Open Access

The fire engulfment of storage tanks of hazardous materials is among the most critical scenarios in hazard assessment of industrial value chains. Laboratory and full-scale experimental trials are used to test the tank performance and integrity in such scenarios. However, strong uncertainties usually affect the actual fire load experienced by the tank, in particular when large-scale experiments are carried out in open test fields. Such uncertainties arise from several factors difficult to control during experimental tests, such as the atmospheric conditions as there is the influence of wind drifts influencing the actual fire engulfment, the flame temperature and the flame dynamic distribution around the target. Consequently, verifying the concordance of an experimental test with standard test criteria and defining accurate boundary conditions in correlated model simulations is challenging. In this study, the development of a novel method for the analysis of fire conditions based on image processing is presented. The approach allows identifying the flame coverage on the target surface during the test and provides an accurate map of the flame distribution on the equipment over time. The approach is tested using experimental data from a full-scale fire test campaign carried out on liquid hydrogen cryogenic tanks. The results prove to be accurate in replicating the experimental temperatures measured on the outer tank shell during the test. The proposed methodology can be used to better understand the results of experimental fire tests and to characterize realistic fire scenarios, also supporting the definition of fire test requirements. Moreover, the approach produces results that can be implemented as advanced space-time-varying boundary conditions in simulation models, improving their accuracy in reproducing real cases.

Liquefied Hydrogen (LH2) or Liquefied Natural Gas (LNG) establish themselves as important energy carriers in the transport sector. Its storage requires tanks with Thermal Super Insulations (TSI) to keep the transported fluid cold. TSI has proven itself in various applications over a long time, but not in the land transport sector, where accidents involving collisions, fires, and their combination are to be expected. The focus of this study is to investigate the behavior of different types of TSI when exposed to a heat source that represents a fire. Therefore, a High-Temperature Thermal Vacuum Chamber (HTTVC) was used that allows the thermal loading of thermal insulation material in a vacuum and measuring the heat flow through the TSI in parallel. Within this study, 5 samples were tested regarding 3 different types of MLI, rock wool, and perlites. The thermal exposure caused different effects on the samples. In practice, this can be connected to the rapid release of flammable gases as well as a Boiling Liquid Expanding Vapour Explosion (BLEVE). These results are relevant for the evaluation of accident scenarios, the improvement of TSI, and the development of emergency measures.

In the context of green energy transition, cryogenic tanks insulated by MLI and vacuum are emerging as a leading solution to store hydrogen in heavy-duty vehicles. However, the integrity of such tanks can be jeopardized by fire. In such a scenario, MLI materials degradation can occur, leaving the tank unprotected from the fire heat flux, with consequent rapid pressurization and a high risk of failure. This study presents a safety assessment of non-combustible MLI under fire exposure based on the estimation of the time to mechanical failure of the equipment. This is calculated through an innovative model that simulates the thermomechanical response of the tank, including the MLI thermal degradation and the pressure-relief valve (PRV) operation. The application to several case studies that consider a typical LH2 tank featuring a wide range of MLI configurations demonstrated the likelihood of failure in case of exposure to a hydrocarbon pool fire, providing also comprehensive insights into the impact of the insulation characteristics and operating conditions on the time to failure.

Liquefied Hydrogen (LH2) and Liquefied Natural Gas (LNG) establish themselves as important energy carriers in the transport sector. Their storage requires tanks with thermal super-insulations to keep them at cryogenic conditions for a long time. These insulation systems have proven itself in various applications over a long time. However, these insulations are still new in land transportation, where accidents involving collisions, fires, and their combination are to be expected. This study summarizes the results of the ongoing research program in which insulations commonly used in industry were analysed through experimental and numerical studies under fire-like conditions. It was found that there are strong differences among the various insulation systems. Several safety concerns and research gaps exists for layered insulations, which are typically used in land transport. To further analyse these insulation systems, a new test concept called Cryogenic High Temperature Thermal Vacuum Chamber (CHTTVC) was developed and manufactured. This concept enables the testing of large insulation samples under industrial conditions and the consideration of cryogenic conditions relevant for the investigation of various phenomena. The results are important for the evaluation of accident scenarios, the improvement of thermal super-insulations, and the development of emergency measures.

Hydrogen is recognized as a keystone of the global energy transition, offering a clean, high-energy-density energy carrier ideal for storage and transportation. Among various storage options, liquid hydrogen (LH2) is especially advantageous for both mobile and stationary applications. However, ensuring the safety and performance of LH2 storage systems under extreme thermal conditions, such as fire exposure, remains an engineering challenge. This study introduces an experimental framework, called the Cryogenic High-Temperature Thermal Vacuum Chamber (CHTTVC), designed to investigate the thermal-hydraulic response of vacuum-insulated cryogenic tanks under fire-like conditions. The apparatus enables evaluation of insulation performance, such as perlite and multilayer insulation (MLI), with a focus on thermal degradation, heat ingress, and vacuum stability. Results indicate that combustible MLIs undergo substantial thermal degradation, leading to heat ingress rates of up to 6.5 kW and the formation of hazardous combustion by-products. In contrast, non-combustible MLIs and bulk insulation materials restrict heat ingress to approximately 3 kW while more effectively preserving vacuum integrity. Combustible MLIs also exhibit pronounced pressure increases in the evacuated section, reaching ∼6 × 104 Pa, nearly six times higher than those observed for non-combustible counterparts. Analysis of effective emissivity further reveals an enhancement in radiative heat transfer, approximately five times, for combustible MLIs following degradation. Additionally, marked thermal stratification develops under both nominal and extreme heat loads, with temperature gradients approaching 10 °C per 100 mm during sustained thermal exposure.