Subsea Compressor Module Seawater Ingress Prevention
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Solution Overview
Problem
Subsea compressor modules face challenges in preventing seawater penetration during lowering and retrieval, which can lead to contamination and corrosion issues, especially affecting the motor, and result in unsafe hydrocarbon concentrations that may cause explosions.
Innovation Solution
The compressor module is equipped with a filling pipe, drainage pipe, and overflow pipe, each with shut-off valves, allowing for the filling with an inert fluid such as nitrogen or deionized water before lowering or retrieval, ensuring seawater exclusion and safe handling of hydrocarbons, with optional discharge of residual production fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the compressor module is left open during lowering and retrieval, then installation and maintenance operations can be performed easily, but seawater penetrates into the module causing contamination and corrosion
Solution Approach 1:
The compressor module is pre-filled with inert gas (nitrogen or helium) before lowering to the seabed. This preliminary action creates a protective atmosphere that prevents seawater contamination during installation and retrieval operations, allowing the module to remain open while protected from harmful effects.
Solution Approach 2:
An inert gas atmosphere (nitrogen or helium) is introduced into the compressor module to displace air and prevent corrosion. The inert gas fills the module cavity, creating a protective environment that prevents seawater contamination and chemical reactions with sensitive components during subsea operations.
2Reliability
If the motor is drained and dried before start-up, then corrosion and short-circuit risks are reduced, but residual contaminants still cause problems during operation
Solution Approach 1:
The motor is filled with inert gas (nitrogen or helium) to create a protective atmosphere that prevents oxidation and corrosion of residual contaminants. This inert environment stops chemical reactions between moisture/contaminants and motor components, eliminating the harmful effects of residual impurities while maintaining operational reliability.
Solution Approach 2:
The chemical composition of the atmosphere inside the motor is changed from air (oxygen-containing) to inert gas (nitrogen or helium). This parameter change transforms the environment from corrosive to protective, preventing further degradation of residual contaminants and protecting sensitive motor components during operation.
3Object-affected harmful factors
If the compressor module is filled with filling fluid, then seawater penetration is prevented during lowering, but the module requires additional filling and drainage operations
Solution Approach 1:
The compressor module uses its own internal volume to store inert gas, eliminating the need for external filling systems. The module self-regulates the inert atmosphere through simple valve operations on existing pipes, performing the protective function using its own structure rather than requiring complex external equipment.
Solution Approach 2:
The inert gas filling system serves multiple functions: it prevents seawater penetration during lowering, protects against corrosion during operation, and provides a safe atmosphere for hydrocarbon handling. The same inert gas atmosphere accomplishes multiple protective tasks, reducing the need for separate systems for each function.
4Object-affected harmful factors
If hydrocarbons are discharged from the compressor module before retrieval, then explosion risks are reduced, but additional discharge operations and time are required
Solution Approach 1:
The inert gas atmosphere (nitrogen or helium) displaces hydrocarbons from the compressor module, creating a non-flammable environment. By filling the module with inert gas before retrieval, hydrocarbon concentrations are reduced below explosive limits, eliminating explosion risks during the retrieval operation without requiring separate discharge procedures.
Solution Approach 2:
The inert gas filling is performed as a preliminary action before retrieval operations begin. This advance preparation ensures that hydrocarbon concentrations are already reduced to safe levels before the module is brought to the surface, preventing explosion hazards during the retrieval process and eliminating the need for time-consuming discharge operations.
Data Source
AI summary
An apparatus for preventing seawater from penetrating into a compressor module during lowering to or retrieval from a compression plant on the seabed, with optional discharge of residual production fluids, as for instance hydrocarbons, from the compressor module prior to retrieval, wherein the compressor module comprises an electric motor (1) and a compressor (2) which are respectively connected via at least one shaft (8) and are arranged in a common pressure shell (3), an inlet pipe (5) and an outlet pipe (6) to and from the compressor module which respectively are provided with an isolation valve (7, 7′). The compressor module is distinguished in that it includes at least one filling pipe (16) which has a shut-off valve (15), at least one drainage pipe (12) which has a shut-off valve (13), and which is located at a lower end of the compressor module, and at least one overflow pipe (14) which has a shut-off valve (17), and which is spaced apart from the at least one filling pipe (16), and that prior to lowering to or retrieval from the seabed, with optional discharge of residual production fluids prior to retrieval, the compressor module is filled with filling fluid via the at least one filling pipe (16) until overflow of filling fluid through the at least one overflow pipe (14). The present invention also relates to a method which correspondingly prevents such penetration of seawater into and discharge of residual production fluid from the compressor module.