A Viper for the Copper King

he Morenci mine in the south eastern

part of Arizona started its life in

the late 1800s under ground. Today,

it is a major open pit operation and the

largest copper mine in North America.

It is a massive operation covering an

area of 3,055 acres, which will increase

to 4,683 acres in 2006. A total of 4.37

million feet of blast hole drilling is

carried out annually including 570,000

feet in ore ? the ideal proving ground for

the rotary rig Pit Viper 351.

Weighing 375,000 pounds, measuring

53 feet long and equipped with seven

on-board computers, the Pit Viper 351

was the largest and most advanced rig of

its kind on the market when it was introduced

at the MINExpo show in Las Vegas

in 2000.

After the fair,Morenci took the prototype

and put it to work in a fleet of 16

rigs from a variety of other manufacturers.

Today, four years down the line, it is

still performing to expectation.

Since April 2001, the rig has

been in production full time and

operates on a cost-perfoot

basis. By August

2004, it had drilled 2.2

million feet and is currently

averaging about

60,000 feet per month,

although in some months

it has drilled more than

80,000 feet.

In fact, the rig has been so

productive that the unit number

?20R? has had to be changed towards

the end of each year because the rig

drills more than 10,000 holes per year

and the mine?s automated, annual holenumbering

system stops at 9,999.

Most of the production rigs at the site

are electric, which, due to their power

cables, makes them difficult to move

from bench to bench. The PV 351, however,

with its Cummins 45-litre diesel

engine (1500 hp at 1800 rpm) moves

easily and frequently between the benches.

Also contributing to the rig?s productivity

is the hydraulic design that uses

one gearbox and five pumps for the complete

unit as well as the cable-feed

system and positive lubrication oil pump

for the air compressor.