EN 746-3:2021

This part of the EN 746 series specifies safety requirements for generation and use of protective and reactive atmosphere gases that are part of industrial thermo-processing equipment (TPE). The general safety requirements common to TPE are provided in EN 746 1:1997+A1:2009 (see Introduction). This part of the EN 746 series deals with significant hazards, hazardous situations and events relevant to the generation and use of protective and reactive atmosphere gases created by thermochemical reactions and their use in TPE that are part of TPE as listed in Clause 4 and Clause 5, when used as intended and under the conditions foreseen by the manufacturer. This part of the EN 746 series covers: - pipework downstream of and including the manual isolating valve, - equipment for the generation of atmosphere gases, - additional equipment for the use of atmosphere gases in TPE, - safety devices, and - functional requirements for safety related control system for the generation and use of protective and reactive atmosphere gases. It applies to the supply of atmosphere gas, source gas, inert gas and process liquids to TPE and their removal from TPE, confined to equipment integrated in the TPE. This part of the EN 746 series also details the anticipated significant hazards associated with atmosphere gas systems and their use in TPE and specifies the appropriate preventative measures for the reduction or elimination of these hazards. The pressure hazard of the piping and components covered by this standard is within the maximum pressure/size relationship of group 1 as described in Annex C. This part of the EN 746 series: - specifies the requirements to be met to ensure the safety of persons and property during installation, commissioning, start up, operation, shutdown and maintenance, - does not cover the relevant risks involved in the flue gas ducting system when it is not considered a part of TPE, - is not applicable to utility supply upstream of the TPE main disconnects, - does not apply to TPE for semi-conductor devices, - does not apply to TPE with atmosphere, such as air and flue gas from an over stoichiometric combustion, - does not cover the decommissioning of the TPE, - does not cover vacuum furnaces, - does not cover blast furnaces, converters (in steel plants), boilers and equipment not covered under EN ISO 12100:2010. - does not deal with the hazard of noise which is covered in EN 746 1:1997+A1:2009, - is not applicable to generation and use of atmosphere gas in TPE and associated plant which is manufactured before the date of its publication, and - gives the necessary requirements for the information for use. A TPE designed according to this part of EN 746 series does not create any potentially explosive atmosphere in the area around the TPE and is not designed to be located in an area with a potentially explosive or hazardous atmosphere. This part of the EN 746 series deals with significant hazards which are described in Annex A. A table of typical protective and reactive gases is given in Annex B.