Abstract: An arrangement for mounting a tube (4) provided with a flange in a hole (3) formed in a wall (2) comprises a locking ring (8) with at least three peripherally spaced apart seats (10) adapted to cooperate with a corresponding number of pins (9) which are fixed to the wall and which each have an oblique surface against which a cam surface (13) provided adjacent to the seat (10) on the periphery of the locking ring is arranged to be applied so that, when the locking ring is turned, the locking ring is urged against the wall in order to compress an elastic sealing ring (7) provided between the locking ring and the wall.