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The
tiny Fløyrli hydro power plant, tucked away neatly at the
foot of towering cliffs in a remote Norwegian paradise of fjords
and mountains, has spent the last 80 years doing its job efficiently.
Now it's time to take a new generation of power-producing technology
underground.
Early this century, Norway
started harnessing the vast potential of its countless high-altitude
lakes to generate hydro electric power.
Dozens of low-capacity
generating plants were installed to serve the needs of a small
population scattered across harsh and often inaccessible terrain.
| The
Rocket Boomer 353S: Coping effortlessly in the 1:5 gradient
tunnels. |
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A typical example - and one
of the oldest - is the Fløyrli plant, at the foot of the
precipitous east side of the Lyse Fjord in the wild and beautiful
region of south-west Norway. Built in 1917 and extended during
World War II, its five generators have a total output of 27 MW
and produce 166 GWh annually.
Water for the
old plant is taken from lakes above the fjord - and alongside
the pipeline is one of the world's longest wooden stairways. It
descends 700 metres to the plant and has 4,400 steps.
No road access
The plant is owned by Lyse
Kraft, the fourth-largest power producer in the country, which
has decided to close the outdated facility and replace it with
a more efficient, twin-generator installation of 160 MW, boosting
production to 300 GWh without increasing water consumption. Another
factor is that new environmental legislation from 2006 will outlaw
surface pipelines like the one at the site.
Construction of
the new power station is being carried out by Selmer, Norway's
biggest contractor. There is no direct road access from the site
and transportation of equipment and materials is by helicopter
- one of the drill rigs was airlifted - or by ferry, using a heavy-duty
quay which Selmer had to install before the project could start.
The quay has an adjustable ramp to cope with the tidal waters
of the fjord, which connects to the North Sea at Stavanger.
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Tight
team: Deputy Site Manager Eirik Moe (left) with Vegard Halden,
Atlas Copco Sales Engineer. |
Tunnelling at the
project is all drill and blast and involves a 2,200 m-long spiral
road tunnel with a 1:5 gradient and a cross-section of 27.5 m2,
a 1,500 m-long pressure tunnel with the same incline and cross-section,
and a 280 m-long, 20 m2, headrace tunnel. There is also a 16.8
m2 pressure shaft, 412 m deep, on which hand-held drills and a
raise lift will be used. The power house excavation is now complete.
Total excavation
for the tunnels and turbine halls is 170,000 m3 - all of which
is being tipped into the fjord. The composition of the rock is
identical to the glacial scree that falls into the fjord daily.
Men and machines
There are 35 tunnellers and
a drill rig fleet of three Atlas Copco jumbos at the site - Selmer
is a long-time user of Atlas Copco equipment. The tunnellers work
two weeks on, one week off, with two 10-hour shifts per day, six
days per week.
The fleet comprises:
A new Rocket Boomer 353S with three drilling booms, and COP 1838
rock drills on 18-ft feeds; a three-boom Rocket Boomer H 188,
upgraded with COP 1838 rock drills on 18-ft feeds; and a 20-year-old
Boomer H 115 with two booms fitted with COP 1032 rock drills on
12-ft feeds.
Atlas Copco Rock
Tools drill steel equipment is used throughout and rounds are
drilled to a depth of 5.1 m. Each round includes 62 blastholes
of 45mm and four 102 mm centre holes, drilled with Atlas Copco's
new R 35 Enduro drifter equipment (see Products & Progress,
Page 17). The tunnellers are achieving an advance of 4.7-5.1 m
per round.
| Inside
the control room: Newer technology will soon be replacing
the old Fløyrli hydro power station. |
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However, varying rock conditions
and water-logged fissured zones have caused some problems, says
Eirik Moe, Deputy Site Manager. These include difficulties in
charging the holes and the need for considerable grout injection
to seal against water leaks with a pressure of 35 bar.
There have also
been considerable rock bursts. Extensive shotcreting and bolting
is being carried out in the weak zones, using resin-grouted rebars
2.4 and 4 m long.
Face to face
The pressure tunnel is being
driven with the old Rocket Boomer H 188 and 600 m has been completed
so far. High speed drilling is necessary to reach the point where
access is gained to begin work on the pressure shaft. The Boomer
H 115 has started the headrace tunnel, having finished the access
tunnel, and the Rocket Boomer 353 S has reached the 650 m mark
in the spiral road tunnel.
Shift boss and
rig operator Erik Saltvik, a driller for 21 years, switches from
face to face to work with two of the Boomer rigs - the 188 and
the 353. He says: "I like the old 188 very much. I've handled
it from day one and there have been no real problems with it.
It's an extremely reliable rig which performs well.
"In fact,
it drills as well as the new 353 which we got in May, one reason
being that the 188 is equipped with the modern COP 1838 rock drills.
But the 353 is a good rig, as you would expect. A big difference
is the cabin, which makes working with the rig so much more comfortable."
| Lifeline
to the outside world: With no road access, transportation
for men and materials is by boat or helicopter. |
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Erik Saltvik is also a fan
of Atlas Copco's rock drills. "When I started in the job,
I was using Atlas Copco's first hydraulic drill - the COP 1038,
which I liked a lot. Its successors, the COP 1238 and the 1440,
were even better.
"But the
COP 1838 is outstanding. It's not only fast - it can go much longer
between overhauls and it's kind to the drill steel. I can drill
up to 75 metres between regrindings, and our average drilling
speed is 2.20 metres per minute."
Tough challenges
Workshop Manager Vidar Sundquist
has been with Selmer for 24 years and says: "I've learned
to appreciate Atlas Copco drilling equipment - it's reliable and
easy to work with. The old Rocket Boomer 188 has long been a favourite,
especially after I fitted the COP 1838 rock drills.
"However,
I'm convinced that the new rig will come out on top once we've
got a grip on its new technology and learned how to get the best
out of it. It has great advantages, such as the comfortable cabin,
excellent traction and high braking power - all of which are a
considerable help in these one-in-five gradient tunnels.
"This project
has, in fact, the steepest gradients I've ever come across."
And that is just
one of the many tough challenges in the construction of the new
power station, which is due to come on stream in January, 1999.
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