SECTION 4 – GUIDANCE FOR DRILLING APPLICATIONS
4.1 DRILL ROD HANDLING
To enable rotary drilling work to be carried out efficiently it is essential that all
practical steps should be taken to enable the drill rods to be handled as
easily and quickly as possible. It is recommended that particular attention
should be paid to the following points:
1) The drill rod joints usually have wrench flats cut in to them. By placing
the wrench in position on these flats the rods are not only supported but also
locked ready for making or breaking the joints.
2) The rods should be suitably positioned in front of the rig. Valuable time
can be saved by the provision of suitable stands, preferably with roller tops.
3) It is advisable to keep the threads clean and coated with high pressure
tool joint grease.
Drill rods are connected and disconnected from the rotary drill head by
handling them to and from the horizontal in front of the rig.
The drill head itself is tilted by attaching the tilt wire to the hook provided on
the head as the carriage is being lowered. Continued downward movement
on the carriage will automatically tilt the head to the desired angle.
The drill rod box end can then be lifted and offered up to the driving pin, and
by rotating the head the joint will be screwed up. By raising the carriage
assembly, the drill rod will be lifted and the head will automatically swing
back allowing the tilt wire to be detached.
When handling the rod, the carriage assembly is quickly raised and lowered
by operation of the spring loaded Rapid Hoist/Feed Control Lever - No. 26.
4.2 D.T.H. HAMMER DRILLING
The main requirements for D.T.H. hammer drilling are slow speed rotation
and requisite feed control combined with accurate load control by operation
of the spring-loaded Hoist/Feed Control Lever – No. 14.
The necessary slow speed rotation is obtained by moving the Holdback
Pressure Control - No.30 towards the DECREASE position.
The feed control must be set to suit the rate of penetration of the hammer
which will vary according to the type and hardness of the formation.
It is important that the load on the hammer should be maintained as
accurately as possible within the limits recommended by the manufacturer in
order to allow for efficient drilling. This load must be varied according to the
type of formation being penetrated and in hard formations it is possible to
judge from the size of the particles being ejected in the return air stream as to
whether the controls are correctly set.
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