Subsea Compressor Motor Seal Protection Against Contaminated Gas
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Solution Overview
Problem
Subsea compressor modules face challenges with contamination from hydrocarbon gases, leading to corrosion, deposit buildup, and reduced reliability due to the use of non-canned magnetic bearings, which require a clean atmosphere and are prone to issues with lubricating oil dilution and degradation.
Innovation Solution
A pressure housing with sealed compartments separates the compressor and motor, using compressed gas from a withdrawal point to protect the motor and introducing it between seals to prevent direct contamination, and employing a closed cooling circuit that recirculates gas through a motor cooler outside the pressure housing for cooling, utilizing seawater to dissipate heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-canned magnetic bearings are used in subsea compressor modules, then the compressor module can operate without lubricating oil, but the magnetic bearings are exposed to contaminated gas leading to corrosion and deposit buildup
Solution Approach 1:
The pressure housing is divided into two separate compartments: a first compartment for the compressor and a second compartment for the motor with magnetic bearings. This segmentation isolates the magnetic bearings from direct exposure to contaminated hydrocarbon gas while maintaining the benefits of oil-free operation.
Solution Approach 2:
A seal system acts as an intermediary barrier between the compressor compartment and the motor compartment. The seal prevents contaminated gas from reaching the magnetic bearings while allowing the shaft to transmit rotational force, thus protecting the bearings without compromising the drivable connection.
2Temperature
If the motor and magnetic bearings are continuously flushed with compressed gas from the compressor, then cooling is achieved, but contaminants are carried into the motor and bearings causing corrosion and deposits
Solution Approach 1:
The sealing system divides the cooling function from the contamination risk by allowing controlled gas flow through the seal. The seal enables thermal management through gas circulation while simultaneously blocking the pathway for contaminants to reach the magnetic bearings.
Solution Approach 2:
The seal system serves as an intermediary that permits beneficial gas flow for cooling purposes while blocking harmful contaminants. It selectively allows thermal management functionality while preventing corrosion and deposit formation.
3Object-affected harmful factors
If filters or separators are installed in the gas supply line to remove contaminants, then cleaner gas reaches the motor, but the system complexity increases and maintenance requirements arise
Solution Approach 1:
The harmful function of gas treatment is eliminated by removing filters and separators from the system. Instead of adding complexity to treat the gas, the design extracts the protection function directly at the point of need through the seal system, simplifying the overall architecture.
Solution Approach 2:
The seal system provides self-service protection by automatically preventing contaminant ingress without requiring external gas treatment systems. The seal inherently performs the protection function that would otherwise require complex filtration equipment.
4Reliability
If subsea compressors are operated without maintenance for long periods, then operational reliability improves, but access for maintenance is difficult at great ocean depths
Solution Approach 1:
The seal system is designed as a long-life component that protects critical magnetic bearing elements during the entire operational period. By providing robust protection upfront, the system enables extended operation without maintenance, accepting that the seal itself may eventually require replacement but protecting the more critical and expensive magnetic bearings throughout.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly reduces exposure to contaminants, enhances motor efficiency, and maintains reliability by isolating the motor from direct contamination, allowing for long-term operation without maintenance, especially in deep-sea environments where access is difficult.
Implementation Method 1
Magnetic bearings are more reliable and make the compressor module less expensive to operate. Of particular importance is the fact that magnetic bearings eliminate the use of lubricating oil
Implementation Method 2
introducing the compressed gas directly into the seal or in between two or more seals so as to flow through the at least one seal back to the first compartment with compressor
Implementation Method 3
employing a closed cooling circuit that recirculates gas through a motor cooler outside the pressure housing for cooling, utilizing seawater to dissipate heat
Data Source
AI summary
A method for protection of compressor modules against undesirable influx of contaminated gas, comprising a pressure housing (3) which by means of one of more sealing elements (4) is generally divided into a first compartment (8) equipped with a compressor (2) and a second compartment (7) equipped with a gas-filled motor (1), the compressor and the motor being drivably connected to each other by at least one shaft (9), is distinguished by protecting the second compartment (7) with motor (1) against direct influx of contaminated gas from the first compartment (8) with compressor (2) by means of compressed gas that is supplied from a withdrawal point (13) at the first or intermediate stage of the compressor, or from the compressor outlet (16), and by introducing the compressed gas directly into the seal (4) or in between two or more seals so as to flow through the at least one seal (4) back to the first compartment (8). The invention also relates to an apparatus for use in connection with the method.