Hi

Im currently installing a 50kw solar pv system to the roof of a grain dryer, 17 strings of 12 panels to a string collector.
The job would be far simpler if I could install the string collector high up within the grian dryer itself.
My first instinct is that this is not possible as it will need to be 'ex' rated due to the risk of the dust igniting.
The collector itself is ip55 which is 'dust protected'.
I have spoken to the ECA and they could not give me an answer!

Can anyone help me??

Hi,

New one on me, I haven't come across any solar panel installations within an ATEX zone.

When ever I have had something new like this I have contacted BASEEFA or SIRA for advice.

BASEEFA Website

SIRA Website

Kind regards

Donald

Thanks Donald

Will send them an email, the more I think about it the more i'm inclined to think i'll put it in the agricultural store next door!

Paul

You need to fully establish if the area you propose to install the 'string collector' is Atex classified, I suspect it may be zone 22 but there is no point guessing. I would consult with original installer/manufacturer of the dryer, they should have zoning information.

If the area is zone 22 say, then you really need to install equipment that is marked as being suitable for a zone 22 environment, this would be Atex 3D or better that has a suitable IP rating (IP5X for zone 22) and a suitable temperature class for the grain dust which I would estimate to be T3.

Ultimately the main protection against dust is the enclosure IP rating but you also need to consider the maximum surface temperature of the equipment, including the insulating effect the dust has on it when it has piled up on top (which it will do over time).

If it comes back as being zoned I would not recommend installing your equipment if it is not Atex marked, regardless of IP rating. If there is a future fire (even if it's not electrical related) it will come back to haunt you.

Unfortunatly the dryer is as old as the arc so any information from the manufacturer will be lost in the depths of time!

Because it conatins food, the building is thoroughly cleaned and vacuumed before the grain is loaded in for drying so I dont think it will get a chance to really build up on the equipment.

I take your point about the future fire risk tho!

Its prob worth noting that there are standard metal clad socket outlets instlalled within the dryer, probably by the farmer himself!!!

thanks

It's difficult to make a judgement on an individual piece of plant without seeing it but there is always the possibility it may not warrant being a zone if the housekeeping is really good and there are no dust clouds present, but gut feel would still be zone 22.

In the 'perfect world ' the farmer should have had a risk assessment carried out on the plant and equipment before 2006 (requirement of the DSEAR regs when they came out) to see if it was suitable for continued use but in the real world this only happens on large sites.

I have seen many standard socket outlets (IP bugger all) installed in Atex areas. No one cares until it goes bang!

If you want to see the true extent of what can happen during a dust explosion google 'imperial sugar explosion 2008' and watch the CSB investigation video. Real eye opener.

Are we talking about a floor store here (ie a big barn that they tip grain into and blow from below with fans) or are we talking about a dryer with burners ??

There's quite a bit of difference.....


I'm guessing it's a big barn and your PV is on the top of it ??
I don't know of a single grain store in Essex that is considered a problem from the dust point of view. They normally load with extraction running and the doors open which results in very little dust in the store. Once the store is loaded and being "blown" the dust is minimal as nothing moves around, Don't be deceived by the size of the fans.


Stu

Thats exactly what it is Stu.

Massive barn, big fan blowing air in with a gas burner in it, on that basis the explsoion risk you would think would be minimal!

I wouldn't want to stake my PI on it, but I've never heard of a problem in one. Granted sugar/custard/flour etc, but in a big grain store never (yet)

I've seen several continuous flow dryers catch fire but that's generally because they either haven't been maintained correctly or the exhaust fans have failed but the burners are still running which ends up setting fire to the cereal inside.... but they are a different beast.

When you consider that most stores have the fan control panel situated in them (as designed by the barn / dryer suppliers) and the panel is at best IP55 but probably IP44 it doesn't appear they consider it a risk.

We work with some of the leading crop drying control suppliers in the UK and none of their kit is atex approved which either means someone is going to take a big hit on their insurance or they've considered the risk and it's minimal.


Stu

Thanks for that.
I have lifted this off a motor manufacturers web site, think it should apply in this case

Zone 22 is a place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only. Areas in which dust escapes and forms deposits are included in this category. Here the certification covers non-conductive dusts for motors having minimum ingress protection IP55 and for conductive dusts IP65.

Think grain is 'non conductive' dust!!!!

Yep, I'd go with that.

It's certainly non conductive (until it gets damp)


Stu

what about getting a dsear report done for the owner,prior to deciding what is and what isn't safe

I wouldn't - I'd get the owner to do the report if he feels it's required - it's his duty not the designers

Personally, I wouldn't be telling anyone what the zoning should be (not in this case at least) - as a designer, that information should form a core part of the design brief - in fact I wouldn't start the design unless I had possession of a hazardous area classification.

That said, if this is a drying shed rather than a grain drying silo, the probability of an explosive dust concentration is low, as Stu says - and the ignition point if it does exist would be quite high.

Going with a reasonable IP rating of IP 65 and a temperature limit of 90C should cover almost all scenarios for Zone 2 and 22.

For avoidance of doubt, don't put your kit in the shed internal area - no risk then to you

Regards

OMS

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Failure is always an option