Centrifugal pump for conveying a fluid

Abstract

A centrifugal pump for conveying a fluid includes a pump housing, an impeller to convey the fluid from an inlet to an outlet, a shaft to rotate the impeller, a first sealing device to seal the shaft at a suction side, a second sealing device to seal the shaft at a discharge side, a balance drum connected to the shaft between the impeller and the second sealing device, the balance drum defining a front side facing the at least one impeller and a back side facing the second sealing device, a relief passage between the balance drum and a stationary part, a balance line connecting the back side with the suction side, a discharge opening arranged at the relief passage between the front side and the back side, and a connecting line connecting the discharge opening with the first sealing device.

What is claimed: 
     
         1 . A centrifugal pump for conveying a fluid, comprising:
 a pump housing with an inlet at a suction side and an outlet at a discharge side;   at least one impeller configured to convey the fluid from the inlet to the outlet;   a shaft configured to rotate the impeller about an axial direction;   a first sealing device configured to seal the shaft at the suction side;   a second sealing device configured to seal the shaft at the discharge side;   a balance drum fixedly connected to the shaft and arranged between the at least one impeller and the second sealing device, the balance drum defining a front side facing the at least one impeller and a back side facing the second sealing device;   a relief passage disposed between the balance drum and a stationary part configured to be stationary with respect to the pump housing, the relief passage extending from the front side to the back side;   a balance line connecting the back side with the suction side;   a discharge opening arranged at the relief passage between the front side and the back side; and   a connecting line connecting the discharge opening with the first sealing device.   
     
     
         2 . The centrifugal pump in accordance with  claim 1 , wherein the connecting line comprises at least one flow controller configured to control the flow through the connecting line. 
     
     
         3 . The centrifugal pump in accordance with  claim 1 , wherein the connecting line comprises a first branch and a second branch, the first branch connected with the first sealing device, and the second branch connected with the second sealing device. 
     
     
         4 . The centrifugal pump in accordance with  claim 3 , wherein the first branch comprises a first flow controller configured to control the flow through the first branch, and the second branch comprises a second flow controller configured to control the flow through the second branch. 
     
     
         5 . The centrifugal pump in accordance with  claim 3 , wherein the connecting line comprises a third branch, the third branch is connected to the suction side. 
     
     
         6 . The centrifugal pump in accordance with  claim 5 , wherein the third branch comprises a third flow controller configured to control the flow through the third branch. 
     
     
         7 . The centrifugal pump in accordance with  claim 6 , wherein at least one of the flow controllers is an adjustable valve. 
     
     
         8 . The centrifugal pump in accordance with  claim 2 , wherein the at least one flow controller includes a plurality of flow controllers and each flow controller is an adjustable valve. 
     
     
         9 . The centrifugal pump in accordance with  claim 1 , wherein the first sealing device comprises a mechanical seal. 
     
     
         10 . The centrifugal pump in accordance with  claim 1 , wherein the second sealing device comprises a mechanical seal. 
     
     
         11 . The centrifugal pump in accordance with  claim 1 , wherein the pump is a multistage pump and the at least one impeller includes a plurality of impellers, and the impellers are arranged one after another on the shaft. 
     
     
         12 . The centrifugal pump in accordance with  claim 11 , wherein the pump is a between-bearing pump. 
     
     
         13 . The centrifugal pump in accordance with  claim 11 , further comprising an outer barrel casing, in which the pump housing is arranged.