May 2009 Vol. 64 No. 5
Features
New Ditch Witch System Tackles Line & Grade HDD
A new Ditch Witch guidance system for making on-line, on-grade pipe installations with horizontal directional drilling (HDD) equipment soon will be available, the Charles Machine Works has announced.
The patented OnGrade system simplifies the process of making precisely controlled on grade HDD installations, said Richard Levings, Ditch Witch senior product manager. He said the new system eliminates the need for preliminary surveys to establish reference points along the projected bore path or to make vertical sight bores to verify product location at points during the installation. Correctly used, the system can provide a continuous, real time reference during drilling of the pilot hole.
“Presentations of the capabilities of the new system at the 2009 UCT show and other industry events have been extremely well received,” said Levings. “Extensive testing under various conditions have been made, and plans are for the product to be available this summer.”
Basic components of the system, said Levings, include:
- Laser plane (laser generating transmitter);
- Grade pole with integrated laser receiver; and
- Ditch Witch 8500 tracker.
For best results, Levings said specific downhole tools and drill pipe are recommended for use with the system.
How it works
To use the OnGrade system, the initial depth and grade are established and then the laser plane unit and grade pole are positioned on the surface.
As the pilot hole is drilled, the tracker receives information from the drill head, and the grade pole sensor reads the laser beam. The system computes the difference between the two readings and provides the drill operator with information necessary to keep the pilot hole on grade.
Levings said the system can make installations longer than typical on grade HDD installations which go from manhole to manhole or about 400 feet. The longest test to date with the new system is 1,100 feet.
“The system has been tested in various soils,” said Levings, “and is not recommended for non cohesive soils beneath the water table or on grade entry or exit through rock shelves.”
The 8500 tracker is an important element in the system, said Levings.
“The 8500 is a stand alone tracking system for all HDD applications,” he explained, “and it was designed with capabilities that are suited to on grade installations and it integrates perfectly with the laser receiver of the new system.”
The 8500 is capable of 0.1 percent grade resolution, has a target steering function for left/right alignment, can accurately track the bore head from the side of the bore path, and is accurate to depths of 30 feet in most soil conditions.
Specialized downhole tools and pipe can increase the effectiveness of on grade installations when used with the OnGrade system, added Levings.
“We have developed backreamers that help keep the enlarged bore hole on grade,” he explained. “Special beacon housings are stiffer and have rear stabilizers to keep the bore on target. Drill pipe used with our All Terrain (AT) model drill units also is stiffer than standard pipe and is less prone to ‘wander’ in the hole.”
AT
Levings said tests show that AT equipment which has a dual pipe drilling system provides better on grade control with the OnGrade system in soft soils because the inner pipe that does the drilling does not wear away or “float” in the hole.
Available as an option for use with the system is an inexpensive trolley with closed circuit television camera to check the installation before the final inspection.
“On line, on grade directional drilling is a discipline that requires skill, experience and patience, and it is not a job all drilling contractors want to undertake,” said Levings. “However, there is increasing demand for on grade drilling and for contractors, consultants, engineers and project owners, the new Ditch Witch OnGrade system is another tool to help make on grade installations more efficient and effective.”
In addition to HDD equipment and tracking systems, the Ditch Witch product line includes trenchers, vibratory plows, compact utility equipment, vacuum excavators and support equipment which are sold and supported through the worldwide Ditch Witch dealer organization.
FOR MORE INFORMATION:
Ditch Witch, (800) 654-6481, www.ditchwitch.com
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