Design fire for the safety approval of thermally insulated storage and transport tanks - experimental and analytical investigations

The number of vehicles using or transporting cryogenic fuels such as Liquefied Hydrogen (LH2) or Liquefied Natural Gas (LNG) is growing rapidly in the land transportation sector. This development raises the question of whether new risks—such as those associated with a BLEVE (Boiling Liquid Expanding Vapor Explosion)—are emerging. A key aspect in addressing this concern is the investigation of the behavior of cryogenic storage tanks under fire conditions, including the characterization of representative fire scenarios. The heat load to the tank in such scenarios can be reproduced by design fires, which can be used reproducibly in the approval process for such tanks. The paper presents results of a series of fire tests regarding pool, tyre, and truck cabin fires interacting with a calorimeter, arranged at BAMs Test Site Technical Safety (BAM TTS) in Germany. The calorimeter represents a device in the fire that measures the incident heat flow over time. The results enable the analysis and characterization of the fires and the identification of a design fire representative of a wide range of fire scenarios. The study demonstrates that a comprehensive fire characterization — based on a maximum temperature of 1000 °C and a flame emissivity of 0.5 — is well-suited to simulate a broad range of realistic fire conditions. In contrast, current standards for cryogenic tanks often assume lower temperatures and do not specify the flame emissivity, which significantly influences heat transfer to the tank. These insights are crucial for developing representative design fires for tank approval processes and for improving the understanding of accident scenarios and their potential consequences.