Optical sources of ignition in hazardous areas

There is a considerable amount of information about ignition from optical sources, which can be utilised to solve problems relating to specific applications with specific hazardous materials. Wherever possible using the limits of 5 mW/mm2 and 35 mW is the most acceptable solution and is likely to be internationally acceptable and more widely applicable. The application of the fault count to apparatus used in Zones 0 and 1 inevitably means that the useable power is lower than these values. It is not easy to anticipate how the light pattern may be distorted under fault conditions and hence the 35 mW limit becomes the principal useable restriction. However, fibre optic links and some laser analysis techniques can all achieve solutions with operational integrity at this power level with an adequate margin of safety.

 

Take note

• Data transmission by fibre optics has some advantages in process industries.

• The amount of power to ignite a dust cloud is dependent on many factors, making the risk difficult to evaluate.

• Fibre optic links and some laser analysis techniques can achieve solutions with operational integrity at the 35 mW limit with an adequate margin of safety.

 

Published as:

Optical sources of ignition in hazardous areas

By LC Towle, MTL Group

Electricity+Control, December 2012 (page 24-27)

Enquiries: Gary Friend. Tel: 011 791 6000 or  email Gary@extech.co.za