Something Old, Something New: A Rotary Connection

Engineering and Mining Journal, Dec 2007

P&H Mining Equipment's new C-Series drill rigs are designed to outperform their capable predecessors

Beneath a ridge of brown clay overburden capped with aspen, birch and maple trees, a P&H 320XPC production drill advances a steel tri-cone bit into reddish-brown taconite. Onboard during this rainy day in the Minnesota Iron Range, the drill operator and a visitor monitor the P&H 320XPC's automated drilling system on a computer terminal mounted in the console array.

"I like this rig," the operator said after the drill completes a GPS-guided move to the next targeted blast hole drill coordinates. "You enter a few basic commands via the touch-screen terminal here and the drill basically manages the drilling process on auto pilot. I can intervene if necessary, but this machine is set up in such a way that you really just manage by exception. It's a smart machine."

Halfway around the world in the East Kimberley region of Western Australia at roughly the same point in time last autumn, a diesel-hydraulic P&H 250XP rotary drill surpassed 1 million m of cumulative blasthole depth in service at a remote diamond mine operated by Argyle Diamonds Ltd. (ADL).

Placed into service in December 1999, the P&H 250XP has dealt with rock formations that include Henzman quartz , an extremely hard material that requires 26,000- 60,000 psi of force to fracture during the drilling process. In fact, the toughness of the Henzman quartz has been compared to that of iron ore-considered to be one of the most challenging materials encountered in hardrock mining.

These two instances represent milestones of different significance for P&H Mining Equipment, a Milwaukeee-based business group within parent company Joy Global Inc. The 250XP line represents the previous generation of rotary drill design, while the C-Series drills, introduced in mid-2006, characterize P&H's most advanced technologies.

The 250XP model, introduced in 1998, was P&H Mining Equipment's first diesel-powered rotary blasthole drill designed for surface mining applications. The 250,000-lb 250XP can drill holes up to 13.75 in. in diameter to a maximum depth of 240 ft. It was designed to operate in temperatures up to 120°F and at altitudes up to 15,000 ft. ASL or more. It was also equipped with a touch sensitive Graphical User Interface (GUI) to provide operator-to-drill interactivity, monitor machine status, optimize performance and facilitate troubleshooting.

Over the years, P&H MinePro, which provides service support for the rig at the ADL mine, has worked with mine management to optimize their machine's productivity and reliability. Structural reinforcement of the drill mast and carriage and new vibration-dampening hoses and plumbing changes were among the primary upgrades applied to enhance drill performance. MinePro and the mine also developed a support-logistics and preventive maintenance program aimed at sustaining the drill's availability level at about 90% in the difficult and remote mining environment. The 250XP has racked up more than 38,000 production hours since 2000-in the process liberating about 300,000 mt of rock with each production blast.

The new-to-the-market 320XPC, on the other hand, is the successor to the 120A and GD120 models that P&H Mining Equipment upgraded and marketed after acquiring Gardner-Denver's rotary drill line in 1991. P&H's two new C-Series models-the 300XPC and 320XPC-replace the 100XP and 120A rigs, respectively.

The 320XPC is the most advanced of the P&H production drilling rigs. It's designed to produce large holes-up to 22 in. diameter-down to a standard depth of 65 ft, providing bit loading forces of up to 150,000 lb and rotary torque of up to 25,000 ft-lb. Bailing air capacity is 3,000 cfm with the standard air compressor, and up to 3,850 cfm with an optional compressor package.

P&H's Centurion control system, among other duties, provides machine diagnostic information and manages the rig's automated drilling system through continuous monitoring to balance and optimize bit loading, bailing air and rotary torque. Its constant monitoring of drilling conditions, says P&H, allows the drill to maintain a high level of production and accuracy from shift to shift without variations caused by different operator skill levels. Centurion also can help manage add-on control systems including GPS guidance.

Information contained in this article was provided by P&H Mining Equipment.