Dos And Donts Of Cable Recovery
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
notbecause in the real world, the task is distinctly
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.
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.
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.
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.
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
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.
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
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).
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 requireduse your judgement!
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.
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
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
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.
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.
site drawings plus jumpering and patching records,
then make copies.
walk the site and identify cable routes.
any anomalies on drawings and investigate.
active circuits; do they correspond with jumpering
remaining circuits for live condition. Are they connected
to switch or hub?
all new cabling required, test this and then cut over
users to new cables.
for the future!
Nagendra, Manager-Premise Networks, KRONE Communications
Ltd, India, can be reached at firstname.lastname@example.org