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The privately owned Swedish utilities and quarrying
contractor BEFAB Schakt AB has been successfully
pioneering a Schaeff WS-30 excavator mounted milling
cutter attachment on major hot water pipeline
trenching projects in Sweden. BEFAB has found
the special, versatile cutting unit attachment,
to be more efficient, faster, cheaper, quieter
and less disruptive to traffic and local residents
than conventional road trenching techniques using
saws and noisy hydraulic breakers.
BEFAB, based at Mjölby, about 230km south
west of Stockholm, has used the WS-30 Cutting
Unit on numerous trenching projects, including
its most recent SEK4 million contract for trenching
3.5km of 200mm diameter insulated hot water pipeline.
The pipeline is part of an approximate 100km long
extension to the existing 310 km network of hot
water pipelines from the Linköping combined
district heating water and electricity generating
plant to residential and industrial properties
in the surrounding area.
BEFAB mounted the Schaeff WS-30 Cutting Unit
on a rotating quick hitch attachment, which is
fitted on the end of the dipper arm on one of
the company's Cat 315 or Atlas 1304 wheeled hydraulic
excavators in place of the host machines' standard
buckets. The WS-30 Cutting Unit is driven off
the host machine's hydraulic system and with its
rotating tungsten carbide tipped 398mm diameter
cutter, is initially pushed down to cut its way
about 200mm into the asphalt road surface. The
excavator is then operated to pull the cutter
towards the host machine leaving an approximate
700mm wide swath of pulverised material. Working
like a small cold planing machine the sequence
can be repeated in a series of steps to the desired
pulverising depth and length of trench.
After pulverising, the material can be left in
the shallow trench for traffic to run on prior
to the WS-30 Cutting Unit being replaced by the
excavator's standard bucket. The pulverised and
graded spoil, together with underlying base course
and some crushed rock, is dug out and placed in
a windrow alongside the trench for reuse, while
the remaining underlying material is excavated
to the required depth and taken away. The insulated
hot water pipe is placed on a 100mm thick bed
of sand, which is also used to cover the pipe,
prior to the pulverised material being placed
back into the trench on top of the compacted covering
of sand. The recycled material is also compacted
and the trench completed with new asphalt overlay
wearing course for a return to traffic.
"The WS-30 is a very good machine and nobody
else has used it for trenching operations before
in Sweden," says BEFAB production director
Nils-Gunnar Karlsson "We're pioneering it
here on trenching, but we originally bought it
for concrete demolition before we realised its
potential for trenching. The WS-30 gives us many
advantages over conventional trenching techniques.
Traffic can run on the pulverised material and
we don't need to keep long stretches of trench
open as long as we would need to to make conventional
trenching economically viable. With normal trenching
we would also have to temporarily cover the open
trench with steel plates until it was ready for
placing the pipe and backfilling."
Schaeff - Terex, Wortley Road, Rotherham, S61
1LZ, UK.
Tel: +44 (0) 1709 556076; Fax: +44 (0) 1709 552356;
Mobile: +44 (0) 7775 938811;
Email fpitkin@websterschaeff.co.uk; Web Site:
www.websterschaeff.co.uk
"The WS-30's milling operation also leaves
a jagged edge to the trench, which provides a
much better and stronger bonding interface with
new asphalt overlay than the clean saw cut edges
produced with conventional trenching. The WS-30
is also far less disruptive to traffic and local
residents with fewer lorries needed to take away
the unusable excavated spoil, making it especially
ideal for inner city operations. We can also work
through the winter with it in frozen ground, whereas
before with normal methods we had to stop. In
fact the WS-30 works better in frozen ground.
Average production is about 50m2/hour in 100mm
thick asphalt, but is dependent on strength and
age of the material and weather conditions."
BEFAB has further increased the versatility of
the WS-30 Cutting Unit by mounting it on a rotating
quick hitch. It can be used as a mini planer on
patchwork repairs, chamfering the sides of trenches
and by slowly turning the WS-30 on the special
quick hitch can also cut circular holes. "The
WS-30 is far more environmentally friendly, faster
and cheaper than normal trenching with saws and
breakers," adds Nils-Gunnar Karlsson, who
declines to be specific and reveal details to
potential competitors. "The WS-30 has generated
considerable interest here in Sweden and we have
had so many enquiries about it. I am sure these
excavator mounted Schaeff milling drum attachments
will become extremely popular on trenching projects
in the future replacing the traditional sawing
and breaker techniques."
The WS-30 Cutting Unit is one of a range of five
Schaeff cutting units available in Sweden through
distributor Sandhurst AB, based in the southern
Stockholm suburb of Älvsjö. Schaeff
has the world's most extensive range of cutting
units and is market leader world-wide.
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