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Posted By Sean Nuttall
Quick query,
we are preparing plans for starting some minor construction activity on an area between two existing buildings. The client has powered one of the existing buildings by running a 415v cable at height from the top of the roofs. We need to move vehicles and plant underneath this cable to access the work area. The lowest point of the cable (in the middle) is 5 metres which would give a clearence of 0.80cm from the highest point of the tallest vehicle that will pass underneath (This is for the delivery of a container and its removal at the end of the project). Everything else is much lower. As there is no danger of arcing; is there any guidance on minimum clearence requirements ?
All the guidance, I can find, quite rightly refers to be for HV cables.
The erection of a warning layout as per HV cables seems a little overkill especially given the only vehicle coming close to the cables will still give 80cm clearence however I accept that the consequences of a contact are somewhat unpleasant.
Any ideas ?
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Posted By Mark Mace
i work for a transport operation and clearance is usually generally believed to be 16 feet,
if you are unsure whether the vehicle will fit ensure the vehicle is watched closely on initial entry and final exit from the site.
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Posted By Alan Hoskins
Hi Sean,
I presume that the cable is an insulated one?
If so then the only risk would be if the trailer caught the cable and pulled it down, so with almost a metre clearance, keeping a good lookout should be sufficient.
Alan
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Posted By Cr8r
Hi Sean
Will anyone else's vehicles have to pass under here? eg skip lorries, waste removal lorries? You mention your own plant as well, is there any likelihood that the plant will work in this area or that their height will be different - eg a skip lorry's height will go up when it works, as will a digger, dumper, grab lorry or crane. If you have anything like this going on, I strongly suggest you think of re-routing the cable, as sooner or later someone will bring it down.
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Posted By Sean Nuttall
Am inclined to agree with the use of a banksman as one will be in place to reverse the vehicles across an adjacent car park prior to entering the compound.
To answer a few questions;
The cable is insulated hence no risk of arcing.
Activities will take place some 30 metres beyond the cable at the place of work such as use of excavators that could technically approach 5 metres if fully extended and aimed skywards but this is unlikely.
All tippers approaching the construction area are low bodied 8 leggers.
Banksman it is I suspect.
And yes the client should have excavated a trench and buried the cable but that is outside the remit of our work.
Thks for replies
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Posted By ian mcnally
Sean,
If you control this access route I would concur with much of the advise already given. I agree with Mark that 16 feet AGL should be enough to clear most high sided vehicles.
I think rerouting the cable may be unnecessary in this instance but do consider good clear signage red/white barber shop style poles with bunting across the entrance as far as practical below the cable and if you can ensure that the companies likely to be involved with any planned deliveries are given written warning then all the better, all this should help minimise the risks. Having said all best made plans……..
Good luck
Ian
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Posted By Robert.
I would assume that the cable is an SWA. Hieght is fine----but
May be worthwhile considering the sag element and add a supporting catenary wire with tensioner. Although you mention a 415 supply you haven't mentioned the CSA of the cable or No of cores, which could be a critical weight factor and that may require additional support.
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