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70 E&MJ; • MARCH 2016 www.e-mj.com Boart Longyear's Newest Jackleg Tops On-the-job Drill Comparison Test By Jared Kessen S U P P L I E R S R E P O R T While many underground mines are look- ing to avoid handheld rock drills for the safety of the miners, there are still many mines in North America, for example, where jackleg drilling is a must. For these narrow-vein mines, located primarily in eastern Canada and throughout Mexico, cabbed jumbos, bolters and long-hole rigs are not feasible due to cost and size restraints, and these operations depend on handheld rock drills—a technology that has changed relatively little in more than 70 years. In 2010, the Boart Longyear engi- neering team began to take a hard look at the design of these drills, including their own Secan S-250. The goal was to reduce the noise and vibration the drill puts out. The outcome was a new, top-of- the-line handheld rock drill—the S250- M3—which instantly made jackleg drilling a much safer operation. Introduced in early 2013 to a recep- tive market, the S250-M3 represented a major step forward in rock drilling. Reflecting Boart Longyear's commitment to making a truly better and safer drill, it significantly improved upon the Secan S- 250 by introducing advanced noise sup- pression. The new technology directs more energy to the face of the rock and less into the body of the driller. Independent tests showed the S250-M3 reduced the noise level by 6 decibels— resulting in half the noise—while in- creasing torque and penetration rates. In fact, one driller commented that it was the first time he could feel his feet and hands after a full shift using a rock drill. An independent, third-party compari- son test at an underground site in the western U.S. pitted the new S250-M3 against three other leading jacklegs head-to-head. After that test—conducted under actual mine conditions—Boart Longyear's S250-M3 emerged as the evaluation team's product of choice for rock drilling at the site. PHQ 250 JHSL pneumatic jacklegs were already being used for the installa- tion of ground support at the site where the comparison testing took place. While a hydraulic rock bolting jumbo had been purchased to help reduce risk to drillers, management determined that handheld drills would still be required in the shafts. Therefore, they wanted to consider alter- native products that were reported to reduce exposure to sound and vibration hazards. Selected for testing were the PHQ 250 JHSL, the PHQ250 JHNAVL (a variant with an antivibration buffer on the handle), the Boart Longyear S250-M3 and the Hilti TE MD20 electric jackleg. Representatives from the various drill suppliers were on hand but did not par- ticipate directly in the independent test- ing, which involved the services of four drillers for four consecutive shifts over two days. Performance data was collect- ed to determine sound production (dBA), vibration (m/s 2 ) and penetration rate. A 185-cfm diesel-powered compressor pro- vided compressed air, and each drill and leg was connected to the same 100 ft length of 1-1/2-in.-diameter air hose to ensure that a consistent volume and pressure of compressed air would be pro- vided to each drill. Air pressure was measured at the drill and recorded for each test. Water for drilling came from a 2-in., high-pressure industrial water line with water pressure reduced from approx- imately 350 psi to 75 psi with a pressure reducer. Electricity was provided from an existing service at 220 volts. A Quest Technologies 2100 Sound Level Meter was used to measure sound pressure levels at the driller's ear. Vibration was measured using an accelerometer that was taped to the drill handle while each driller wore a monitor on his bib overalls. To ensure that all holes would be drilled in a consistent rock mass, they were all drilled in the same general area. This location also provided for the hardest drilling that would be encountered to pro- vide a worst-case scenario for penetration rates. Each unit was used to drill three holes, varying between 1-3/8 and 1-1/4 in. in diameter and up to 6 ft deep. Holes from the Hilti drill were limited to 2 ft in depth because the Hilti drill didn't have a drill string longer than 2 ft. Each set of holes was drilled with a new bit, and each pneumatic drill used the same leg so any variations in leg operation would not The company says its newest jackleg rock drill—the S250-M3—has been shown by independent testing to be capable of reducing noise by 6 decibels while increasing torque and penetration rates.