Safe Handling and Storage of Cryogenic Liquids

Abstract

Safety in the handling and storage of cryogenic liquids is a major requirement for all users. The advisory first point of reference is the “Cryogenic Safety Manual: A Guide to Good Practice”, published by the British Cryogenic Council with the 5th Edition being published in 2018. This Chapter does not cover all the material in the Cryogenic Safety Manual but raises points from 60 years of cryogenic practice. Personal safety relates to cold burns and asphyxia. Spillage of cryogenic liquids creates the main problem, which is the 700 fold increase in volume of the evaporating vapour from liquid spill, displacing atmospheric air and reducing the oxygen composition to below 7%. Use of personal oxygen monitors is the answer to this hazard. Care is also needed to avoid spillage from accidentally over-filling a vessel. The construction of safe laboratories is needed for research work on cryogenic liquids, and the experience of building one at the University of Southampton is described and discussed. Some recommendations are made for the safe handling of a list of cryogenic liquids, including helium, hydrogen, neon, nitrogen, argon, and oxygen as single components; also liquid air, LNG, LPG hydrocarbons, together with minor impurity solutes, all as multi-component mixtures. Liquid hydrogen is a particular problem arising from its increasing use as an energy fuel, since any spillage is likely to create a hydrogen explosion and BLEVE fire ball. Finally, the safety of cryogen-free systems using cryocoolers has particular safety hazards, which need attention during both cooling and warming procedures.