pulp possibly attached to it the drum 1 and the pressing roll 2 rotate in the direction shown by the arrows the pressing roll 2 is pressed downwards towards the drum surface so that the liquid will be pressed out from the pulp through the perforation of the drum 1 if so desired also the roll 2 may be perforated for other components than the feeding means 3 reference is made to above noted finnish patent the operation of the device has been illustrated by showing the incoming dirty pulp 10 by black and the outgoing washed pulp 11 by white and the intermediate phases in respective grey tones the dirtiness of the liquid coming through the drum 1 is shown respectively the pulp to be washed 10 is fed to the washing device at the point 5 it is advantageous to feed the pulp coming from the preceding washing step without diluting at least in 12 per cent consistency in order not to increase the length of the drying drum excessively or by using any suitable pre drying method the liquid is leaving pulp and with it also some of the solid state matter when it for the first time passes the pressing point between the roll 2 and the drum 1 if needed the pulp can also be dried further by directing it several times through the pressing point but in practice this is seldom necessary next washing.