Flexible Hoses for Offshore Loading

Offshore loading of LNG from a floating process unit to a tanker requires a transfer system capable of adapting to large relative movements. Several concepts are being developed, based essentially on two different principles:

• Steel piping incorporating a number of swivels to provide flexibility.
• Flexible hoses.

For both concepts operational reliability and safety are key issues.

MARINTEK operates two test rigs for full-scale dynamic testing of flexible hoses. The larger rig can accommodate specimens up to 15 metres long and 20 inches in diameter. The loading is a combination of tension and bending, simulating the loading of a hose in operation. Internal cooling is provided by liquid nitrogen (-196 degrees C). In a typical test the fatigue loading of the design life is simulated with an accelerated block loading programme of 1 – 2 million cycles.

The figure shows a test of a seven metre-long section of 10-inch ID hose with end couplings and bend stiffener. The hose consists essentially of a double-wall bellows structure, with the annulus evacuated to provide thermal insulation. Dynamic bending was applied at the far end, static tension at the near end. The test was fully instrumented in order to provide a full record of the load history and response parameters.

Ref.: J. Eide, S.I. Eide, A. Samuelsen, S.A. Løtveit:  A new solution for tandem offloading of LNG, Offshore Technology Conference, OTC paper 14096, Houston, 2002.

Contacts:
MARINTEK: Oddvar Eide
NTNU: Stig Berge -

(Article in MARINTEK Review No 1-2004)