Optical Radiation | A Source of Ignition in Hazardous Areas
Published 29 May 2020
Optical Radiation is a Source of Ignition in Hazardous Areas.
The use of optical radiation in hazardous locations has increased significantly in measurement, control system applications, analysis, lightning technology, signal and power transmission and telecommunications.
Optical radiation, especially when the optical signal is unconfined, can be considered as a source of ignition in gas and dust explosive atmospheres. One of the the main mechanism for ignition by optical radiation is absorption of optical energy by the solid surface of equipment. As a result, optical radiation energy can be converted into thermal energy and cause a rise in temperature that might exceed the minimum Auto Ignition Temperature (AIT) of the surrounding explosive atmosphere, potentially causing ignition.
Standard IEC 60079-28 has introduced three types of protection to prevent ignition by optical radiation:
1) Inherently Safe (Ex op is): Hazardous Area Zones 0/20, 1/21, 2/22
2) Protected Optical Radiation (Ex op pr): Hazardous Area Zones 1/21, 2/22
3) Optical System with Interlock (Ex op sh): Hazardous Area Zones 1/21, 2/22
IEC 60079-28:2015
(Reference: IEC 60079-28:2015 Ed. 2). IEC 60079-28:2015Â Standard | Explosive atmospheres – Part 28: Protection of equipment and transmission systems using optical radiation.
IEC 60079-28:2015 is available as IEC 60079-28:2015 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60079-28:2015 specifies the requirements, testing and marking of equipment emitting optical radiation intended for use in explosive atmospheres. It also covers equipment located outside the explosive atmosphere or protected by a Type of Protection listed in IEC 60079-0, but which generates optical radiation that is intended to enter an explosive atmosphere. It covers Groups I, II and III, and EPLs Ga, Gb, Gc, Da, Db, Dc, Ma and Mb. This standard does not cover ignition by ultraviolet radiation and by absorption of the radiation in the explosive mixture itself.
Information Courtesy
Author Behzad Nejad, P. Eng. (Hazcon)
Director & Consulting Engineer at Hazcon Inc.; Hazardous Locations Consulting Services; IECEx, ATEX, CEC & NEC
Specializing in the design, safety and approval of electrical equipment for hazardous locations.Â
Mr. Nejad has over 15 years of experience as an Electrical Engineer and is a sought after professional in the hzardous area and explosion protection industry. He is fully-qualified at the advanced level of all hazardous locations protection techniques including Intrinsic Safety & Non-incendive, Explosion Proof & Flame proof, Increased Safety, Non-arcing, Purging and Pressurization, Encapsulation, Optical Radiation, and Dust-tight enclosures. Mr. Nejad’s tenure in the industry includes six years at the CSA certification agency, working closely with manufacturers (Emerson, GE, ABB, Siemens, Endress-Houser, VEGA etc.) as a technical and certification engineer for Hazardous locations equipment.
The opinions expressed in this article are those of the author.
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