This information is transmitted through a wire-line fitted within the drill string. The guidance system also has a secondary means of location verification that utilizes wire grids laid on the ground surface. Wire-line locating system: With a Magnetic Guidance System (MGS) the tool reads inclination and azimuth. A handheld receiver is manually positioned over the transmitter where the signal is decoded and steering directions are given to the machine operator. This information is encoded into an electro-magnetic signal and transmitted to the surface. Rotation, direction, and temperature data. Walk-over locating system: A sonde or transmitter located behind the drill head registers angle, There are three types of guiding systems for locating and steering the drill head. Guiding the drill head is an important part of the drilling operation. The categories represent the drive length, depth, torque and pullback capabilities of each system. There is no significant difference in the operation of these systems. Horizontal directional drilling machines are divided into three categories large-diameter HDD (maxi-HDD), medium-diameter HDD (midi-HDD), and small-diameter HDD (mini-HDD). The final size of the drilled hole is 50% larger than the pipe diameter to drain drilling fluids and to accommodate the bend radius of the pipe.ĭirectional drilling machines come in a range of sizes, with the largest machines capable of drilling to depths of 200 ft. For larger pipes an additional step of reaming will be required. As the reamer is pulled back the pilot hole is enlarged and pulls the pipe or conduit back with it. The second step involves replacing the drill head with a reaming device such as a fluid-assisted drill, a high pressure fluid jetting system, or a dry bore system to enlarge the hole to the desired size. The first step is to use a drill head to drill a one- to five-inch pilot hole at an angle, using the ground as reference. Installation is typically a two-step process. Materials used for pipes include PVC, polyethylene, polypropylene, ductile iron, and steel.ĭirectional drilling machines install both small and large diameter lines (3 to 48 inches). Horizontal drilling machines are typically heavy-duty vehicles fitted with track drives, operator controls, and drilling machinery. Horizontal directional drilling (HDD) machines are steerable, trenchless drilling rigs for the installation of pipes, conduits, and cables underground in a shallow arc. They are commonly used for installations below waterways and roadways to avoid disturbing the ground above.
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