A vertical multi-stage pump includes a rotation shaft extending in a vertical direction, a plurality of impellers fixed to the rotation shaft, a multi-stage pump chamber accommodating the plurality of impellers and comprising a suction port for a first-stage impeller at a lower end, a lower casing comprising a suction nozzle extending in a horizontal direction and forming a communication space communicating the suction nozzle and the suction port, and an inner cylinder member interposed between the multi-stage pump chamber and a lower casing and expanding the communication space in a vertical direction.

A vertical multi-stage pump includes a rotation shaft extending in a vertical direction, a plurality of impellers fixed to the rotation shaft, a multi-stage pump chamber accommodating the plurality of impellers and comprising a suction port for a first-stage impeller at a lower end, a lower casing comprising a suction nozzle extending in a horizontal direction and forming a communication space communicating the suction nozzle and the suction port, and an inner cylinder member interposed between the multi-stage pump chamber and a lower casing and expanding the communication space in a vertical direction.

A multistage centrifugal pump for conveying a fluid includes a pump housing, two first stage impellers, a last stage impeller and a shaft. The two first stage impellers and the last stage impeller convey the fluid from a housing inlet to a housing outlet. The shaft rotates each impeller about an axial direction, each impeller comprising a suction side to receive the fluid and a discharge side to discharge the fluid. The last stage impeller is a double suction impeller, having a first suction side and a second suction side, and the last stage impeller is arranged between the two first stage impellers with respect to the axial direction. Each impeller of the two first stage impellers is arranged with the suction side of a respective first stage impeller facing one of the first and second suction sides of the last stage impeller.

A multistage centrifugal pump for conveying a fluid includes a pump housing, two first stage impellers, a last stage impeller and a shaft. The two first stage impellers and the last stage impeller convey the fluid from a housing inlet to a housing outlet. The shaft rotates each impeller about an axial direction, each impeller comprising a suction side to receive the fluid and a discharge side to discharge the fluid. The last stage impeller is a double suction impeller, having a first suction side and a second suction side, and the last stage impeller is arranged between the two first stage impellers with respect to the axial direction. Each impeller of the two first stage impellers is arranged with the suction side of a respective first stage impeller facing one of the first and second suction sides of the last stage impeller.

A rotary machine is provided with a plurality of impellers (3) which have a disk (31) rotating with a rotary shaft (2), the impellers being arranged side by side; and a casing (4) in which a casing flow passage (43) is formed to distribute a working medium therein. An impeller (3) disposed farthest away from a second side in the axial direction is disposed in a space communicating with an upstream part of the casing flow passage (43), and a protrusion portion (5) protruding from a back side (311) of the disk (31). The protrusion portion (5) has a sealing surface (51) which is formed to be parallel to an outer surface (21) of the rotary shaft (2) to seal a gap between itself and the casing (4), and a pressure receiving surface (51) which extends from the outer surface (21) to the sealing surface (51).

A rotary machine is provided with a plurality of impellers (3) which have a disk (31) rotating with a rotary shaft (2), the impellers being arranged side by side; and a casing (4) in which a casing flow passage (43) is formed to distribute a working medium therein. An impeller (3) disposed farthest away from a second side in the axial direction is disposed in a space communicating with an upstream part of the casing flow passage (43), and a protrusion portion (5) protruding from a back side (311) of the disk (31). The protrusion portion (5) has a sealing surface (51) which is formed to be parallel to an outer surface (21) of the rotary shaft (2) to seal a gap between itself and the casing (4), and a pressure receiving surface (51) which extends from the outer surface (21) to the sealing surface (51).

A process fluid lubricated pump includes a housing with an inlet to receive the fluid, and an outlet to discharge the fluid, a shaft extending from a drive end to a non-drive end and rotatable about an axial direction, the drive end of the shaft arranged outside the housing, a hydraulic unit including impellers mounted on the shaft, a collection chamber to collect leaking process fluid, the collection chamber comprising an exit, through which the shaft passes, and an exit to discharge the process fluid, and a throttle device arranged between the hydraulic unit and the collection chamber, the throttle device comprising a stationary throttle part having first and second axial faces delimiting the stationary throttle part, the first axial face facing the collection chamber, and the throttle device including a throttle gap surrounding the shaft and extending from the first axial face to the second axial face.

A process fluid lubricated pump includes a housing with an inlet to receive the fluid, and an outlet to discharge the fluid, a shaft extending from a drive end to a non-drive end and rotatable about an axial direction, the drive end of the shaft arranged outside the housing, a hydraulic unit including impellers mounted on the shaft, a collection chamber to collect leaking process fluid, the collection chamber comprising an exit, through which the shaft passes, and an exit to discharge the process fluid, and a throttle device arranged between the hydraulic unit and the collection chamber, the throttle device comprising a stationary throttle part having first and second axial faces delimiting the stationary throttle part, the first axial face facing the collection chamber, and the throttle device including a throttle gap surrounding the shaft and extending from the first axial face to the second axial face.

A cylindrical gap is formed between a production pipe and a pump stator, the pump stator has a tubular pump casing that surrounds a plurality of pump bodies, the pump casing is provided with a penetrating portion that penetrates the pump casing in a radial direction and communicates with the gap, and the penetrating portion is formed in a portion of the pump casing that faces a pump body, which is located in an intermediate stage of the plurality of pump bodies, in the radial direction.

A cylindrical gap is formed between a production pipe and a pump stator, the pump stator has a tubular pump casing that surrounds a plurality of pump bodies, the pump casing is provided with a penetrating portion that penetrates the pump casing in a radial direction and communicates with the gap, and the penetrating portion is formed in a portion of the pump casing that faces a pump body, which is located in an intermediate stage of the plurality of pump bodies, in the radial direction.