Retrofit Helical Strake Latching for Minimal-Tool VIV Suppression
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Solution Overview
Problem
Existing VIV suppression devices require expensive and infrequently used large tooling for installation, are difficult to maintain underwater, and can detach in high currents, leading to high mobilization and maintenance costs, as well as challenges with ROV operation in deep waters.
Innovation Solution
A VIV suppression latching system with a strake design featuring a cylindrical body, radially extending fins, and a connecting assembly with hinges and latches that allows for easy operation and secure attachment to tubulars using minimal tooling, including a compression spring and guide flanges to enhance stability and ease of installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If previous generations of retrofit helical strakes or fairings are used, then VIV suppression is achieved, but large and expensive tooling is required for installation
Solution Approach 1:
The strake is divided into two separable halves that can be installed independently and then joined together using a latch mechanism. This segmentation allows the device to be installed without requiring large, expensive tooling, as each half can be positioned and secured separately on the tubular structure.
Solution Approach 2:
The latch mechanism incorporates a spring-loaded pin that dynamically engages with the nut housing to secure the two strake halves together. This dynamic latching system provides reliable connection without requiring complex or large-scale installation equipment.
2Reliability
If previous generations of retrofit fairings are used, then VIV suppression is provided, but the devices can come off in high currents or storms due to inadequate latching
Solution Approach 1:
The latch mechanism utilizes a circular engagement geometry where the pin fits into the nut housing with rotational symmetry. This circular configuration provides uniform distribution of forces from current loads around the entire circumference, creating stable and secure attachment that resists detachment in high current conditions.
Solution Approach 2:
The spring-loaded pin mechanism provides visual and mechanical indication of proper engagement. When the pin is fully inserted and engaged with the nut housing, it indicates secure latching, providing confidence that the device is properly attached to withstand high currents and storms.
3Reliability
If retrofit VIV suppression devices are installed with traditional latching systems, then attachment is achieved, but the latching system must be easy to operate due to ROV positioning difficulties and limited manipulator arm movements
Solution Approach 1:
The complex multi-step latching operations are extracted and simplified into a single primary action: inserting the pin into the nut housing. This extraction of the essential latching function eliminates unnecessary operational complexity, allowing ROV manipulators with limited degrees of freedom to easily secure the device without requiring precise positioning or multiple sequential actions.
Solution Approach 2:
The spring-loaded pin mechanism is designed to be self-aligning and self-securing. The spring force automatically pushes the pin into engagement with the nut housing, and the circular geometry provides self-centering, reducing the precision required from the ROV manipulator and making the latching operation more tolerant of positioning variations.
4Ease of manufacture
If systems for installation of VIV suppression devices are mobilized, then installation is achieved, but the costs of mobilization and use are very high with large mobilization rates and hourly rates
Solution Approach 1:
The strake is segmented into two halves that can be installed separately, reducing the complexity and duration of the installation operation. This segmentation allows for more efficient use of ROV time and resources, directly reducing the high hourly rates associated with mobilized installation systems.
Solution Approach 2:
The latch mechanism uses simple, inexpensive components (pin, nut housing, spring) that can be easily replaced if needed, eliminating the requirement for expensive, specialized installation tooling. This approach trades small, replaceable parts for large, expensive, single-use tooling systems.
Data Source
AI summary
A vortex-induced vibration (VIV) suppression apparatus comprising: a strake having a cylindrical body portion dimensioned to encircle an underlying tubular, a fin portion extending radially outward from the body portion and helically positioned around the body portion, and a gap formed through the body portion and the fin; and a connecting assembly configured to facilitate attachment of the strake to an underlying tubular.