evation and creep feed circuits have flow control
valves in line to limit the maximum component
speeds. The boom elevation rates are controlled
from within the cab. The creepfeed speed valve,
used to limit the infeed speed of the drum into the
face of the tunnel while driving the tunneler for-
ward, is located in the rear of the tunneler near
the solenoid valve controlling the circuit. The
boom's slew circuit pedal on the floor has been
covered with a metal guard to prevent its actua-
tion, which will potentially damage the wiring and
hydraulic hoses added during the equipment
modifications and running adjacent to the boom.
Cab swing is restricted using the swing lockup pin,
located to the right of the operator. This allows a
few degrees of rotational motion of the cab for cor-
nering and alignment, but not enough to damage
the hydraulic hoses running beneath the cab.
Inside the cab, various readouts critical to the
operation of the system are available (Fig. 11). A
vacuum gauge, which taps into the ejection line
adjacent to the cab, allows the operator to moni-
tor available suction on the discharge system.
Available suction with no load is approximately
18 in. of water (4.5 kPa) at the cab when all chip
transfer components are on line. When the read-
ing drops below 10 in. (2.5 kPa), the system is over-
loading and needs time to recuperate. This gauge
was critical to the smooth operation of the system
and saved us many shutdowns. The reduction in
Figure 10. Control pendant in tunneler operating cab.
the number of times the fan had to recover from
Figure 11. System function readouts in tunneler cab.