Abstract: A centrifugal pump, the impeller (2) of the pump having one or more holes through the impeller adjacent to its hub. The hole or holes (7) are positioned between the vanes (3) of the impeller and closer to the hub than the periphery of the impeller. The total area of the holes is more than 0.4% of the area of the impeller, preferably 0.5-0.6% of the area of the impeller or more than 2% of the inlet area of the pump, preferably 2.5-5% of the inlet area. Preferably there is a cavity or a pit (8) at the back of the impeller.

Abstract: Centrifugal pumps for pumping a pulp suspension and conducting gas away from the pulp suspension are disclosed including a pump housing having an inlet and an outlet, a rotary shaft, an impeller mounted on the rotary shaft within the pump housing, the impeller including a hub and pump blades extending outwardly from the hub, a wheel disk adjacent to the impeller so that the pump blades extend outwardly along the wheel disk, a vacuum impeller within the pump housing behind the wheel disk and including a vacuum pump housing, vacuum impeller blades, a seal for sealing the vacuum pump housing to the rotary shaft, the vacuum pump housing including a suction port for drawing gas into the vacuum pump housing and an exhaust port for expelling gas therefrom.

Abstract: The present invention is for a centrifugal pump, the impeller (2) of the pump having one or more holes through the impeller adjacent to its hub. The hole or holes (7) are positioned between the vanes (3) of the impeller (2) and closer to the hub than the periphery of the impeller. The total area of the holes is more than 0.4% of the area of the impeller, preferably 0.5-0.6% of the area of the impeller or more than 2% of the inlet area of the pump, preferably 2.5-5% of the inlet area. Preferably there is a cavity or a pit (8) at the back of the impeller.

Abstract: The present invention is for a conductivity metering device. The invention is primarily for conductivity meters which are used for level gauging of fouled liquids where the fouling materials may cause functioning problems of the metering probe. The probe is intended for metering of the conductivity between the probe body 1 and a tube 14, made from metallic material, in order to determine if there is liquid inside the tube. The probe body 1 is the outer tip of a piston 6 and it may be made as one piece with the piston or as a separate part which is mounted onto the piston. The piston 6 and parts connected thereto are movably mounted in the cover part 15 and the cap 8 by sealing slide bearings 4, 7. When metering does not take place the tube 14 is mostly filled with water at a certain overpressure relative to its surroundings. As the metering piston 6 is kept retracted by an active overpressure between the sealings 4 and 7 liquid is prevented from leaking in.

Abstract: Apparatus for providing a mechanical planar seal, as for example for use with a centrifugal pump having a rotating shaft, includes a primary seal formed of a movable first part rotatable with the shaft and a fixed second part or seat, a secondary seal axially spaced along the shaft from the primary seal, an inlet for flushing liquid, an outlet for the flushing liquid and for pump medium that leaks through the primary seal, a collection chamber defined between the primary and secondary seals for flushing liquid and leaking pump medium, and a drain passage connecting the collection chamber and outlet. The collection chamber is divided into at least two portions in liquid communication with each other and with the drain passage by at least one predeterminately-configured wall so as to assure that the flushing liquid is maintained between the primary and secondary seals for an extended period of time for advantageously efficient use of the flushing liquid in lubrication and cooling of the primary seal.

Abstract: In the disclosed method of determining the current or instantaneous operating conditions of a centrifugal pump, the radial forces impressed on the impeller shaft by the operatively rotating pump impeller are measured at a shaft-supporting bearing disposed proximate the pump housing and impeller. In a preliminary or test operation of the pump, this radial force measurement is taken at a plurality of volumetric liquid flow rates through the pump so as to develop a relationship between the radial force and liquid flow. Then, during normal operation of the pump, the current or instantaneous radial force is measured at the bearing and this measurement is compared to the previously-developed relationship to accurately determine the instantaneous operating conditions of the pump by identifying the point along the pump's characteristic curve--which defines for the pump a relationship between lifing height and volumetric liquid flow--at which the pump is currently operating.

Abstract: Apparatus for providing a mechanical planar seal, as for example for use with a centrifugal pump having a rotating shaft, includes a primary seal formed of a movable first part rotatable with the shaft and a fixed second part or seat, a secondary seal axially spaced along the shaft from the primary seal, an inlet for flushing liquid, an outlet for the flushing liquid and for pump medium that leaks through the primary seal, a collection chamber defined between the primary and secondary seals for flushing liquid and leaking pump medium, and a drain passage connecting the collection chamber and outlet. The collection chamber is divided into at least two portions in liquid communication with each other and with the drain passage by at least one predeterminately-configured wall so as to assure that the flushing liquid is maintained between the primary and secondary seals for an extended period of time for advantageously efficient use of the flushing liquid in lubrication and cooling of the primary seal.

Abstract: A centrifugal pump wheel (4) comprises a rear (6) and/or a front (9) covering plate or dish, which has a plurality of gas evacuation openings (8) located leeward of the pump wheel vanes (5). To increase the effectivity of the gas evacuation and thereby improve the performance characteristics of the pump that fraction of the area of the openings which is located nearer the circumference of the pump wheel than the center of the pump wheel has been made larger than the remaining portion of the area of the openings.The invention also relates to a method of pumping a liquid which contains gas and possibly also solids, by means of a centrifugal pump having a pump wheel with the above characteristics. The gas pressure in a conduit (12) which is in communication with said openings (8) is measured.