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Trying to
locate
damaged
subsea power
and
communications
cables has
always been
a difficult
job.
Regulations
require
cables be
buried from
several feet
to several
meters under
the ocean
bottom to
prevent
snagging by
boat
anchors,
fishing
nets,
lobster
trawls, etc.
The amount
of
overburden
on a cable
often means
it’s too
deep to be
located with
conventional
metal
detection
equipment.
The device
that has
proved most
effective in
finding them
is a cable
tracker.
This system
has two
parts, a
signal
injector and
a probe.
The injector
is attached
to the shore
end of a
line and
induces a
signal into
one of the
conductors.
The probe is
carried by a
diver, or
used from a
boat in
shallow
water, and
detects the
electrical
pulse
transmitted
through the
wire.
Live power
cables do
not require
a signal to
be induced.
The probe
can easily
detect the
50 or 60
hertz
frequency in
the line.
Live
communications
cables can
also be
detected
without the
use of the
signal
injector as
the probe
will detect
the 1,024 Hz
tone.
One
company that
recently
completed a job
with help from
this tool is
Hydo
Marine
Construction, a
division of The
Castle Group.
Company founder
William Castle
has been
providing marine
and structural
engineering
services for
almost 30 years,
and has served
on a number of
industry boards
including the
Association of
Diving
Contractors
(ADC). Hydro
Marine was
called on to
assist Atlantic
City Electric in
locating and
repairing a
damaged
submarine power
line off the
New Jersey
coast. The
first hurdle
they faced was
finding the
cable, which was
buried 4 to 9
feet under the
ocean floor.
Using JW Fishers
CT-1 cable
tracker, a
signal was
induced into the
shore end of the
line.
Hydro’s
divers then used
the CT-1 probe
to locate and
follow the cable
until they
pinpointed the
exact location
of the break.
Buoys were
deployed to mark
the spot, and a
water jet was
employed to
excavate the
cable. Divers
rigged it with a
sling, and
raised it to the
surface with a
crane. Once on
top, the cable
was anchored
onto the
company’s barge.
A crew from the
electric company
worked with
Hydro’s
team to cut out
the faulty
section and
splice in a new
piece. When
repairs were
complete, the
power line was
lowered back to
bottom and
reburied.
Another
outfit using
the cable
tracker is
Michigan
based
Durocher
Marine,
which
specializes
in difficult
marine and
heavy
construction
projects
throughout
the
US and
Caribbean.
The company
performs a
broad range
of work that
includes the
installation
and
maintenance
of submarine
power and
communication
cables.
Durocher
was
contracted
to locate
several
underwater
cables at
NRG Energy’s
Norwalk
Harbor
Generating
Station in
Connecticut
and mark
their
position.
Project
manager Tim
Paquette
contacted JW
Fishers, a
leading
manufacturer
of
underwater
search
systems, for
the right
equipment.
Fishers
supplied a
CT-1 cable
tracking
system,
several
acoustic
pingers,
and the PR-1
pinger
receiver.
Paquette
reported.
“With this
equipment we
were able to
quickly find
the cables,
follow their
path, and
mark their
position
with the
pingers.”
Located
in the
United Arab Emirates
is Southern
Gulf
Surveys, a
company with
substantial
knowledge
and
experience
in
Hydrographic,
Topographic,
and
Geophysical
surveys.
Best known
for their
work in
dredging and
reclamation,
they have
provided
services to
many
international
clients.
Recently the
company was
hired to
find and
track
several
power
cables.
Managing
director
Stephen Hart
reports,
“The
CT-1 cable
tracker is
doing its
job. The
cables we’re
searching
for are 11
KVA and
50Hz. We
got good
signals both
on the beach
and
offshore.
We found the
cables 70
meters out
of position
and buried
down 1.5 to
2 meters.
They were
supposed to
be 15 meters
apart and
buried down
half a
meter. The
client
commented
that we’ve
done what no
one else
managed to
do!”
For more
information on
JW Fishers
complete line of
underwater
search equipment
go to
www.jwfishers.com.
For more
information on
Hydro Marine
Construction go
to
www.wjcastlegroup.com. For
more information
on Durocher
Marine go to
www.durocher.biz.
For more
information on
Southern Gulf
Surveys go to
www.sgsurveys.ae. |
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