Technical Resources
We have gathered together a number of technical resources for use as reference on electrical projects.
DISCLAIMER: The information on this page and the PDF is for information only and R&M Electrical Group Ltd can not be held liable for any information therein.
IECEx Scheme
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The objective of the IECEx Scheme (International Trade of Electrical Equipment used in Explosive Atmospheres) is to facilitate international trade in electrical equipment intended for use in potentially explosive atmospheres by eliminating the need for multiple national certification.
The IECEx Scheme provides a means for manufacturers to obtain Certificates of Conformity that will be accepted at national level in all participating countries. A Certificate of Conformity may be obtained from any certification body accepted into the scheme. The objective of the IECEx Scheme is world-wide acceptance of one standard, one certificate, and one mark.
The Ex scheme applies to manufacturers of:
- Electrical apparatus for explosive gas atmospheres
- Electrical apparatus for the detecting and measurement of flammable gases
- Electrical products such as switches, outlets and outlet boxes, circuit breakers, electric motors, and lighting used in hazardous environments
The obvious benefits of the IECEx scheme are:
- reduced testing and certification costs to manufacturer
- reduced time to market
- international confidence in the product assessment process
- one international database listing
- maintaining International Confidence in equipment and services covered by IECEx Certification
Background
IECEx is a certification scheme championed by the IEC (www.iec.com) , and it is fast becoming the preferred route for international safe certification of products for use within all hazardous areas.
The IEC test report provides detail not included within an ATEX certificate and can be locally ratified to overcome any destination market legislative difficulties that may arise.
In contrast to ATEX, IECEx was designed from the outset as an ISO/IEC Type 5 Certification Scheme, employing a single third party (The IECEx Certification Body) to combine all aspects of design evaluation and production control before issuing a certificate.
IECEx Relationship with ATEX
ATEX is a mandatory legal requirement within Europe. Therefore the IECEx certification is complimentary to the ATEX standard, making the choosing of equipment that has compliance to both standards advantageous if the final destination is outside the EU.
IECEx and ATEX marking differs and dual marking is becoming increasingly common. Dual marking enables products to gain an equal acceptance status in the countries signed up to the IECEx scheme as they currently receive in Europe.
The Future
The IECEx scheme is a very positive step towards a world certification system.
However, while total global harmonisation is still some way off, more and more countries are adopting this international certification scheme.
Many manufacturers have acknowledged this shift and have begun adding IECEx compliance to their list of approvals.
Countries Participating in the IECEx Scheme
| Australia | Germany | New Zealand | South Africa |
| Canada | Hungary | Norway | Sweden |
| China | India | Romania | Switzerland |
| Czech Republic | Italy | Russia | UK |
| Denmark | Japan | Serbia and Montenegro | USA |
| Finland | Korea | Singapore | |
| France | Netherlands | Slovenia |
Protecting Electrical Equipment Marking System & Standards
Type of Protection for Gas / Vapour Hazards
| Equipment Code | Description | Suitable for zones... |
|---|---|---|
| Ex ia | Intrinsic safety 'ia' | 0, 1, 2 |
| Ex ib | Intrinsic safety 'ib' | 1,2 |
| Ex ic | Intrinsic Safety 'ic' | 2 |
| Ex d | Flameproof protection | 1,2 |
| Ex p | Purge/pressurized protection | 1,2 |
| Ex px | Purge/pressurized protection 'px' | 1,2 |
| Ex py | Purge/pressurized protection 'py' | 1,2 |
| Ex pz | Purge/pressurized protection 'pz' | 2 |
| Ex e | Increased safety | 1,2 |
| Ex m | Encapsulation | 1,2 |
| Ex ma | Encapsulation | 0,1,2 |
| Ex mb | Encapsulation | 1.2 |
| Ex o | Oil immersion | 1,2 |
| Ex q | Sand / powder (quartz) filling | 1,2 |
| Ex n | Type - n protection | 2 |
| Ex s | Special protection | Normally 1 and 2 |
Type of Protection for Gas / Vapour Hazards
| Equipment Code | Description | Suitable for Zones... |
|---|---|---|
| tDA20 | Protection by enclosure | 20, 21, 22 |
| tDB20 | Protection by enclosure | 20,21,22 |
| iaD | Intrinsic Safety | 20,21,22 |
| maD | Encapsulation | 20,21,22 |
| tDA21 | Protection by enclosure | 21,22 |
| tDB21 | Protection by enclosure | 21,22 |
| ibD | Intrinsic Safety | 21,22 |
| mbD | Encapsulation | 21,22 |
| pD | Pressurization | 21,22 |
| tDA22 | Protection by enclosure | 22 |
| tDB22 | Protection by enclosure | 22 |
| icD | Intrinsic Safety | 22 |
Equipment Protection Levels – EPL
From 2007 onwards, the IEC Technical Standards in the series IEC 60079, and in particular IEC 60079 Part 14, have recognised that there may be occasions where it is necessary to increase, above the normal levels, the protection against ignition sources. This concept allows for consideration of risk (ie consequences of an explosion) as opposed to just the probability of a flammable atmosphere existing – the conventional selection criteria between the types of protection and the zone of use.
Three Equipment Protection Levels are specified as shown in the table below.
In normal circumstances the effect of these EPLs will be to retain the normal zone/equipment protection relationship. If, however, the risk is considered especially severe, then the required EPL for the zone may be increased. Similarly, if the risk is deemed to be especially small or negligible, the EPL may be reduced from the norm.
The following two tables show the normal relationship between EPL and zone, and the EPL awarded to each type of protection
| Equipment Protection Level (EPL) | Normal Applicable Zone(s) |
|---|---|
| Ga | 0 (and 1 and 2) |
| Gb | 1 (and 2) |
| Gc | 2 |
| Equipment Code | Description | EPL |
|---|---|---|
| Ex ia | Intrinsic safety 'ia' | Ga |
| Ex ib | Intrinsic safety 'ib' | Gb |
| Ex ic | Intrinsic Safety 'ic' | Gc |
| Ex d | Flameproof protection | Gb |
| Ex p | Purge/pressurized protection | Gb |
| Ex px | Purge/pressurized protection 'px' | Gb |
| Ex py | Purge/pressurized protection 'py' | Gb |
| Ex pz | Purge/pressurized protection 'pz' | Gc |
| Ex e | Increased safety | Gb |
| Ex m | Encapsulation | Gb |
| Ex ma | Encapsulation | Ga |
| Ex mb | Encapsulation | Gb |
| Ex o | Oil immersion | Gb |
| Ex q | Sand / powder (quartz) filling | Gb |
| Ex n | Type - n protection | Gc |
| Ex s | Special protection | Refer to equipment marking and documentation |
For dust hazards, the EPLs are as follows:
| Equipment Protection Level (EPL) | Normal Applicable Zone(s) |
|---|---|
| Da | 20 (and 21 and 22) |
| Db | 21 (and 22) |
| Dc | 22 |
Standards for Equipment
IEC 60079 – ELECTRICAL APPARATUS FOR EXPLOSIVE GAS ATMOSPHERES
| Part 0 | General requirements |
| Part 1 | Construction and test of flameproof enclosures of electrical apparatus |
| Part 2 | Electrical apparatus – type of protection ‘p’ |
| Part 3 | Spark test apparatus for intrinsically safe circuits |
| Part 4 | Method of test for ignition temperature |
| Part 5 | Powder filling ‘q’ |
| Part 6 | Oil-immersion ‘o’ |
| Part 7 | Increased safety ‘e’ |
| Part 11 | Construction and test of intrinsically safe and associated apparatus |
| Part 15 | Electrical apparatus for explosive gas atmospheres, type of protection ‘n’ |
| Part 18 | Encapsulation ‘m’ |
| Part 25 | Intrinsically safe systems |
| Part 26 | Special requirements for construction test and marking of zone 0 electrical apparatus |
| Part 27 | Fieldbus intrinsically safe concept (FISCO) |
Standards for Installation etc. (gases and vapours)
IEC 60079 – ELECTRICAL APPARATUS FOR EXPLOSIVE GAS ATMOSPHERES
| Part 10 | Classification of hazardous areas |
| Part 14 | Installation (and selection) of equipment in hazardous areas |
| Part 17 | Inspection and maintenance of equipment |
Note that the 60079 series of standards will gradually address dust hazards as well as gas/vapour hazards. The standard number will have an additional suffix 1 or 2. Thus, for example, 61241-14 (see below) will be replaced by 60079-14-2 [installation for equipment in dust hazards], with 60079-14-1 dealing with installations in gas/vapour hazards.
Standards for Dust Hazard Equipment and Installation
IEC 61241 – ELECTRICAL APPARATUS FOR USE IN THE PRESENCE OF COMBUSTIBLE DUST
| Part 0 | General Requirements |
| Part 1 | Protection by enclosure ‘tD’ |
| Part 2-1 | Methods for determining the minimum ignition temperature of dusts |
| Part 2-2 | Method for determining the resistivity of dust in layers |
| Part 2-3 | Method for determining minimum ignition energy of dust air mixtures |
| Part 4 | Type of protection ‘pD’ |
| Part 10 | Classification of areas where combustible dusts are or may be present |
| Part 11 | Protection by intrinsic safety ‘iD’ |
| Part 14 | Selection and installation |
| Part 17 | Inspection and maintenance |
| Part 18 | Protection by encapsulation ‘mD’ |
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