A sealing device is for sealing fluid transmittable openings in well components. The sealing device includes an elastic element which is arranged between two shoulders. The elastic element, before being placed in the fluid transmittable opening, has a larger external dimension than the fluid transmittable opening to be sealed. A gap is arranged between at least one of the shoulders and the elastic element, allowing liquid to enter between the shoulder and the elastic element. The ridge is arranged on an intermediate piece which is located between the shoulder and the elastic element. The intermediate piece is constituted by as ring in which the ridge is surrounding and divided, and projects from an end surface opposite an abutment surface facing the elastic element.