The Use of Non-electrical Equipment in Hazardous Locations
It is well known that hazardous locations pose risks because of the presence of ignitable gas, dusts, or fibres. For this reason, many safety Standards and procedures govern electrical devices that are to be installed in those locations, to ensure that they do not become a source of ignition. Non-electrical equipment may also be sources of ignition or explosion. Mechanical equipment, because of its moving parts, can generate sparks and hot surfaces. Mechanical failure can cause bearings to overheat, for example. Friction can cause elevated temperatures of mechanical devices, during even normal operation.
In this animation we will discuss the ways in which the risks related to non-electrical devices in hazardous locations are identified, assessed, and minimized in order for the devices to be certified within the Zone classification system.
Standards ISO/ IEC 80079-36 and IEC/ ISO 80079-37 within the international IECEx) and European (ATEX) certification schemes address the basic requirements and protection concepts for mechanical equipment in hazardous environments. Such non-electrical equipment must be explosion-protected.
Two steps are involved in achieving compliance with these Standards. The first step is a comprehensive ignition hazard assessment to identify all potential ignition sources – to determine if the non-electrical device can become an effective ignition source during the expected lifetime of the mechanical equipment.
The second step is to assign protective measures, depending on the required Equipment Protection Level (EPL), to minimize the probability that these ignition sources will become effective.
Three protection techniques are indicated in the Standard ISO/IEC 80079-36 and IEC 80079-37 which specify the design and construction requirements of nonelectrical equipment intended for use in explosive atmospheres:
- Protection by constructional safety “c” (avoiding ignition sources from mechanical failure through good engineering practice during design & construction of the device).
- Protection by control of ignition source “b” (controlling ignition sources through an appropriate ignition prevention system that monitors critical control parameters)
- Protection by liquid Immersion “k” (avoiding ignition sources by coating with a liquid or by total immersion)
Non-electrical products that are found to be in compliance with any of these protection methods will result in an “Ex h” marking on the equipment and its certificate. Then the products can be installed in Zone -classified hazardous locations.
In summary, the danger of non-electrical devices in hazardous locations cannot be ignored! They can become a source of ignition! A precise ignition hazard assessment needs to be conducted and protective measures incorporated.
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