A washing arrangement for washing and dewatering cellulose pulp, comprising a rotary drum (1) with a plurality of external compartments on the drum for the pulp to be washed, which compartments are defined by axial compartment walls distributed along the circumference of the drum, a stationary cylindric casing enclosing the drum, whereby a ring-shaped space is defined between the casing and the drum, and where the ring-shaped space by means of longitudinal seals in axial direction of the drum is divided into a forming zone for forming the pulp in the compartments of the drum, at least one washing zone for washing the pulp and a discharge zone for feeding out the washed pulp where the casing (6) is provided with longitudinal through openings (7) in axial direction for each longitudinal seal (11), in which the longitudinal seals are placed so that the seal (11) can be removed from the washing arrangement in a direction outward from the drum centre.