Bonding of machinery control panels

[dasrik]

Hi Guys,

I work for a large food factory, a couple of days ago a chap was electrocuted from a machine that had a bonding issue. Now we are being asked to check all the bonding on our machines.

But before i do i want to be sure what the requirements are, so far what i have found on machinery is pretty vague.

On the majority of our panels the incoming supply goes to an isolator and the earth is made off there and then taken to a bonding terminal or din rail earth connector. Is this ok or should the earth go to a MET first?.

The accident was caused by an earth coming off the din rail and not being connected to the MET a fault occured and the panel became live.

I want to find out what the right way is and what regs cover it if possible.

Cheers

 

[telectrix]

are these panels supplied by SWA? if so, the SWA should be glanded to the metalwork of the cabinet,

 

[dasrik]

No they are plug and socket 3 phase and single phase 16/32/64A depending on machine.

Sorry should of mentioned that before.

 

[Marvo]

The DIN mounted terminals usually extend the earth onto the rail via the mechanical clamp which in turn is fixed to the chassis plate which is fixed to the enclosure. This earth path shouldn't be relied on as a safety earth. Where the earth is first made-off at the isolator it should be extended directly to the chassis of the enclosure and there should be a fly lead earth to the door as well. Also extended directly to the earth rings (banjos) of any glanding etc.

 

[dasrik]

Cheers, thats how most are at the moment. Do you know what regs would cover this? would it be BS EN 60204?

 

[Inteificio]

One of the guidance notes covers purely earthing/bonding. If I could remember which one it would be more help, but google will help.

 

[netblindpaul]

dasrik,
You are correct it is 60204-1, there are a few others, but, that is the most important.
You really need to understand the root cause here.
Also you should check the machine design drawings.
If you have had an electrocution on the premises then this is reportable under RIDDOR and you must not do anything until HSE & the Police have completed their investigation into the death.
Once you have their report then you should address this with the machine builder.
HSE will almost certainly request the technical file from the machine builder for proof of compliance with the machinery directive and the low voltage directives.
This is a very serious scenario and I strongly recommend that you get external professional support.
You may find that any actions you take could be found to be criminal until the investigation is completed as there could be charges of manslaughter brought.

Inteificio,
BS7671 GN's have no relevance to machinery, by the way it is GN8 that you are thinking of.

 

[telectrix]

but does the OP mean electrocuted, or that the guy had a shock? big difference.

 

[netblindpaul]

tel,
He has stated electrocuted, hence my post, there is a HUGE difference.
Correct terminology is quite important, I have been drumming this into my 2391 students today!

 

[Inteificio]

60204-1 is on my to buy list ;-)

 

[dasrik]

It wasn't fatal, but was a severe shock and is still in hospital with multiple fractures, it could of easily been a different story.
i'm sure the HSE will be involved. I haven't touched the machine although it has been modified - i refused to work on it and it is currently out of service.
There are no drawings for this piece of kit.
My original question is so i know how the machines should be wired to cover my own arse when fitting supply cables etc. We don't always have the luxury of wiring diagrams and the ones we do have might not cover the specifics of earthing arrangements.
I don't have access to BS 60204 although the company should have one.

The problem with working for large companies especially in the manufacturing industry, from what i have seen in my 12 years + we are pressured to keep lines going safety is often ignored by the people in charge and it is left to us who want to be sure we are doing the job right to try to find out the right way often in our own time and at our own expense. When things go wrong and there is an accident things change (sometimes) it shouldn't be this way but unfortunately in many factories it is.

 

[netblindpaul]

Inteificio,
You must be minted then, because 7671 is one of the cheapest standards on a £ per page level & most people seem to moan about this.
60204-1 is currently £224.00.
The pdf is only 130 pages!
Check the value on 7671 now!

 

[telectrix]

tel,
He has stated electrocuted, hence my post, there is a HUGE difference.
Correct terminology is quite important, I have been drumming this into my 2391 students today!

paul, that's why i raised the point. a lot of people will say electrocuted instead of " received a shock/belt". in either case H&S should be involved before it is a case of sudden death. obviously, if it were just a shock, then the investigation will not be as rigorous or as intensive as in a case of fatality, but either way, this could be a potential death trap and needs investigating and rectifying. any environment subject to vibration should have "belt &braces" terminations so that the failure of 1 connection doesn't lose the earthing from a metal fixture. ( this is also a good reason to fly lead the cpc to knock-out boxes ).

 

[netblindpaul]

OK, dasrik in that case he was not electrocuted, else he would be dead, he suffered an electric shock.
As he has suffered fractures it is doubtful that it will not be reportable under RIDDOR, unless he has only got broken fingers, though as he has been hospitalised then it will almost certainly be reportable, and if he is off work for more than 3 days then it WILL be reportable.
I have a very good understanding of manufacturing and the line techs are to blame for most of the bad workmanship.
They must stand their ground and refuse to undertake unsafe work.
Thing is just like outside if one does this there will be another who will just do the mod/repair etc. and to hell with the consequences.
That is what is wrong, the ramifications are either misunderstood or they don't care.
You must remember that you are working under statute law.
This could open up a whole new can of worms.
This could well cost jobs or even the business once HSE get a hold.
Let me put it like this, IF I were the HSE inspector I would be pushing for a prosecution and a custodial sentence from somewhere.
If that were a line tech then so be it.
If that were the MD even better.
If you are working to a Std. then you must have access to that std. if you are modifying machinery then to comply with statute law you need to be working to 60204 thus you must be familiar with it and have access to it.
How are you complying with statute law if there are no machine drawings?
Is the machine CE marked?
What does your statutory PUWER98 assessment say about the machine control systems?

Don't tell me I can probably guess!

Your employer is probably an "almost" household name or at least well known in the business and their HSE "bods" are more interested in Hi-Vis, gloves & eye protection rather than fatal things like electricity, because like almost ALL HSE bods they have no real grasp of electrical safety.

 

[netblindpaul]

tel,
You posted while I was typing.
This is a constant battle and it is almost lost due to the level of training of craftsmen, technicians and engineers we have in the UK at the moment.
Also you have the "little dictators" who wear the HSE hat who have little grasp of electrical issues.
As you say with regard to vibration, any rotating machine & I mean ANY WILL vibrate end of.
It is just the level of vibration that will vary.
There are so many machines wired with say 6491x or SWA, which is not an acceptable solution for vibrating machinery unless correctly applied that this is unreal and could be a death trap.
Thing is the correct connection methods are not taught any more!
Apart from the fact 6491x is never suitable for machinery anyway!