Explosibility of Polyamide and Polyester Fibers
The current research is aimed at investigating the explosion behavior of hazardous materials in relation to aspects of particulate size. The materials of study are flocculent (fibrous) polyamide 6.6 (nylon) and polyester (polyethylene terephthalate). These materials may be termed nontraditional dusts due to their cylindrical shape which necessitates consideration of both particle diameter and length. The experimental work undertaken is divided into two main parts. The first deals with the determination of deflagration parameters for polyamide 6.6 (dtex 3.3) for different lengths: 0.3 mm, 0.5 mm, 0.75 mm, 0.9 mm and 1 mm; the second involves a study of the deflagration behavior of polyester and polyamide 6.6 samples, each having a length of 0.5 mm and two different values of dtex, namely 1.7 and 3.3. (Dtex or decitex is a unit of measure for the linear density of fibers. It is equivalent to the mass in grams per 10,000 m of a single filament, and can be converted to a particle diameter.) The explosibility parameters investigated for both flocculent materials include maximum explosion pressure (Pmax), size-normalized maximum rate of pressure rise (KSt), minimum explosible concentration (MEC), minimum ignition energy (MIE) and minimum ignition temperature (MIT). ASTM protocols were followed using standard dust explosibility test equipment (Siwek 20-L explosion chamber, MIKE 3 apparatus and BAM oven). Both qualitative and quantitative analyses were undertaken as indicated by the following examples. Qualitative observation of the post-explosion residue for polyamide 6.6 indicated a complex interwoven structure, whereas the polyester residue showed a shiny, melt-type appearance. Quantitatively, the highest values of Pmax and KSt were obtained at the shortest length and finest dtex for a given material. For a given length, polyester displayed a greater difference in Pmax and KSt at different values of dtex than polyamide 6.6. Long ignition delay times were observed in the BAM oven (MIT measurements) for polyester, and video framing of explosions in the MIKE 3 apparatus (MIE measurements) enabled observation of secondary ignitions caused by flame propagation after the initial ignition occurring at the spark electrodes.
Dust Explosion Quantitative Risk Management for Nontraditional Dusts
The current paper describes an approach for dust explosion quantitative risk management of the following nontraditional particulate fuel systems: (i) nanomaterials having particles with dimensions between 1 and 100 nm, (ii) flocculent (fibrous) materials characterized by a length-to-diameter ratio rather than a particle diameter, and (iii) hybrid mixtures consisting of a combustible dust and a flammable gas (or a combustible dust wetted with a flammable solvent). Experimental results are considered as input to a quantitative risk management framework so as to provide a comprehensive procedure to analyze, assess and control the likelihood and consequences of explosions of nontraditional dusts. Using concepts drawn from previous studies, the framework consists of three main components: (i) a new combined safety management protocol, (ii) use of the CFD (computational fluid dynamics) software DESC (Dust Explosion Simulation Code) and FTA (Fault Tree Analysis) to determine explosion consequences and likelihood, respectively, and (iii) application of the hierarchy of controls (inherent, engineered and procedural safety) to achieve residual risk reduction.
A new stochastic factor model: General explicit solutions
We present a new stochastic factor model. In doing so, we provide general, explicit solutions to the portfolio optimization problem.