This work presents field test results of silane releases from a cylinder valve into an open environment and into a gas cabinet. The following release tests were performed: (1) Leak from the valve outlet connector with and without a restrict flow orifice (RFO), (2) Leak directly from the two leak check holes of a capped Diameter Index Safety System (DISS) after the cylinder valve with and without a RFO, (3) Leak from cylinder valve stem retainer thread (via the loosened valve), and (4) High pressure releases from a 0.32-and 0.64-cm tube into a ventilated single cylinder gas cabinet.Release pressures varied from 120 psig to the full cylinder pressure of 1,250 psig. Both digital video and high speed cameras were used to record the ignition, pop, and explosion behavior. The results confirmed that the ignition behavior of a silane leak is strongly related to the release pressure, flow rate, aperture, and the exit environment.This study has shown that silane leaks from a fully opened cylinder valve (without an RFO) or the loosened retainer thread will not autoignite while a silane leak from fully opened cylinder valve (with an RFO) or a loosened DISS cap with and without an RFO will ignite immediately even at full cylinder source pressures.The RFO results show that the RFO increases the likelihood of the autoignition of the release, and significantly decreases release rate and the intensity of the flame. This information is important when designing systems and developing safe practices for handling silane cylinders in the semiconductor and thin-film transistor liquid crystal display (TFT-LCD) industries. The results also demonstrates safe cabinet ventilation rate to prevent explosions.
A second possible cause of a previously described silane explosion is proposed based on a more detailed examination of the physical evidence. The explosion and fire occurred in a silane gas room in a photovoltaic fabrication plant. This investigation recommends more research to investigate the characteristics of a silane release and the resulting fires and explosions. Suggestions are also made for a better silane cylinder valve design and cabinet design. Silane leaks are difficult to detect; therefore the recommendations include the need for a silane gas detector to warn the operator when there are leaks. © 2007 American Institute of Chemical Engineers Process Saf Prog, 2007.
The manufacturing process of HMX produces high-purity products, greater than 98 wt %, of which 60 wt % belongs to β form HMX for military use and the remaining 40 wt % belongs to different types (R and γ) of HMX. In the past, the remaining products have been regarded as waste materials and were burned. After improvement of the reuse technique, the remaining 40 wt % products become a reusable high explosive by using the method of slow-cooking and solvent cleaning. This high explosive is named RDXH because its chemical, physical, and detonation properties are between those of RDX and HMX. To determine safe use of RDXH, this study utilizes thermal analysis calorimetry, explosive sensitivity test equipments, X-ray diffraction techniques, and HPLC analysis to investigate the thermal properties, reaction kinetics, energy limits of explosive sensitivity, and chemical composition of RDXH. On average, the DSC experimental results of RDXH present the exothermic onset temperature 233.22 °C, release heat 3287.94 J/g, activation energy 201.16 kJ/mol, and frequency factor 2.31 × 10 17 L/s. In comparison with high explosives RDX and HMX, RDXH has the onset temperature of exothermic reaction between that of RDX and HMX, releases the least heat, and possesses the highest kinetic parameters. The explosive sensitivity test results demonstrate that RDXH belongs to a passive grade and has energy limits similar to those of RDX and HMX. Results of XRD patterns and HPLC analyses indicate that RDXH contains molecular structures of 47.32 wt % RDX and 52.67 wt % HMX. Conclusively, the reusable waste product from HMX producing process, RDXH, could be safely used and transported as a high explosive.
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