Cable ladders 2

[carlosmelim]

We have to install a cable ladder in a big fuel storage compound. The cable ways are steel made and hot dip galvanized. Following the costumers demands we will only use steel armoured multiconductor cables.
The costumer also requires aluminium lids on the cable ladders to assure mechanical protection of the cables.

Since all the cables are steel armoured, multiconductor and the steel sheat will be connected to ground, is it really necessary to use aluminium lids? Can´t it be steel too?

Should we connect the metal sheat to ground only in one end of the cables or at both?

Looking forward to hearing from you all.

Carlos Melim

 

[busbar]

I wonder if maybe aluminum is specified for covers to limit rigging effort for cable access?

 

[carlosmelim]

Well busbar usually we use aluminium lids on cable ladders to prevent electromagnetic induction currents on the cable ladder itself.
This is very common when we use single-core cables even if they are laid in terns. If the lid is not aluminium ( or any other non-magnetic material ) there may be electrical sparks when removing the lid.

The client wants aluminium lids to prevent this type of situations.

But since the cables are steel armoured and multiconductor I wonder if the aluminium lids are really necessary...

 

[Ares]

I would ground the cable at both ends and derate the ampacity accordingly.
As far as cover material - even if you ground each cover to eliminate the induced spark, the posibility of steel hiting steel when closing the cover remains and that may produce spark.