Abstract: A method for ensuring fluid-tightness is applicable to a submersible motor for operation under conditions of total and permanent immersion, especially in oil wells and geothermal boreholes. The emergent end of the drive shaft of the motor is fitted with a rotary packing-gland. The motor casing is filled with oil which is circulated via an axial duct of the drive shaft, the impulse being produced by a disk pierced by radial ducts. A second circuit constituted by a system of ducts including radial ducts comes into contact with the packing-gland which is at overpressure with respect to the external medium. This results in a controlled leakage flow between the two portions of the packing-gland.

Abstract: A motor pump set having two coaxial shafts is provided with a fluid circuit for protecting the rotary packing-gland against any ingress of solid particles such as sand. Pumped fluid is withdrawn from an intermediate space of the pump and returned upstream via a duct within the pump shaft in order to lubricate the bearings as it passes. The fraction of the fluid stream which is discharged from the last bearing flows in the vicinity of the packing-gland and is driven through radial discharge ducts under the action of centrifugal force.