Safety of cryogenic storage facilities of flammable gases

In recent years, cryogenic storage of flammable gases spread beyond conventional applications. Actually, besides large-scale cryogenic transport by ship, loading/unloading and bulk storage, a number of smaller scale applications are proposed, in particular for liquefied natural gas (LNG). However, this growth comes with safety concerns arising from the flammable nature of natural gas and the amounts of this hazardous material stored and processed in LNG facilities. A long-lasting experience is present in the chemical industry concerning the medium and small-scale cryogenic storage of flammable gases as e.g. ethylene and propylene. In the present study, the operating experience deriving from such technologies is used as a basis to assess the safety of new supply chains based on small-scale storage of LNG and other cryogenic fuels. Preliminary hazard identification studies were used to identify credible accident scenarios. Based on current industrial practice and on proposed new installations, reference technologies were defined and considered in the study. A comparative analysis of the relevance and severity of reference accident scenarios was carried out. Safety key performance indicators based on the concept of inherent safety were defined, providing a simplified tool to support safety assessment and emergency response in cryogenic storage facilities.