Help required for Explosion proof equipments


Thread Starter

Rafat Ali

I have an equipment tnat have code written as (Ex) II 2 G EEx edm IIC T4. my question is about adm in the code dose it mean that it has there types of safty e- increased safety d-flame proof m encaplusation? The equipment is for use in zone 1 dont you think that this saftey is more then the required.

Bruce Durdle

The coding edm does mean that the equipment uses 3 types of protection, but this does not necessarily imply that they are redundant. Typically, increased safety protection does not cover components which may be sparking or otherwise capable of causing ignition and these components may use other means of protection and be installed in an Ex e enclosure. So a start-stop station may be made in an increased safety Ex e enclosure but the actual switching contacts will use Ex d protection - the combination will then be rated as Ex ed.

The coding you have given is quite common for fluorescent luminaires with the m protection being applied to the ballast.

Hope this helps

can we use equipment designed for zone 0 in zone 20 it will work properly or having some problem?

Bruce Durdle

For Zone 20 you should have equipment certified as Ex iD - ie, especially for dust service. However, the only difference between the requirements for Ex I for gas/vapour service and Ex iD for dust service is the need to comply with the surface temperature limits for dusts which must be derated from the figure used for gas/vapour.

Prior to Ex iD specifications being developed there were some additional restrictions relating to the permissible energy levels and the minimum ignition energy of the dust.

Dear Bruce,
I am following the issue of "Explosion Proof equipments", May I ask you to explain more or give me a link to find out more about the points you have stated in your reply.
I also have a question, suppose I have a module suitable for zone 2, then can I put it in a box approved for zone 1 or even zone 0 and installing the whole in zone 1 or zone 0?
Thank you for your time.


Bruce Durdle

Hi Vahid,
Like so many of the topics in this area...

It All Depends.

If you have a box or enclosure approved for Zone 1, it will have a temperature rating. This temperature rating will depend on the external temperature of the box if it is certified as Ex d or Ex p, or on the maximum internal or external temperature of the box if Ex e.

If your enclosure is Ex d or Ex p, then you can generally add components to the interior without violating the explosion protection. However, you are adding to the power dissipation inside it. A certified enclosure should come with documentation stating the maximum internal power that can be accepted for a given temperature rating. You then need to assess the effect of your added equipment.

You also need to assess the cabling requirements. If you have spare cable entries, or can connect your added module using spare cores in an existing cable, then there is no problem. However, you cannot simply drill another hole in the side of an Ex d rated box to add another cable entry.

However, if your box is certified to Ex e then you cannot add components that are not Ex e certified unless they are protected by another means - such as the Ex d contacts I mentioned in an earlier post.

This probably doesn't help ...