Dando TERRIER Mk 1, Руководство по эксплуатации и техническому обслуживанию, Страница: 49 / 276

When drilling with large diameter bits it may well be necessary to increase bit
loading, by the addition of drill collars.
When carrying out rotary drilling, it is advisable to turn the top rod through a
guide held on the support table fitted at the bottom of the mast. The guide
table can be fitted with different sizes of replaceable wearing brushes to suit
the diameter of the drill rods being used. These guide brushes are subjected
to considerable wear and are easily replaced.
4.5 CORE DRILLING
Core drilling normally requires the application of high rotational speeds
combined with very precise bit loading. Where necessary additional
rotational speed is readily available by the fitting of a standard 4:1 oil bath
gear type speed increaser which simply bolts to the drive flange below the
rotary head.
Infinitely variable controlled and precise bit loading can be achieved at
shallow depths by using the Variable Feed Control - No.28 as described in
the previous paragraph under "Rotary Drilling" or at greater depths by using
gravity feed controlled by the Holdback Pressure Control - No.30 as
described in the previous paragraph "D.T.H. Hammer Drilling".
4.6 POINTS TO REMEMBER
1. LOSS OF ROTATIONAL SPEED AND TORQUE
Movement of the Holdback Pressure Control - No.30 will automatically affect
both the maximum speed and torque output of the rotary head.
Consequently, if there appears to be a loss of rotational speed and torque,
the first thing to check is that this valve is fully closed. As a general rule, this
valve should only be opened either to obtain a very slow rotational speed, as
may be required for air hammer drilling, or for screwing up rods, but generally
it should remain completely closed.
2. LOSS OF HYDRAULIC PULLDOWN HOISTING
This will automatically arise if the Variable Feed Control - No.28 is open.
WARNING: Holdback Pressure Control - No.30 should only be used when
drilling with holdback or gravity feed. Otherwise, this control should remain
fully closed, turned completely towards decrease. It should be borne in mind
that opening this control will also allow the rotary head to travel freely down
the mast under its own weight.
PRIOR TO RAISING THE MAST FROM THE HORIZONTAL POSITION
WHEN RIGGING UP, THIS CONTROL MUST BE CLOSED
.