Venting system for fuel tank

The ventilating device (5) has a movable area (6) assembled of two telescopic segments (11, 12) accommodating a helical spring (14). The segments (11, 12) are sealed against each other by several layers of sealing rings (13). The inner telescopic segment (11) is permanently joined to the ventilation device (5) whereas the outer pipe (12) is attached to a valve (7) supported by the spring (14) against the upper shell (3) of the tank (1) with a projection (16) protruding from its upper surface. A hook (17) located at the inner telescopic segment (11) engages with a slot (18) in the outer segment (12).