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HARIDAS.P.V  
#1 Posted : 28 July 2011 15:52:16(UTC)
Rank: Forum user
HARIDAS.P.V

What is the best way of doing body earthing of scaffoldings. Do you feel it is required to do earthing provisions for scaffoldings in construction industry. Is this a requirement for third party approval of scaffolding to pass scaffolding certification.
What is the most effective earth resistance kit available at the market. Please provide any manufacturer details?
Regards,
Haridas
Darach  
#2 Posted : 29 July 2011 08:01:25(UTC)
Rank: Forum user
Darach

Hi

As far as I know there is a BS standard for the earthing of scaffolds. And also I believe it is a specialist area. I have not worked on many projects where it is a requirement. If you search BS on line I'm sure you will find it, I don't have the code off hand.

Hope this helps,

Darach.
Zimmy  
#3 Posted : 29 July 2011 09:25:31(UTC)
Rank: Super forum user
Zimmy

I have never heard of such a requirement and I'm an electrician. If on a PME supply then DON'T ever do it. It would be impossible to effectively earth a scaffold in any case (tower or independent tied etc.)
zimmy
Sandan  
#4 Posted : 29 July 2011 14:08:19(UTC)
Rank: Forum user
Sandan

Stupid question from a non-scaffolding or electrically experienced person -

Is not the scaffolding earthed by the very nature of it's 'feet' being on the earth? May be a bigger problem if on concrete or other non-earthy surface...

I was under the impression that electrickery always looked for the easiest path to earth..?
Zimmy  
#5 Posted : 29 July 2011 14:26:12(UTC)
Rank: Super forum user
Zimmy

If any electrical gear is to be used on scaffolding it should be supplied via 230/110V centre tapped to earth transformer.

On a PME/TN-C-S intake you would be connecting the scaffold to the neutral conductor of the intake and exporting any fault conditions outside the equipotential zone (TN-S included but no connection to N at the intake).

If you were to bond the scaff to any means of earthing you would need to have electrical earthing conductors linking every and all pipe work together, every joint. Think about it, pointless having just one pole earthed, and by the nature of the construction, one could never guarantee the integrity of the clamps liking the scaff poles to each other. A bit like trying to earth a ceiling grid of an office building.

Concrete can and is earthy in the dry and when wet....

By the way, earthing water and gas etc is done for equipotential voltage reasons not for earh paths although they can and do take a certain current to earth in the event of a Phase to earth fault.
Zimmy  
#6 Posted : 29 July 2011 14:40:11(UTC)
Rank: Super forum user
Zimmy

And another thing...
What ever you do Don't even think about connecting an Earth-loop-impedance-tester to the scaffold. You will kill someone. Some electricians will do it if you ask as some electrician don't know what they are doing with the things (true, not kidding here)

For test kit take a peep at my old web site. Bit dated now but still ok for a few things. I hope this don't break the rules but the sites are for free info.

http://www.fortunecity.c...e/438/test_equipment.htm

If you like talk a peep at

http://electrical-testing-safety.blogspot.com/ and I'm happy to point you in the right direction if any more help needed.

zimmy
Guitarman1  
#7 Posted : 29 July 2011 14:44:41(UTC)
Rank: Forum user
Guitarman1

In my current chosen industry, events and rock and roll, we earth spike all outdoor stages and structures
Zimmy  
#8 Posted : 29 July 2011 14:45:57(UTC)
Rank: Super forum user
Zimmy

Run on generators G?
Guitarman1  
#9 Posted : 29 July 2011 15:11:03(UTC)
Rank: Forum user
Guitarman1

yep... 13 amp supplies seem to run out of power after a couple of hundred yards, no matter how thick we make the cables
Zimmy  
#10 Posted : 29 July 2011 15:17:19(UTC)
Rank: Super forum user
Zimmy

Gen sets are a little diff to what were are taking about re construction scaff but the links between joints need to be secure.

By the way, Less Harvey (Stone the Crows and Bro of Alex ) got killed in the top rank club here is Swansea many years back. If there had been RCDs on the circuit he'd still be here!

Please don't think I being funny here G but do you work out the loading/Volt drop/cable size etc to gen output mate? You may well need to use 16A/32 outlets and 20mm wiring and then drop down to 13A on stage?
Zimmy  
#11 Posted : 29 July 2011 15:18:22(UTC)
Rank: Super forum user
Zimmy

for 20mm please read 10mm
Darach  
#12 Posted : 30 July 2011 01:08:42(UTC)
Rank: Forum user
Darach

Hi again,

Forgot!, the NASC provide guidance on the earthing of scaffold structures as well,

http://www.nasc.org.uk/P...idance/Health_and_Safety



HARIDAS.P.V  
#13 Posted : 02 August 2011 14:36:05(UTC)
Rank: Forum user
HARIDAS.P.V

Thanks to all for the reply, especially to Zimmy.
In one of our site what we did is; for one of the cuplock we inserted an anchorbolt and connect it to the earthwire. This earthwire we have connected to the building earthing with a rod. After this we have calculated the earthing through the earth resitence meter and the resistance value is less than 0.5 oms. According to electrical engineer the whole structure of scaffolding is now earthed. Hope, this can be followed for every scaffoldings.
Zimmy  
#14 Posted : 02 August 2011 15:02:17(UTC)
Rank: Super forum user
Zimmy

HARIDAS.P.V. STOP!!!!!

THE ENGINEER HAS IT WRONG!!!!

Am I to understand that the resistance of the conductor you have connected to the rod is .5 Ohm? It should be no more than 0.05 Ohm for an equipotential bond (gas/water or any service pipe work). Or have you measured the Ra of the rod? If that is the case what method di you use? Battery tester or mains?

Have you connected the scaff to the main earth rod of the building and why?

As I said before, I have never heard od a scaff being bonded to earth before... please ask the elect eng to email me as I would love to follow this up on a pro level.
Zimmy  
#15 Posted : 02 August 2011 15:04:03(UTC)
Rank: Super forum user
Zimmy

You simply cannot be sure that every clamp on the scaff has good continuity and therefore between one section and the next you may have a leathal voltage difference
HARIDAS.P.V  
#16 Posted : 02 August 2011 15:27:19(UTC)
Rank: Forum user
HARIDAS.P.V

Zimmy,

I will inform my electrical engineer to go in deep in to this subject. The reason behind this study was becasue one of our technician while working in an elevator shaft on top of the scaffolding got electric shock and injured very badly.
As a control measure, HSE dept has insisted to go for all the scaffoldings inside the shafts should be earthed.

Earthing checking has been done at building earthing, all the shafts for checking the continuity and we found almost similar value which is less thand 0.5

I shall wind up this for the time being and we are going to make a detailed study on this.
Zimmy  
#17 Posted : 02 August 2011 15:36:41(UTC)
Rank: Super forum user
Zimmy

Forgive me Haridas

I was under the impression that the scaffold was external to the building. Internal is something quite different.

In this case it may well be a good thing. I just hope that the testing was not done with a Earth-fault-loop-impedance tester as this was not the thing to do. Re the bonding to any extraneous metal work such as water pipes etc the bonding cable should be no more than 0.05 Ohm end to end. 0.5 Ohm will give a voltage difference between bonded parts and hence a shock risk.
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