Horizontal Directional Drilling
Horizontal Directional Drilling (HDD) is used for the steerable installation of new pipelines, ducts and cables. The term applies to a crossing in which a pilot bore is drilled, and then enlarged to the required sizeto install ducts, pipelines or cables. The drill path can be straight, curved or on grade. The direction of the drilling head can be adjusted at any stage during the pilot bore to steer around or under obstacles.
Installation of the product (Pipe, duct or cable) is usually a two-stage operation. A pilot hole is drilled along the required path (straight, curved or on grade). The pilot hole is then reamed in a single or multi-stage, depending on the ground conditions and project requirements, to a larger diameter to accommodate the product (Pipe, duct or cable).
During the final ‘Pullback’ stage, the product is attached to the reamer by means of a swivel connector and is pulled into the enlarged pre-reamed hole as the drill strings are withdrawn. The drilling machine uses a drill fluid Bentonite which lubricates, stabilizes, discharge and remove the soil cuttings in the bore hole. Bentonite creates a filter cake wall that stabilizes the bore hole and protects the ground water from running.