Study On The Failure Process Of Liquid Storage Tanks In Fire Environment

Clean fuels represented by natural gas and hydrogen are widely used in energy and chemical industry.For storage tanks that store such substances in liquid form,they are major hazard sources.Once a rupture accident occurs,it will bring great harm to surrounding facilities and personnel.The fire caused by the leakage of flammable medium is one of the reasons for the rupture of liquid storage tank.Under the comprehensive influence of many reasons,the rupture of storage tank under the condition of fire mainly has two forms of local cracking and overall cracking,among which the overall cracking is easy to cause boiling liquid expanding vapor explosion(BLEVE)and generate shock wave and projectile fragments.Therefore,revealing the influencing factors of the liquid storage tank failure process and the conditions that cause the overall cracking failure has important theoretical and practical significance for the prevention of explosion accidents and emergency rescue of flammable liquid tank farms.Aiming at the problems of temperature and pressure response and failure of metal storage tank exposed to high temperature environment for a long time,this paper studies the failure mode of storage tank by carrying out fire experiment of small storage tank,taking the filling rate of pressure vessel itself and fire scene environment as the breakthrough point,starting from the pressure response,temperature response,release mode,macro explosion analysis,micro material analysis and so on.The main work and conclusions are as follows:(1)Independently designed and built a small horizontal storage tank fire experiment platform,which mainly includes horizontal storage tanks(internal medium is water),protective devices used to control the fire area of the storage tanks,support structures and controllable fire environment(Use kerosene as fuel).In the experiment,static pressure sensors and high-frequency dynamic pressure sensors are used to monitor the pressure rise inside the storage tank and the pressure change at the time of release.Thermocouples are used to record temperature changes in the storage tank,and cameras are used to monitor the entire fire experiment in real time.The camera collects the release process.(2)Using experimental methods,the factors affecting the failure form of storage tanks in a fire environment and their influence laws are studied,including the filling rate of storage tanks,fire area and wind direction at the fire site.The results showed that when the filling rate of the horizontal storage tank is low,the failure mode tends to crack locally;when the filling rate is high,the storage tank stores more energy and the container tends to rupture as a whole;when the fire area of the storage tank is small,the storage tank The pressure-bearing time of the tank is long,and the overall cracking tends to occur.When the fire position is mainly on the gas phase wall,it is difficult to form an overall natural convection cycle inside the storage tank,which leads to the failure time of the storage tank relative to the case where the gas and liquid walls are simultaneously exposed to fire Advance;the impact of environmental winds reduces the fire area of the storage tank and is prone to overall cracking.In short,the influence of the fire environment on the failure of liquid storage tanks is a process involving the gas-liquid-solid coupled heat and mass transfer of the tank body and the medium in the tank.(3)For partially cracked storage tanks,the cracks extend along the axis of the storage tank.The cracking mechanism is mainly due to the degradation of material properties in the local high temperature area on the top of the storage tank,and thinning occurs until ductile fracture occurs in the weak zone.The fracture morphology mainly shows tensile characteristics.For storage tanks with overall failure,the overall deformation of the storage tank is larger than that of limited cracking,and the cracks are easier to propagate after the initial cracks.The fractures of the storage tanks show two morphological characteristics of tension and shear in the main crack direction.After the storage tank ruptures,the limited crack release time is significantly longer than the overall cracking.The pressure rebound in the overall cracking failure mode is more intense.The higher the internal pressure before the storage tank fails,the greater the power of the explosion.