Location: Madison, TN
Equipment: StraightLine HDD® RockEye 5.0 Hammer System on a Vermeer 24×40 Series 3 and 1150 X 350 compressor.
The Challenge:
The Nelms Contracting crew knew the job of installing fiber optic conduits in the Nashville, Tennessee area was going to be a challenge. Conditions in the area contained a mix of soils, ranging from solid to fractured, extremely hard limestone with a mixture of clay. The unforgiving conditions produced a well-deserved reputation for low production and high costs.
Soils were a challenging mixture of solid and broken limestone with clay.
In sizing up the challenge, Nelms Contracting owner, Mike Nelms, identified hammer technology as the best option to tackle the multiple 300- to 400-foot shots. Nelms’ tool choice was driven by the known ability of hammers to produce good production rates with maximum control through tough rock. Control, was critical, as the typical Nashville bore profile required contractors to maintain a tight depth window of 4 feet, +/- 12-inches, while leaving at least 2 feet clearance from a dense assortment of installed utilities.
Nelms’ plan of attack was simple: Use a 4-inch hammer to drill the pilot and then back-ream using a 10-inch hole opener to pull bundles of 3, 2-inch fiber-optic conduits.
Re-Thinking Tooling Choice
Several critical issues surfaced early on. Pilot hole production rates came in less than originally planned, due mainly to the varying ground conditions. Issues continued to mount on the pullback, with the hole opener recording slow production rates, while also requiring large fluid volumes. Fluid volumes proved to be a serious logistical problem in the congested urban work area. Spoils removal added cost and slowed production further.
Determined to avoid the fate of many Nashville crews, Nelms decided to adjust his game plan. After a quick online search, Mike contacted the experts at StraightLine HDD. They recommend a larger RockEye hammer to avoid a large back ream. Nelm’s believed the RockEye 5.0 Hammer’s 6 7/8-inch diameter pilot hole would allow his crew to pull conduit back on the first ream—saving a tremendous amount of time. Also intriguing was the RockEye’s support pack, which allowed fine control over fluid volumes—a feature not available on the previous hammer. With minimal fluids needed on the pilot, Nelms calculated the RockEye’s large diameter pilot would significantly reduce back ream fluid volumes.
With fluid volumes drastically reduced, it was possible to carry all fluids & equipment on a single truck – a huge advantage in tight urban job sites.
The Outcome:
After finalizing the revised plan, StraightLine HDD Lead Field Engineer, Ron Becker, arrived in Nashville a few days later with a pair of the RockEye 5.0 Hammer Systems. Accessing the day’s bore and conditions, Becker set up the Nelms Contracting Vermeer 24×40 Series III with the RockEye 5.0 hammer.
Knowing the broken rock would have a tendency to roll under the bit and push the hammer up, Becker’s initial focus was on control. After working to achieve and maintain the correct depth, Becker’s training focus shifted to acquainting the operator with the hammer operation, starting with using a light touch and allowing the bit to do all the work.
In just 6 hours and using just under 200-gallons of fluid, the RockEye hammer completed the first 300-foot bore. While encouraging, Nelms knew true validation would come on the back-ream. Pulling a small fluted reamer and using just enough bentonite/water mixture to lubricate the hole, the Nelms crew achieved a production rate of 3-4 minutes/per rod—completing the job in a matter of hours, rather than the days it took using previous methods.
The ability to make production on the pilot shot facilitated a smooth back ream with 80% less fluid required to complete the bore. This dramatically decreased the need for support equipment on the jobsite and allowed them to complete project with a smaller more specialized crew.
RockEye Hammer: Change the Way You Approach Tough Rock Bores
Join a growing number of elite drillers who are pounding out superior production rates and profit — all while maintaining incredible steering dexterity with drastically reduced fluid volumes.
