Volumetric removal rate: 18 m3/hr (0.005
large speed reductions may even have saved the
m3/s: no bulking factor)
replacement blower motor. A temperature gauge
for the hydraulic oil is also located in the cab. Keep-
Mass flow rate (snow): 2.5 kg/s
Working air temperature: 40C
ing the oil temperature at an acceptable level was
difficult because the tunnel was 10C warmer than
Working elevation: 3,500 m
predicted. When oil temperatures exceeded 50C,
Working air density: 0.98 kg/m3.
measures such as removing guarding were carried
out. If the temperature exceeded 60C, additional
Using these parameters, the fan manufacturer
measures were taken to lower the temperature. If
(TILCO, Hampton, N.H.) sized a system with the
a temperature of 80C was reached, the system was
following parameters:
shut down and allowed to cool. A 45C tempera-
Volumetric flow rate: 1.287 m3/s
ture drop in 20 minutes was recorded during one
shutdown, so the time required for the system to
Static pressure: 6.76 kPa
cool is not long. Tilt sensors allow the operator to
Power requirement: 16 kW
Impeller size: 57.5 cm diam. 26 cm wide
gauge the position of the drum as well as deter-
mine the pitch and roll of the machined tunnel. A
(304L SS)
tilt indicator on the boom provides the operator
Impeller speed: 3318 rpm.
with an indication of the boom position. As cur-
rently configured, the indicator reads "0" when
Tests conducted at CRREL indicated that the
the tangent point at the bottom of the drum is co-
impeller speed was too high, so the sheaves on
planar with the bottom of the tunneler tracks on
the fan were changed out to decrease the speed.
level terrain. A negative reading brings this point
The volumetric flow rate of the fan is now 1.210
m3/s. Using this information, the following val-
below level, and a positive readout raises this
point. Boom angles for specific tunnel heights can
ues were derived for the new configuration:
be empirically determined using a measuring tape.
Mass flow rate (air): 1.164 kg/s
Mass flow rate (combined): 3.664 kg/s
Chip disposal system
Volumetric flow rate (combined): 1.215 m3/s
Disposal of the chips generated while machin-
ing the tunnel was the demise of the Russell Miner
Snow concentration in stream (steady state):
0.4% (volumetric) 68.2% (mass)
at Camp Century and difficult at best with the rail
Mixture density: 3.01 kg/m3.
system deployed at Camp Tuto. The main prob-
lem with the Russell Miner system was the heat-
The fan is attached to a sled-mounted vibration
ing of the chips during transport and their subse-
isolation platform designed to be either towed by
quent refreezing to the vane-axial fans powering
a Spryte or forked into place. A tapered inlet has a
the system. Pneumatic conveyance, if made to
built-in shutoff (blast gate) to assist in startup, and
work, is vastly preferable to the trolley system de-
the outlet has a directional chute for guiding the
ployed at Camp Tuto or mechanical conveyance
debris (Fig. 12). Although the manufacturer noted
systems, such as the screw augers used to replace
that the fan can be placed anywhere along the dis-
the Russell Miner's pneumatic system. To work
charge, we located it on the surface due to the ex-
reliably in the harsh environment of the South
treme sound power levels (116 dB). The fan origi-
Pole, a mechanical system would have to be so
nally came equipped with a 30-kW electric motor
robust as to make deployment by hand arduous.
that was replaced with a 37-kW motor after the
Maintenance, especially lubrication, would also be
original failed. The motor is protected with a
difficult. For these reasons, pneumatic conveyance
Baldor/Lectron soft-starter, rated to 75 kW.
was once again considered.
In the tunnel, the chips are conveyed longitu-
The parameters for sizing a pneumatic convey-
dinally through a series of four sets of expanding
ance system are air temperature, air density, sol-
tubes on adjustable trucks (Fig. 13). Directly be-
ids density, solids volume, and conveyance dis-
hind the tunneler is a two-tube unit that allows
tance. The following parameters and derivations
1.5 m of travel. This allows the operator to move
were used in sizing the fan used to power the
the tunneler back and forward without stressing
transport system:
the large units. The large units consist of three
Tunnel cross section: 2 m wide 3 m high
tubes, two sliding, and allow 6 m of travel before
full extension each. Collapsed total length is 16 m;
Production rate: 3 m/hr
10
Previous Page
