Aim: The article describes methods for eliminating the risk of an electrostatic discharge formation which could initiate an explosive atmosphere conflagration.
Introduction: An explosive atmosphere, according to Directive 2014/34/EU, is defined as a mixture with air, under atmospheric conditions, of flammable substances in the form of gases, vapours, mists or dusts, in which combustion spreads to the entire unburned mixture after ignition. Electrostatic discharge is considered a process of rapid electrification decay, accompanied by a release of energy, together with light and acoustic effects.
Project and methods: A resistance measurement result and/or a resistivity parameter, determined on the basis of the measured resistance, were used to determine the electrostatic properties of materials, i.e. to classify them as conductive, dissipative or insulating. The electrification ability test (also called “the electrification test”) was performed to determine whether a non-conductive material can charge up to a degree sufficient to result in a brush discharge, and thus become an explosive mixture-ignition source. Electrostatic brush discharges are discharges from small areas (the literature and standards consider a 100 cm2 area to be an effective surface area). Each pipe was tested at no further than one metre from the mouth of the pipe. Information regarding the magnitude of the electrostatic charge, e.g. in the middle of the pipe, was not available.
Results: Based on the performed tests, it can be concluded that: 1. A polyethylene pipe is an electrostatic insulator with very good electrification and surplus electric charge accumulation abilities. 2. The pipe is not able to carry a charge to the ground when in contact with the ground. 3. The entire metal structure is conductive and connected to the ground, so it cannot be electrified by induction. 4. Due to their connection to the studied construction, metal signal wires inserted into the plastic pipes constitute a grounded object with an electric potential equal to zero; therefore, a discharge to the metal wire is very likely. 5. A polyethylene pipe with a very large inner surface has many effective 100 cm2 areas from which the gathered electrostatic charge can initiate a sparkover.
Conclusions: The conclusions in this paper shown actions needed to eliminate electrostatic discharges and ignition possibilities. The proposed preventive measures should be classified into the following groups: – removing discharge sources in the form of electrostatic charges, – eliminating potentially explosive atmospheres, – preventing the possibility of electrostatic discharge formation.
Keywords: static electricity, pipes, explosive atmosphere, electrification ability
Type of article: original scientific article