Explosion-proof equipment must be designed so that the ignition of the surrounding explosive atmosphere to be avoided. This is very important because an explosion can have particular implications over goods, life and not least over the environment. One of the ignition sources of an explosive atmosphere is represented by hot surfaces. Each equipment designed to operate in explosive atmospheres develops a maximum surface temperature. The specific standards used to assess explosion protection characteristics cover only indirectly and in part the factors influencing the maximum surface temperature. By this study, using a standardized testing methodology, the factors influencing the maximum surface temperature in case of explosion-proof luminaires with type of protection flameproof enclosure "d" and increased safety "e" were pointed out and analyzed (i.e. maximum designed ambient temperature of the luminaire; placement of temperature sensors to capture the points where the maximum surface temperature is recorded; type, power and size of the light source installed in the luminaire; operating position of the luminaire; supply voltage of the luminaire). The measures to be taken, in order to determine as accurately as possible the maximum surface temperature, in relation with the influencing factors, were also identified.
During the last decade, extensive research has been carried out on the subject of low-cost sensor platforms for air quality monitoring. A key aspect when deploying such systems is the quality of the measured data. Calibration is especially important to improve the data quality of low-cost air monitoring devices. The measured data quality must comply with regulations issued by national or international authorities in order to be used for regulatory purposes. This work discusses the challenges and methods suitable for calibrating a low-cost sensor platform developed by our group, Airify, that has a unit cost five times less expensive than the state-of-the-art solutions (approximately €1000). The evaluated platform can integrate a wide variety of sensors capable of measuring up to 12 parameters, including the regulatory pollutants defined in the European Directive. In this work, we developed new calibration models (multivariate linear regression and random forest) and evaluated their effectiveness in meeting the data quality objective (DQO) for the following parameters: carbon monoxide (CO), ozone (O3), and nitrogen dioxide (NO2). The experimental results show that the proposed calibration managed an improvement of 12% for the CO and O3 gases and a similar accuracy for the NO2 gas compared to similar state-of-the-art studies. The evaluated parameters had different calibration accuracies due to the non-identical levels of gas concentration at which the sensors were exposed during the model’s training phase. After the calibration algorithms were applied to the evaluated platform, its performance met the DQO criteria despite the overall low price level of the platform.
The explosion risk is one of the major industrial risks, being present in all units which produce, use, handle, store or transport hazardous substances, products with flammable and explosive properties. Equipment designed for use in potentially explosive atmospheres must be manufactured so that the ignition of the surrounding explosive atmosphere is avoided. One of the ignition sources of an explosive atmosphere is represented by surface temperature. The paper presents the influence of surface temperature in the process of selection of electrical equipment from technological installations operating in explosive atmospheres, as well the test method used to determine it.
The paper describes a measuring system for testing of the combustible gases detectors used in domestic premises. The general requirements are presented for the electrical equipment used in gas detection. A theoretic analytical model is proposed for measuring the test gas concentration and assessing the influence of air humidity. The requirements considered for designing the measuring system are presented for the experimental setup. The presented assembly structure was tested and the results were presented. Consequently, the measurement uncertainty was determined. It was found that the use of a high precision oxygen analyzer is reliable in the process of calibration testing. It was also found that the variation of relative humidity during the measurement influences the gas concentration measured.
The purpose of this paper is to analyse the results of a new experimental method for the evaluation of energy supply of electrical circuits used in potentially explosive atmospheres, enabling a more accurate and thorough assessment of the processes. It is expected the improvement of energy transfer parameters of circuits deserving equipment used in potentially explosive atmospheres, by keeping the security level required by the technical rules in force.
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