| 摘要 |
To detect escape or spillage of a cold liquid, for example liquefied natural gas, a narrow, robust, flexible, resilient, plastics tube 4, placed where the escaped or spilled cold liquid can contact it, is filled with carbon dioxide gas from a gas supply 24 via a non-return valve 34 and a pressure regulator 30 which ensures that the maximum pressure in the tube 4 is at a desired value which is preferably greater than the pressure of the ambient atmosphere surrounding the tube. A gas pressure drop detector 38 is provided to observe a pressure drop in tube 4. Should escaped liquefied natural gas contact the tube 4 the latter is so cooled that the carbon dioxide gas inside de-sublimates to a solid of greatly reduced volume causing a marked drop in pressure in the tube 4. This is observed by the detector 38 which initiates a warning or some safety action. A gas flow restrictor 36 ensures the gas supply 24 cannot rapidly re-charge the tube 4 before the detector 38 has responded to the pressure drop. <IMAGE>
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