The safety device damps or blocks the movement of a ruptured section of a flow medium line (1) contained within a sleeve (4) fitting through a concrete wall (3), using at least two tension rods (6) extending across the possible rupture point (2). The tension rods are secured to the line on one side of the possible rupture point and are secured to the sleeve on the opposite side of the latter. At least one of the fixings for each tension rod
