Kentucky field crew uses rock bit on line-relocation project.
A devastating ice storm knocked out power to 25,000 customers of Nolin Rural Electric Cooperative Corp. (RECC; Elizabethtown, Kentucky) last January. The storm, which was considered one of the biggest natural disasters in Kentucky's history by the state's governor's office, inflicted significant damage to power lines and poles throughout the state.
Linemen faced major challenges trying to repair three of the utility's poles that crashed down to the ground during the ice storm. Field crews had to drive their trucks across a large field behind rows of houses to reach the 1-mile stretch of line.
When the ice and snow melted, the hard ground transformed into a soft, wet and sticky swamp. Referred to by the linemen as the “bottom ground,” this low-lying land is located a significant distance away from the main road. For that reason, it stays wet, especially following a major storm.
To make sure they can access the poles at any time, the field crews spent a couple of weeks relocating the three-phase line to a more-elevated position.
By moving a portion of the line to the top of a hill, the linemen greatly improved the access to the line because it is now closer to the main road. The tradeoff, however, was that linemen encountered rock when drilling holes for the poles. Unlike the bottom ground, the higher elevation featured limestone. The limestone rock holes could not be drilled with a standard auger.
In the past, field crews would use dynamite to blast holes into the rock. This strategy, however, often created quite a mess, took a long time and posed a safety hazard to the crews.
Over the last dozen years, RECC linemen have relied on a Rok-Away digger derrick drill bit from Gator Rock Bit (New Haven, Kentucky). The company, which is owned by a family who grew up in the power line business, manufactures a drill bit that allows linemen to drill holes faster, easier and safer.
Oftentimes, the crew doesn't hit rock on every hole they dig. Instead, linemen often drill down 3 or 4 feet, and then they hit rock. If the linemen do encounter rock on the one-month-long project to relocate the line, they use the drill bit to bust through the rock.
Digging Pole Holes
To use the drill bit, the linemen first make a starter hole with the auger and then begin digging. If they hit rock immediately, then they remove the traditional drill bit and replace it with the Rok-Away bit, which has carbide teeth. Before drilling through the rock, the linemen check the teeth to make sure that they are not worn. If they need to be replaced, the teeth can be changed out in a matter of a few minutes.
After they have checked the bit's teeth for wear and tear, the linemen then begin drilling. For maximum effectiveness, the linemen dig slowly and let the auger do the work by placing some down pressure on it.
Throughout the process, the linemen pour water in the hole to keep the level of dust and dirt down until the chamber fills up. If the linemen don't have access to water on the job site, then they'll throw buckets of water on to the back of their trucks before they go into the field. Typically, they need between 5 and 10 gallons of water to get the job done.
When the linemen have finished drilling the hole, then they pull out the drill bit and knock off the excess rock with a digging bar or sledgehammer.
The field crews then change the bit back to normal, place the drill bit back on the truck and go on to the next hole.
Right on Target
The linemen used to spend almost half a day to drill a hole into solid rock. Now most holes can be dug in about an hour.
In addition to saving time, the linemen also have improved the accuracy of the holes. Before the linemen had the drill bit, they would have to use an auger to poke around into the ground to find a place for the desired hole. With a regular dirt auger, a conventional bit would often wander or drift away from the desired position.
With the Rok-Away bit, however, where the linemen start is where their hole will end up. There's no question that the hole goes where the field crew wants it. There is no movement from left to right, it's much more precise, and there's no problem with wandering or drifting.
It also helps to minimize the risk of hitting underground utilities when changing out a pole or relocating a portion of the line.
Because the drill bit is relatively easy to use, the linemen are becoming trained on how to use the drill bit by watching it in action. RECC stores the drill bits in its warehouse, and the crews often take one with them on jobs that require drilling holes in rock.
The bits range from 10 inches to 16 feet in diameter and weigh from 200 to 2,000 pounds. The linemen drive their digger over to the warehouse, load the appropriate size bit on the truck, and then carry it with them until they are done with the job.
If they are at a job site and hit rock unexpectedly, they can also call the warehouse manager, who will use a fork lift to load the bit on to the truck and then drive it out to the site.
The linemen expect to use the rock bit on about five or six of the 30 holes they plan to dig during the line relocation project. By using the drill bit, the five-person crew is able to drill holes in the rocky terrain, while at the same time making it easier for linemen to access the poles. In the past, linemen couldn't access the line from the main road, and as a result, they had to drive through homeowners' backyards. Now they can simply drive up to the poles and do their work, which will most certainly come in handy the next time an ice storm rolls into town.
Josh Hess (firstname.lastname@example.org) is a line technician and crew leader for Nolin Electric Cooperative in Elizabethtown, Kentucky. He has been with the company for the last 13 years.