Do you really have an internal Zone20?

Do you really have a continuous potentially explosive atmosphere?

Have you had a lot of dust explosions in your machines over the years you have been making them?

Maybe you've over-zoned the internals of your machine?

Maybe you've been persuaded by "experts" to over-zone the internals of your machine?

Why not buy/hire a portable machine to measure the dust concentration in your machine and check the results against the necessary concentration for a dust explosion to occur. ■

If my memory serves me right I think I used something like this.

http://www.instruments4hire.co.uk/MicroDustPro.htm

I also look into my machines. If the "fog" prevents me seeing what's going on then I've a problem, but if I can see then I've got at worst a Zone 21.

IMO, too much speculation and conjecture, not enough measurement! ■

Originally Posted by Roland Heilmann

But this must be discussed with a legal specialist (ATEX / 2006/42/EG), seeing your specific points & problems.

Oh dear, referring to a "specialist", a consultant by any name who'll take your money and give you the worst case advice to protect his own back. ■

Refering to IEC 61241-10 (or its CENELEC equivalent), examples of dust transport systems in this hazardous area classification standard may provide examples of equipment similar to yours, which do have Zone 20 areas within them.

Any device detecting material flow, level, density or blockages in your transport system will have to be certified for use in Zone 20.

Any openning into this transport system (maintenance hatches, joints, and the like) are likely to be sources of release (albeit secondary ones) and could create small Zone 22 areas about them.

I would be surprised if your system did not have any of the above.

While your system may not have to be certified (or approved) an installation of it would require hazardous area classification and certified equipment, suitable for any hazardous zones defined in the classification processes, would have to be installed if these items were either potential mechanical or electrical sources of ignition. ■

Originally Posted by epeeconsulting

examples of dust transport systems in this hazardous area classification standard may provide examples of equipment similar to yours, which do have Zone 20 areas within them.

By actual measurement or speculation? ■

I appreciate this discussion very much because it touches the daily work and daily questions coming up when working with the woolly atex regulations.

we as machine manufacturer in the same situation like Asnong. We decided to go the following way, also after having a lot of discussions with notified bodies and atex expert.

For cat. 2 and 3 equipment a certifying by a notified body is not necessary. The ignition hazard assesment has to be made by the manufacturer itself. Of course our design of mechanical parts and electrical equipment is according to atex regulations for Zone 21, 22 and/or Zone 1 and 2. The ignition hazard assessment together with the documentation, drawings and quality certificate about manufacturing process is deposited at notified body for Cat. 2 equipment. For cat. 3 equipment we store it according to ATEX regulations in house.

For cat. 1 equipment we offer the customer monitored inertization of our machinery to overcome Zone 20, 0 inside of the machine. With using inertization the zone inside is changed into (sometimes no zone) or zone 22 / 2 (depending on atex expertise. With this the internal of the machine isn´t any more Zone 20 and the machine is designed according to cat. 2 and 3 in the way described above. Of course for some dusts like St1 or (St2 < 250 bar/ms) burst discs with flame quenching were discussed as alternative or also explosion suppression techniques to overcome Zone 20/0. We haven´t found a final solution with these alternatives so far and still offer inertization for these cases. Because of this we try not to over-zone the internal of the machine. But this is done together with the customer (he is responsible for zoning according to ATEX 137) and/or addition atex experts ordered by our customer. ■

Originally Posted by Asnong

Machinery must comply, as far as the risk of explosion due to its use in a potentially explosive atmosphere is concerned, with the provisions of the specific Community Directives.

Note the use of the word "IN".

So first consider the entire machine "IN" a potentially explosive atmosphere i.e. the working environment.

Then consider the inside of the machine

is there a potentially explosive atmosphere?

if there is, what "machinery", if any, is in this potentially explosive atmosphere? ■

Originally Posted by Asnong

From the ATEX Guidelines, second edition:

[I]In the light of these ideas the place of installation "in, at or beside" a potentially explosive atmosphere is not decisive for the application of Directive 94/9/EC. The decisive fact is whether the potential sources of ignition of an equipment are in contact – or have an interface – to a potentially explosive atmosphere, with the effect that the combustion may spread to the entire unburned mixture (see definition "explosive mixture").

so as always

1) is there a potentially explosive atmosphere, yes or no

2) is there a potential source of ignition, yes or no

...

Equipment may have an internal explosive mixture (without limitation to dangerous quantities), which has an interface in the sense of a spreading of the combustion to a potentially explosive atmosphere even in the case it is not installed completely inside a potentially explosive atmosphere.



So what is happening INSIDE the equipment

1) is there a potentially explosive atmosphere, yes or no

2) is there a potential source of ignition, yes or no



...

It is nevertheless common understanding of the Standing Committee that after the date of application of Directive 94/9/EC, both electrical and non-electrical equipment used in machinery having a potentially explosive atmosphere inside must comply with Directive 94/9/EC. This position is also reflected in the draft revision of the machinery directive.



So machinery, if there is any, inside equipment if it contains a potentially explosive atmosphere has to be considered under ATEX

Sorry, I thought that's what I said ?? ■

Asnong

If your products are the same type of unit but just different sizes you can certify a generic design to encompass all sizes and configurations.

A simple way of doing it, is to pick the largest size, all smaller sizes will be covered. ■