Apparatus for transferring pressurized fluid in a back-to-back multi-stage pump

A multi-stage pump comprising:

• an outer housing integrally formed as a hollow body having an inlet and an outlet;
• a first set of pump stages disposed at a first end of the outer housing for directing fluid in a first direction from the inlet of the outer housing to a central portion of the outer housing;
• a second set of pump stages disposed at a second end of the outer housing, the second end being opposite to the first end of the outer housing, the second set of pump stages directing the fluid in a second direction, opposite to the first direction, from the second end of the multi-stage pump to the central portion of the outer housing;
• and
• a diffuser disposed in the central portion of the outer housing at a location between the first set of pump stages and the second set of pump stages, the diffuser comprising:
• an outer circumferential passage extending in a longitudinal direction through the diffuser for directing fluid in the longitudinal direction from an outlet end of the first set of pump stages to an inlet end of the second set of pump stages, and
• an inner passage extending in a radial direction through the diffuser for directing fluid exiting an outlet end of the second set of pump stages in a direction tangential to the direction fluid flows through the outer circumferential passage wherein the fluid flowing in the inner passage is directed radially away from the diffuser,
• wherein the outer housing is separate from the first set of pump stages and the second set of pump stages, wherein a reservoir is defined as a space between an inner surface of the outer housing and an outer surface of the second set of pump stages, and wherein the reservoir directs the fluid expelled from the outer circumferential passage of the diffuser to the inlet end of the second set of pump stages.

A multi-stage pump comprising:

• a first set of pump stages directing fluid in a first direction from a first end of the multi- stage pump to a central portion of the multi-stage pump, wherein the first direction is parallel to a longitudinal axis of the multi-stage pump;
• a second set of pump stages directing the fluid in a second direction, opposite to the first direction, from a second end of the multi-stage pump to the central portion;
• a diffuser casing disposed at the central portion and having a first inlet that receives the fluid directed from the first set of pump stages, a first outlet that expels the fluid received by the first inlet, a second inlet that receives the fluid directed from the second set of pump stages, and a second outlet that directs the fluid to a chamber within the diffuser casing;
• and
• an outer housing that encases the first set of pump stages, the second set of pump stages, and the diffuser casing,
• wherein the diffuser casing further comprises a first casing and a second casing, the first casing having a first vane that defines a first internal passage from the first inlet to the first outlet, and the second casing having a second vane that defines a second internal passage from the second inlet to the second outlet,
• wherein a through-hole is formed in the first vane, and wherein the through-hole directs the fluid in a radial direction with respect to the longitudinal axis of the multi-stage pump and expels the fluid received in the chamber to an outside of the diffuser casing, and
• wherein a reservoir is defined as a space between an inner surface of the outer housing and an outer surface of the second set of pump stages, and wherein the reservoir directs the fluid expelled from the first outlet to the second end of the multi-stage pump.