Device for washing and dewatering a fibre pulp suspension, which device comprises two hollow, circular-cylindrical screen members (1), which screen members contain evacuation chambers, internally in the screen members, for conducting away liquid. The screen members rotate towards each other for the purpose of forming a nip (2), with at least one of the said screen members (1) being arranged in a trough (7, 8) which partially encloses the casing (3) of the screen member and which converges towards the casing of the screen member in the direction of rotation of the screen member. At least one pulp inlet box (4) is arranged at the highest point (1) of the screen members, which are provided with troughs, for the purpose of introducing pulp between the casing (3) of the screen member and its trough (7, 8) for the purpose of forming a fibre pulp web. The pulp inlet box is provided with a pressure equalization section in which a certain equalization of irregularities in pulp qualities takes place before the pulp is fed into the actual washing or dewatering gap. The invention provides improved operability, especially at high pulp concentrations, and reduces the risk of plug formation.
