Trelleborg Seawater Intake Hoses Meet Unique Demands of FLNG Applications
Trelleborg’s oil and marine hoses operation is once again pushing the boundaries of technology for the sector, this time with the launch of a dedicated seawater intake hose engineered specifically to meet the unique requirements of floating liquefied natural gas (FLNG) extraction facilities.
Remote gas extraction presents a variety of challenges due to the crucial role of the cooling process in reducing the volume of the gas by compressing it into liquid form (LNG) to maximize efficiencies in transportation. For this reason, the new Swiline range of hoses from Trelleborg can be used in lengths of up to 600m /1,968ft or even more, enabling the use of sea water from greater depths, which can be up to 20ºC / 68ºF cooler than water at the surface, for the liquefaction process and so making it more effective.
Trelleborg oil & marine hoses project manager Jonathan Petit explained: "FLNGs offer the potential to effectively extract vast amounts of LNG for industrial and domestic use but to do that – and ensure the LNG is transported as cost-efficiently as possible – effective cooling is crucial. This means using seawater which is as cold as possible. This therefore needs to be extracted from greater depths and pumped in higher volumes than is the case with FPSOs, for example. Our Swiline solution draws on proven proprietary Trelleborg technology to deliver a guaranteed solution in even the most demanding conditions, accredited to the international API 17K standard."
Swiline hoses are fully certified to the API 17K standard, which certifies up to 30 years’ maintenance free service life with a safety factor of ten. The seawater intake hoses are designed to deliver optimum performance in even the most demanding process conditions. Employing a unique design incorporating an integrated bending stiffener with a continuous inner liner and rubber outer cover, the hoses minimize the risk of corrosion while offering optimal thermal insulation. The combination of steel cables in a rubber matrix minimizes creep and offers typical tensile strength as high as 1,600t for 40in ID hose, a key attribute when the higher weights required to maintain the position of the hose in high currents are considered.
Swiline hoses can be easily installed vertically from the FLNG deck. Assembly can take place beside the hull with connection on the intake flange by divers, or in the riser caisson. Hydraulic simultaneous tightening of the flange ensures reliable, homogeneous pre-loading of the bolts for optimum performance.
Diameters from 24in to 40in ID are available to enable the hoses to cope with the greater quantities of water – up to 50,000m³/h – while minimizing the pressure drop to avoid the risk of cavitation. Swiline products are suitable for use with both bundled and stand-alone riser configurations.
Trelleborg can offer a complete solution also encompassing riser/ hull interface design and supply, strainer design and supply and hypochlorite injection lines. Injection from hypochlorite lines can take place at the inlet point or the riser top level depending on the inlet depth.
The Swiline range has already been fully qualified and specified for the US$12.6bn Shell Prelude project, the world’s first FLNG, located in the Timor Sea, where production will commence in 2017. Verification has also included uniaxial and multi-axial load tests, extreme and survival loads, as well as fatigue testing with combined tensile and bending loads to validate predictions from finite element analysis (FEA).
As well as FLNGs, the new technology has the potential to significantly optimize the topside architecture on FPSOs by collecting cool water from up to 1,000m/ 3,280ft below sea level.