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Electrical Safety
Published in W. David Yates, Safety Professional’s Reference and Study Guide, 2020
Arc blasts occur when powerful, high-amperage currents arc through the air. Arcing is the luminous electrical discharge that occurs when high voltages exist across a gap between conductors and current travels through the air. This situation is often caused by equipment failure owing to abuse or fatigue. Temperatures as high as 35,000°F have been reached in arc blasts. There are three primary hazards associated with an air blast. Arcing gives off thermal radiation (heat) and intense light, which can cause burns;A high-voltage arc can produce a considerable pressure wave blast;A high-voltage arc can also cause many of the copper and aluminum components in electrical equipment to melt. These droplets of molten metal can be blasted great distances by the pressure wave.6
Introduction
Published in P. Chakravarthy, M. Agilan, N. Neethu, Flux Bounded Tungsten Inert Gas Welding Process, 2019
P. Chakravarthy, M. Agilan, N. Neethu
The welding arc is a high-current and low-voltage electrical discharge which flows from the cathode to the anode. The flow of current through the gap between the electrode and the workpiece needs a column of charged particles to have reasonably good electrical conductivity. The electric discharge is sustained through a path of ionized gaseous particles called plasma. Various mechanisms such as field emission, thermal emission, secondary emission etc. cause the generation of these particles. The temperature inside the arc and at the surface of the arc is approximately 15,000°C and 10,000°C, respectively. The open-circuit voltage for a typical arc welding process ranges from 30 to 80 volts, and typical currents are between 50 and 300 A. The energy developed in the arc per unit time equals V × I, where V is the arc voltage and I the current. The welding arc acquires the shape of hot gas formed between the electrodes, and due to its low density, hot gas tends to rise and form a bell-shaped arc. Further, fusion welding processes are categorized based on the type of electrode used. Consumable electrode processes – shielded metal arc welding (SMAW), submerged arc welding (SAW), flux cored arc welding (FCAW), gas metal arc welding (GMAW) and electroslag welding (ESW) processes. Non-consumable electrode processes – gas tungsten arc welding and plasma arc welding processes.
Advanced optics
Published in John P. Dakin, Robert G. W. Brown, Handbook of Optoelectronics, 2017
Nevertheless, we can very conveniently measure the temperature of a radiating body by measuring the wavelength at which the spectrum peaks, using Wien’s law, or, if the peak is not at a convenient (for our detector) position in the spectrum, by measuring the total energy emitted (using a bolometer) and applying the Stefan–Boltzmann law. Very often we require a source that emits over a broad range of frequencies, and a convenient way to obtain this is to create a discharge in a gas. An electrical discharge creates a large number of free, energetic electrons, which cause a large range of atomic excitations, thus giving rise to radiation over a broad frequency range. Intensities can be quite high, so that the experimenter or designer can then pick out those frequencies that are needed, with frequency-selective optical components such as prisms or diffraction gratings.
Optimizing singly-charged electrosprayed particle throughput of an electrospray aerosol generator utilizing a corona-based charger
Published in Aerosol Science and Technology, 2022
Muhammad Miftahul Munir, Widya Sinta Mustika, Casmika Saputra, Martin Adrian, Asep Suhendi
Most neutralizers utilize radioactive ionizers to produce bipolar ions. However, radioactive sources have always met legal restrictions (Mustika et al. 2021; Saputra et al. 2021; Qi and Kulkarni 2013; Kwon et al. 2005). A neutralizer based on a corona discharge can solve this problem. Corona discharge is a plasma that occurs as a relatively low-power electrical discharge at or near atmospheric pressure (Romay, Liu, and Pui 1994; Whitby and Peterson 1965). Corona discharge has been proposed to reduce the charges of electrosprayed particles (Laschober et al. 2006; Lu and Koropchak 2004; Ijsebaert et al. 2001; Ebeling et al. 2000; Meesters et al. 1992). However, there is little literature investigating the charge reduction performance of neutralizers in the EAG system. Laschober et al. (2006) reported that for nanosized particles, a unipolar corona charger could be used as a neutralizer in a commercial EAG. Unipolar corona discharge acquires a charge distribution that significantly depends on ion properties and abundance, flow/residence time variation, the preexisting charge on particles, and particle properties (Qi and Kulkarni 2013). Thus, more work is needed to minimize multiply charged particles (Laschober et al. 2006). Therefore, a bipolar charger is required for creating a bipolar environment in the charge reduction process. The bipolar charger can reduce multiple charges (Qi and Kulkarni 2013).
SARA fractions evaluation during microwave-assisted upgrading of an oil refinery vacuum residue: effects of operational conditions
Published in Petroleum Science and Technology, 2021
Also, the selected catalysts for upgrading process using microwave are required to have two properties. The first property includes enough dielectric or magnetic dissipation, which can be affected by microwaves. The second is catalytic properties, including selectivity, long life, and activity. Heavy hydrocarbons exposing to electric arc or electric discharge produce valuable products, especially in the presence of a catalyst. During electric discharge, electrons are emitted from metal surfaces and are speeded up in an electrical field (Klepfer et al. 2001). The energy of the released electron is enough to break the chemical bonds containing free radicals (Sharivker and Honeycutt 2004). Also, the catalysts active sites are warmed up to the needed temperature under microwave irradiation, before the reactants have time to absorb. So, the reaction happens on the active sites of the catalysts, and the reaction rate is increased (Loupy 2006). Based on Bera and Babadagli (2015), for upgrading heavy oil using different catalysts, iron had the best performance.
Design reviews on a multipurpose power sockets for different applications
Published in Cogent Engineering, 2018
Chin jie Wong, Umar Nirmal, Sharmeeni Murugan
By selecting the right material in fabrication, problems like electrical sparking can be avoided. Electric sparking is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an ionized, electrically conductive channel through a normally insulating medium, often air or other gases or gas mixtures. Faraday described this phenomenon as “beautiful flash of light attending the discharge of common electricity (Faraday, 1832). By rapid transitioning of electric field from a non-conducting to a conductive stats, it will produce a brief emission of light and a sharp crack or snapping sound.