Abstract: A seal provides for the gastight separation of a cooling-gas side and an air side of a shaft, in particular a generator shaft, including an annular basic body having a sealing ring and an outlet for a sealing oil. The sealing oil forms an oil film in a radial gap between the sealing ring and the shaft. The sealing ring has segments made of a heat-resistant plastic or of a soft brass alloy which are disposed at the interior of the sealing ring facing the shaft. The plastic or soft brass alloy acts as an emergency lubricant in the event that the shaft comes into contact with the sealing ring. The segments are releasably fastened to the basic body, so that they can easily be exchanged. The basic body is preferably formed of two half-shell bodies.