What is HDD(Horizontal Directional Drilling )?
HDD is a low impact method of installing a length of pipe from a launch pit to a reception pit below ground while avoiding obstacles.
Suitable for use with pipe, conduit and cables within a relatively shallow arc or radius, HDD is used for a number of different projects within many different industries.
How does it work?
A tracking operative will steer the drill from the launch pit to the reception pit via a pre-agreed drill route, avoiding any existing utilities and obstacles. Once the drill head reaches the reception pit, it is removed and, then, a reamer (a kind of rotary cutting tool) is then attached in its place.
The reamer will then be rotated back toward the launch pit, thereby enlarging the bore to the required size. Once the reamer has been driven back into the reception pit, the pipe can be attached to the back of the reamer and then drawn back through the bore to the launch pit.
HDD Process
HDD works in six separate stages and, these are:
One
The drill is directed from the launch pit into the ground via an entry point, allowing the drilling process to begin.
Two
As each drill rod is attached and drilled through the ground, the highly experienced tracking operative will relay information back to the rig operator via a two way radio.
The front of the drill head features a special, angled design which means that, if the tracker wants to steer the drill, he will instruct the rig operator to push the drill head in a particular direction. The drill can be steered around and above or below existing utilities in order to avoid them – this is extremely important as it helps to prevent damage and inaccuracies. If a straight line is required, then the rig operator rotates the rods and drills through the ground.
Three
Drilling fluid (also known as Drilling Mud), is pumped through the rods to the drill head to help lubricate the drill head and drill string of rods and to assist in steering.
Four
Once the drill has reached the reception pit, the drill head is removed and a reamer is attached. The reamer is then rotated back through the ground, thereby enlarging the hole that the pilot drill has created. Depending on the size of the pipe to be installed, this process will sometimes be repeated in order to further increase the size of the reamers each time until the required bore diameter is accomplished.
Five
Once the required sized bore has been reached and the reamer is back in the reception pit, the reamer is attached to the pipe via a towing head (also known as a pulling head).
The pullback commences and the pipe is drawn back along the drill path. Drilling fluids are then pumped through the rods to the reamer to stabilise the bore and, also, to lubricate the reamer and pipe.
Six
In this final stage, the pipe is pulled back into the launch pit where the reamer and towing head are removed and the final pipe connections are made.
Permit to drill
Before any drilling activities can take place, a survey of all the existing underground utilities must be carried out. Where necessary, trial holes may be dug to expose and locate the exact depths of utilities crossing the drill path. Once all the utilities have been duly located, this information is then relayed onto a ‘permit to drill’ along with details for the depth and the direction of the drill path. This is then signed by the client and our lead drilling operative will confirm that all the required information is accurate for the site.
