An Experimental Study on Importance of Bushing Used in Flameproof Enclosure for Hazardous Area
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TECHNICAL ARTICLE—PEER-REVIEWED
An Experimental Study on Importance of Bushing Used in Flameproof Enclosure for Hazardous Area Bhagirath Ahirwal . Gautam Banerjee
Submitted: 25 June 2020 / in revised form: 16 September 2020 / Accepted: 27 October 2020 Ó ASM International 2020
Abstract The flameproof (Exd) enclosure is used to make a complete flameproof equipment by putting many non-explosion proof components within it which are intended to be used in explosive atmospheres. A flameproof bushing is interconnected with the common wall of the flameproof enclosures to facilitate the electrical connections. An experimental study was carried out on the Ex d enclosures to understand the importance and effect of bushing on flamepath, gap/clearance, volume of Exd enclosure and explosion reference pressure. The reference pressure tests were carried out to measure the pressure on the Exd enclosures having spigot and threaded joints fitted with and without interconnecting Exd bushing. Results indicated that the reference pressures increased for the enclosures without fitted bush tested with gas group IIB and IIC representative gas mixture. Present study was carried out to explore the importance of the bushing in the flameproof enclosures to enhance the safety of hazardous area. Keywords Flameproof bushing Flamepath Torque test Explosion reference pressure
Introduction Fire and explosions often cause major loss of property and life in the hazardous area of industries. Exploration and development are increasing day by day globally. The need for explosion proof (Ex) equipment and installation B. Ahirwal (&) G. Banerjee MMATD Department, CSIR- Central Institute of Mining and Fuel Research, Dhanbad, India e-mail: [email protected]
methods geared toward these areas also increases. Both the safety of equipment and its functionality must be taken into account while developing specifying, or installing products for safe use in hazardous area. It is well known that the transmission of gas-air explosion through gap/clearance of an enclosure becomes source of ignition for surrounding explosive atmospheres [1]. After many studies gap and flame path are suggested to maintain in all joints of the enclosure to avoid any transmission of hot gases from it. The developed explosion pressure in the enclosure/vessel should be reduced by providing any pressure relief device [2]. Canu et al. [3] tuned the semi-empirical mathematical model of Chippett [4] by comparison of more than 160 experimental results taken from the literature and found that initial pressures were greater than 1 bar. Chippett reported some data for 10% methane-air mixtures at initial pressures of 2 bar and 3 bar, and Cousins et al. [5] presented data for 5% propane-air mixtures at initial pressures from 1 bar up to 4 bar. Other data also available for 4.8% propane-air mixtures in a vessel with initial pressures from 1 bar up to 7 bar, as reported by Pegg et al. [6]. The change in explosion pressure and explosion time when explosions were conducted with several h
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