Pumping arrangement

Abstract

A pumping arrangement includes first and second multistage pumps. Each pump includes a housing with a pump unit, the housing includes a pump inlet and a pump outlet, the pump unit includes a plurality of impellers to convey fluid from the pump inlet to the pump outlet, and a pump shaft extending from a drive end to a non-drive end, each impeller mounted to the pump shaft. The second multistage pump includes a first mechanical seal having a process side facing the pump unit. The pump outlet of the first multistage pump connected to the pump inlet of the second multistage pump, so that the first multistage pump and the second multistage pump are arranged in series. The process side of the first mechanical seal of the second multiphase pump is in fluid communication with the pump inlet of the first multistage pump.

What is claimed is: 
     
         1 . A pumping arrangement comprising:
 a first multistage pump; and   a second multistage pump, each multistage pump comprising   a housing with a pump unit arranged in the housing, the housing comprising a pump inlet to receive a fluid with a suction pressure, and a pump outlet to discharge the fluid with a discharge pressure, and the pump unit comprising a plurality of impellers configured to convey the fluid from the pump inlet to the pump outlet, and   a pump shaft configured to rotate about an axial direction, with the pump shaft extending from a drive end to a non-drive end, and each impeller of the plurality of impellers being mounted to the pump shaft in a torque proof manner,   the second multistage pump comprising at least a first mechanical seal to seal the pump unit at the pump shaft, with the first mechanical seal having a process side facing the pump unit,   the pump outlet of the first multistage pump being connected to the pump inlet of the second multistage pump, so that the first multistage pump and the second multistage pump are arranged in series, and   the process side of the first mechanical seal of the second multiphase pump in fluid communication with the pump inlet of the first multistage pump.   
     
     
         2 . The pumping arrangement in accordance with  claim 1 , wherein each of the first and second multistage pumps comprises a first balance drum fixedly connected to the pump shaft between the pump unit and the drive end of the pump shaft, the first balance drum defining a first front side facing the pump unit and a first back side, a first relief passage is provided between the first balance drum and a first stationary part configured to be stationary with respect to the housing, the first relief passage extending from the first front side to the first back side, and a balance line is configured to recirculate the fluid from the back side to a low pressure side of the multistage pump. 
     
     
         3 . The pumping arrangement in accordance with  claim 2 , wherein the second multistage pump comprises a second balance drum, fixedly connected to the pump shaft between the pump unit and the non-drive end of the pump shaft, the second balance drum defining a second front side facing the pump unit and a second back side, a second relief passage is disposed between the second balance drum and a second stationary part configured to be stationary with respect to the housing, the second relief passage extending from the second front side to the second back side, and the second back side is in fluid communication with the pump inlet of the first multistage pump. 
     
     
         4 . The pumping arrangement in accordance with  claim 3 , wherein the balance line of the second multistage pump is configured to connect the first back side of the second multistage pump with the second back side of the second multistage pump. 
     
     
         5 . The pumping arrangement in accordance with  claim 3 , wherein the second front side is exposed to suction pressure of the second multistage pump. 
     
     
         6 . The pumping arrangement in accordance with  claim 3 , wherein the second multistage pump comprises a second mechanical seal to seal the pump unit at the pump shaft, with the second mechanical seal having a process side facing the pump unit, and the second mechanical seal is arranged between the second balance drum and the non-drive end of the pump shaft of the second mechanical seal. 
     
     
         7 . The pumping arrangement in accordance with  claim 1 , wherein in each of the first and second multistage pumps the plurality of impellers comprises a first set of impellers and a second set of impellers, the first set of impellers and the second set of impellers are arranged in a back-to-back arrangement, so that an axial thrust generated by the first set of impellers is directed opposite to an axial thrust generated by the second set of impellers. 
     
     
         8 . The pumping arrangement in accordance with  claim 7 , wherein each of the first and second multistage pumps comprises a center bush fixedly connected to the pump shaft between the first set of impellers and the second set of impellers, and a balancing passage is disposed between the center bush and a third stationary part configured to be stationary with respect to the housing. 
     
     
         9 . The pumping arrangement in accordance with  claim 1 , wherein each of the first and second multistage pumps comprises a drive unit arranged in the housing, the drive unit comprises a drive shaft configured to drive the pump shaft, and an electric motor configured rotate the drive shaft about the axial direction, and a coupling configured to couple the drive shaft to the pump shaft. 
     
     
         10 . The pumping arrangement in accordance with  claim 9 , wherein in each of the first and second multistage pumps the first mechanical seal is arranged between the first balance drum and the drive unit. 
     
     
         11 . The pumping arrangement in accordance with  claim 9 , wherein each of the first and second multistage pumps is configured as a vertical pump with the pump shaft extending in the direction of gravity, and the drive unit is arranged on top of the pump unit. 
     
     
         12 . The pumping arrangement in accordance with  claim 3 , wherein each of the first and second multistage pumps comprises a throttle bush fixedly connected to the pump shaft between the pump unit and the drive end of the pump shaft, the throttle bush defining a throttle front side facing the pump unit and a throttle back side, a throttle passage is disposed between the throttle bush and a stationary throttle part configured to be stationary with respect to the housing, the throttle passage extending from the throttle front side to the throttle back side, a first supply opening is disposed at the stationary throttle part to supply fluid to the throttle passage at a location between the throttle front side and the throttle back side with respect to the axial direction, the first supply opening is connectable with an intermediate take-off arranged to deliver the fluid with a pressure higher than a suction pressure of a respective one of the first and second multistage pumps, and a second balance line is configured to recirculate the fluid from the throttle back side to a low pressure side. 
     
     
         13 . The pumping arrangement in accordance with  claim 12 , wherein a second supply opening is disposed at the second stationary part to supply fluid to the second relief passage at a location between the second front side and the second back side with respect to the axial direction, wherein the second supply opening is connectable with the intermediate take-off. 
     
     
         14 . The pumping arrangement in accordance with  claim 1 , wherein the pumping arrangement is configured to be installed on a sea ground. 
     
     
         15 . The pumping arrangement in accordance with  claim 1 , wherein the pumping arrangement is configured to inject a compressible fluid being in the dense state at the pump outlet of the second multistage pump into a subterranean region.