Electrical heat tracing in hazardous (Ex) areas
Explosion protection in flammable atmospheres
A hazardous area is a location where, under normal atmospheric conditions, a flammable gas-air mixture or dust-air mixture is present, at least for a short period of time. This includes facilities where flammable gases, substances and liquids are transported, stored or processed, e.g. the oil and gas industry, cement works, the chemical industry or paint manufacturers. The above-mentioned facilities therefore require electrical equipment that can be operated safely even in the presence of an ignitable atmosphere. This can be achieved if the electrical equipment is designed, manufactured, installed and operated in accordance with explosion protection requirements.
Ex-zones
Areas at risk of explosion are divided into zones, known as Ex zones, according to their explosion risk. This is because the risk of explosion is not the same everywhere or 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.
In the ATEX Directive, Ex zones are defined according to how long or how frequently the hazardous substance is present in dangerous concentrations:
| Presence of flammable atmosphere | Gas | Dust |
|---|---|---|
| constant, frequent | Zone 0 | Zone 20 |
| occasional | Zone 1 | Zone 21 |
| rare and short-lived | Zone 2 | Zone 22 |
Interpretation of ‘Ex’ markings
The different equipment groups
All relevant key data for selecting suitable equipment, such as equipment category (zone classification), temperature classes, etc., must be specified by the operator in accordance with Directive 99/92/EC. There are specific codes for the conditions of use of the substance groups to make them easier to manage. A distinction is made between:
- Mining – Group I (ATEX only)
- Non-mining – Group II (ATEX only)
Our eltherm products relate exclusively to equipment group II.
Legal requirements
There are specific legal regulations in force worldwide governing both the manufacture and the use of electrical equipment in potentially explosive atmospheres. These regulations have an impact on both eltherm’s processes and the characteristics of eltherm’s products.
In principle, EU legislation distinguishes between equipment safety (the responsibility of the manufacturer) and workplace safety (the responsibility of the operator). For us as a manufacturer, the ATEX Directive (Directive 2014/34/EU) “…legislation of the Member States relating to equipment and protective systems intended for use in potentially explosive atmospheres” is therefore applicable.
Explosion protection in North America
The North American ‘Division’ system
For electrical equipment and installations 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, areas at risk of explosion are referred to as ‘hazardous locations’ and are classified into Division 1 and Division 2 rather than into zones. These include areas where flammable gases, vapours or mists (Class I), dusts (Class II) or fibres and lint (Class III) may be present in hazardous quantities.
- Division 1 is comparable to Zones 1 and 0. Here, flammable gases, vapours or dust particles are present continuously or intermittently during normal operation.
- Division 2 is comparable to Zone 2. In Division 2, flammable mixtures are unlikely to occur during normal operation, or occur only rarely and for short periods.
Our Ex poster summarises explosion protection for you at a glance.