Abstract: Arrangement 1 for washing and dewatering a fiber pulp suspension, which arrangement comprises two hollow, circular-cylindrical screen members 2a, 2b delimited by envelope surface and end walls. The screen members rotate towards each other to form a nip 10, at least one of the said screen members 2a, 2b being arranged in a vat 6 which partially encloses the envelope of the screen member and which, in the direction of rotation of the screen member, converges towards the envelope of the screen member. The invention relates to a sealing arrangement 8 at the end wall of the screen member. By retracting the seal a distance X from the envelope surface of the screen member in a limited area &agr; near the nip 10, the seal is relieved of the very high hydraulic and mechanical pressures which occur in the nip. Wear between the end wall of the drum and the seal at the press nip is reduced. A simple pressurized seal can thus be used with the same low pressure applied along the entire circumference.