November 2012, Vol. 67, No. 11
Equipment Spotlight
New Auger Boring System Handles Large Diameter, Line & Grade Projects
American Augers has introduced a new guided auger boring system — the Model 48GM8000 — designed to make bores in diameters from 48 to 60 inches to lengths of 1,000 feet, depending on site specific geological conditions.
The new, single-pass system was developed to address a growing demand to place larger diameter casings on line and grade, said David Vidovic, American Augers product manager.
“The single-pass system allows for the installation to be made from start to finish by boring and guiding only the product pipe,” Vidovic said. “It does not require a pilot bore nor does it require “stepping up” or reaming the bore in successive passes. It only requires guiding the finished bore one time, rather than relying on pilot bores or previous bores that need to be enlarged by reaming in order to guide the tool successfully each time.”
Components of the 48GM8000 precision line and grade system include four primary subsystems:
• Auger boring machine;
• Secondary casing system;
• Cutter head/steering unit; and
• Guidance/position sensing system.
The 48GM8000 is available now with two other models scheduled for introduction during the first quarter of 2013, Vidovic said.
“The concept for the machine was developed based on the growing number of projects requiring large-diameter, long-length installations at line and grade,” explained Vidovic. “This type of work continues to grow for culvert and sewer projects. Today, such jobs of more than 600 feet usually are done by microtunneling. Our goal is to provide a system that is a less costly method of installing product of large diameters with the ability to navigate more precisely through heavily-populated areas crowded with existing underground infrastructure.”
Features
Vidovic said features that set the 48GM8000 apart from other guided boring systems include the combination of its method of steering, large diameter capability, the ability to do long bores and easy retractability.
These features, he continued, provide positive benefits.
“For example,” he said, “with pilot boring systems, the bores necessary after the pilot bore are supported by the pilot drill string while the American Auger systems are supported by the full surface of the product pipe. When compared to the traditional microtunneling machines, there is a definite advantage to the retractability of the system coupled with easily-installed, less-costly kit modifications for different bore diameters. In general, the system offers greater flexibility than other equipment currently on the market.”
Regarding steering, Vidovic said other pilot boring systems operate with a LED (light-emitting diode) in the cutting head which is scoped with a theodolite through the drill pipe through a window no larger than 3.5 inches in diameter.
“This means if the cutting tools deflect off of center more than 1.75 inches, the position will be lost,” he added.
Guidance
The American Augers system utilizes a laser that is pit mounted and strikes a target on the cutting head. Because the American Augers system is a single-pass system, Vidovic said the target is mounted downhole on the product casing, ensuring that the pipe be placed accurately.
“The beam path is between the 24-inch diameter secondary casing and the primary casing of 48-inch or larger diameter,” Vidovic continued. “This gives a window of approximately 12 inches diameter at a minimum, allowing a better view of the actual product pipe position.
“The American Augers system employs a laser/theodolite and a camera, with the camera mounted downhole and always at a fixed distance from the target, assuring that distance is not a challenge to the system to provide accurate positioning. Bores of 800 to 1,000 feet are possible,” he explained.
For comparison, Vidovic said pilot boring systems employ a pit-mounted camera to monitor the head position.
“Because the camera is in the pit,” said Vidovic, “its ability to scope the target is challenged by distance, usually limited to the 500-foot range.”
In addition, Vidovic said that other boring equipment available using lasers are designed for smaller diameter bores than the 48GM8000, and that attempting a bore of larger diameters with such equipment is cost prohibitive.
After the laser guidance system, Vidovic said the other feature to emphasize is the 48GM8000’s retractability.
“If the system becomes blocked or inoperable for any reason,” he explained, “there is a two-stage component withdrawal process. Removing only the secondary casing will open a path as large as the product casing’s inside diameter to the back of the steering section. This allows service in an access area 24-inches in diameter to the back of the cutter head for removing small blockages or tool change. For the removal or destruction of larger blockages, the steering system cutter head can be removed, allowing full access to the face to clear obstruction, perform any necessary maintenance, or do blind hole boring with no exit pit necessary.”
For bores less than 500 feet, torque is provided through the auger and thrust applied through the casing from the ABM. The 48GM8000 is used in conjunction with the 48/54-900 or 60-1200 auger boring machines. The 48/54-900 would be adequate for lengths less than 500 foot and the 60-1200 would be used for greater lengths.
For bores greater than 500 feet, the torsional power from the boring machine is replaced with an onboard electric motor/reducer combination that will provide 51,000 foot pounds of torque to the cutting head. Thrust of 1.2 million pounds is supplied by the 60-1200 boring machine.
Regardless of distance being bored, the cutting head can be equipped with backhoe-type cutters for dirt applications, bullet-bit carbide cutters for soft rock applications, disc cutting heads for rock to the 25,000 psi UCS (unconfined compressive strength) range, and roller cone bits for rock in excess of 25,000 psi UCS.
Vidovic said two additional guided boring system models are scheduled to be available in the first quarter of 2013: First will be the 36GM8000 for bores in diameters from 36 to 42 inches, followed by the72GM8000 with bore range diameters from 72 to 84 inches.
American Augers was established in 1970, and its offices and manufacturing facilities are located in West Salem, OH. In addition to auger boring equipment, American Augers manufactures mid-range and large horizontal direction drilling (HDD) equipment, downhole tools and accessories, drilling fluid systems and oil and gas drilling rigs. American Augers is part of the Astec Industries Underground group.
FOR MORE INFORMATION:
American Augers, (800) 324-4930, www.americanaugers.com
System For Maintaining Line & Grade
A road bore made during testing of American Augers new 36GM8000 guided auger boring system illustrates its benefits on the job.
The 320-foot-long bore of 48 inches in diameter was to install a culvert beneath Interstate 20 in Brandon, MS. Contractor was Fornea Road Boring, Jackson, MS.
The pipe was placed in the ground on line and on grade, said Jim Lee, American Augers field service technician, who played a key role in development of the machine.
“Using a laser and target to monitor line and grade, this system saved time on this job,” said Lee. “Cameras watch the target and sensors monitor the windows so the operator knows how far to open them to make steering corrections. The windows are hydraulically controlled at the operator’s station. A push of the button opens and closes the windows.”
Under normal circumstances, Lee said the auger would have had to be pulled out just to check the line and grade. Then if a correction was needed, it would be necessary to go into the casing, cut windows with a torch to open them to a desired position, weld the window in place, put the auger back into the casing, drill another pipe, and repeat pulling the auger and changing the position of the windows as necessary.
“The American Augers 36GM8000 guided auger boring system saves time and labor,” said Lee. “I believe it is the method of the future for maintaining line and grade on large-diameter bores.”
FOR MORE INFORMATION:
Fornea Road Boring, (601) 362-0139
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