Depends on the situation - for example if it's an environment for telecoms or IT equipment it might be required under BS EN 50310 - where additional bonding to form a mesh or grid might be needed for EMI or functional reasons rather than just shock protection.

  - Andy.

It looks a bit belt and braces to me - there appears to be excellent metal-to-metal contact without the straps.


Could the ladder be functioning as a CPC? If that is the case, the straps are part of the CPC rather than bonding.

It is carrying armoured sub mains cables.

If the tray is a CPC,  these little links serve no purpose - like the proper joints, if the bolts are loose, neither connect.

Also for EMC / EMP handling, there is little point in adding a relatively high resistance braid in shunt with a nano-henry micro-ohm connection of the fishplates.

Specifying Nordlock washes would be more used if coming loose is a risk.

IF the jointing plates were painted, perhaps there would be some point.

The  purpose here is to give someone something to inspect, and perhaps to oblige someone allow time for an extra task to go along

and be very careful to tighten the bolts.

If any BS really requires this for any electrical purpose, then in this application it is indeed BS.

..and yet almost every specification I see calls for it...

There are four strong bolts and nuts each side of the joint, so the braided link seems unnecessary. The joint seems quire capable of carrying thousands of Amps if necessary, under fault conditions, whilst automatic protection operates without the braided link.


Z.

mrf:

..and yet almost every specification I see calls for it...

Mine don't - except where the containment system has deliberate fishplate joints for variable angles to be adopted, where the ladder or tray may be discontinuous and where I actually wan to introduce a bond (if the containment is extraneous)


In a previous life I had the opportunity to be involved in some cable ladder tests - just adding bonds to splice joints might just achieve about 0.12% improvement in conductivity over a substantial length. Credibly loosing all the connections one side is highly unlikely.


We also hit the containment with test currents in the 80kA region - both with and without links - no credible differences recorded.


If it's put in using proper materials and workmanship, the bonding links don't  have any useful purpose. The requirements however are still in such places as US based standards, UL certification and a host of glabal company standards


Regards


OMS

I hope those are not gutter bolts I can see through the perforations..................


Regards


BOD

I suspect not, Bod - judging by the square sections designed to stop rotation in the slotted section.


Shortage of washers at installation however


Regards


OMS

I worked on a little project on the Isle of Grain Natural Gas hub. We used 3 lengths of 6 inch cable tray on its own with 3 small SWA cables. They insisted we bonded the lengths together but couldn't give me a reason why the connections using the couplers wasn't sufficient, just "thats the rules here"