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Hazardex 2017 Conference - The basic physics of explosion hazard situations at the surface of thermocatalytic sensing elements

Author : Alexander Zalogin – IECEx / Nanio CCVE

03 November 2016

Thermocatalytic sensors are widely used for leakage control of flammable vapours and gases. These sensors are cost efficient due to a simple design.  A thermocatalytic sensor incorporates a sensing element of a thin platinum wire.  A thermocatalytic sensing element (TSE) is a small heated body.

Under operating conditions in the controlled environment containing flammable gas, this flammable gas at the surface of the TSE is oxidised, that is, gas concentration on the TSE surface is equal to 0. The TSE is surrounded by temperature and concentration boundary areas.

Generally, in a still environment, the areas of ignition temperatures do not coincide with explosive concentrations. However, if natural or forced convection arises, the areas become deformed and another area is formed where the ignition temperature and concentrations over the LEL exist at the same time.

Thus in the presence of high concentrations of easily oxidised flammable gases (including hydrogen) a thermocatalytic sensor becomes a source of ignition due to the development of autocatalysis reaction even if it is not energised.

About the Speaker

Dr. Sc. (Tech.) Alexander S. Zalogin
is Vice-Chairman of the IECEx System and since 2009 has been the General Director of NANIO CCVE, the
Russian certification centre for explosion protected and mine equipment. He is the Chairman of the Russian Technical Committee for Standardisation TC 403 Equipment for explosive atmospheres, and is an expert in industrial safety and certification of Ex-equipment in the GOST R Certification System.

In 1985 he graduated from Donetsk Polytechnic Institute as an electrical engineer. From 1985 to 1996 he worked in MakNII (Research Institute on Safety in the Mining Industry) in Makeevka as a senior research worker. In 1996 he joined Skochinsky Institute of Mining (Lyubertsy, Moscow region) where he worked as Head of Laboratory and then Head of Department of Electrification of Mines.

As well as being Vice-Chairman of the IECEx System, he also assesses certification bodies and laboratories that are candidates for acceptance within the IECEx System.

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