HDD Rig
Trenchless horizontal drilling technology: the HDD Rig is an economical and environmentally friendly pipeline installation technology.
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Simple but functional

With HDD (Horizontal Directional Drilling), pipelines are installed in three steps. First, the HDD rig bores a pilot hole from the launch point toward the reception point. The rotating drill rods are precisely guided along the planned alignment by a surveying system directly behind the drill bit. During drilling, mud pumps convey a bentonite suspension directly to the nozzles attached un the drill bit. In soft geologies, the soil is excavated hydraulically at high pressure. In rock drilling, excavation is carried out mechanically using a mud motor. The bentonite mixes with the excavated material and flows back to the starting point through the annular gap between the drill rods and the borehole wall. A separation plant separates liquid and solid components from each other and returns the treated suspension to the bentonite circuit.

The pilot bore is followed in a second step by reaming. After exiting at the reception point, the pilot drill gear including the surveying system is removed and replaced by a reamer. With cutting tools and bentonite nozzles, the soil is removed both hydraulically and mechanically when the drill string is pulled back. The water-bentonite mixture supports the enlarged borehole, removes the soil and simultaneously cools all components. Reaming is usually performed in several passes until the final borehole diameter is achieved. This is about 30 to 50 percent larger than the pipeline diameter. In a third step, the pipeline is inserted. The prefabricated pipeline is connected to the drill string. Lifting the front end creates a so-called overbend and the entry angle of the pipeline is adjusted to the exit angle of the borehole. At the same time, falling below the minimum bending radius is prevented. Behind a reamer and a swivel joint, the pipeline is pulled back to the entry point by the HDD Rig to its final position. During this process, bentonite minimizes friction between the pipe casing and the soil.