The use of high speed electric motors to drive compressors is commonplace in many applications; in particular, canned motors are largely employed in wet, sour gas environments. During the operation of the electric canned motor, a large amount of heat generated by the electric device must be addressed to preserve the integrity of the electric canned motor. Cooling of the electric canned motor is provided by cooling oil in the motor stator. A can surrounding the motor stator provides a leak-proof separation of the working fluid and the cooling oil. The can is typically made of a thin material layer and therefore is sensitive to pressure differences between the cooling oil and the working fluid.
Based on the desire to protect the can from failure due to excessive pressure differences between the cooling oil and the gas working fluid, mechanisms have evolved for controlling the differential pressure between the cooling oil and the working fluid. These methods include the use of external vessels, with at least one vessel containing at least one bellow and one spring means for maintaining the differential pressure between the cooling oil and the working fluid thus keeping a higher pressure on the side of the cooling oil to prevent flow of the working fluid into the cooling oil.
Based on the above described electric canned motor/compressor operating conditions, a system and associated methods are desired allowing a system to manage the pressure differential between the cooling oil and the gas working fluid of a motocompressor. The system should allow at least a slightly higher pressure on the cooling oil side of the can thus preventing the gas working fluid from leaking into the cooling oil. The system should compensate for changes in the cooling oil pressure based on thermal expansion of the cooling oil and on changes in gas pressure based on downstream gas utilization.