Abstract: This device comprises a directional stage including a slide (30,32) of a directional valve, which slide carries a drain valve (34) and a valve of communication (36) with a vessel to be protected.The slide is controlled by the pressure in an intermediate cavity (42). A piloting stage comprises communication valves (48,50) for putting the cavity (42) of the directional valve in communication with the vessel and the drain (24) respectively under the differential action of an adjustable and calibrated system and of the pressure in the vessel. The system comprises a plurality of independently adjustable elements (62,70,72) which in particular modify the travels of the communication and drain valves (48 and 50).