Removing The Drill Bit; Breaking The Driver-Chuck Joint Using Percussion Only; Breaking The Driver-Chuck Joint Using The Bit Removal Tool; Dirt In The Hammer - Atlas Copco SECOROC COP 34 Manual

Breakout bench
It is always most convenient to
break the hammer threads on the
rig. For circumstances, when the
threads cannot be broken or tend to
get stuck, there is a breakout bench
available. Ordering No. 9178.
N.B. Failure to attach the wrench
as illustrated (B, C) may result in
damage to the cylinder. Any such
damage will not qualify for compen-
sation.

Removing the drill bit

The drill bit can be removed in a number of different ways, depending
on the tools available. The following two meth-
ods are commonly used:
A. Breaking the driver-chuck
joint using percussion only
Run the hammer into the rock or a thick plank.
Apply light feed force.
Carefully start the impact mechanism of the
hammer.
Stop the impact mechanism as soon as the
driver-chuck joint "cracks".
Run the hammer up the feed beam to a
suitable working height, and unthread the driver
chuck and drill bit.
N.B. Beware of the weight of the drill bit. It could
be too heavy to hold.
B. Breaking the driver-chuck joint
using the bit removal tool
If the driver-chuck joint is very tight, the special bit-
removal tool should be used to break the joint.
Important: Never use a sledge-hammer on down-
the-hole hammers.
Place the bit-removal tool in the drill steel support.
N.B. Looking from behind the feed beam, make sure
that the shaft of the bit-removal tool is touching the left-
hand edge of the feed beam.
Carefully run the bit down into the bit removal tool.
Slowly start up the impact mechanism of the hammer.
Stop the impact mechanism as soon as the
driver-chuck joint "cracks".
Unscrew the driver chuck by rotating the COP
hammer to the LEFT (anti-clockwise).

Dirt in the hammer

Stoppages and breakdowns caused by dirt in the percussion mecha-
nism are practically inevitable with all rock drills, and DTH hammers are
no exception. However, it should be remembered that, while DTH ham-
mers are no more sensitive to dirt than tophammers, there is obviously
a greater risk of dirt ingress in down-the-hole drilling, especially during
pipe jointing. Any dirt that enters the drill pipes goes straight into the
percussion mechanism. To ensure reliable operation of the hammer,
every effort should therefore be made to prevent dirt from entering the
drill pipes. The following rules should be observed:
Always keep drill pipes clean. Always store or stack drill pipes
in such a way that the risk of dirt ingress is minimized. Do not let
the thread ends rest on grit or mud. Use thread covers wherever
practicable.
Always keep the open thread end of the drill pipe covered during
jointing, and remove the cover just before the pipe is coupled up.
Before coupling up, check that the drill pipe is clean around the
threads and on the inside. If in doubt, blow clean the pipe. Remember
to cover the pipe end that is already in the hole.
If threads are dirty, they should be cleaned using a strong bristle
brush or a cloth.
N.B. Always clean away from the hole in the pipe. Do NOT let grit fall
into the hole in the pipe. After cleaning, always coat the threads with
Atlas Copco thread grease before jointing.
Take extra care during jointing operations when drilling in abrasive
rock formations, since the ingress of quartz particles into the hammer
will cause heavy wear.
When drilling holes in water-bearing rock, never leave the hammer
at the hole bottom with the air supply switched off. If drilling is to be
suspended temporarily, always pull up the hammer by at least two
pipe lengths.
Clean around the driver chuck before changing the drill bit. Make
sure the shank of the new drill bit is clean.
Keep the hammer clean and plug both ends when not in use.
Change worn or damaged parts in good
time.
All Secoroc COP down-the-hole hammers
contain a check valve that is designed to trap
a quantity of air inside the hammer when the
air supply is switched off. In most conditions,
this prevents the ingress of water and dirt
into the hammer during jointing operations.
The check valve A and O-ring B must be
fault-free when drilling in water-bearing for-
mations. When drilling deep holes in rock
with a high water infl ow, however, it is pos-
sible that some seepage of water into the
front of the hammer will take place during
jointing. Since only very small particles of
dirt would be able to penetrate the
hammer in this way, the threat to the
hammer is not serious.
The sealing effi ciency of the check
valve can be checked by pouring
a small quantity of lubricant through
the top sub of the hammer, with the
hammer held vertical. If the lubricant
passes through the checkvalve, then
the valve spring and/or valve seal
is worn or damaged and should be
replaced immediately.
WARNING
Take great care when jointing the drill pipes and handling the drill
bit.
Mind your fi ngers!
Keep your clothing, hair etc. well clear of rotating components!
Carelessness can result in serious injury.

Other instructions

Wear to the driver chuck and hammer cylinder
Since the driver chuck and hammer
cylinder are "sand-blasted" continuously
by large volumes of abrasive cuttings
during drilling, they eventually be come
worn out. The areas adjacent to the
cuttings grooves in the drill bit will
be subjected to the most wear. To pre-
vent uneven wear of the hammer cylin-
der, therefore, the driver chuck and bit
should be marked as shown in fi gure,
before the chuck is lifted off the bit.
When fi tting the driver chuck back on
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