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The Do’s And Don’ts Of Cable Recovery

On the face of it, recovering old cabling is a total no-brainer. Tug the unwanted cable fairly hard and that's it. If that doesn't do it, you just pull a bit harder. Or perhaps not—because in the real world, the task is distinctly trickier.

Like so many practical tasks, recovering communications and data cable that is no longer needed is a straightforward operation. Straight-forward, that is, if it is carried out in a methodical fashion, taking all necessary precautions. Problems occur rapidly, however, if the job is rushed or undertaken without making preparations.

Preparation For Perfection
Groundwork is in fact the key secret of success, so let's start with this first. Before cutting and removing any cable, it truly must be redundant so identifying what's what is vital. You'll need the relevant cable plans plus all related jumpering or patching records (and work from copies, not originals). The task now is to confirm the accuracy of these and determine by physical inspection which cables are truly redundant.

In small self-contained buildings the task of tracing cable routes is normally simple; across far-flung factory and office sites or in campus locations with multiple occupancy, the job will be far more difficult. It's up to you to walk the routes and check that the plans accord with reality. Cables do not always take the shortest or most logical route; once ducts are full, installers often take alternative routes. Also, just because a building is now cleared of occupants, you cannot assume all its cables are no longer needed. We'll return to both these points later.

Any discrepancies or anomalies in the records will now be apparent and should be rectified by standard testing techniques; each and every pair must be identified. After all this, you'll be closer to being absolutely certain the cable you are about to cut is truly the one you imagine it to be. If some thoughtful soul has pencilled cable assignments in the lid of a distribution box, you're more than halfway there; even better if each cable carries individual markings.

Frequently this is not the case, however, and you may need to use a multimeter and apply tone tests to be certain a pair is really not in use. Even then, the absence of volts is no certain indication that a circuit is out of use; it could be a 'dry' speech circuit or one that is activated intermittently. Fire and alarm circuits may be bundled in with elderly telephone wiring, whilst inductive hum picked up from nearby circuits may mislead you. Mission-critical circuits, such as security alarms and fire sensors, must be double-checked.

How The Main Job Is Done
At this stage we assume you have installed replacement cabling, users have been transferred to this without loss of service and "all" that remains is to remove the old materials. Before starting this operation, however, it will be extremely prudent to have someone competent standing by and ready to do an emergency re-wiring job, just in case you failed to spot a working circuit in the cable you are removing.

Indoor runs of standard air-spaced cable are usually easy to remove, especially if you have access to the full extent of the cable. Lengths up to 20 metres can be released in one go if circumstances permit. Where physical damage might be caused to fitments and furniture or where the run passes through several rooms, it should be cut into more manageable lengths. Twisted-pair data cable tends to pull and snag; remove the whole lot in one go if at all possible.

External cable will be harder to remove and you will have to use all your ingenuity. The cable may need releasing from overhead catenary or else it may be laid underground, in ducts or buried direct. Old material is normally recovered but direct buried cable is best left where it is, especially if jelly-filled. With ducts you need to consider future requirements; if space is critical it may even make more sense to pull everything out and install new cable for circuits still active. Bear in mind too that a single cable (say a 600-pair) occupies less room than three separate ones (e.g. three 200-pair cables).

If you do need to remove cables from ducts remember they were new and flexible when originally installed, probably using lubrication. Now they will be stiff and dry, so beware of snapping them or snagging another cable that's still required—use your judgement!

Rules And Regulations
There are no specific health and safety regulations governing cable recovery, so good practice, common sense and standard safety precautions are all that need concern you. The cables we are dealing with are generally sealed and the only "risks" you are likely to encounter are (a) lead-sheathing on elderly telephone cables and (b) the petroleum jelly that can ooze from external underground cables (and this is merely messy, not hazardous to health). The only equipment you need is a hard hat, hard boots, some gloves and the normal tools of the trade.

Where People Go Wrong
Traps for the unwary abound in cable recovery. One of the most common pitfalls is cutting through cables without thorough checking. It can take days, not hours, to install replacements. Avoid working without proper planning or getting into a position where you can't go back or cannot consolidate the same day. Don't create problems for the future.

Avoid the classic blunder of running new cables into trays before the old ones have been recovered. Install additional trays if necessary, then recover the old ones along with the unwanted cables.

Beware of cable pairs taking "illogical", indirect routes. For some reason, usually shortage of cable pairs, a circuit takes not the direct route but the "long way round" to reach a user. The result is that a cable that appears to be completely redundant still carries a few pairs taking a circuitous route, and these must be diverted before the cable is removed. As well as "going round the houses", cables can in extreme cases take a long "out and back" path from the MDF or comms room to a user location that's not far at all from the point of origin. It's your task to sort out these oddities.

Finally, What Do You Do With The Old Cable?
That's simple. Take it to a scrap merchant who handles cables. He will burn off the plastic for the copper content and pay you money! Never even think of re-using cable; it has a finite life expectancy and old materials may conceal brittle fractures or moisture ingress points.

Summary Check List

  • Obtain site drawings plus jumpering and patching records, then make copies.
  • Physically walk the site and identify cable routes.
  • Mark any anomalies on drawings and investigate.
  • Verify active circuits; do they correspond with jumpering records?
  • Check remaining circuits for live condition. Are they connected to switch or hub?
  • Provide all new cabling required, test this and then cut over users to new cables.
  • Remove redundant cables.
  • Plan for the future!

D.S Nagendra, Manager-Premise Networks, KRONE Communications Ltd, India, can be reached at dra.ds@krone.com

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