Double-Barrier Pressure Compensation for Subsea Transformers
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Solution Overview
Problem
Traditional subsea transformers face challenges with bellows made of thin-walled stainless steel, which are prone to failure due to pressure changes and are difficult to fabricate and ensure quality assurance, especially when multiple bellows are required, increasing cost and complexity.
Innovation Solution
A pressure compensation system with a double dynamic barrier using first and second flexible walls or bellows, separated by an intermediate volume, to balance pressures and prevent seawater ingress, ensuring reliability and reducing the risk of leaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional thin-walled stainless steel bellows are used for volumetric changes, then the transformer can accommodate pressure changes, but the fabrication is complicated and quality assurance is difficult
Solution Approach 1:
The single bellows structure is divided into multiple bellows segments (first bellows, second bellows, third bellows) arranged in series. Each bellows is a simpler, standardized component that can be manufactured independently, reducing fabrication complexity while maintaining the overall volumetric change capability through cumulative expansion and contraction of all segments
Solution Approach 2:
The bellows are arranged in a nested configuration where the first bellows, second bellows, and third bellows are positioned concentrically or in series within the tank structure. This nesting allows each bellows to contribute to volume compensation while sharing the mechanical load, simplifying individual manufacturing requirements
2Volume of stationary object
If the size of the transformer increases, then more capacity is available, but a much larger number of bellows is needed which increases cost and complexity
Solution Approach 1:
Multiple bellows are combined in a series arrangement within a single compensation system. The first bellows, second bellows, and third bellows work together as an integrated unit, where each bellows handles a portion of the total volume compensation requirement, allowing the system to scale with transformer size without proportionally increasing complexity
Solution Approach 2:
The bellows structure serves multiple functions simultaneously: it provides volumetric compensation for pressure changes, acts as a dynamic barrier against seawater ingress, and distributes mechanical stresses across multiple components. This multi-functionality reduces the need for additional specialized components
3Adaptability or versatility
If thin-walled steel bellows are used for pressure compensation, then volumetric changes are accommodated, but pressure changes cause movement of the bellows making them potential sources of failure
Solution Approach 1:
The system employs a double barrier configuration with the first bellows and second bellows positioned in series, creating redundant protection. If one bellows fails or develops a leak, the second bellows continues to provide sealing, preventing seawater ingress into the transformer. This beforehand cushioning through redundancy significantly reduces the risk of failure
Solution Approach 2:
The third bellows acts as an intermediary element between the first bellows and second bellows, providing an additional sealing layer and mechanical buffer. This intermediary structure distributes pressure movements and reduces the stress on any single bellows, enhancing overall system reliability
4Reliability
If multiple bellows are used to increase reliability, then a double barrier is achieved, but fabrication complexity and cost increase
Solution Approach 1:
The bellows are constructed using flexible shell structures that can be manufactured as standardized, modular components. These flexible shells are designed to be collapsed or expanded in a controlled manner, allowing for simpler fabrication processes compared to rigid multi-component assemblies, while still achieving the double barrier reliability requirement
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
The double barrier system effectively balances pressure and volume changes, providing an additional layer of protection against seawater penetration, enhancing the reliability and durability of subsea transformers.
Implementation Method 1
first and second flexible walls or bellows, separated by an intermediate volume, to balance pressures
Implementation Method 2
The first and second volumes are configured to balance pressures relative to one another. The fourth volume is configured to balance pressures between a surrounding seawater and the second volume.
Data Source
AI summary
A subsea system includes a tank configured to house a transformer surrounded by a first volume, and a compensation system coupled to the tank. The compensation system includes a housing disposed about a central axis, first and second flexible walls disposed about the central axis inside the housing, and a compensator cover coupled to the first and second flexible walls. The first flexible wall and the compensator cover defines a second volume with a first axial end of the housing. The housing and the first and second flexible walls define a third volume. The second flexible wall and the compensator cover define a fourth volume. The first and second volumes are configured to balance pressures relative to one another. The fourth volume is configured to balance pressures between a surrounding seawater and the second volume. The first and second flexible walls define a double barrier separated by the third volume.