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 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.
The intrinsic safety type of protection significantly increased in complexity during the last decades. Thus, it even provides the opportunity to use highly complex electronic circuits without involving a significant explosion risk within the oil industry or in power plants, but not limited to those two. In order to achieve this performance, the type of protection is based on three pillars: limiting of energy, heat and also fault tolerance. The potential failure of components, connections, and separations are taken into consideration for intrinsic safety evaluations. This paper focuses on scenarios of separation faults in intrinsic safety circuits. The introduction part of the paper provides a summary of requirements for the intrinsic safety type of protection. The separation requirements are also highlighted. This part also explains the "countable" concept regarding the separation faults. The second part of the paper is dedicated to the fault scenarios assessment. Also, this part shows the theoretical model which yields the magnitude of the fault scenarios group. The built-up algorithm for effective localization of the separation faults on a real electronic board is presented in the second part of the paper. This algorithm was implemented using Visual Basic for Applications script and National Instruments Ultiboard software. In the third part of the article, the obtained results are reported and discussed. In order to have a comprehensive image, there was proposed a graph in which links are considered separation distances and elements conductive tracks. Another tool proposed and used was separation distances histogram. The influence of increased finesse on the number of non-countable separation faults was also discussed. The main outcome of the paper is represented by the high impact of non-countable separation faults number over the number of separation failure scenarios. For example, the circuit analysis showed the potential for over sixteen million failure scenarios.
In the field of industrial activities the actual trends shows a growing need for risk assessment. Regarding the risk of explosion assessment a rough but important qualitative step was made by defining categories and levels of protection for equipments and installations together with the zone classification of areas where combustible substances can be released and accumulated. By presented methodology, in this paper are presented theoretical models for calculation of explosive atmospheres ignition probability, starting from the parameters of the low currents electrical circuit. Are also presented some future research directions and the importance / need for a finesse quantitative assessment of explosion risk by evaluation of contribution to ignition probability of explosive atmospheres, from low currents electrical installations protected by the intrinsic safety type of protection.
Based on the experience accumulated over time on the evaluation of equipment and installations in environments with potentially explosive atmospheres, this paper is intended to be an element of synthesis on issues related to the “in situ” assessment and solutions of solvency the deficiencies found. The assessment of these installations is very important in order to verify the implementation of measures that lead to minimizing the risk of ignition of explosive atmospheres. Evaluation of these installations is made through an on-site visit and on the basis of the technical documentation developed by the care of the user. In first part of the paper were presented the legal aspects regarding the placing on the market and the use of equipment designed for potentially explosive atmospheres. The paper is continuing with the presenting the technical aspects regarding the evaluation of equipment and installations operating in potentially explosive atmospheres followed by requirements for electrical equipment. The main conclusion, of the paper is that the explosion protection of the equipment intended for use in potentially explosive atmospheres may be invalidated by the incorrect selection of the equipment, incorrect installation of the product, inadequate: performance of inspection operations, maintenance or repairing of equipment.
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