The Mesabi Range in the northeastern corner of Minnesota has been supplying iron ore to U.S. steel mills for more than a century. The formation of extremely hard, flinty rock called taconite extends 110 miles from Babbitt to Grand Rapids. At present production levels, Minnesota's taconite reserves are sufficient to sustain mining through the 22nd century.

In working conditions sometimes as formidable as the taconite itself, the ore is extracted in open pits. After earth and other overburden materials are removed, blast holes are drilled in the ore-bearing rock. The holes are loaded with charges which, when detonated, reduce the rock to manageable chunks.

A large share of the North American steel industry's renewed vitality and competitiveness in the late 1990s is due to cost and quality improvements in the taconite mines. The taconite industry has become dramatically more productive, largely through the application of new technology, improved work processes, and billions of dollars in capital investment for new and larger equipment. Since the early 1980s, Minnesota taconite mines have doubled the number of tons produced per worker-hour.

A long-time partner of the mining companies is Bucyrus International Inc., builder of the massive blast hole drills, electric shovels, and draglines that are the mechanical heart of open pit mining operations. "As soon as a mining company announces plans to open a new mine or enlarge an existing site, we start working with them to make sure their equipment plan matches their mine plan," says Dick Janswig, senior administrator for blast hole drills at Bucyrus. "An open pit mine consists of benches, like giant steps. Bench height is matched to the size of the equipment, typically about 50 feet. The shovel must have the capability to dig to the top of the bench, and the shovel's dumping height must be sufficient to allow a truck under the open bucket. Truck builders have recently introduced 310-ton trucks to replace 240-ton trucks. This is driving us, in turn, to build larger equipment to match capacities."

For sure, the drills and shovels are plenty big already, with price tags to match. Weighing more than 200 tons, a blast hole drill can bore holes 17-1/2 inches in diameter to a depth of 260 feet down into hard ore. Want one? That will be about $2 million, please. A loading shovel - standing 64 feet high and capable of moving 80 tons with a single scoop - goes for $7 million, or more.

"Equipment that represents such a huge capital investment simply can't be out of service," says Janswig. "We will go to any lengths to put our equipment back in service if there is a parts breakdown, no matter where in the world it's located.

"A drill typically works two or three days ahead of the loading shovel, which means we've got two or three days to get the drill back in service. Otherwise, we're going to idle the shovel plus a fleet of trucks."

Bucyrus design engineers, therefore, are strong proponents of "An ounce of prevention is worth a pound of cure." Fire prevention is of particular concern, given that the electrically driven mining equipment operates at 4,160 volts, or even 6,600 volts. Aboard the drills and shovels, electric motors are more efficient than diesel engines, and don't wear out as quickly. But the power appetite of the equipment is so voracious, a mine usually has its own electrical substation, which is connected to the shovels and drills by an umbilical cord nearly 1 foot in diameter.

"The main machinery house of a drill rig or shovel is packed with a motor, pumps, compressors, switching devices, controllers and other high-voltage electrical devices," explains Greg Barker, sales engineer in the Engineered Systems Department of Automatic Fire Protection Inc. "With this much power in a confined space, there's always the possibility an electrical arc could start a fire. Or the hydraulic system could spring a leak that would send a stream of fluid into a compressor or motor where it could ignite.

"For adequate fire protection," he continues, "machinery houses are equipped with total flood systems that must suppress a fire rapidly with a life-safe agent, meaning it won't harm anyone if they are present in the room during discharge. For the cold environment of the Mesabi Range, the system must work at 40 degrees below zero." The 59R model drill Bucyrus recently put into service at a Mesabi mine is equipped with a fire system that will not be daunted by Minnesota winters. Designed by Automatic Fire Protection using components manufactured by Kidde-Fenwal Corp., the system is charged with DuPont FE-13™ fire suppressant.

For 35 years, the fire protection industry relied on Halon for its critical fire protection needs. But in response to the mandated phaseout of CFCs and Halons, DuPont developed the FE family of fire extinguishants offering the highest possible fire suppression performance in combination with environmental compliance. According to Barker, a number of products have been used as substitutes for Halon, but none have the characteristics needed in cold mining regions. These substitutes remain a liquid when discharged, refusing to turn to gas.

DuPont FE-13™ is a "people friendly" replacement for Halon as a total flooding agent in normally occupied spaces. It is an effective alternative to CO2 because of its far lower toxicity and extinguishing concentration. Short-term and extended inhalation studies on animals, including histologic examination, indicate that FE-13™ is chemically and biologically unreactive. FE-13™ is a clean agent, quickly extinguishing fire without leaving behind residue to contaminate electronic circuit boards and electromechanical devices.

"In addition to mining equipment," continues Barker, "flooding systems with FE-13™ will be particularly effective in control centers and natural gas pumping stations in Canada and Alaska - high value areas where fires must be minimized and sprinklers can't be used."