Trelleborg leverages Raman effect
James Hermary, LNG Product Manager, Trelleborg Oil & Marine, told The Motorship in an interview at Gastech about the practical benefits the Cryoline LNG floating hose system offers.
LNG solutions provider Trelleborg has introduced an integrated monitoring system into its Cryoline LNG floating hoses. The system makes use of Distributed Thermal Sensing Technology using Raman effect to add real-time temperature monitoring to the solution.
“The cryogenic floating hose unlocks new possibilities in ship-to-ship and ship-to-shore configurations, offering an ideal solution in many locations,” Hermary said. The company expects that such integrated monitoring systems will become standard features in future LNG transfer systems.
The concept was proven when the 15,600 cbm LNG carrier Coral Energy transferred LNG to an onshore terminal at the Norwegian industrial park of Herøya in October 2017. This marked the first LNG transfer to be conducted using this technology.
Importantly, the LNG transfer system was a ‘plug and play’ solution, and no modifications to the LNG carrier were required. The LNG transfer was made from the upper deck of the LNG carrier, demonstrating the flexibility of the LNG transfer system and adaptability to different size of LNG carriers.
Trelleborg previously collaborated with ConnectLNG in the development of the universal floating transfer system (UTS) that will enable ship to-shore LNG bunkering without a jetty, reducing infrastructure investment for small to mid-scale projects.
The key to Trelleborg’s cryoline floating hose is a hose-in-hose design that provides a containment structure that all but eliminates the risk of spillage into the atmosphere.
The hose-in-hose structure, includes an annular insulation structure, which efficiently protects the outer hose from cryogenic temperatures.
Integrated Monitoring System
The hose also includes an Integrated Monitoring System, which allows any potential leaks from the inner hose to be detected and located as soon as it happens. In addition, the efficiency of precooling can be monitored while the liquid evacuation from the hose at the end of the operation can also be monitored.
“This is an extra benefit of the system. By ensuring gas is only transferred when the hose is sufficiently cooled, we can minimise boil-off,” Hermary added.
If a leak does occur, the liquid entering the annular space lowers the temperature in the innermost insulation layer and is immediately detected by the monitoring system.
The monitoring technology uses established Raman technology, which has been used as a leak detection device on LNG tanks and LNG and LPG pipelines in the Oil and Gas industry.
This non-electrical, explosion proof technology makes uses of the effect of temperature variations on the optical spectrum of backscattering light to detect any change in temperature all along the fibre line.
Short light pulses are injected into optical fibre wound around the inner LNG hose, inside the annular space. As the scattering of a small fraction of its intensity permits real-time temperature measurement, it allows the operator to monitor the entire operation from the control room. The system offers detailed resolution, of below one meter, which allows accurate leak detection. This allows the temperature status and integrity of the hose to be controlled remotely, from outside the safety zone.
Applicability of solution
By extending the flexibility of LNG transfer system, the solution potentially addresses several niches in the LNG market.
Floating LNG production units (FLNG) need to meet stringent safety standards, but also maintain production and transfer of the LNG to carriers in the most demanding conditions.
This is a particular requirement for some of the newest FLNG locations under consideration, in areas where sea conditions, wind and currents are likely to be more challenging than those seen in earlier FLNG installations.
LNG tandem offloading system using floating cryogenic hoses would increase the range of potential operating locations, opening up areas where prevailing wave conditions previously prevented transfer. The system is able to operate in environments with significant waves of up to 4m and improves safety by introducing larger distances between vessels. Tandem offloading configuration is extensively used all over the world in the most demanding sea states conditions, such as Norway and Australia.
The technology is also aimed at rapidly and easily deploying jettyless ship-to-shore transfer at a much lower cost than fixed infrastructure.
“This transforms the economics of small scale and midscale LNG projects, by reducing the capex required for the construction of new harbours, quaysides and jetties,” Hermary said. He noted that there were particular opportunities in Central and South America, as well as in southern Europe.
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