Type of protection ‘op’ — Optical radiation

EMMUA 214 States: Page 26

Equipment with optical radiation shall be installed in accordance with manufacturer’s documentation.

Optical equipment in the form of lamps, lasers, LEDs, optical fibers etc. is increasingly used for communications, surveying, sensing and measurement. In material processing, optical radiation of high irradiance is used. Where the installation is inside or close to explosive atmospheres, the radiation from such equipment may pass through these atmospheres. Depending on the characteristics of the radiation it might then be able to ignite a surrounding explosive atmosphere. The presence or absence of an additional absorber, such as particles, significantly influences the ignition.

Optical radiation types of protection

inherently safe optical radiation “op is”

visible or infrared radiation that is incapable of producing sufficient energy under normal or specified fault conditions to ignite a specific explosive atmosphere. This definition is analogous to the term “intrinsically safe” applied to electrical circuits.

protected optical radiation “op pr”

visible or infrared radiation that is confined inside optical fibre or other transmission medium under normal constructions or constructions with additional mechanical protection based on the assumption that there is no escape of radiation from the confinement.

optical system with interlock “op sh”

system to confine visible or infrared radiation inside optical fibre or other transmission medium with interlock cut-off provided to reliably reduce the unconfined beam strength to safe levels within a specified time in case the confinement fails and the radiation becomes unconfined

3.10 Type of Protection ‘s’ - Special protection

EMMUA 214 STATES: Page 25

3.10.1 Definition Special protection, is a type of protection that, by its nature, does not comply with the constructional or other requirements specified for equipment with established types of protection, but that nevertheless can be shown, where necessary by test, to be suitable for use in hazardous areas in prescribed zones.

3.10.2 Standards and selection

Current standards

IEC 60079-33: Explosive atmospheres - Part 33: Equipment protection by special protection ‘s

Superseded standards

BS 5345 Part 8 Installation and maintenance requirements for electrical apparatus with type of protection I s’.

EPL/category and zones of use

Ex ‘s t equipment may be used in areas requiring EPL ‘Ga t , ‘Gb l and ‘Gc i , or Category 1, 2 and 3. Equipment protected by special protection was permitted to be used in areas in Zones 1 or 2. if specifically certified, it could also be used jn Zone 0.