Dual integrated pump having a first and second pump portion connected in series and driven by a common shaft

A method for controlling an inlet pressure of a pump, the method comprising:

• rotating a drive shaft coupled to a first pump portion and a second pump portion, wherein the first pump portion and the second pump portion are enclosed in a common housing, the drive shaft additionally coupled to a magnetic coupling portion of a magnetic drive that drives the drive shaft;
• and
• moving a fluid through the first pump portion and the second pump portion, the fluid entering the first pump portion at a first fluid pressure and exiting the first pump portion at a second fluid pressure at a fluid discharge, the fluid entering the second pump portion at the second fluid pressure at a fluid inlet and exiting the second pump portion at a third fluid pressure;
• wherein the fluid inlet of the second pump portion is in direct fluid communication with the fluid discharge of the first pump;
• wherein the drive shaft includes a longitudinal bore, one end of the longitudinal bore in fluid communication with a cavity in the magnetic coupling portion, wherein a radial bore intersects, and is in fluid communication with, another end of the longitudinal bore and is further in fluid communication with the fluid discharge of the first pump portion;
• and
• wherein a pressure differential between the fluid discharge of the first pump portion and an intermediate stage of the second pump portion causes a working fluid to circulate through the longitudinal bore and the cavity in the magnetic coupling portion to remove heat from the magnetic drive via the working fluid.