Side-by-Side Concept for LNG and LPG Transfer in Open Sea Conditions

The new transfer system ‘SOTLL (Sideways Offshore Transfer of LNG and LPG)’ enables the ship-to-ship transfer of cryogenic fluids (e.g. LNG, LPG or LH2) in a side-by-side configuration in open sea conditions. The system thus closes the technological gap between the more challenging cargo transfer in tandem configuration, which is considered and suitable for use in harsh environments and the cargo transfer via rigid loading arms, which should only be used in benign conditions in ports, bays or other sheltered waters.

Compared to rigid loading arms the new SOTLL system requires less deck space and less deck substructure as it works with only one crane instead of 4 to 5 rigid loading arms which also reduces the maintenance effort. The required flexibility for ship-to-ship transfer in open sea conditions is achieved by the use of corrugated pipes certified up to 16-inch ID (EN-1474-2) providing a monitored double containment system for highest safety standards. Thus, no fluid swivels are required with the SOTLL system. Nevertheless, in the rare case of a malfunction a pipe can be easily replaced by a spare in short notice, guaranteeing an optimal uptime of the SOTLL transfer system.

In order to cope with differently sized shuttle tankers for LPG, LNG and other cargos a flexible positioning of the cargo transfer system and the fender system has been designed. This gives the possibility to accommodate each tanker at the most favourable position alongside the FLNG or FSRU during cargo transfer. As this position depends on the vessel size and the environmental conditions extensive numerical analyses and model tests have been carried out. These have shown that all relative motions in x-, y- and z-directions as well as all occurring loads in the mooring lines between the both ships resulting from second-order wave (drift) forces can be accommodated with standard mooring lines and the new innovative fender system.

Scope of Work: 

Project Management

Integrated Project Development

Complete Concept Design

Motion and Mooring Analysis

System Verification by means of model tests (in co-operation with partner TU Berlin)

Flexible positioning of the transfer system patented

IMPaC‘s Services: 

8 000 hours