Tandem offload system could extend FLNG to harsher areas

Saipem has teamed up with Trelleborg to develop a new LNG offloading system.

Offshore staff

SAN DONATO MILANESE, Italy – Saipem has teamed up with Trelleborg to develop a new LNG offloading system.

Use of cryogenic LNG floating hoses will enable safe offshore transfer of LNG in a tandem configuration, Trelleborg claims, and could allow floating LNG (FLNG) projects to be considered in harsher conditions.

Vincent Lagarrigue, marketing and project manager at Trelleborg Industrial Solutions, said: “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 shutdown….

“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, flow rate 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, in which vessels line up stern to bow, allows them to be separated by greater distances – 328 ft (100 m) or more – and to cope better with greater wave heights. This limits the risk of collision between the vessels, also simplifying approach, berthing and residence operations.

Lagarrigue said: “Our cryogenic floating hose has been further enhanced to meet the parameters required for the new system. For example, the choice of a 20-in. 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 cu ft/hr (12,000 cu m/hr.)”

The tandem offloading system will employ three Cryoline LNG floating hoses, a hose storage system, a connection head with a dedicated storage platform on the LNG terminal and a bow loading platform on the LNG carrier.

It is designed to operate in sea states with significant wave heights of up to 11.5 ft (3.5 m) at connection and 13 ft (4 m) during transfer and disconnection, even with non-collinear wind or current directions. These figures, Trellebrog claim, should guarantee good offloading availability at almost any location in the world.

Saipem developed the offloading system and equipment to store/handle the hoses. Trelleborg’s system comprises an inner cryogenic hose, an outer protective hose, an insulation layer, and an integrated leak monitoring system.

The equipment is undergoing full-scale tests to ensure compliance with the EN1474-2 standard. Various reduced scale prototypes have been made and tested since 2009 at ambient and cryogenic conditions. The design has been validated by numerous characterization tests and qualification tests on 4-in., 12-in. and 20-in. ID hoses.


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