- Atlas Copco

Talking Technically
Development through interaction
Single- or multi-pass
drilling
The medium scale Pit Viper 270
series drilling rigs provide 75,000 lbf
(340 kN) force on bit and can be
equipped for either rotary or downthe-hole (DTH) drilling. They combine structural features of the
PV-351, and components successfully used on the DM45, DM-M2
and DM-M3 models, and some
new ones, including Tier II engine
options. These features were incorporated as a result of extensive discussions with customers
already using the Drilling Solutions equipment range and with
other professionals interested in
the application of the Pit Viper
concept at this scale of rig.
Low center of gravity
Clearly an essential quality for this market is f lexibility, though the design
engineering team could not ignore the
across-the-board industry requirement
for maintenance convenience and cost
effectiveness. These two characteristics
are evident from the PV-270 crawler
tracks through to the choice of singlepass or multi-pass drilling.
The PV-270 machines offer a choice
of proven Caterpillar and Atlas Copco
undercarriages to enhance their compatibility with other mine fleet members.
The PV-271 is built with the extended
version of either the CAT 345XL or
the Atlas Copco GT3400, while the
PV-275 can have either the standard
19-foot 6-inch (5.9 m) CAT 345XL with
GFT110 final drive or the ACGT 3400
tracks.
The design and testing process used
for the PV-270 main frame was generally similar to that for the Pit Viper 351.
To ensure long frame life without rebuilds, the I-beam used is 24 inches
thick with a cross section of 162 lb./ft.
– smaller than the PV-351 frame but
larger than the one used on the DM-M3
rig. The structure achieves a low center of gravity for good stability and
Pit Viper 275 used for blasthole drilling in South African coal mine.
reduces drilling vibration. Single pass
stability ratings, adjusted for dynamic
conditions, are 5° with cab facing
downhill and 8° tramming across the
slope, both with tower up, and 10° with
tower down, cab facing uphill. The equivalent multi-pass figures are respectively 11°, 13°, and 16°. The rigs also
offer the customer a choice between a
standard three jack configuration and
four, with the rear jacks tied as on the
Pit Viper 351.
Power options
The power system setup for the PV-270
series machines is structurally similar
to that on the Pit Viper 351 but includes
a choice of matched engines and compressors suitable for the rotary or downhole drilling options. The engines offered, which are Tier II compliant, are the
760 hp (567 kW) Cummins QSK 19,
the 800 hp (597 kW) Caterpillar C27,
and the larger 950 hp (709 kW) Caterpillar C32. There is a single side-by-side
hydraulic/compressor/radiator cooler
package.
The Ingersoll-Rand compressor options are a 1,900 CFM (900 l/s) unit or a
2,600 CFM (1230 l/s) supplying 110 psi
(760 kPa), plus a 1,450 CFM (680 l/s)
air compressor delivering air at 350psi
(2,400 kPa) for downhole drilling. The
CAT C32 engine is fitted on those rigs
using the 2,600 CFM compressor.
The electric power pack option comprises alternatively a 700 hp (520 kW)
WEG 6808 motor running on 6,000 V
AC/50 Hz current and coupled with
an 1,800 CFM/50Hz Ingersoll-Rand
air compressor, or a 900 hp (671 kW)
WEG 6811 motor running on 4,160 V
AC/60 Hz power that is coupled to
the Ingersoll-Rand 2,600 CFM/60 Hz
air compressor. An electric powered
version for downhole drilling is available for the PV-270 machines, albeit
limited to 1,070 CFM and 350 psi for
50 Hz application. The motor is totally
enclosed and is cooled by a fan with
the highest rating in the industry, which
allows the unit to operate without a machinery house. An oil-immersed nonflammable 40 kVA transformer protects the motor, providing 380 V AC
for the extensive heating package used
for all the reservoirs. The high voltage
safety circuit and the operator controls
run on 110 V AC that is converted to
Blasthole Drilling in Open Pit Mining73
Talking Technically
The PV-275 can be used for angle drilling with 0 - 30° adjustment in 5° increments.
Photo from an Australian coal mine.
24 V DC so that the electric machine
can use the same components as the
diesel-driven rigs.
Experience shows that electric motors typically last 20,000 – 30,000 hours
before replacement or rebuild in this application, as compared with the 10,000
– 14,000 hour life usually attained by
diesel engines. This is one reason why
there is growing interest in the electric
Pit Vipers, to which Atlas Copco has
also responded by matching the electric
power pack to a mine’s available power
supply. For example, four PV-275 rigs
have been delivered to the Moroccan
phosphates producer Office Chérifien
des Phosphates (OCP) for operation at
5,500 V AC.
Like that on the PV-351, the hydraulic system for the 270 series utilizes a
leak-free, clean specification. However
it has the single gearbox and three
pumps configuration used on the
DM-M3 rig, albeit with larger units;
using fewer components has proved to
reduce operating cost. There are two
main pumps for feed, rotation and propel, while the double pump supplies the
auxiliary functions.
The air cleaners are similar to those
on the PV-351, with one provided for
the Cummins engine, two for the CAT,
one for the 1,900 CFM air compressor
and two for the 2,600 CFM unit. These
and the other serviced units are easily
accessed from the PV-270 deck, which
is designed on similar lines to that of
the PV-351, while retractable ladders
are also available.
Three towers
The PV-271 live tower is dimensioned for 55-foot single-pass drilling, there is also a 65-foot clean hole single
pass drilling tower option where the rotary head and tower has to be down when moving the drill rig.
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The two machines comprising the Pit
Viper 270 series are primarily differentiated by their towers. These are of similar construction to those on the PV-351
but are new designs, not stretched or
lighter weight versions of the existing
design.
The PV-271 live tower is dimensioned for 55-foot (16.7 m) clean hole
single-pass drilling. Like the PV-351
it does have a two-rod changer, in this
case for 25-foot rods enabling drilling
to a total depth of 105 feet. With a fourrod carousel holding 40-foot pipe, the
PV-275 is designed for multi-pass drilling to a maximum depth of 195 feet.
Blasthole Drilling in Open Pit Mining
Talking Technically
The PV-271 Rotary head.
The rigs with the RCS option are fitted with the new state of the art PV-235 cabin, featuring excellent
visiblity and comfort..
There is also a 65-foot clean hole tower
option, but with this unit one drill pipe
must be racked and the rotary head
brought down in order to lower the
tower for relocation.
Like the power pack, the variable displacement rotary head for the PV-270
rigs is very similar to the proven design
used on the DM-M2 machine. The rotary head also has a filtered lubrication
pump to keep the motor splines lubricated. Equipped with two motors the
188 hp (252 kW) rotary head delivers
up to 8,700 foot pounds (11.8 kNm) of
torque. Maximum speed is 150 rpm.
Internal spur gear speed reduction gives
better torque on rough ground and in
other circumstances where the head
stalls later than other designs.
The hydraulic rod support with
automatic actuation is essentially the
same as that proven on the DM-M3 rig.
There is also an upper fixed rod catcher.
Again like the PV-351, the Pit Viper
270 series drilling rigs use the cable
feed system introduced on the DM-M3,
however with some redesign to achieve
faster feed speeds. The feed rate is 127 ft.
/min. (38 m./min.) and the retract
rate is 158 ft./min. (48 m./min.). The
automatic tensioning is derived from
the PV-351 system which has proved
problem-free to date. The pipe handling
system on the PV-271 is similar to that
on the PV-351, and the PV-275 is similar to the DM-M3. The PV-270 series
machines also use the same patented
system for angle drilling as the Pit
Viper 351, with 0 - 30° adjustment in
5° increments for the multi-pass PV-275
and 0 - 20° adjustment in 5° increments
for the single pass PV-271. These rigs
are quite widely used for angle drilling,
both in coal mines and in metal mines
for toe blasting.
Cab commonalitys
There are two different cab options
available for the PV-270 series. With the
development of the RCS option, we
have incorporated the new state of the
art Pit Viper 235 cabin into the PV-270
machine design. While rigs without the
RCS control system are fitted with the
same single piece cab as that used for
concurrent DM45, DML, and PV-270
machines. It meets the FOPS requirements of ISO 3449 Level 2, is thermally insulated and pressurized, and has
adjustable vents for climate control. The
air conditioning unit is side mounted,
which, along with other detailed features, makes this cab easier to service
so no roof access is required. The sound
damping has been tested down to 70
dB(A). The operator enjoys excellent
visibility over the ergonomically designed wrap-around console. The controls are predominantly electric-overhydraulic sticks.
Options
As well as the four jack system, options
available for the PV-270 series rigs when
they were introduced included a dry
dust collector with 9,000 CFM blower,
four-camera system with LCD monitor,
buddy seat, water injection, fire suppression, cold weather package, a central fast
service system, high intensity Nordic
lights, and a hydraulic test station (that
is now standard). The integrated tower
access ladder, a fall restraint system and
an extended tower infill for accessing the
tower for service and maintenance while
it is in horizontal position is an available
option. A new option is the Atlas Copco
computerized RCS control system (See
Blasthole Drilling in Open Pit Mining75
Talking Technically
article page 25.) Several PV-270 machines
have been delivered with RCS. There
is also an option for non-drill tower
access ladder, fall restraint system, and
extended tower infill for accessing the
tower while in horizontal position.
Rapid acceptance
The Pit Viper 270 series rigs were rapidly
accepted since its launch at MINExpo
2004. It was a machine that got it right in
terms of all the parts wor-king together
perfectly, and customers seem to agree.
In only four years the sales of the PV-270
series sur passed the accumulated
14-year sales record of its predecessor,
the DM-M2.
Barrick was one of the first mines to
use a PV-271 at their Goldstrike operations, and the company now has nine
of them. Newmont was another early
customer, buying four PV-271 machines
for the Yanacocha gold mine in Peru,
and now has 17 of these rigs. Copper
mining customers include FreeportMcMoRan which now has over 20 machines. Most recently, the PV-270 series
has broken into the Australasian coal
and metals markets.
Many of the PV- 270 series rigs have
been ordered for coal applications
mainly in South Africa, Russia and
the USA. The other major applications
are in copper and gold, mostly in the
Americas, and iron ore mines in Africa,
Latin America, Russia and Ukraine.
Almost all of the PV-275 machines
are equipped for rotary drilling, but a
significant number of the PV-271 units
have ben configured for downhole
drilling, mainly single-pass drilling of
8-inch diameter holes at gold mines.
Since the first PV-275 was shipped
for testing at Peabody’s Kayenta coal
mine in 2003 and the 2004 MINExpo
launch of the new models, more than
two hundred units of the PV-270 series
rigs have been shipped to customers.
PV-270 series rigs have been shipped
to customers.
Dustin Penn
PV-271 working in copper mine.
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Blasthole Drilling in Open Pit Mining