

A U-Tank Anti-rolling system as first developed by FRAHM uses the double hull spaces and can be the appropriate choice for open hatch ships. The U-Tank can be combined with Blower Anti-Heeling equipment.

A FRAHM-type roll damping system is a controlled passive U-tube type anti-roll tank. Two properly sized wing tanks are interconnected via a crossover duct either through or above the double bottom. The resulting fluid flow is used for creating a stabilizing moment opposing the roll motion of the vessel. The natural response period of this type of tank is fixed by its structural boundaries, which means it cannot be changed once the tank is built. The approach is to design the tank for the expected shortest roll period of the vessel. An increase of the tank’s response period can be accomplished by restricting the airflow in between the connected wing tanks.

Monitoring & Control System

Hoppe Marine has developed the monitoring & control system MOCON to assist the shipboard personal in operating the stabilizer safely at its peak efficiency. The system constantly measures the dynamic tank liquid level and the roll period of the ship. The measurements are basis for automatically adjusting the tank water oscillating period by restricting the air flow in between the interconnected tanks to achieve the required phase lag of approximately 90 degrees. The system is self-controlled including automatic safety procedures in case of malfunctions of components or sea/ship conditions are outside of the systems working range.