This paper relates to the safe use of thermocatalytic sensors (TSE) in explosive atmospheres. Thermocatalytic sensors with a platinum sensing element and with the protective grid removed from the sensing element have been shown to ignite a mixture of 21.0% v/v hydrogen and air flowing across the sensing element after the sensing element was exposed to a flowing mixture of 35.0% v/v hydrogen and air.

This phenomenon is due to the development of autocatalysis reaction, even without any power supply. Four stages of tests have been performed to verify this thesis. It has been shown that the behaviour of a thermocatalytic sensor in the presence of high concentrations of hydrogen, both in the presence and in the absence of a power supply, is identical due to the development of an autocatalytic reaction, i.e. under certain conditions a thermocatalytic sensor with a damaged protective metal flame arrester, even in the absence of a power supply, is a potential source of ignition and, therefore, the absence of a flame arrester of a sufficiently reliable design evaluated as an element of explosion protection, for example, as a flameproof enclosure of the "d?" type, is unacceptable.

Dr. Alexander Zalogin

Dr. Alexander Zalogin is the General Director of NANIO CCVE – Certification Centre of  Explosion-proof and Mine Equipment, Chairman of the Interstate Technical Committee for Standardization MTC 42 "Explosion-proof and Mining equipment", Chairman of the National Technical Committee for Standardization of the Russian Federation TC 403 " Equipment for explosive atmospheres (Ex-equipment)", and Deputy Head of the Russian National Body (RNO) of the IEC System for certification to standards relating to equipment for use in explosive atmospheres (IECEx System).

Alexander is also Head of  WG 16 " On safety of equipment for working in hazardous environments” of the EU – Russia Industrialists’ Round Table Task Force 8 «Technical regulations» for the approximation of provisions of the legislation in the field of technical regulation between the Customs Union and the European Union, an Assessor in the IECEx System recognized in three categories: certification of Ex-equipment, testing, evaluation of the quality system.

In the period from 2011 to 2016, he was the Deputy Chairman of the IECEx System. In the period from 2016 to 2017 – Acting Chairman of the IECEx System. As an Assessor of the IECEx System, Alexander takes an active part in the assessment of bodies and laboratories that are candidates for the acceptance in the IECEx System, the re-assessment of accepted ones, and the interim inspection control of the ExCBs and ExTLs. He is a member of the working groups ExAG IECEx Assessment Group, ExMCWG05 Assessment and Audit of Manufacturer’s Quality systems, ExMCWG04 Technical Reference Group for Assessment of ExCBs and ExTLs  and ExTAGWG11  Material Data. Alexander is the author of 90 scientific papers and has 16 inventor’s certificates.