8
Too little water tends to bind the drill cuttings into a paste, which
sticks to the drill pipes or the hole wall and can easily form collars
or plugs. The problem can be lessened by adding water to the
flushing air, thus increasing the fluidity of the cuttings. Fluidity can
be further improved by adding washing detergent to the water.
N�B� Remember to increase the lubrication dosage when injecting
water into the flushing air!
If the inflow of water is so great that it restricts the bailing of cut
-
tings and water from the hole, then extra flushing will be needed.
See "Extra flushing".
Water injection
Water injection is normally used to suppress dust when drilling
dry holes. COP down-the-hole hammers are designed to function
with a certain amount of water injection. As an example, only 2—6
litres of water per minute (at 18 bar air pressure), injected into the
main air line, is sufficient to control the dust when drilling with the
COP 64. Too much water injection will have a very negative influ-
ence on the penetration rate of the hammer.
Rule of thumb: 0,25 l water per m
3
com pressed air consumed by
the hammer during the drilling sequence�
The injection point for water and foaming concentrate should
always be located after the main shut-off valve on the rig.
If not, there is a danger of the mixture being pumped back
through the main air line and into the compressor. This could
seriously damage the compressor.
CAUTION
Flow chart for water flushing
A = Main inlet valve on drill rig K = Water tank
B = Container for air tool oil N = Compressor
C = Filter O = DTH-hammer
D = Lubricator valve
E = Pressure gauge Optional
F = Check valve L = Separate foam pump
G = Valves M = Separate foam tank
Foam injection
Foam can be used in DTH drilling to improve the flushing perfor-
mance (especially in non-consolidated formations). It does this by
“lifting up” the cuttings out of the hole, and also has the desir able
effect of sealing the hole walls. Foaming concentrate is pumped
into the compressed-air line in the form of a concentrate/water
mixture. Atlas Copco foaming concentrate has lubricating proper-
ties and contains corrosion inhibitors, which prevent seizing in the
hammer.
N�B� Before using foaming concentrates not supplied by Atlas
Copco, please consult your Epiroc representative for advice.
With Atlas Copco foaming concentrate, a mixture of 0,5–2 percent
concentrate/water is normally recommended. When drilling in
water-bearing rock and other difficult formations, it might be nec
-
essary to increase the percentage of concentrate, and also to add
polymers to the operating air. This will help to stabilize the hole
walls and increase the lifting capacity of the foam. The concentrate/
water mixture is injected into the main air line by means of a high-
pressure pump.
Minimum requirements for the water-injection pump are as fol
-
lows:
• min. pressure = 30 bar
• min. flow = 20 l/min.
After drilling with foam, it is recommended that residual foam
should be flushed out of the hammer to prevent corrosion. This is
done by injecting water only into the air, and so flushing the foam
out the hammer. Oil should then be poured into the drillstring and
the hammer operated for a few minutes before the drill string is
withdrawn from the hole. If the hammer is then to be stored for a
long time, it should be dismantled and all parts cleaned and oiled
thoroughly.
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