Shorter lead times and lower capex are making hose-based solutions attractive for compressed natural gas applications
With the rapid growth in floating storage and regasification units (FSRUs), hose-based solutions are joining marine loading arms (MLA) as key cargo transfer technologies for ship-to-jetty discharge of compressed natural gas (CNG).
Speaking at Riviera’s LNG Ship/Shore Interface Conference, Awards and Exhibition in London in November, ContiTech Oil & Marine senior project engineer Gergely Szekely said hose-based CNG transfer solutions are gaining traction for FSRU projects because they offer short lead times.
“There are certain fast-tracked projects that would not have been possible using loading arms because of their longer delivery times,” said Mr Szekely. “A complete hose-based solution can be designed, manufactured and installed in a course of six months.”
Mr Szekely said it is also a case of simple economics.
“(Hoses) have lower capital and operational expenditures over their lifetime compared to loading arms,” he said. Their simple design, with no swivels or moving parts, translates into lower maintenance and fewer possibilities for leaks and, unlike loading arms, hoses can be more easily replaced if repairs are needed.
ContiTech Oil & Gas has been designing and manufacturing hoses for marine and oil and gas applications for 60 years, including cryogenic hoses for LNG cargo transfer applications.
The main component of ContiTech’s non-cryogenic CNG transfer solution is a flexible bonded hose or hoses, typically 12 inches in diameter, that connects the jetty to the FSRU piping.
The bonded hose is composed of multiple layers, with the innermost layer being a stainless-steel carcass that acts as its backbone. This carcass protects the hose from collapsing in case of a sudden decompression.
A rubber layer encompasses the stainless-steel carcass to seal in the hydrocarbons. This rubber layer is wrapped with a carbon-steel reinforcement cable layer. There is an additional rubber layer, above which is a fire-resistant glass fibre layer that allows the hose system to survive in heavy fire situations for up to 30 minutes. The final top layer is a UV-resistant material that protects the hose from sun damage. Mr Szekely said this layer should provide UV protection over the expected 20- to 25-year service life of the hose.
To ensure a long service life, ContiTech recommends a visual check of the hose for damage after each transfer, and a pressure test every five years to verify the hose’s integrity.
Among the other components of ContiTech’s CNG transfer solution is an optional emergency release system (ERS), located between the hose and the FSRU piping. In its development, Continental teamed up with ERS pioneer MIB Italiana, which placed the first LNG-powered ERS coupling into service at the Montoir terminal in France in 1982. The ERS disconnects the hose from the piping in an emergency situation, preventing damage to the hose, piping and FSRU.
Fitted with the ERS is a distance-sensing system that has several alarm levels, the last of which triggers the ERS, disconnecting the hose from the FSRU piping.
An additional component of the CNG transfer solution is the restraining sling which supports the weight of the hose when the ERS engages. A typical length of hose, about 20 m, can weigh between two to three tonnes. The sling prevents the hose, piping, ship and jetty from damage.