Horizontal Directional Drilling – How does it work?
Step 1: Pilot drilling
The pilot drilling is the most important phase of Horizontal Directional Drilling (HDD). This phase determines the final route of the pipeline. During this pilot drilling, you need a drill head with a jet at the end of the flushing pipe. On this drill head, you can find a “steering plate”. The drill head will move in different directions by rotating the steering plate. By turning the steering plate in a certain direction, the drill head will follow.
The figure on the right illustrates how the control plate (diagonally flat on the chuck) guides the chuck upwards.
By turning the rods 90 ° left or right (or 180 °), the drill head can be steered “unlimited”. This way, obstacles can be avoided. The position of the drill head is displayed on a “clock”.
By rotating the rods continuously, the drill head will simply go straight and not change direction.
In the pilot drilling, it is important that a sufficient amount of bentonite is present to obtain a borehole and ease the execution of the next steps.
B = Drilling fluid S = Soil R = Return fluid (= B + S)
The figure shows how the jet at the front of the drill head loosens the sand and uses the drilling fluid to guide the sand out of the borehole.