It is easy to get lost in detail when you specify explosion-proof equipment. Do you find yourself pondering over ATEX and IECEx, and what certification you need for each? Before explaining the differences, it’s worth recognising that all the standards and legislation have the same goal, preventing an explosion and broadly speaking, they all use the same principles. The details come in how they classify a given environment and the certification of the equipment.
Okay here’s some detail, are you are ready?
INDEPENDENT TESTING OR SELF-CERTIFICATION?
IECEx is a globally accepted standard, while ATEX only applies to countries in the EU. There is another difference. However, ATEX is a legal requirement and manufacturers are accountable for the entire certification process, whereas IECEx is standard driven and you can only get an IECEx certificate from an external certification party.
As an aside, at Air Control Industries, we believe that our equipment should always be independently certified for both ATEX and IECEx. After all, you need equipment that you can trust in these environments – but that’s the subject of another debate.
The big advantage of IECEx is that it allows products and equipment to be traded across countries without having to be retested and recertified – it acts as a common set of safety standards among those countries. End users can also inspect vendor certificates on the IECEx website to confirm their validity.
In addition, ATEX certification can be based on an IECEx test report, but ATEX documentation will not necessarily support an IECEx certificate – remember that bit about self-certification?
IDENTIFYING THE HAZARD
Now let’s explore how the IECEx and ATEX classify explosive atmospheres because it will help you define your risk analysis for equipment and what information to provide suppliers, such as ourselves, with.
First, there are three groups to think about; group 1 covers mines, 2 covers gases and 3 covers dust. ATEX does the same thing but classifies the groups as Mines and Surface – with gas and dust both being part of the Surface category. Okay, let’s move swiftly on. Where gas or dust is the hazard, the next question that needs answering is how frequently is it present? In zone 0 it is present continuously, in zone 1 it is there occasionally, and zone 2 means it is only present in abnormal conditions.
This is a critical question because it will define what equipment protection you need. Some equipment cannot be used in zone 0 at all, motors, for example.
You will also need to identify which gas or dust is present. This will allow the supplier to define the gas or dust group and temperature class, which in turn defines the thermal energy allowed in an area or produced by specific equipment to avoid ignition.
EXPLOSION PROOF IN NORTH AMERICA
When you move across the pond to North America, you will find that they do not operate the IECEx or ATEX schemes. While they have adopted similar classification systems, the standards are not interchangeable.
For North America, the classification system is based on the National Electrical Code. Here they classify the hazard by class, division and group.
Class 1 refers to gas and class 2 to dust. Division 1 means the hazard is always present, and division 2 means it is less likely to be present. Finally, the “Group” specifies what type of gas or dust is present.
On the face of it, that seems quite simple, but sadly there is always a but.
While two materials may be in the same group due to having similar explosive potential, they can have very different ignition temperatures. This means that all explosion-proof or HAZLOC approved equipment for class 1 must also carry a separate temperature rating stating the device's maximum surface operating temperature. If this equipment rating is 85C and the gas present has an ignition temperature of below 85C, then you cannot use it in that environment.
Stay with me here because you also need to think about the approval procedure in North America.
Approval and verification of equipment for use in explosive atmospheres in North America are done by federally, and state recognised independent testing laboratories. Remember that I mentioned that North America does not operate the IECEx scheme? That means that as the supplier of equipment into the USA or Canada, you will need to get separate certification from one of these laboratories for any equipment used in an explosive environment.
Whatever region in the world you are specifying explosion-proof equipment for you will need to complete a thorough risk assessment and understand what the hazard is and how prevalent it will be where the equipment is.
Unfortunately, while the equipment design may be largely the same, for different countries the classification and certification methods can be different, and you need to be aware of these local differences to ensure that you are compliant. Let’s hope that we move towards a more harmonised global system in the future – it will certainly make life easier for equipment manufacturers.
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