Adapter flange for fitting on a pipe provided with a through opening that defines a flow cross-section, the adapter flange comprising: - a first inner part comprising: • an armature made from a first material and having a curved first surface configured to come into mechanical contact with an inner wall of the pipe, a second surface opposite the first surface and at least one side wall joining the first surface to the second surface, the armature comprising a deformation zone configured to allow movement of the armature between a first position where the first inner part presents a first cross-section larger than the flow cross-section and a second position where the first inner part presents a first cross-section smaller than the flow cross-section, • a seal made from a second material different from the first material and at least partially covering the first surface of the armature and arranged to come into contact with the inner wall of the pipe and to continuously surround the through opening, the seal continuously covering the side wall and the second surface of the armature so as to separate the armature from an effluent flowing in the pipe, • fixing means for securing the first inner part with the outer wall of the pipe. - a first inner part comprising: • an armature made from a first material and having a curved first surface configured to come into mechanical contact with an inner wall of the pipe, a second surface opposite the first surface and at least one side wall joining the first surface to the second surface, the armature comprising a deformation zone configured to allow movement of the armature between a first position where the first inner part presents a first cross-section larger than the flow cross-section and a second position where the first inner part presents a first cross-section smaller than the flow cross-section, • a seal made from a second material different from the first material and at least partially covering the first surface of the armature and arranged to come into contact with the inner wall of the pipe and to continuously surround the through opening, the seal continuously covering the side wall and the second surface of the armature so as to separate the armature from an effluent flowing in the pipe, • fixing means for securing the first inner part with the outer wall of the pipe. • an armature made from a first material and having a curved first surface configured to come into mechanical contact with an inner wall of the pipe, a second surface opposite the first surface and at least one side wall joining the first surface to the second surface, the armature comprising a deformation zone configured to allow movement of the armature between a first position where the first inner part presents a first cross-section larger than the flow cross-section and a second position where the first inner part presents a first cross-section smaller than the flow cross-section, • a seal made from a second material different from the first material and at least partially covering the first surface of the armature and arranged to come into contact with the inner wall of the pipe and to continuously surround the through opening, the seal continuously covering the side wall and the second surface of the armature so as to separate the armature from an effluent flowing in the pipe, • fixing means for securing the first inner part with the outer wall of the pipe.