Liter's Quarry Inc. has six quarries in the Louisville, Ky., area and produces several sizes of concrete stone, riprap and backfill, manufactured sand and aglime. With overall annual output of several million tons per year, the term “economies of scale” might well apply to this operator — but not in the conventional sense.

At the Rocksprings quarry, one of three underground quarries operated by the 63-year-old company, scaling blast-loosened rock had been a problem for years. After trying methods ranging from manual scraping to a custom-built hydraulic pick mounted on an hydraulic excavator, Vice President of Operations Cecil Banta wanted a safer and more cost-efficient approach that wouldn't be a production bottleneck.

The 100-acre Rocksprings operation produces about 1 million tpy, mainly 1-in. clean stone to supply two nearby concrete plants. The quarry's underground workings are designed with 26½-ft-high ceilings, 45-ft-wide tunnels and 40-ft-square support pillars. “We shoot three to four rounds every day at Rocksprings, and the faster we can complete the scaling work, the faster we can get back to production,” explains Banta.

The company's experience with scaling equipment mounted on hydraulic excavators wasn't encouraging. “We wore out the previous excavator in 18 months,” Banta says. “The machine just couldn't take the vibrations from the hydraulic pick we were using.”

Banta then considered a Tramac's series of rotary, double-drum cutter heads from 21 to 43 in. in width, operated by the carrier's hydraulic circuit and configurable with a variety of bit sizes and lacing patterns. Liter's purchased a Tramac TCH-160 cutter head mounted on a Komatsu PC400 LC-5 excavator, and has since put about 4,000 hours on the machine without major problems.

“In addition to taking less time to scale a face, we've also had 80% lower operating costs with the new machine, compared with the previous excavator,” Banta says. “And, it's passed all of the MSHA workplace noise tests. About the only difficulty we've had was initially selecting the correct bits and rotational speed for the job and learning how to correctly weld the bit blocks to the drum. We also had to install a better magnet system to protect the rock plant from tramp metal.”

The TCH-160 cutter head is the largest of the product line and requires a carrier weighing between 33 and 60 tons. The 4,190-lb unit has a drum diameter of 27¾ in. and rotates at up to 67 rpm. Other models in the product line are designed for carriers in the 3- to 40-ton range and offer rotational speeds up to 120 rpm.

Liter later added a TCH-80 at the 1 million tpy Lockport underground operation. The 25-in.-diameter, 33-in.-wide cutter head is mounted on a Komatsu PC300 LC-6 excavator.