ATEX Zone 20 and Category 1D Equipment

Posted in: , on 29. Oct. 2010 - 17:10

A colleague has asked me to comment on a situation he's facing and I could do with other opinions.

His situation is he is receiving assorted biomass type materials into his plant from standard road going lorries, both rigid and articulated. The intention is for the lorries to tip into a bulk materials handling machine which will feed the materials onward via conveyors and elevators to storage.

The concern is the area around the tipping point into the receiving point which has been declared as Zone 20 under ATEX, therefore requiring Category 1D equipment.

The handling machine at the reception point could, I think, conform with the requirements of Category 1D equipment subject to type examination and certification from a Notified Body.

But the tail of the lorry to discharge will be in the Zone 20 area, thus must conform to the requirements of Category 1D equipment.

But as far as he is aware the material suppliers just use any haulier so the vehicles are unlikely to be Category 1D compliant. (possible sources of ignition being hot rear brakes, brake lights, reversing lights etc)

I think he's between a rock and a hard place on this one, short of buying his own bespoke vehicles certified 1D at the tail.

I'd be interested in other opinions.

Re: Atex Zone 20 And Category 1d Equipment

Posted on 30. Oct. 2010 - 10:39

Typical example of over zoning. It should have been zoned 22. If the material is being dumped in open

pit hopper then explosion is not an issue as explosion will not occur as confined space is required for explosion, deflagration might but then it is a different case. If the reception hopper is covered with a hood and has an extraction system then dust will be present for short time and infrequently and since there will be no other equipment in the hood area to act as ignition source it should be zoned as 22. The boundary limit of zone 22 should finish within the hood as there will be not dust present outside the hood due to extraction system. The trucks will remain in the safe area while dumping.

Getting the trucks certified for the zones is a nice one. No comments !


Re: Atex Zone 20 And Category 1d Equipment

Posted on 31. Oct. 2010 - 12:12

Yes, another case of over zoning is what I thought.

Trouble is the end user (or his consultant) has stated that the intake area which has an enclosure over it, and into which the tail of the lorry enters to tip, IS a Zone 20 and they will not be swayed from this. But what about the lorries ......

Interestingly I've since been sent the following link, so someone must have been spending money with Notified Bodies -

Re: Atex Zone 20 And Category 1d Equipment

Posted on 1. Dec. 2010 - 10:50

Ex II 1/3c D135<--- isn't 1 for internal and 3 for external this makes it 3D suitable for external zone 22 which makes it self certifiable. If there is any doubt just ask them for the certification number from the notified body and everything will be crystal clear.

I remember the classic example of paint-booth in the EU atex guideline document. It clearly stated you cannot certify the booth but all the equipment side should be suitable for that zone. If this is the case then every silo with explosive dust should have an atex plate ! but I have yet to see one.


Re: Atex Zone 20 And Category 1d Equipment

Posted on 1. Dec. 2010 - 11:47

Yes indeed, Cat 3 equipment is Zone 22 and as you say self certifiable, equally CAT 1 equipment requires Notified Body certification. Maybe some discrete enquiries may reveal the certification number, although I don't suppose the equipment manufacturers will read this thread and respond directly.

When first introduced ATEX seemed straightforward, the end user defined the Zone the equipment was required for, the manufacturer supplied conforming equipment. Now the end user defines the Zone internal to the equipment, and increasing numbers are saying Zone 20. I presume this is on the basis that there must always be a dust cloud so lets say Zone 20 to cover our backs. But of course the question is "is the dust cloud an explosive concentration". The kitchen in my house always contain dust clouds, and I have a source of ignition, my gas hob, but the dust cloud is not of an explosive concentration so the kitchen hasn't blown up!