Case Study of an Aerosol Explosion and a Method to Determine Explosion Temperatures
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Case Study of an Aerosol Explosion and a Method to Determine Explosion Temperatures Michael Fox Æ Richard Hastings Æ Scott Lovald Æ Juan Heinrich
Submitted: 24 February 2007 / in revised form: 4 May 2007 / Published online: 26 June 2007 ASM International 2007
Abstract A failure analysis case study is presented for a two-piece aerosol containing tetrafluoroethane, commonly referred to as Refrigerant 134a. A gentleman was preparing to recharge the air conditioning system of an automobile when the bottom exploded off the aerosol container, propelling the body of the aerosol container like a rocket, which hit the man in the eye and blinded him in that eye. The aerosol was never connected to the air conditioner, therefore backpressure from the air conditioner (AC) compressor was ruled out as a cause for the explosion. The objective of the study was to determine why the aerosol exploded. Several recently developed test methods were used, including two types of heat-to-burst tests and a puncture chamber to measure the pressure-versus-temperature behavior of aerosols. More common test methods were also used, such as water bath pressure tests, hydro pressure burst tests, pneumatic pressure burst tests, hardness measurements, weight measurements, metallography, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and an accident scenario recreation. A semi-empirical correlation between the hardness and weights of the container bottoms was used to determine the explosion temperature and/or pressure. This semi-empirical
M. Fox (&) Chemical Accident Reconstruction Services, Inc., 9121 E. Tanque Verde Rd. #105, Tucson, AZ 85749, USA e-mail: [email protected] R. Hastings Materials Science Department, University of Arizona, Tucson, AZ 85719, USA S. Lovald J. Heinrich Department of Mechanical Engineering, University of New Mexico, Albuquerque, NM, USA
correlation agrees in principle with an analysis of the explosion pressures using finite-element analysis (FEA). The root cause for the explosion was determined to be a lack of strength of the bottom of the two-piece aerosol coupled with heating the aerosol to temperatures significantly above room temperature. Keywords Aerosol container Burst pressure Failure analysis FEA Predictive method
Introduction A middle-aged man purchased a kit to recharge the air conditioning (AC) units on several vehicles he owned. The kit was a do-it-yourself package consisting of three 425gram, two-piece aerosol containers of Refrigerant 134a (tetrafluoroethane) and several adaptors plus a connection hose with a built-in pressure gage. From here forward the aerosol being used will be referred to as R134a. After successfully recharging one vehicle, he moved to a second auto. Using the connectors that came with the R134a kit, he attached one of the kit adaptors to what he believed to be the correct air conditioning fitting to determine the fill requirement per the instructions, and then restarted the engine. It
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