The Ex marking of explosion-protected equipment according to the requirements of IECEx standards includes the marking of electrical equipment intended for explosive gas and dust atmospheres (60079 series standards) and the marking of non-electrical equipment intended for explosive gas and dust atmospheres (80079-36 and 80079-37 standards).

The Ex marking contains a certain sequence of special symbols, each of which carries information such as: Type of protection, Equipment Protection Level and zone.

The Ex marking string shall be placed in the order in which they are given in 29.4 (IEC 60079-0) and shall each be separated by a small space.

Ex marking electrical equipment for explosive gas and dust atmospheres shall include the following:

① The symbol «Ex», which indicates that the Ex Equipment corresponds to one or more of the types of protection.

② Type of protection and the symbol for each Level of Protection 

③ The symbol of the gas groups and typical representative of a group of gases

3.1. For Ex Equipment for mines susceptible to firedamp «I»

3.1.1. The symbol of the gas groups: I (Mine methane);

3.2. For Ex Equipment for places with an explosive gas atmosphere other than mines susceptible to firedamp «II»

3.2.1. The symbol of the gas groups: IIC (Acetylene);

3.2.2. The symbol of the gas groups: IIB (Ethylene);

3.2.3. The symbol of the gas groups: IIA (Propane);

Notes

*When the Ex Equipment is for use only in a particular gas, the chemical formula or the name of the gas in parentheses.

*When the Ex Equipment is for use in a particular gas in addition to being suitable for use in a specific equipment group, the chemical formula shall follow the equipment group and be separated with the symbol “+”

For example: IIB + H2 

❸ The symbol of the dust groups and a type of dust

3.3. For electrical Ex Equipment for places with an explosive dust atmosphere «III»

3.3.1. The symbol of the dust groups: IIIC (Metal dusts);

3.3.2. The symbol of the dust groups: IIIB (Non-conductive dusts);

3.3.3. The symbol of the dust groups: IIIA (Solid particles and combustible flyings).

For Group I electrical explosion-proof equipment there is no marking indicating the temperature class.

④ For Group II:

The symbol indicating the temperature class:

4.1. T1 (Maximum surface temperature, ≤ 450 C);

4.2. T2 (Maximum surface temperature, ≤ 300 °C);

4.3. T3 (Maximum surface temperature, ≤ 200 °C);

4.4. T4 (Maximum surface temperature, ≤ 135 °C);

4.5. T5 (Maximum surface temperature, ≤ 100 °C);

4.6. T6 (Maximum surface temperature, ≤ 85 °C).

Notes

*If the maximum surface temperature greater than 450 °C, only the maximum surface temperature must be marked.

❹ For Group III:

The maximum surface temperature marking, according to the assigned EPL.

4.1. For EPL Da:

The maximum surface temperature must be specified as a temperature value in degrees Celsius and units of °C, and the depth of the dust layer 200 mm must be indicated with a subscript.

For example: T 200 320 °C;

Note

* A dust layer depth of more than 200 mm does not lead to a further temperature increase, which must be taken into account.

4.2. For EPL Db:

When tested without a dust layer, the value of the maximum surface temperature shall be shown as a temperature value in degrees Celsius and unit °C preceded by a «T».

For example: T 90 °C;

The maximum surface temperature T max layer of dust can be indicated, in addition to marking without a dust layer, in the form of a temperature value in degrees Celsius and a unit of measurement °C, with a specified layer depth in mm indicated as a subscript.

For example: T 150 320 °C;

The maximum surface temperature TL shell also be shown, in addition to the marking without a layer of dust, as a temperature value in degrees Celsius and the unit of measurement °C, with the layer in a specified orientation L indicated as a subscript.

For example: TL 320 °C.

4.3. For EPL Dc:

When tested without a dust layer, the value of the maximum surface temperature shall be shown as a temperature value in degrees Celsius and unit °C preceded by a «T».

For example: T 90 °C.

Notes:

* If equipment has multiple temperature classes or multiple maximum surface temperatures, it is permissible not to mark them all on the equipment, but then the marking must contain the symbol "X" and full information on the temperature class must be included in the certificate or the range of the temperature class must be marked with the lower and upper limits of the temperature class separated by "...".

* If the equipment is marked for use with a specific gas, it may not be marked with a temperature class or maximum surface temperature.

*Cable glands, blanking plugs, and threaded adapters may not be marked with a temperature class or maximum surface temperature.

⑤ The Equipment Protection Level (EPL), “Ma”, “Mb” “Ga”, “Gb”, “Gc”, “Da”, “Db”, or “Dc”

Notes:

* The Ex marking for explosive gas atmospheres and explosive dust atmospheres shall be separate and not combined.

* The EPL marked on the Ex Equipment may be more restrictive than that normally applied for a specific Type of Protection to account for other aspects of the equipment such as material limitations.

* Where different types (or levels) of protection are employed for different parts of Ex Equipment or an Ex Component, the Ex marking shall include the symbols for all of the Types (or Levels) of Protection employed. The symbols for the types of protection shall appear in alphabetical order, with small separating spaces. When associated apparatus is incorporated, the symbols for the type (or level) of protection, including the square brackets as applicable, shall follow those symbols of the type (or level) of protection for the equipment.

Ex marking non-electrical equipment for explosive atmospheres shall include the following:

① The symbol «Ex» which indicates that the Ex non-electrical Equipment corresponds to one or more of the types of protection.

② Letter “h”;

Notes:

* A Level of Protection is not applied to the letter “h”. 

* No additional marking is needed regarding the type of protection used "c", "b" or "k". A description of the type of protection shall be given in the instructions and other documentation.

Ex non-electrical Equipment has three main types of protection:

Ex non-electrical Equipment has three types of protection can be applied "d", "p" and "t". The nature and ignition sources of non-electrical equipment shall be considered when applying types of protection "d", "p", or "t" to non-electrical equipment. All technical requirements apply.

③ Where appropriate, the symbol of the equipment Group I, IIA, IIB, IIC or IIIA, IIIB, IIIC. When the equipment is designed for use only in a particular gas, the chemical formula, or name.

For Group I electrical explosion-proof equipment there is no marking indicating the temperature class.

④ For Group II:

A symbol indicating the temperature class or maximum surface temperature in °C or both, in which case the temperature class is indicated last in parentheses.

For example: T1 or T 350 °C or T 350 °C (T1).

If, the maximum surface temperature of the equipment greater than 450 °C, only the maximum surface temperature in °C shall be indicated.

For example: T 600 °C.

Equipment designed and marked for use with a particular gas may not have a reference temperature. If the manufacturer cannot indicate a single temperature class or maximum surface temperature, a range of temperature classes or a range of maximum surface temperatures must be indicated.

For example: T6...T4 or T 85°C...150°C

❹ For Group III:

For Group III equipment, the maximum surface temperature in degrees Celsius and the unit of measurement °C preceded with the letter «T»

For example: T90 °C.

⑤ The Equipment Protection Level (EPL), «Ma», «Mb», «Ga», «Gb», «Gc», «Da», «Db», or «Dc».

Special symbols used in Ex marking of explosion-proof equipment:

For Group III equipment, the maximum surface temperature in degrees Celsius and the unit of measurement °C preceded with the letter «T»

Special symbols may be used in the marking of Ex equipment, such as:

Symbol “X”

Used to indicate the special conditions of use of explosive equipment indicates that essential information on the installation, use and maintenance of the equipment is contained in the certificate.

Note

The symbol "X" can be used to indicate specific application conditions for equipment designed for use in an ambient temperature range other than normal (-20 °C to +40 °C).

The symbol "X" is used if, at the request of the manufacturer, the equipment is submitted to tests corresponding to a low risk of mechanical hazards.

The symbol "X" is used if the temperature of the equipment is only determined for certain positions.

The symbol "X" is placed after the certificate reference if special conditions of use of the equipment apply.

Symbol “U” 

Used to denote an Ex Component. The symbol “U” is used to identify that the equipment is incomplete and is not suitable for installation without further evaluation

Note

* For Ex Component The symbol “X” is not used

Square brackets […..]

The presence of square brackets in the marking indicates associated apparatus or Ex associated equipment. Square brackets separate the symbols for the Type of Protection of the associated apparatus and Ex associated equipment from the symbols for the Type of Protection of the Ex equipment. If both associated apparatus and Ex associated equipment are provided, the symbols for the Type of Protection are shown within separate square brackets.

For example:

Ex db [ia Ga] IIC T4 Gb

Ex tb [ia IIIC Da] IIIB T100 ºC Db

Ex db [ib Gb] [pxb Gb] IIC T4 Gb

For associated apparatus suitable for installation in a hazardous area, and where the energy limitation is provided from outside the Ex Equipment in a hazardous area, the symbols for the Type of Protection shall not be enclosed within square brackets.

 For example: Ex db ia IIC T4 Gb

Notes

* For associated apparatus not suitable for installation in a hazardous area, a temperature class is not included

* Ex associated equipment, not for installation within the hazardous area, will not include a temperature class.

Equipment installed in the boundary wall

For equipment which is intended to be installed in the boundary wall between an area requiring EPL Ga or Da and a less hazardous area; both Levels of Protection and both EPLs are marked on the label, each separated by a slash “/”,

For example:

Ex ia/db IIC T6 Ga/Gb

Ex ia/tb IIIC T85°C Da/Db

Equipment which includes both an electrical part and a non-electrical part

Equipment which includes both an electrical part and a non-electrical part shall have combined marking.

For example:

Ex db h IIA T4 Gb

Ex h tb IIIC T135 °C Db

Note

* For equipment where separate certificates have been prepared, with one for the electrical parts, and one for the non-electrical parts, it is appropriate to have separate electrical and non-electrical marking strings, each with its own associated certificate number.

Equipment assembly

The equipment assembly shall be marked in accordance with IEC 60079-0 and ISO 80079-36, except for the symbol for each type (or level) of protection used, which is replaced by «60079-46». As the types of protection are not included on the marking, the equipment protection level (EPL) for the complete equipment assembly shall be marked.

For example:

Ex 60079-46 IIB T4 Gb