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Lifting
the burden
of overburden
Bench
drilling through overburden can be a frustrating and messy business.
Rock fragments, stones and debris invariably tumble into the hole,
making it difficult - if not impossible - to keep clean.
So how does the
driller combat this problem? To start with, a sound general principle
is to disturb the overburden as little as possible and to stabilize
the hole when necessary.
There are various
methods of trying to clean the rubble out of the hole. One of
the ways is to wet the hole. This is often enough to stabilize
the walls of the hole sufficiently, as the moistened mud sticks
like shotcrete on the walls of a tunnel.
Golden
rules
And this is where Atlas Copco's
crawler rigs can make a great contribution towards easing the
driller's burden in overburden and saving time and money. An optional
water injection system on the rig, combined with reduced flushing
air, produces the so-called water-mist system - which does the
job and is simple, reliable and inexpensive.
| Equipped
to operate the water-mist system: An Atlas Copco ROC F7 crawler
rig, fitted with a pressurized water tank. |
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The water in a
pressure tank is pressurized by compressed air through a hose
with an adjustable nozzle. The right amounts of water and flushing
air are then easily controlled from the cab. The golden rules
for a successful operation are:
position the
feed on the ground so that it will not cause unnecessary vibrations
lift the drill
support and suction hood so that the operator can see to flush
the hole or check water flow
regulate the
flushing air pressure by constricting the flow
also regulate
the impact mechanism and feed pressure, preferably with one
or two pre-set combinations.
In order to
meet customer demands, all rigs can be equipped with the water-mist
system - whether they are tophammer, DTH, pneumatic or hydraulic.
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