Marking of explosion-protected equipment

1 Devices for use in potentially explosive at-mospheres have to be marked. The require-ments on markings come from different sources. So EU Directive 94/9/EC (ATEX 95) stipulates in Europe, which information has to be given on the type label. These are the minimum requirements that have to be sup-plemented by further information required for safety. The required safety-relevant data and their order on the type label are stipulated in the European requirements on electrical devices for use in explosive gas atmospheres are includ-ed in standard series EN 60079. For devices that are intended for use in areas with com-bustible dust standard series EN 61241 has to be applied. For many years now these stand-ards have been prepared on an international level by the IEC and then adopted as Europe-an to now Marking has been specified in IEC 60079-0 / 2004 and in IEC 61241-0 / 2004. To clearly identify the device, the type identifi-cation and the serial number have to be stat-ed as well as, the manufacturer s name or his trademark.

2 For devices subject to certifica-tion the name of the notified body issuing the certificate and the certification number have to be given. Additionally, a special coding is required that describes the applicable use of the device:New ruling in IEC 60079-0, 2007 and EN 60079-0, 2009by Roger Peters the symbol for an explosion-protected device the symbol of each type of protection that has been applied group IIA, IIB or IIC for explosive gas at-mospheres temperature class for explosive gas at-mospheres or the maximum surface tem-perature in C for areas with combustible dust. Examples: Ex d e IIC T4 Ex d [ia] IIB T5 Ex pD21 T120 C With associated electrical equipment in type of protection intrinsic safety that is to be installed in the safe area, the symbols for this type of protection have to be put into square brackets, [Ex ia] IIC. If the equipment is to be mounted in hazardous areas it has to be protected by another type of protection.

3 Then only the mark for intrinsic safety is put into square brackets, Ex d e [ib] IIC T6. In the past, the Marking pursuant to the European standard changed from Ex to EEx . This was done to relate to the Europe-an standards (EN 50014 serie) that then dif-fered from the IEC-standards. With the cur-rent state of the standards this is no longer required so that in Europe the new devices are only marked Ex as the previous Marking the protection lev-el of the device in regard to explosion protec-tion cannot be clearly seen right away. Marking of explosion-protected equipmentLegislation, Standards and TechnologyPage 56 | Ex-Magazine 2010 Only knowledge of the possible application of the different types of protection indicates the application of the device in the respective zones. This problem was noticed in Europe at an early stage. So with the European Direc-tive 94/9/EC (ATEX 95) the equipment catego-ries 1, 2 and 3 were introduced. Transfer of these categories from the Directive to the standards, however, has only been done in the EN-standards and not in the Marking In the IEC 60079-0 / 2007 the devices for use in explosive dust atmospheres have been included.

4 So the general requirements on de-vices for use in explosive gas and dust at-mospheres are covered in this standard. Marking has now been supplemented with the protection level of the equipment . This equipment protection level (EPL) con-sists of two letters. The first one gives infor-mation on the type of explosive atmosphere: G for gas, D for dust. The actual protection level is defined by the letters a, b or c (table 1). These letters are already used for some types of protection to mark the respective protection level: ia, ib, ic. The symbol for the equipment protection level is added to the existing standard mark-ing: example: Ex d e IIC T4 Gb. With associat-ed electrical equipment , the EPL-symbol has to be mentioned after the type of protection: example: [Ex ia Ga)] IIC. When an associated electrical equipment with an intrinsically safe circuit ia has been fitted into a flameproof enclosure , for exam-ple, make it possible to install it into Zone 1, the following Marking is required: Ex d [ia Ga] IIC T4 suitability of devices for use in different hazardous areas is determined by groups.

5 Up until now two groups have been defined: de-vices intended for use in mines at risk through firedamp belong to Group I. Group II stands for devices that may be used in areas other than mines, specifically areas that are at risk through flammable GaEquipment for explosive gas atmospheres, having ensuring a "very high" level of protection for use in explosive gas atmospheres, which is not a source of ignition in normal operation, during expected malfunction, or during rare GbEquipment for explosive gas atmospheres, ensuring a "high" level of protection, which is not a source of ignition in normal operation or during expected malfunc-tions,EPL GcEquipment for explosive gas atmospheres, ensuring an "enhanced" level of protec-tion, which is not a source of ignition in normal operation and which may have some additional protection to ensure that it remains inactive as an ignition source in the case of regular expected occurrences (for example failure of a lamp)

6 EPL DaEquipment for explosive dust atmospheres, ensuring a "very high" level of protec-tion, which is not a source of ignition in normal operation, during expected mal-functions, or during rare malfunctionsEPL DbEquipment for explosive dust atmospheres, ensuring a "high" level of protection, which is not a source of ignition in normal operation or during expected malfunc-tionsEPL DcEquipment for explosive dust atmospheres, ensuring an "enhanced" level of pro-tection, which is not a source of ignition in normal operation and which may have some additional protection to ensure that it remains inactive as an ignition source in the case of regular expected occurrences (for example failure of a lamp)Table 1: Marking and definition of equipment Protection Level EPL Ex-Magazine 2010 | Page 57 Further sub-division of this Group II into three sub-groups IIA, IIB and IIC determines which type of gas the device is suitable for. With the IEC 60079-0 / 2007 a new group III has been introduced.

7 It stands for devices that are in-tended for areas in which an explosive dust atmosphere may be expected. Devices have to meet different requirements for different dusts. So, similarly to Group II, further sub-di-vision are also planned for Group III : IIIA: combustible flyings IIIB: non-conductive dusts IIIC: conductive dusts Thus the devices can be assigned to the different types of dust and their different re-quirements. Example: Ex tb IIIC T120 C Marking Standard IEC 60079-0 / 2007 allows alter-native Marking to the one described in the previous chapter, which gives information twice in some cases. With the introduction of Group III the suitability of a device for gas at-mospheres (II) or dust atmospheres (III) can be seen directly through the group number. So the letter G or D in the equipment protec-tion level does not give additional informa-tion. With some types of protection the protec-tion level is marked by supplementing the let-ters a, b or c to the symbol of the type of pro-tection.

8 Alternate Marking intends to add this distinguishing letter to all types of protection. , flameproof enclosures d will then be marked db . This then clearly shows the ap-plication range of a device in regards to the potentially present explosive atmosphere and the protection level without stating the EPL. So EPL Marking can be : Ex db eb IIC T4 Ex db [ia] IIB T5 Ex tb IIB T120 C Table 3 shows the currently possible alter-nate Marking of the different types of protec-tion. Old, new and alternate Marking is shown in table 2. The manufacturer may decide which Marking he will use. However, the alternate Marking seems to be more coherent as re-dundant information are marketingnew marketingalternate marketingEx d IIB T4Ex d IIB T4 GbEx db IIB T4Ex de IIC T4Ex de IIC T4 GbEx db eb IIC T4Ex ia IIC T4Ex ia IIC T4 GaEx ia IIC T4Ex d [ia] IIC T6Ex d [ia Ga] IIC T6 GbEx db [ia] IIC T6Ex tDA21 IP 65 T225 CEx tb IIIC T 225 C DbEx tb IIIC T 225 CTable 2: Comparison of the different markings according to IEC 60079-0 Marking of explosion-protected equipmentMarking according to ATEX 95 In Europe, in addition to the Marking ac-cording to standard, the requirements ac-cording to EC Directive 94/9/EC (ATEX 95) have to be 95 Directive Annex II requires the fol-lowing Marking : name and address of the manufacturer serial number, year of manufacture mark with the identification number of the notified body and category 1, 2 or 3 and for Group II the letter G (gases) or D (dust)Example.

9 2 II G Example for Marking according to ATEX Directive and standard EN 60079-0: 0158 2 II G Ex d b eb IIC T4 On devices that are marketed within the EU, Marking according to the Directive has to be added to the required Marking of an inter-national standard Page 58 | Ex-Magazine 2010 Type of protectionuse for gas atmospheresuse for dust atmospheresZone 0 Zone 1 Zone 2 Zone 20 Zone 21 Zone 22 Flameproof enclosuresdbIncreased safetyebIntrinsic safetyiaibiciaibEncapsulationmambmcmambm cOil-immersionobPower fillingqbPressurized enclosurepxb, pybpzcpbpcProtection by enclosuretatbtcNon-sparking devicenAcDevices and componentsnCcRestricted breathing enclosuresnRcTable 3: Symbols of the type of protections according to the alternate markingTable 4: Marking of the types of protection of non-electrical equipmentType of protectionsymbolConstructional safetycControl of ignition sourcebFlow restricting enclosuresfrPressurized enclosurepLiquid immersionkFlameproof enclosuredNon-electrical devicesStandards for non-electrical devices have up until now only been prepared by CEN for Eu-rope.

10 On an international level only the first steps towards standardization have been strongly follows the definitions for electrical : Ex is not stated as the Marking according to ATEX Directive already includes the symbol which indicates explosion pro-tection. equipment protection level is not stated as this has not been defined in the re-spective standards up until now. By stat-ing the category as required by the Direc-tive it can be seen which protection level the device has and in which zone it can be mounted. Marking of the different types of protec-tion for non-electrical devices is given in table 4. Example for Marking according to Direc-tive and standard EN 13463-1: 2 II G d IIB T4Ex-Magazine 2010 | Page 59