Is my facility at risk? Understanding the risks associated with low burning velocity compounds
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A key factor when performing risk assessments and facility siting studies is to assess the explosion and flash fire risk of combustible fluids. There are accurate and established methods to do so when dealing with flammable fluids that have laminar burning velocities (LBVs) around 40 cm/s (e.g., most hydrocarbons). There is currently a need to establish equivalently accurate methods for mildly flammable fluids that have LBVs less than 10 cm/s (e.g., R-32 and ammonia). The use of such fluids is growing, particularly in the heating, ventilation, air conditioning, and refrigeration (HVAC&R) industries as the result of on-going efforts to phase out working fluids with high global warming potential. Without an accurate method of assessing the explosion and flash fire risk of mildly flammable fluids, a very conservative approach is often applied. The approach is to assume the explosion properties of mildly flammable fuels are close to those of methane when evaluating the potential explosion consequences. This will, however, grossly over-predict the potential explosion consequences as flame speed and overpressures during explosions and flash fires are directly correlated to the LBV of the fuel. Furthermore, the likelihood of an explosion or flash fire may also be overpredicted when assuming flammability properties are equivalent to those of methane. Therefore, it is important to not only understand the explosion consequences but also the likelihood of having an explosion, which includes the probability of flammable mixtures forming and subsequently being ignited. Flammability properties and characteristics of mildly flammable fluids must be thoroughly understood to accurately evaluate the probability and consequence of the fire/explosion hazards associated with their use. This study examines post-ignition consequences at large scales through experimentation and with computational fluid dynamics. Fundamental flammability properties of mildly flammable fluids are also measured and presented along with previously reported data in the literature to evaluate potential measurement uncertainties. The flammability properties are then discussed in the context of the likelihood of having an explosion or flash fire, specifically in regard to the probability of forming a flammable mixture and the probability of a flammablemixture being ignited. The combined large-scale consequence testing, fundamental flammability and ignitibility experiments, and modeling results will allow for more accurate assessments of risk.
Pagliaro, John; Davis, Scott; van Wingerden, Kees (2017). Is my facility at risk? Understanding the risks associated with low burning velocity compounds. Mary Kay O'Connor Process Safety Center; Texas &M University. Libraries. Available electronically from