Maximum Traction Power for Pipeline Building.
The horizontal directional drilling technique (HDD) enables utility tunnels and pipelines to be laid under rivers, roads or other obstacles quickly, inexpensively and with minimum environmental impact.
Essentially, installing utility tunnels using the HDD technique comprises the following three stages:
In the first stage a pilot bore is made from the point of attack in the direction of the exit point. The steerable drill string made up of individual drill rods is conducted along the target route by a guidance system located directly behind the cutterhead.
During the drilling process a bentonite suspension is pumped to the nozzles fitted to the cutterhead where it excavates the native soil hydraulically. The bentonite mixes with the excavated soil and flows back through the annulus between the drill rods and the bore hole to the point of attack at the surface, where it is processed by a separation plant and returned to the drilling cycle.
In order to increase the diameter of the pilot bore hole in the second stage, the pilot cutterhead is removed at the exit point and a so-called muck bucket lips is attached to the drill rod. As the drill string is retracted, the diameter of the bore hole is enlarged with the help of the muck bucket lips. All the muck bucket lips are fitted with nozzles and excavation tools in order to excavate the soil both hydraulically and mechanically. A mixture of water and bentonite or other additives can be used dependent on soil conditions in order to stabilize the bore hole and reduce friction forces. In the third stage the prefabricated and pipelines that have been checked are retracted.
The front part of the pipeline laid out in front of the bore hole is lifted to line up with the exit angle of the bore hole in order to keep outside the minimum bend radius. The pipeline is retracted section by section from the rig behind a muck bucket lips and in this way reaches its final position in the soil.
HDD technology can be used in this way in geological conditions ranging from soft to very hard formations.
If you need further information, please contact our Media Service for our HDD brochure or our animation on CD-ROM.
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