The safety distances to be applied for LNG fueling and bunker operations are critically influenced by gross failure (rupture) of transfer hoses or loading arms. This project aims to prove that for small scale LNG hose based transfer systems a full bore rupture scenario is much too conservative for existing technology and that much less LNG outflow can be substantiated. This on its turn allows a reduction of the necessary safety distances around LNG service facilities.
The report describes two experiments for 2” and 4 ‘ hoses , the first where a loaded trailer tire was running several times across composite and metal corrugated hoses while being pressurized by liquid nitrogen, the second experiment where a degradation of a composite hose in service due to fatigue was executed until a first gas leak was observed.
The first experiment was conducted in 2 different set-ups, one where the hoses (pressurized by liquid nitrogen therefore colder than they would be during normal LNG operations) were laid down on a flat service while the trailer tire was crossing 8 times each of the hoses, in the second set-up the hoses were fixed on top of a sharp edge while the tires were passing. Results from this experiment showed that the majority of the tested hoses did not leak at all and those that started t leak released a very small amount of gas only.
The second experiment created a longitudinal cyclic force on a short test-hose which was stretched and released with a frequency of 2 Hz. The cycling was stopped after significant leakage of gas was noticeable. Subsequently, the hose was pressurized with water up till 110 bar, far above its normal operating point (about 10-14 bar) showing that the remaining pressure capacity of that hose, despite the initial leak was well above normal operating pressures.
From the two experiments it can be concluded that it is successfully demonstrated that, limited to the 4 tested hoses, a ‘leak before burst’ is the expected response of the hose.