IT1087872B - paper making pressing section exploiting viscosity of heated water - feeds steam and ensures heat retention by web and felt - Google Patents

Abstract

The dewatering in the pressing section of a papermaking machine having at least two and for pref. three or four consecutive nips is improved. The web of paper runs between the pressing nips along an enclosed path with a pressure nip formed by two felts between a cylinder taking in water and a suction cylinder, and a following nip formed between the suction cylinder and a cylinder with a smooth surface, which may be a cylinder belonging to a following nip. As the web passes between the first two nips it runs over a sector of the suction cylinder whilsts lieing against the felt, and is exposed from its outer surface inwards to hot steam, a large quantity of which condenses and gives up its heat to the web. To make better use of the diminished viscosity of water at higher temperatures, and apply the heat so that the web and the felt do not cool off again before the nip is reached. The dewatering is made more efficient and the web leaves the pressing section in a dryer and more coherent condition. The speeds of fast running machines and the security of operation can thus be optimised. In the first nip the water is evacuated in two directions so that no easily removed water is heated wastefully.