Offshore natural gas is converted into liquid form – LNG – for cost effective storage and transportation over long distances. LNG takes up about 1/600th the volume of natural gas in its gaseous state.
In remote areas floating liquefied natural gas – FLNG – units are ideal, and they have caught the interest of both major oil and gas players and many nations.
So far only a few projects have come to fruition, for a combination of reasons. Most importantly, health, safety and environment (HSE) requirements must be met as LNG is highly flammable and very large offshore platforms need to be moored and maintained for as long as 20 years.
“We expect that FLNGs have the potential to become a major game changer,” says Xavier Delineau, Managing Director of the oil and marine hoses business of Trelleborg Industrial Solutions.
“Using FLNGs, the supply chain takes a shortcut,” he continues. “The gas can be efficiently processed, treated, liquefied, stored and exported on the same vessel, directly at the source. There is no need for a permanent pipeline transportation network. It is very cost-effective. Positioned remotely from the coast, the operation is also much safer in certain locations in the world.”
In the quest for a solution that would contribute to making FLNG operations safer and more reliable than existing ones, Trelleborg started development of Cryoline LNG in 2009 together with oil and gas companies Saipem and Total. The resulting LNG tandem offloading system is said to be safe even under extreme weather and environmental conditions.
Vincent Lagarrigue, Marketing and Project Manager for the oil and marine hoses business of Trelleborg Industrial Solutions, says: “With traditional side-by-side offloading solutions, the distance between the LNG carrier and the FLNG terminal is typically no more than five meters. Using our new cryogenic floating flexible hoses, this can be increased to as much as 150 to 250 meters, significantly limiting the risk of collisions.”
The operator will be able to connect the system at wave heights of up to 3.5 meters, and to offload with four-meter waves. This means improved offloading availability and less downtime than with conventional loading arms or mechanical aerial systems.
The liquefaction process for natural gas involves cooling to cryogenic temperatures as low as -165°C. Producing a hose to handle media at this temperature has been difficult.
The patented system is made of one vertical reel along with three cryogenic hoses and a connection head. There are two lines for the LNG transfer and one for vapor return to the FLNG unit.
The hoses feature a hose-in-hose design with an inner hose that transports the cryogenic fluid. It is protected by an outer hose, which in turn is protected by an insulation layer between the hoses. The hoses are fitted with an integrated leak-monitoring system that detects even very small leaks, enabling the operator to react in good time. There is also a specially designed connection system.
“It is based on proven technologies within the Trelleborg Group,” says David Mayau, Technical and Engineering Manager for Trelleborg’s oil and marine hoses. “Tandem offloading floating operations have been used for many years in oil transfer, and it is a configuration that operators know how to handle. Apart from the safety, it is a flexible and reliable solution.”
Given the risks involved in LNG operations, there have been numerous tests to fulfill tough customer requirements, including material, fatigue and characterisation tests as well as extreme thermal tests.
“Since 2012 there has been an extensive third-party-verified program to qualify the hoses according to the EN1474-2 standard,” says Delineau. “We expect to conclude this during 2013 and be ready to launch early 2014.”
1. Inner cryogenic hose Derived from composite hose technology, 2. Innovative and efficient insulation material. Reduces heat loss and ensures hose buoyancy, 3. Outer protective marine hose. Derived from conventional flexible bonded hose technology, designed for harsh environments and with high fatigue resistance, 4. Leak monitoring system. Based on optical fiber technology for leak detection, 5. Compact and specific connection system. Ensures load transfer and leak integrity. Minimises heat loss.
Trelleborg has acquired SBM Offshore’s cryogenic hose system technology. The technology will be embedded in and strengthen Trelleborg’s development of Cryoline LNG.
For a long time, Trelleborg has been offering oil hose systems for offshore offloading. The offering has now broaded to the LNG market. Along with the Cryoline LNG hoses, Trelleborg has also engineered and qualified Flexible Water Intake hoses (FWIH) for FLNG vessels.
The FWIH is used to suck water from great depths for FLNG and FPSO (floating production, storage and offloading) cooling applications. “To liquefy the gas, you must use huge quantities of cold seawater and spread it within the FLNG unit to cool the equipment,” explains David Mayau, Technical and Engineering Manager for Trelleborg’s oil and marine hoses. “The deeper you collect water, the better the cooling efficiency.”
For this purpose Trelleborg developed, tested and qualified a large one-meter (40-inch) water suction hose with integrated hypochlorine lines.
“For FLNGs we have, together with Seal Engineering, certified our FWIH with API 17K and can now offer 20 year design service life with FWIHs qualified to go down to 800 meters,” Mayau says.