ATEX equipment and gland hole drilling

You are correct that in general -for an end user- it is permitted to drill/tap entries into an Ex e enclosure, following the manufacturer's instructions and certificate special conditions of use. However, things may be different if you are planning to modify the enclosures and then resell them (perhaps as part of a larger project or system). In this case you would become an "economic operator" as per https://www.legislation.gov.uk/uksi/2016/1107/contents/made and potentially become classed as a manufacturer.


I don't want to second guess Hawke, but it looks like their advice was on this basis.


So the two key questions I would have are

1) are you (in the generic sense ie you personally or your employer etc) the end user, or are you going to sell them on to the end user?

2) are you actually looking at PL6 series ie fitted with terminals and certified as equipment with a certificate ending in "X"; or are they empty component enclosures, ZPL6 series I think, with no terminals and a certificate ending in "U".


If they are equipment do they already come with entries and blanking plugs fitted by Hawke? And then you want to fit extra entries?


Assuming you are an end user, then BS EN 60079-14 is a good place to start for an overview of the requirements.

f you are re-selling then there is a lot more to it, but be aware than it is not permitted to self-certify Category 2 (ie Zone 1/21 ) equipment, which might be relevant if you are modifying them.


As background info, be aware that it is more complicated to make additional entries into GRP enclosures, because it is easy to weaken the structure so that it wouldn't meet the impact requirements. It *might* that they already have the maximum number of entries permitted by the certificate when supplied by the manufacturer - hence the advice that if you want to add more it is up to you to get it re-certified. The other issue is that insulating enclosures often have a metal plate internal to maintain the electrical conductivity. So as well as drilling the main enclosure you might have to punch holes in this plate. Again this *might* affect the certification.  


Hope this helps as a starter. We really need to understand what exactly you intend to do with the enclosure to advise further (ie are you an installer covered by DSEAR or manufacturer/distributor covered by the equipment regulations).I'm far from an expert on the former, but believe you have more flexibility than the latter.

The Hawke documentation states:

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b) The enclosure may be ready supplied with cable entries. Where the customer drills cable entries they must be installed in accordance with

the component certificate BAS06ATEX0116U or IEC Ex No: BAS06.0027U and enclosure limitations, these specify a maximum clearance on

the entry thread of 0.7mm for plain holes and where adjacent cable entries are installed suficient clearance must be maintained to allow

for the fitting of sealing/retaining washers and the rotation of the cable gland hexagons, and leave a minimum of material between

adjacent holes in line with the above certificate number(s).

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https://hubbellcdn.com/installationmanuals/HKE_AI273%20PL6%20Junction%20Box%20(Issue%20Y%2003-19).pdf


As I read this you would have to be able to make the hole to the required tolerance -0, +0.7mm and be able to confirm this with a calibrated go -no go gauge. You would also have to demonstrate that you have met the requirements for spacing of adjacent holes in accordance with the stated certificate.


On a purely practical basis you will not be able to acheive those tolerances with a hand held hole saw. A rigid bench drill or mill with an appropriate cutter will be required.

drilling a hole to be within 0.7mm of the diameter of the threaded part that fits inside it is probably possible on-site, but not quickly, but drilling slightly undersize and reaming or filing  up to a tight fit. For a 20mm hole, a length of bar of 20,7mm should not fit.  For smaller holes where drills step up in 0,5mm increments, for example to make a hole that an M6 bolt passes, but a 6,5mm drill bit does not is an easy sort of test -this is not exactly high precision by workshop standards, but it is not just hand held or woodworking tolerance either.

Mike