Part 7 of BS EN 60079 specifies the requirements for the design, construction, testing and marking of electrical apparatus with type of protection increased safety ‘e’ intended for use in explosive gas atmospheres. This standard applies to electrical apparatus where the rated voltage does not exceed 11kV r.m.s a.c. or d.c. Additional measures are applied to ensure that the apparatus does not produce arcs, sparks, or excessive temperatures in normal operation or under specified abnormal conditions.
Part 28 of BS EN 60079 explains the potential ignition hazard from equipment using optical radiation intended for use in explosive gas atmospheres. It also covers equipment, which itself is located outside but its emitted optical radiation enters such atmospheres. It describes precautions and requirements to be taken when using optical radiation transmitting equipment in explosive gas atmospheres. It also outlines a test method that can be used to verify a beam is not ignition-capable under selected test conditions, if the optical limit values cannot be guaranteed by assessment or beam strength measurement.
The standard contains requirements for optical radiation in the wavelength range from 380 nm to 10 µm. It covers the following ignition mechanisms:
Optical radiation is absorbed by surfaces or particles, causing them to heat up and, under certain circumstances, this may allow them to attain a temperature that will ignite a surrounding explosive atmosphere.
Direct laser-induced breakdown of the gas at focus of a strong beam, producing plasma and a shock-wave both eventually acting as the ignition source. These processes can be supported by a solid material close to the breakdown point.
The standard does not cover ignition by ultraviolet radiation and by absorption of the radiation in the explosive mixture itself. Explosive absorbers or absorbers that contain their own oxidizer as well as catalytic absorbers are also not covered.
BS EN 60079-7:2007 replaces BS EN 60079-7:2003, which will be withdrawn on 1 October 2009.
EN 60079-7:2007
IEC 60079-7:2006