Swedish Trelleborg has teamed up with Italian oil and gas industry contractor, Saipem, to develop a new LNG tandem offloading system.
Derived from existing and proven technologies, the latest development in cryogenic LNG floating hoses is set to become a key component in offloading systems for future offshore FLNG projects. By enabling offshore transfer of LNG in tandem configuration, the cryogenic floating hose will pioneer a step change in the safety of this critical operation. This innovative system will also allow FLNG projects to be considered in harsher conditions, without excessive downtime due to offloading system availability, and with significantly reduced risk.
Vincent Lagarrigue, Marketing and Project Manager within Trelleborg Industrial Solutions, commented: “The environmental conditions of the current FLNG locations are at present quite mild and only require the use of the most straightforward technology for the unloading of the LNG. But, with prospective new FLNG locations moving away from these ‘mild’ areas, to sites where sea states, wind and currents can be much more severe, this equipment isn’t enough and could result in plant shut down. Instead, where conditions are much more demanding, tandem offloading solutions, which rely on the use of flexible hoses, are a viable alternative for the industry, which not only limit downtime, but also improve safety.
“We wanted to partner with Saipem to develop a new solution which would not only meet LNG operator and contractor’s offloading requirements related to safety, flowrate capacity and operation availability, but also enable LNG transfer operations to take place in difficult environmental conditions by providing offshore operators with a highly flexible, reliable and durable system.”
Tandem offloading, where vessels line up stern to bow, allow vessels to keep more distance between them (328 feet / 100 meter distance between FLNG and LNGC or more) and more easily cope with greater wave heights. This highly limits the risk of collision between the two vessels, enhancing safety, but also greatly simplifying naval operations in approach, berthing and residence.
Lagarrigue continued: “So, in the absence of any mature tandem offloading solutions using floating hoses, we took the initiative to work with Saipem to develop our own. As a key technical component of the tandem offloading solution, our cryogenic floating hose has been further enhanced to meet the parameters required for the new system. For example, the choice of a 20 inch / 50 cm inner diameter LNG hose was required as this enables operators to transfer LNG at least as fast as standard LNG loading arms on traditional jetties, for example, up to 423,776 ft3/h/ 12,000m3/h.”
The innovative LNG tandem offloading system from Trelleborg and Saipem utilizes three Cryoline LNG floating hoses, as well as a hose storage system, a connection head with a dedicated storage platform on the LNG terminal and bow loading platform on the LNG carrier, to provide a highly flexible, reliable and durable alternative to traditional technologies such as marine loading arms.
Floating cryogenic hose
It is designed to operate in sea states with significant wave heights of up to 11.5 feet / 3.5 meter at connection and 13 feet / 4 meter during transfer and disconnection, even with non collinear wind or current directions. These figures guarantee very good offloading availability in almost any location in the world.
Trelleborg was responsible for the development of the 20 inch / 50 cm inner diameter cryogenic floating flexible hoses, while Saipem developed the offloading system and equipment to store/handle the hoses. Derived from existing and field-proven technologies, Trelleborg’s new floating cryogenic hose is made up of the several key components, including an inner cryogenic hose, an outer protective hose, an efficient insulation layer and an integrated leak monitoring system.
The LNG tandem offloading system is currently undergoing a complete set of full-scale tests to ensure it qualifies for the EN1474-2 standard. Several reduced scale prototypes have been manufactured and tested since 2009 at ambient and cryogenic conditions in order to validate theories and demonstrate feasibilities. The design has already been validated by numerous characterization tests and qualification tests on 4 inch, 12 inch and 20 inch / 10 cm, 30 cm and 50 cm internal diameter hoses.
Since September 2012, an extensive qualification program has been underway for the 20 inch / 50 cm new LNG hose according to EN 1474-2 standard’s requirements including mechanical, thermal and flow tests. More than 20 tests will be performed, either destructive or non destructive, at ambient and cryogenic temperature in order to qualify the technology, under survey of Bureau Veritas.
Testing and qualification
Several 20 inch / 50 cm prototypes will hence be tested in both static and dynamic conditions to demonstrate the suitability of a bonded flexible hose for LNG transfer applications. In particular, a fatigue test will be completed on full scale prototypes to prove that Cryoline LNG hose withstands recurrent dynamic loads for long service life.
The qualification of the 20 inch / 50 cm LNG hose is expected to be completed late in 2013.