Abstract: A centrifugal pump for pumping fiber suspensions including a centrifugal pump housing (50) defining a centrifugal pump chamber (54) having a suspension inlet and suspension outlet. Located within the pumping chamber is a centrifugal impeller (60). A vacuum pump chamber (76) defined by a front wall (112) facing the impeller and a rear wall (110) and opposite the front wall is located adjacent the centrifugal pumping chamber (54). A vacuum pump rotor (96) is mounted within the vacuum pump chamber at a distance from the front and the rear walls (112, 110). The axial distance between the vacuum pump rotor and the front and rear walls (112, 110) is adjustable to a value of less than 0.30 mm, and preferably less than about 0.20 mm.

Abstract: A centrifugal pump for pumping fiber suspensions includes a centrifugal pumping housing (50) having an inlet (52) and an outlet for the suspension and a centrifugal impeller within the centrifugal pump housing. A vacuum pump (70) is placed adjacent the centrifugal pump housing (50) and includes a vacuum pump chamber defined by first and second opposed side walls (110, 112) and a vacuum pump rotor which is eccentrically mounted within the vacuum pump chamber. The rotor has radially extending opposed side edges facing the vacuum pump side walls (110, 112) forming a clearance therebetween. The pump includes a conduit within at least one of the vacuum pump side walls (110, 112) for supplying a sealing liquid to the clearance (122) between the rotor and at least one of the side walls of the vacuum pump chamber (76). Flushing liquid may be supplied through the same sealing liquid conduits or separately therefrom. The centrifugal pump may include a fluidizing impeller.

Abstract: A liquid ring vacuum pump includes a vacuum pump housing composed by two opposed end walls spaced by an annular wall defining a vacuum pump chamber; a shaft extends into the vacuum pump chamber; a rotor is mounted on the shaft and is arranged eccentrically in the chamber; the rotor includes a rotor central portion and a plurality of vacuum pump vanes extending therefrom toward the annular wall; the rotor central portion and the vanes having at least one lateral edge adjacent the end walls facing the annular wall, the lateral edges and the end walls form a clearance therebetween; and the clearance between the edges and at least one of the adjacent end walls of the vacuum pump chamber increases towards the annular wall. A combination of the liquid ring vacuum pump with a centrifugal pump for pumping multi-phase liquids such as gas and solids containing fiber suspensions of the pulp and paper industry is also provided.