A method of pumping a liquid medium, a centrifugal pump and an impeller therefor

Abstract

An impeller for a centrifugal pump includes a hub, a shroud extending outwardly from the hub and dividing the impeller into front and rear sides, a working vane on a first face of the hub and the shroud at the front side, a rear vane on a second face of the shroud at the rear side, and a balancing conduit extending through the hub from a first opening at the first face to a second opening at the rear side of the impeller. The first opening is disposed closer to the axis than the second opening, and the first opening is located within a circle formed by a radially innermost part of the working vane, while the impeller is rotated about the axis, and the second opening or the balancing conduit at the rear side of the impeller is located at a smallest diameter of the shroud.

1 - 4 . (canceled) 
     
     
         5 . An impeller for a centrifugal pump, comprising:
 at least a hub having an axis;   a shroud extending outwardly from the hub and dividing the impeller into a front side and a rear side;   at least one working vane arranged on a first face of the hub and the shroud at the front side of the impeller;   at least one rear vane arranged on a second face of the shroud at the rear side of the impeller;   and at least one balancing conduit extending through the hub from a first opening at the first face to a second opening at the rear side of the impeller; the first opening of the at least one balancing conduit in the first face of the hub being disposed closer to the axis of the impeller than the second opening at the rear side of the impeller, and the first opening in the first face of the hub being located within a circle formed by a radially innermost part of the at least one working vane, while the impeller is rotated about the axis, and   the second opening of the at least one balancing conduit at the rear side of the impeller being located at a smallest diameter of the shroud.   
     
     
         6 . (canceled) 
     
     
         7 . The impeller as recited in  claim 5 , wherein,
 the hub has an axial extension from the shroud in a direction opposite the at least one working vane, the extension having an outer surface, and the second opening of the at least one balancing conduit at the rear side of the impeller is located in the second face of the shroud, in a substantially cylindrical outer surface of the hub in at least one of the shaft and a shaft sleeve.   
     
     
         8 . The impeller as recited in  claim 5 , wherein the first opening of the at least one balancing conduit in the first face of the hub is disposed in the rotational direction of the impeller ahead of the second opening of the at least one balancing conduit at the rear side of the impeller. 
     
     
         9 . The impeller as recited in  claim 5 , wherein at least two balancing conduits having a common front opening are disposed at the axial centre of the first face of the hub. 
     
     
         10 . (canceled) 
     
     
         11 . The impeller as recited in  claim 5 , wherein the impeller is semi-open or closed. 
     
     
         12 . The impeller as recited in  claim 5 , wherein the circle has a diameter, the first openings have a radially outermost point forming an other circle with a diameter, and the diameter of the other circle is 0.9 times the diameter of the circle. 
     
     
         13 . The impeller as recited in  claim 5 , comprising, in parallel with the working vanes, two centrifugally acting elements configured to pump fluid in a direction parallel with the working vanes. 
     
     
         14 . A centrifugal pump, comprising:
 a housing with an inlet opening, a volute and a rear wall;   a shaft;   a shaft sealing; and   an impeller as recited in  claim 5 , the impeller being attached on the shaft so as to rotate with the shaft.   
     
     
         15 . The centrifugal pump as recited in  claim 14 , wherein the balancing conduit has a cross sectional flow area ranging between 5 and 20% of an area of the inlet opening of the pump. 
     
     
         16 . The centrifugal pump as recited in  claim 15 , wherein the balancing conduits have a combined cross sectional flow area ranging between 5 and 20% of the area of the inlet opening of the pump. 
     
     
         17 . The centrifugal pump as recited in  claim 14 , wherein the shaft sealing has the same or longer diameter than that of at least one of a surface of the hub and the shaft and the shaft sleeve. 
     
     
         18 . (canceled) 
     
     
         19 . The centrifugal pump as recited in  claim 14 , wherein the hub has an axial extension from the shroud in a direction opposite the at least one working vane, the extension having an outer surface, the impeller having a shoulder area at a junction of the shroud and the hub, the at least one balancing conduit opening to the shoulder area such that the second opening is located in one of the rear face of the shroud, both the rear face of the shroud and the outer surface of the hub, and the outer surface of the hub. 
     
     
         20 . The centrifugal pump as recited in  claim 14 , wherein the impeller having a shoulder area at a junction of the shroud and the shaft, the shaft having an outer surface and a diameter, the diameter extending to the second opening of the at least one balancing conduit such that the at least one balancing conduit opens to the shoulder area so that the second opening is located in one of the rear face of the shroud, the rear face of the shroud and the outer surface of the shaft and shaft sleeve, or in one of the outer surface of the shaft and the shaft sleeve. 
     
     
         21 . The centrifugal pump as recited in  claim 14  comprising, in parallel with the working vanes, two centrifugally acting elements configured to pump fluid in a direction parallel with the working vanes. 
     
     
         22 . The impeller as recited in  claim 5 , wherein
 the circle has a diameter, the first openings have a radially outermost point forming an other circle with a diameter, and the diameter of the other circle is 0.8.   
     
     
         23 . The impeller as recited in  claim 5 , wherein
 the circle has a diameter, the first openings have a radially outermost point forming an other circle with a diameter, and the diameter of the other circle is 0.7.