Electrical Heat Tracing in Hazardous Areas
A Hazardous Area is an area where a flammable gas-air mixture or dust-air mixture is present for at least a short time under normal atmospheric conditions. This includes facilities where flammable gases, substances and liquids are transported, stored or processed, as for example: Oil and gas industry, cement plants, chemical industry or paint manufacturers. The above-mentioned facilities therefore require electrical equipment that can be operated safely even in the presence of an explosive atmosphere. For this to be achieved, the electrical equipment must be designed, manufactured, installed and operated in accordance with explosion protection requirements.
Legal requirements
Specific legal regulations exist worldwide for the production and use of electrical equipment in potentially explosive atmospheres. These regulations have an influence on our eltherm processes as well as on the properties of our eltherm products. Basically, EU legislation distinguishes between equipment safety (responsible: manufacturer) and Occupational Health and safety (responsible: plant operator). For us as a manufacturer, the ATEX Directive (Directive 2014/34/EU) "...Legislation of the Member States concerning equipment and protective systems intended for use in potentially explosive atmospheres" is therefore relevant and applicable.
How are Ex Zones defined?
Hazardous Areas are divided into zones, the Ex Zones, depending on their explosion hazard. This is because the explosion hazard is not the same everywhere and for all substances. In addition to the frequency and duration of the explosion hazard in the respective zone, a distinction is also made as to whether the hazardous explosive atmosphere is caused by flammable gases, vapours or combustible dusts.
Ex zones
In the ATEX Directive, Ex zones are defined according to how long or how often the explosive atmosphere is present:
| Presence of explosive atmosphere | Gas | Dust |
|---|---|---|
| occurs continuously or frequently | Zone 0 | Zone 20 |
| occurs occasionally | Zone 1 | Zone 21 |
| occurs rarely and only for a short time | Zone 2 | Zone 22 |
Interpretation of Ex markings
The different equipment groups
All relevant key data for the selection of suitable equipment such as equipment category (zone classification), temperature classes and so on must be specified by the plant operator according to Directive 99/92/EC. There are special codes for the application conditions of the substance groups in order to make them easier to manage and handle. In this context, a distinction is made between:
- Electrical equipment for mines - group I (only for ATEX)
- Surface industries excluding mines - group II (only for ATEX)
Our eltherm products refer to equipment group II only.
Marking of electrical equipment
For a detailed marking of electrical equipment for explosive gas or dust atmospheres according to ATEX/ UKEX, please refer to our Ex poster.
Ex poster (Click to enlarge)
Ex-protection in North America
The North American "Division" System
When it comes to electrical equipment and systems used in potentially explosive atmospheres, the National Electrical Code (NEC) applies in the USA and the Canadian Electrical Code (CEC) in Canada. In North America, hazardous locations are classified as "hazardous locations" and are still largely divided into Division 1 and Division 2 instead of zones. They include areas where flammable gases, vapours or mists (Class I), dusts (Class II) or fibres and lint (Class III) may occur in hazardous quantities.
- Division 1 is to be compared with Zone 1 and 0, where flammable gases, vapours or dust particles occur permanently or frequently during normal operation.
- Division 2 is to be compared with Zone 2. In Division 2, the ignitable mixtures are unlikely to occur during normal operation or will only occur rarely and only for a short time.
Our Ex poster provides a summary of explosion protection terminology at a quick glance.
Products used
eltherm Designer
eltherm designer provides the tools to calculate, select and plan EHT systems and solutions for vessels and tanks.
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