Being professional inspectors in the field of Ex-protection, the authors of this paper recorded numerous cases of problematic design, installation and maintenance work executed in almost each inspected plant at risk of explosive atmospheres. Although considerable effort has been made during the last decade to improve the situation and to raise personnel competency to a desirable level by periodic training of persons involved in design, installation, maintenance and repair in the field of Ex-protection, the situation seems to be getting better very slowly. This paper presents examples of non-conformities usually found in inspection, gives some practical guidance for reaching the required level of safety while reducing the cost of inspection and maintenance by the use of rationalized design and explains some modern diagnostic methods applicable in the inspection of Ex equipment. At the end, this paper speaks about highly desirable certification of competencies which is essential in making a decision about who is capable of performing its task in a desirable manner.

This paper discusses the risks of ignition sources which may appear due to the utilisation of electrical drives in areas at risk of explosive atmospheres. The main goal is to present the traditional approach to mitigation of those risks, as well as to identify its disadvantages. The option to introduce technical diagnostics in the field of explosion protection presents the central part of this paper which discusses the use of technical diagnostics based on the voltage pulse response analysis and cage rotor bars conductivity measurement on induction motor as a reliable tool for detection of ignition sources. Detection of faults which cannot be identified using the traditional approach tools was analysed. Based on the research results the new approach is suggested which allows for the overall and reliable assessment of the explosion protection properties of the motor during its longtime service. Recognition of the need to timely identify induction motor faults in electrical drives, as potential sources of ignition of explosive atmosphere, is the essential conclusion and contribution of this research.

U radu se razmatraju rizici pojave uzročnika paljenja unutar elektromotora u prostorima ugroženim eksplozivnom atmosferom. Istraživanje pojave uzročnika paljenja zbog oštećenja kaveza rotora asinkronog motora temeljni je dio ovog...

This paper presents the development of a device that creates two or more light pulses with a precision time delay in a range from microseconds to several seconds and for the purpose of the calibration of velocity of detonation (VOD) measurement instruments. The device was assembled, programmed, and tested for functionality. Measurements were conducted using a reference counter. First, a precision OCXO (oven-controlled crystal oscillator) was used as a clock source. For verification of programmed subroutines, a counter oscillator output port was used as a source of clock signal for the microcontroller. This enabled the cancellation of possible oscillator errors. The signal had to be converted from an AC sine signal to a signal with positive values only using a clamper circuit. By the proposed solution, a calculable standard of time delay between two light pulses was achieved. According to the obtained results, this device can be used to calibrate field measurement devices for VOD measurements in explosives or some other use where the measurement device records the time interval between multiple light pulses. This enables more confidence in measurement results, faster recognition of instrument drift and increases the quality of measurement.