Floating support or vessel equipped with a device for detecting the movement of the free surface of a body of liquid

A ship or floating support for transporting or storing a liquid constituted by a liquefied gas, cooled in at least one tank having a width, said tank being thermally insulated and having at least said width greater than 20 m, and a volume greater than 10,000 m3, said tank being supported inside a hull of a ship by a carrier structure, the ship having a plurality of beacons for detecting roughness of the liquid within said tank(s), each of said beacons comprising:

• a) a vibratory accelerometer vibration sensor for measuring the amplitude of acceleration (g) as a function of time (t) of vibratory movements of a wall of said tank or of a wall of the ship that is not in contact with sea water, said wall of the ship including a deck of the ship or a wall of an internal structure of the ship, said vibration sensor being fastened on said wall outside said tank;
• b) an electronic calculation unit having a microprocessor and an incorporated memory, for processing a signal as measured by said vibration sensor, to yield a processed signal, in order at least to eliminate background noise from said measured signal that is specific to the ship, and to detect movement of the liquid inside said tank by comparing values of the processed signal with predetermined threshold values beyond which the roughness of a liquid free surface is considered as constituting a risk of damaging deformation or deterioration of said wall;
• and
• c) a transmitter for transmitting said processed signal of the electronic calculation unit to a central unit.