Ring comprising: - an outer belt (3) equipped with closing means (7) for closing the ring (1) around a duct (2)； - an inner chamber (4) that can be inflated and deflated； - a flexible inflation/deflation tube (5)； wherein the lips have contact surfaces facing each other, the closing means comprising at least one perforation arranged on the contact surface of a first of the two lips and at least one protrusion protruding from the contact surface of a second of the two lips, the protrusion and the perforation being configured so that the protrusion is retained in the perforation by fitting, the fitting being selected to be released in the event of overpressure in the ring.
