Markings
ATEX markings explained
CE marking and Ex marking
Over the years much has changed as regards to standards related to explosion-safe equipment. In years to come, new insights will arise and as a result of globalization the existing standards will be influenced by other techniques, requirements and habits. However, one thing that will always remain is that users must be able to identify an "Ex device", intended for use in an explosion-hazardous environment.
Ex marking exlained
From 1977 to 2003, the pre-ATEX era, standards from the EN 50014 series were used in Europe. These standards were drawn up by CENELEC, which is why this equipment was often described as CENELEC equipment. The well-known Ex marking shown above was also introduced during this period.
At the time, European legislation was still limited to electrical equipment intended for use in a gas environment. Only national legislation existed for explosive dust atmospheres and for non-electrical equipment there were no regulations at all.
North America has a long Ex-tradition of its own, with its own laws, standards and protection methods and associated coding. The major differences lie in a different zoning classification and in a different division of equipment into groups.
Most installations have been in operation for a long time and may contain parts from other eras. For the owner of the installation and for the user it is important to be able to interpret all markings correctly.
Marking requirements from the ATEX directive and standards
From 20 April 2014, manufacturers may only supply Ex equipment that complies with the ATEX 114 directive. The marking found on this equipment is partly prescribed by the European ATEX directive and partly by the standards used to make it explosion-safe.
The marking required by the ATEX 114 directive consists of:
- Name and address of the manufacturer;
- CE sign;
- Type marking;
- Serial number;
- Year of manufacture;
- Ex-sign;
- Equipment group (I = mining or II = industrial application);
- Indication of safety level category (M1 or M2 for Group I and 1, 2 or 3 for Group II);
- G (gas) and / or D (dust) for equipment group II to indicate the environment for which the equipment is suitable;
- All data essential for safe use.
The marking prescribed by the standards used for certification consists of all of the information above and additional markings prescribed by the standards:
- Electrical equipment intended for a gas environment:
- Mode of protection (Ex d, e, i, m, n, p);
- Group (IIA, IIB, IIC);
- Temperature class (T1 ... T6);
- Ambient temperature range (e.g., -40 ºC to +40 ºC);
- Electrical equipment intended for dust environments:
- Mode of protection (Ex i, m, p, t);
- Group (IIIA, IIIB, IIIC);
- Maximum surface temperature (e.g., T 85 ºC);
- IP protection class (e.g., IP65);
- Non-electrical equipment:
- Mode of protection (b, c, d, fr, k);
- Group (IIA, IIB, IIC and/or IIIA, IIIB, IIIC);
- Temperature class;
- Maximum surface temperature;
Product label FlashLED Ex inspection lamp
This figure shows the label of an ATEX certified device for use in zone 1 (gas) and zone 21 (dust). The protection method used is intrinsic safety Ex ib for gas and dust. The maximum temperature (T4) of the unit is 135 ºC. The maximum surface temperature (dust) is 135 ºC.
Overview of EX-markings, categories and IEC EPL
The following table gives an overview of the protection methods for electrical equipment for use in a gas environment.
| Symbol | Protection method | Highest achievable ATEX category (IEC EPL) |
| d or db | Flameproof enclosure | 2 (Gb) |
| e or eb | Increased safety | 2 (Gb) |
|
ia ib ic |
Intrinsic safety |
1 (Ga) 2 (Gb) 3 (Gc) |
|
ma mb mc |
Molding with casting mass |
1 (Ga) 1 (Gb) 1 (Gc) |
|
nA or nAc nC or nCc nR or nRc nL or nLc |
Protection mode "n" |
3 (Gc) 3 (Gc) 3 (Gc) 3 (Gc) |
| o or ob | Oil filling | 2 (Gb) |
|
px or pxb py or pb pz or pzc |
Internal overpressure |
2 (Gb) 2 (Gb) 3 (Gc) |
| q or qb | Powder filling | 2 (Gb) |
Table 12.1 Ex protection methods for electrical equipment in a gas environment
The following table gives an overview of the protection methods for electrical equipment intended for use in dust environments.
| Symbol | Protection method | Highest achievable ATEX category (IEC EPL) |
|
ta tb tc |
Protection by enclosure |
1 (Da) 2 (Db) 3 (Dc) |
|
ia ib ic |
Intrinsic safety |
1 (Da) 2 (Db) 3 (Dc) |
|
ma mb mc |
Molding with casting mass |
1 (Da) 2 (Db) 3 (Dc) |
|
pb pc |
Internal overpressure |
2 (Db) 3 (Dc) |
Table 12.2 Ex protection methods for electrical apparatus in dusty environments
The following table gives an overview of the protection methods for non-electrical (mechanical) equipment for use in a gas or dust environment.
| Symbol | Protection method | Highest achievable ATEX category |
| fr | Flow limiting casing | 3 |
| d | Flameproof enclosure | 2 |
| c | Constructive safety | 1 |
| b | Monitoring of ignition sources | 1 |
| k | Liquid immersion | 2 |
Table 12.3 Ex protection methods for non-electrical equipment
North American markings
Equipment that has a North American approval can be recognized by the presence of a UL, CSA or FM logo. American equipment is usually connected by conduit.
The biggest differences with the European ATEX marking are:
- classification into divisions instead of zones;
- classification of equipment into classes and groups;
- other codes for the protection methods.
In the product marking, division is often abbreviated to DIV, class to CL and group to GP. Below a comparison with the ATEX markings.
| North American Ex area classification | European Ex area classification |
| division 1 |
zone 0 / 20 zone 1 / 21 |
| division 2 | zone 2 / 22 |
Table 12.4 North American Ex area classification
Interestingly enough, the European zones 0, 1, 20 and 21 in North America are combined to form division 1.
| North American classes | European gas / substance codin |
| Class I (gas) | G (gas) |
| Class II (dust) | D (dust) |
| Class III (fibers) | D (dust) |
Table 12.5 North American classes
In Europe, fibers are considered to be large dust particles and there is no additional coding besides gas and dust.
| North American group coding | European group coding |
|
A (acetylene only) B (hydrogen only) |
IIC
|
| C | IIB |
| D | IIA |
| E (magnesium dust) | IIIC |
| F (coal dust) | I or IIIC |
| G (grain dust) | IIIB |
| (fibres) | IIIA |
Table 12.6 North American Group coding
In North America acetylene and hydrogen are seen as separate groups, in Europe these gases are classified together in group IIC. Fibers, in Europe classified in group IIIA, do not appear in the North American group coding because they belong to Class III.
| North American coding protection method | European coding protection method |
| XP (explosion proof) | d (flameproof) |
| IS (intrinsically safe) | ia, ib, ic (intrinsically safe) |
| DIP (dust ignition proof) | t (protection by casing) |
Table 12.7 North American protection method
Ex i barrier
The figure shown above is an example of an intrinsically safe barrier, certified for Europe by Baseefa and for North America by UL and FM. Notice the differences in marking. Another distinctive feature is that both FM and UL approval refer to a drawing (SCI-88 and SCI-193) These so-called control drawings must be included so the user knows exactly how to connect the intrinsically safe device.
