Drilling holes in solid rock used to be a time-consuming and labor-intensive process for Northern Arkansas Electric Cooperative's (NAEC's) field crews. Their service territory contains a significant amount of rocky terrain, making it necessary for the crews to rely on heavy machinery and explosives to get the job done.
For several decades, the workers had to drill pilot holes, drop explosives into the holes and then use a rock auger with bullet teeth to create a hole wide and deep enough for a new pole. The problem with this work method, however, was that it was very time-consuming. At times, field crews would spend almost two days drilling a 6.5-ft hole in solid rock. To make it even more challenging, the rock that the linemen had to drill into was made of a form of silica in some areas. This rock is extremely hard and is made of the same material that is used to sharpen carbide bits.
One day, however, the utility noticed that a local telecommunications contractor was setting poles using a self-contained machine with a down-the-hole hammer. The workers told the utility's crew that they could drill a hole in solid rock in 20 or 30 minutes. Discussions began within NAEC about how that type of drill would drastically improve productivity of setting poles in areas of solid rock. The company then made contact with Workizer Work Products to discuss how such a hammer could be configured to drill rock holes but also be mobile enough to be taken off road into rough rights-of-way.
Months down the road, Workizer sold a configuration of the hammer to a company that was sub-contracted to drill holes on NAEC's system. They then rented an air compressor to run it. For about a year-and-a-half, the contractor worked on parts of NAEC's system. Therefore, the utility's field crews could see the drill in action.
When the contractor reached the area on NAEC's system with the hardest rock, the hammer had a hard time penetrating the rock. After discussions with Workizer, the hammer was changed to an Atlas Copco USA hammer using a 900-cfm air compressor. Using the Atlas Copco hammer, the contractor was able to create a hole in about 30 minutes after everything was set up. This configuration was packaged and sold by Workizer Work Products as the Drill Boss 2.
Modifying the Machine
In 2009, the utility decided to purchase a machine from Dave Workizer, the owner of Workizer Work Products. Workizer listened to the utility's needs and then worked with his team to make custom modifications to the Drill Boss 2.
The manufacturer added a shock absorber and an air swivel to the top of the machine. In addition, NAEC wanted it to have a smaller footprint as well as an on-board air compressor. The utility had to share the machine across three separate districts, so it didn't want the air compressor to be dedicated to just one machine, but rather have the ability to transfer the drill between digger trucks.
Workizer Work Products sold the utility the hammer, the compressor and the hosting components. The utility then packaged all of the parts together on a self-contained trailer. The unit was received and began operation in January 2009.
Using the Machine in the Field
To learn how to use the machine, field crews watched a video and engaged in on-the-job training. They also followed the written procedures and instructions provided by Workizer. After the utility received the unit, Workizer Work Products taught the NAEC linemen how to drill holes and maintain the equipment properly.
NAEC owns one machine with a 17.5-inch bit on the end of the hammer. To create a hole in rock, the linemen first attach it on any standard digger truck and then use the digger truck to lift the bit out of the cradle on the trailer. The linemen then suspend the hammer on the side of the trailer, and a mechanical clamp holds it in place. Then, while the hammer is held on the side of the trailer, the linemen insert the auger shaft into it, and pin it to the bit. They can then move the bit at that point. A hose is stored on a reel attached to the trailer, and the linemen can unreel the amount of hose necessary to match the bit. The hammer and bit are then moved to the location for drilling.
Usually while someone attaches the bit to the truck, another person starts the air compressor and gets it warmed up and running. After it is ready to go, then they can begin drilling. The drill works off of air pressure and the weight of the bit pressing against the ground. To use the machine, the linemen pick the bit up, clamp it to the trailer, clamp the bit to the truck and then begin drilling.
Once they get the hole started, then they can drill straight down. Every once in a while, the linemen pull up the bit and allow the air pressure to blow the fine shavings out of the hole. They usually will drill about 6 or 12 inches, allow the air pressure to clean out the hole and then drill another 6 inches. Usually, it will take 30 to 40 minutes to drill a hole that is 6.5 ft deep.
Saving Time on Conductor Replacement
Over the last few years, NAEC has used the machine on a variety of different jobs. However, in the last year, the company has dedicated the Drill Boss 2 to an ongoing conductor-replacement project.
As part of this job, the workers inspect the system and then designate areas where they need to replace conductor that was damaged during the 2009 ice storm. They are also performing many line upgrades by adding poles and lines, and rebuilding old line sections with new conductor. The linemen are setting some new poles and replacing others that are between 15 and 35 years old.
In 2011 alone, the workers drilled 150 holes in rock using the Drill Boss 2. This year, the workers will continue to rely on the machine. The project spans about 207 miles, and so far, they have completed about 100 miles.
About 40% of the terrain consists of different types of rock from limestone to sandstone to silica. The workers can use the machine to drill through hard rock in about 40 minutes or even faster on softer rock, which breaks up more easily.
After using the machine, the workers have a clean 18-inch cylindrical hole in the rock. After setting the wood pole, the linemen fill the hole with the fillings that are left over from drilling. They then compact it with a tamper for a secure installation.
Over the last few years, the machine has held up well. When first purchased, the utility wasn't sure how long the machine would go before it would have to replace the bit. So far, workers have had to sharpen the bit once, and soon they will have to do it again. After that point, the utility most likely will need to replace the bit.
Before the machine, the linemen were using a lot of explosive material each year; now they hardly use any explosives. As a result, they have saved production on the jobs tenfold. Instead of taking 10 hours to do the job, it only takes an hour or less. In turn, the machine has helped to improve productivity in the field significantly.
James Woody (firstname.lastname@example.org) is the operations manager for North Arkansas Electric Cooperative in Salem, Arkansas. Woody, who has been with the company for 13 years, oversees the construction, operation and maintenance, fleet, dispatching and warehousing departments. Woody is a 1995 electrical engineering graduate from the University of Arkansas.
Atlas Copco USA www.atlascopco.us
North Arkansas Electric Cooperative www.naeci.com
Workizer Work Products www.workizer.com