Aim: In the engineering practice, explosion protection is provided through the following steps: the elimination of the flammable material, the explosive atmosphere and the source of ignition. Another step is to limit the impact of the potential explosion. Electrical equipment might constitute the source of ignition for mixtures of flammable substances with air. The aim of the article is to present a new type of electrical equipment protection. According to the current technical standards, Ex p equipment is defined either as an enclosure with a constant static overpressure inside or purged enclosures with the use of clean air not containing flammable substances that could generate a hazardous atmosphere. This type of protection usually requires regular maintenance, complicated venting and/or frequent control of correct operation.
Project and methods: Electrical equipment designed to work in hazardous areas is designed with various types of protection ensuring safety in the case of a hazardous atmosphere created near the device. In order to present the concept of the new protection type, current technical standards were analysed to gather technical prerequisites. The Solid Edge environment was used to create 3D models of control and indicating equipment (CIE). The diagram presenting the concept of the whole device was also created. The aim of the project was to present the concept of the new mixed-type pressurised equipment.
Results: The design of the device proves that it is possible to create a new type of explosion protection of electrical equipment which has not been described in current technical standards. The concept assumes the use of stationary compressed nitrogen installations present in many factories. The installation will maintain a constant positive pressure inside the enclosure. It is also feasible to use portable inert gas tanks, which will require additional means of protection. The proposed design was checked against the set requirements. For the designed equipment, ready formulae were used to determine screw tightening torques in order to activate the device after exceeding specific parameters, such as the gas flow rate.
Conclusions: The current technical standards give space for designing a new type of electrical equipment protection. The article describes the outcomes of the research and project work conducted to visualise the concept. These types of equipment protection can be certified for all working conditions, which increases their applicability potential.
Keywords: ex equipment, electrical devices, explosion protection, pressurised enclosure
Type of article: original scientific article