Development and Testing of a Friction-Based Post-Installable Fiber-Optic Monitoring System for Subsea Applications

This paper continues to document the design, development, and test of a friction-based (non-adhesive) post-installable fiber-optic strain sensing system for oil and gas applications — especially those that require deployment on existing subsea structures. (Ref: OMAE2017-61494 Development and Testing of a Friction-Based Post-Installable Sensor for Subsea Fiber-Optic Monitoring Systems [1]). The prototype fiber-optic monitoring system collects a wide range of real-time data, which can be used to determine structural loading, fatigue, temperature, pressure, and flow assurance on operational platforms. The primary challenge of a post-installed instrumentation monitoring system is to ensure secure coupling between the sensors and the structure of interest for reliable measurements. Friction-based coupling devices have the potential to overcome installation challenges caused by marine growth and soil contamination on subsea structures, flowlines, or risers. This particular design solution is compatible with structures that are suspended in the water column and those that are resting on the seabed. In addition, the system can be installed by commercial divers in shallow depths or by remotely operated vehicles in deep-water applications. Operational limitations of the initial design concept were identified in the previous series of tests (2016–2017), and several innovative enhancements have been implemented which resulted in significant improvements in sensor system coupling and strain measurement correlation with traditional strain measuring devices. This paper provides a summary of the notable prototype design changes, full-scale test article buildup, and detailed performance data recorded during tension and compression loading that simulated representative offshore conditions. The test results were positive and demonstrated the effectiveness of the design enhancements. Compromises made during mounting of the sensing elements resulted in better performance in tension than compression. These effects are well understood and are fully discussed, and do not influence the viability of the design changes. This study is part of a continuing collaboration between the Houston-based NASA-Johnson Space Center and Astro Technology, Inc. within a study called Clear Gulf. The primary objective of the Clear Gulf study is to develop advanced instrumentation technologies that will improve operational safety and reduce the risk of hydrocarbon spillage. NASA provided unique insights, expansive test facilities, and technical expertise to advance these technologies that would benefit the environment, the public, and commercial industries.