Use of FLACS during the TWA-800 Accident Investigation

PresentationThe TWA flight 800 accident occurred on July 17, 1996 just outside New York City shortly after take-off. The airplane desintegrated as a result of an “explosion” and 230 people were killed. The investigation concentrated on the possibility of a gas explosion in the Centre Wing Fuel Tank (CWT). The hypothesis was that the heating of fuel in the tank by the air conditioning system was the cause of the flammable vapor concentration (temperature above flash-point). The explosion investigation used laboratory experiments, scale-model tests, and numerical simulations to examine the explosion of Jet-A (aviation kerosene) mixtures with air under conditions simulating the center wing tank environment at the time of the accident. Work was carried out over a period of four years to determine the chemical and physical properties of Jet A, particularly the flammability limits, combustion behavior, and the propagation of flames through the compartmentalized structure of the center wing tank. The CFD tool FLACS was adapted and validated against scale-model experiments. The problem of quenching or flame extinction was identified as an issue and addressed through experiments and modeling. FLACS was then used in full-scale simulations to explore the effects of various parameters and assumptions, especially ignition locations within the tank. All of this information was integrated through a rule-based system to attempt to narrow down the number of plausible ignition locations that would be consistent with the observed damage as deduced from the recovered wreckage

Large Scale Detonation Testing – RPSEA Project Award

PresentationAs the size of Ultra Deep Water (UDW) facilities increases in the Gulf of Mexico (GOM), designs must consider the potential adverse effects associated with vapor cloud explosions in large congested areas and understand the potential for more devastating deflagration-to- detonation transitions (DDTs) on these facilities. However, there is a lack of data at the large scale to validate the necessary design tools used to predict the risk of DDT. GexCon was awarded Subcontract 12121-6403-01 under the Research Partnership to Secure Energy for America (RPSEA), whereby the objective of this project is to improve inherently safer offshore facility designs. One of the main goals of this research project is to provide large scale DDT explosion data and validate the tools necessary to predict vapor cloud explosions in early design phase. The work will also be used to develop guidance documents and recommended practices to facility owners and designers in order to minimize the potential consequence of explosion incidents. This paper will present the current updates for the large scale testing being conducted in a newly developed test rig of 51,840 ft3 (1,459 m3 ) gross volume. These tests will involve evaluation of deflagrations and DDTs involving stoichiometric, lean and rich mixtures ethylene, propane and methane. Further phases of the testing will evaluate the effectiveness of other mitigation measures (e.g., water deluge, solid inhibitor) on the explosion consequences. These experiments will be used to validate and further develop industry-accepted CFD tools and more simplified methods in their prediction of DDTs at the large scale including events involving mitigation

Is my facility at risk? Understanding the risks associated with low burning velocity compounds

PresentationA 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

Large Scale Detonation Testing: New Findings in the prediction of DDTs at large scales

PresentationA large vapor cloud explosion (VCE) followed by a fire is one of the most dangerous and high-consequence events that can occur at petrochemical facilities. As the size and complexity of facilities increase, designs must consider the potential adverse effects associated with vapor cloud explosions in large congested areas and understand the potential for more devastating deflagration-to-detonation transitions (DDTs) on these facilities. While the likelihood of DDTs is lower than deflagrations, they have been identified in some of the most recent large-scale explosion incidents including: 2005 Buncefield explosion, 2009 San Juan explosion, and 2009 Jaipur event. The consequences of DDTs can be orders of magnitude larger than deflagration because they have the ability to self-propagate outside the region of high congestion/confinement. Hence, it is critical to understand how a facility’s geometry or equipment layout can affect explosion consequences and assist in their mitigation and/or prevention. Due to the inability to predict such devastating phenomena on the large scale, owners and designers cannot evaluate installations for risk of DDTs and provide “inherently safer” layout or mitigation measures to significantly reduce or eliminate such hazards. However, there is a lack of data at the large scale to validate the necessary design tools used to predict the risk of DDT. One of the main goals of this research project is to provide large scale DDT explosion data and validate the tools necessary to predict vapor cloud explosions in early design phase. This paper will present the results of large scale testing being conducted in a newly developed test rig of 50,000 ft3 (1,500 m3 ) gross volume under award Subcontract 12121-6403-01 provided by the Research Partnership to Secure Energy for America (RPSEA). These tests involve evaluation of deflagrations and DDTs involving stoichiometric, lean and rich mixtures, with propane and methane fuels. The effectiveness of mitigation techniques such as solid inhibitors or deluge is evaluated for preventing DDTs

The Development of Novel Organotin Anti-Tumor Drugs: Structure and Activity

An overview of the development of anti-tumor organotin derivatives in selected classes of compounds is presented and discussed. High to very high in vitro activity has been found, sometimes equaling that of doxorubicin. Solubility in water is an important issue, dominating the in vivo testing of compounds with promising in vitro properties. The cytotoxicity of the compounds was increased by the presence of a bulky group, an active substituent or one or more polar substituents. Polar substituents may also improve the water solubility. Although organotin derivatives constitute a separate class of compounds, the comparison with cisplatin is inevitable. Among the observed toxicities, neurotoxicity, known from platinum cytostatics, and gastrointestinal toxicity, typical for many oncology drugs, have been detected. Further research to develop novel, useful organotin anti-tumor compounds should be carried out

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

Modelling of vented dust explosions – empirical foundation and prospects for future validation of CFD codes

Explosion venting is the most frequently used method for mitigating the effects from accidental dust explosions in the process industry. Optimal design of vent systems and credible execution of risk assessments in powder handling plants require practical and reliable ways of predicting the course and consequences of vented dust explosions. The main parameters of interest include flame propagation and pressure build-up inside the vented enclosure, the volume engulfed by the flame, and the magnitude of blast waves outside the enclosure. Extensive experimental work forms the empirical foundation for current standards on vent sizing, such as EN 14491 and NFPA 68, and various types of software for vent area calculations simply apply correlations from these standards. Other models aim at a more realistic description of the geometrical boundary conditions, as well as phenomena such as turbulent compressible particleladen flow and heterogeneous combustion. The latter group include phenomenological tools such as EFFEX, and the CFD code DESC (Dust Explosion Simulation Code). This paper briefly reviews the empirical foundation behind modern guidelines for dust explosion venting, and explores current capabilities and limitations of the CFD code DESC with respect to reproducing results from one experimental study on vented dust explosions. The analysis emphasizes the influence of geometrical features of the enclosures, discrepancies between laboratory test conditions and actual process conditions, and inherent limitations in current modelling capabilities

Experimental Investigation into the Consequences of Release of Liquified Hydrogen onto and under Water

Large-scale experiments have been performed to investigate the possible consequences of realistic amounts of liquified hydrogen (LH2) encountering water. The experiments aimed at simulating an accidental release of LH2 onto water, for instance during the fuelling of a ship. For liquified natural gas (LNG), it has been demonstrated that physical explosions may occur when it is spilled onto water. These phenomena are referred as rapid phase transitions (RPTs). It cannot be excluded that RPTs are also possible in the case of LH2. The tests were performed at the Test Site Technical Safety of the Bundesanstalt für Materialforschung und –prüfung (BAM) in Horstwalde, Germany. The tests were performed in a 10 m x 10 x 1.5 m basin filled with water. LH2 releases of up to about 1 kg/s were established releasing directly from a trailer carrying LH2. The releases occurred from a height of 50 cm above the water surface pointing downwards, 30 cm under the water surface pointing downwards and 30 cm under the water surface pointed along the water surface. All release configurations resulted in a very chaotic LH2-water mixing zone, causing considerable evaporation and resulting in minor over pressures. No RPTs were observed. The main phenomenon to be observed is, however, an ignition of the released gas cloud resulting in significant blast wave overpressures and heat radiation to the surroundings. The ignition occurred in all under-water releases and in about 90 % of the releases above the water surface.Experimental Investigation into the Consequences of Release of Liquified Hydrogen onto and under WaterpublishedVersio

Experimental Investigation into the Consequences of Release of Liquified Hydrogen onto and under Water

Large-scale experiments have been performed to investigate the possible consequences of realistic amounts of liquified hydrogen (LH2) encountering water. The experiments aimed at simulating an accidental release of LH2 onto water, for instance during the fuelling of a ship. For liquified natural gas (LNG), it has been demonstrated that physical explosions may occur when it is spilled onto water. These phenomena are referred as rapid phase transitions (RPTs). It cannot be excluded that RPTs are also possible in the case of LH2. The tests were performed at the Test Site Technical Safety of the Bundesanstalt für Materialforschung und –prüfung (BAM) in Horstwalde, Germany. The tests were performed in a 10 m x 10 x 1.5 m basin filled with water. LH2 releases of up to about 1 kg/s were established releasing directly from a trailer carrying LH2. The releases occurred from a height of 50 cm above the water surface pointing downwards, 30 cm under the water surface pointing downwards and 30 cm under the water surface pointed along the water surface. All release configurations resulted in a very chaotic LH2-water mixing zone, causing considerable evaporation and resulting in minor over pressures. No RPTs were observed. The main phenomenon to be observed is, however, an ignition of the released gas cloud resulting in significant blast wave overpressures and heat radiation to the surroundings. The ignition occurred in all under-water releases and in about 90 % of the releases above the water surface