Abstract: A pressure compensator for a sub-sea pumping system for pumping an effluent from a deep-sea wellhead comprising a topside module, a sub-sea module, and an umbilical connection between the topside and sub-sea modules. Hydraulic fluid is circulated through the sub-sea module for cooling and lubricating the motor and the pump. The hydraulic cooling and lubricating fluid is preferably a single hydraulic fluid that is compatible with the effluent being pumped. The hydraulic fluid is circulated through a submerged pressure compensator which may include a bellows assembly. The pressure compensator is responsive to the pressure of the effluent being pumped and pressurizes the hydraulic cooling and lubricating fluid to a pressure above the pressure of the effluent. The pressure compensator also responds when the volume of hydraulic cooling and lubricating fluid in the system is reduced or increased, such as by leakage or thermal expansion, in order to maintain the pressure of the hydraulic fluid.

Abstract: A sub-sea pumping system for pumping an effluent from a deep-sea wellhead comprising a topside module, a sub-sea module, and an umbilical connection between the topside and sub-sea modules. The umbilical connection comprises a threephase electrical power line and an hydraulic fluid supply line to an electrical canned motor. The hydraulic fluid is a single medium fluid, is compatible with the effluent being pumped, and is circulated through the sub-sea module for cooling and for lubricating the seal and bearing arrangements of the motor and the pump. The hydraulic fluid is circulated through a submerged pressure compensator which includes a metal bellows assembly. The compensator is responsive to the pressure of the effluent being pumped and pressurizes the hydraulic fluid flowing through the motor and the pump for the cooling and the lubricating of their respective seal and bearing arrangements at a pressure above the pressure of the effluent being pumped.