Steam Evacuation in a Pulp or Fiber Refiner

A first refining disc ( 5) for a defibrator (1) for refining fibrous material， adapted to receive a flow of incoming fibrous material (7) from a feed screw (3a) through a material inlet opening (4) arranged in the first refining disc (5)， is provided with at least one steam evacuating channel (21) comprising at least one steam inlet opening (22) arranged on a side of the first refining disc (5) adapted to face a second refining disc (6)， and at least one steam outlet opening (23) arranged on a side of the first refining disc (5) adapted to face away from the second refining disc (6). The at least one steam outlet opening (23) is arranged centrally of the at least one steam inlet opening (22) with respect to the center of the first refining disc (5)， and centrally of a position where the flow of incoming material (7) is to be received into the first refining disc (5) from the feed screw (3a)， with respect to the center of the first refining disc (5).