SWA Cable Tracing

[caveman78]

I have multiple large looms of various cables that I need to trace. These are various services including power, fibre, copper, other 'unknown' cables etc...
I want to be able to trace a single cable using the SWA. I want to remove a section of the outer sheathing and put a tone on the SWA and do the same further down the line of cables to identify the specific cable.

The area I'm working in is a service tunnel with multiple levels of tray that is now inaccessible due to other installs over the last 20+ years making physically tracing a single cable very time consuming and a high risk of 'losing' the cable during tracing.

I've seen a few of the cable tracing devices on the market but they all either need the cable to be dead, use a pair or core of the cable to tone etc... I can't seem to find anything that I could use in this way.

Any ideas?
Cheers

 

[westward10]

Can't see that working as the armour is almost certainly going to pick up parallel paths.

 

[James]

I think the device you are looking for is yet to be invented.
sorry.

 

[davesparks]

If you can disconnect both ends of the cable completely so that the armour is not connected to earth then any tone generator and probe should work.

 

[Simon47]

Or, instead of disconnecting the screen/armour, I vaguely recall there being devices that will induce a current in it which you then detect with a pickup in much the same way as a tone set.
Be prepared for a lot of crosstalk though. So having detected the induced tone, you need to do secondary tests to make sure you really do have the right cable.

 

[Strima]

I've tried various cable finders on installations like that, none of them worked as the tone ended up on every single MCB in the board... ?

 

[R-fur]

I use a cable identifier made by a company called Lee Vaughn. you put a signal up one core and down another. You get some cross talk but if you move the receiver along the cable you hear the tone rise and fall due to the lay of the cores. It is designed to identify cables in a trench before cutting or spiking.

 

[Marvo]

I had a similar job many years ago in a water treatment plant. It was also a tunnel that was about a kilometer long and had dozens of SWA cables in a mess similar to yours. After trying various live and dead tone sets we just put 2 apprentices in there for a week with packs of cable ties and number markers they manually traced every cable and put a tie and number on them every meter.

 

[freddo]

Load the cable heavily and find the cable that is hot?!

 

[davesparks]

Load the cable heavily and find the cable that is hot?!

Connect the armour to a low frequency signal, say 0.5Hz and hold a compass next to the cables?!

 

[sinewove]

Connect the armour to a low frequency signal, say 0.5Hz and hold a compass next to the cables?!

Connect a known load at far end,switch on and off and have a mate with clamp meter at other end untill you find the right cable.
S

 

[Simon47]

They all assume you know both ends of the cable - that's not always the case.
The other (destructive) technique is to spike the cable. If there's just a little bang (from the spike charge) then it was dead. If there's a big bang (and the spike is now half missing) then you look for somewhere where the lights have gone out, and for a blown fuse/tripped breaker
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Of course, these are metallic cables which means these various techniques are available.
Now consider something like a science park where management have allowed various tenants to install their own fibre optic cables between buildings using the campus owned ductings. And said management have not kept any records, and apparently see no reason to manage such things
So ducts starting to get full of mixed fibre optic cables, all non-metallic (some F/O cables have a tracer wire in them to allow use of tone sets for locating them - but none of these do), and no records of where they might go. Some might be 1/2 mile long (or more) between buildings and only visible at the manholes.