Subsea Assembly Flange Interface Fastening Separation
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Solution Overview
Problem
Conventional subsea sensor mounting flanges are limited in dimensions due to space requirements for boltheads, nuts, and torque tightening tools, restricting the size of the sensor and its electronics, especially under high-pressure conditions where standards like ISO 10423 and API 6A mandate the use of studbolts and heavy hex nuts.
Innovation Solution
The subsea assembly design separates the mounting flange interface from the fastening boltheads or nuts, positioning them at least 30% of the housing's length away from the flange interface, allowing for increased dimensions and accommodating studbolts and heavy hex nuts without reducing the outer diameter, and enabling a single-piece housing without welding, which allows for more space for electronics and improved stress resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional mounting flanges with through holes are used to comply with standards ISO 10423 or API 6A, then the mounting reliability is improved, but the available space for sensor electronics is reduced
Solution Approach 1:
The mounting flange is segmented into two separate components: a flange interface portion that provides the fluid-tight connection with through holes for studbolts, and a separate fastening portion that provides mounting surfaces for nuts. This segmentation allows the sensor housing dimensions to be determined by the flange interface geometry rather than being constrained by tool access requirements, thereby increasing internal volume for electronics while maintaining compliance with mounting standards.
2Ease of operation
If the outer diameter of the flange housing is reduced to accommodate torque tightening tools, then the ease of operation is improved, but the maximum dimensions available for sensor electronics are reduced
Solution Approach 1:
The solution moves the fastening operation from a radial constraint (requiring reduced outer diameter for tool access) to a longitudinal arrangement (along the axis of the housing). By positioning nuts at the end of the housing opposite the flange interface, the design utilizes the length dimension rather than compromising the radial dimension, thereby maintaining full outer diameter for electronics space while still allowing tool access for fastening operations.
3Strength
If studbolts and heavy hex nuts are used as required by subsea standards, then the mounting strength is improved, but the space required for boltheads and nuts reduces the housing dimensions
Solution Approach 1:
The fastening function is extracted from the flange interface area and relocated to a separate portion of the housing. The flange interface is dedicated solely to providing the fluid-tight connection with studbolts passing through, while the fastening function is performed by nuts mounted on the opposite side of the housing. This extraction eliminates the need to accommodate large hex nuts and boltheads at the flange interface, allowing the housing dimensions at the interface to be optimized for electronics space while maintaining full mounting strength through the separated fastening system.
Data Source
Figure 1~2
AI summary
The present invention relates to a subsea assembly (100) comprising a housing (120) having a flange interface (121) for interfacing with a flange of a process fluid carrying component, wherein the housing (120) is configured such that bolt-heads or nuts (150) exerting a fastening force on the subsea assembly (100) when mounted to the process fluid carrying component are spaced from the flange interface (121) so that the dimensions of the housing of the subsea assembly at the flange interface (121) are not affected by a space required for a bolthead or nut fastening tool.