INTRODUCTION
- Directional Boring, popularly known as (HDD).
- The Technology usually preferred in those installation processes where trenching or excavation cannot be implemented.
- This technique in installation of various pipes, conduits, Steel pipes, power cables, water lines, etc., Causing minimum harmful impact on the environment.
- Major applications include crossing waterways, shore approaches, roadways, environmentally sensitive areas, congested areas, etc.
BENEFITS OF HDD TECHNOLOGY
Cheaper than traditional techniques
Quicker to implement.
Provides maximum directional capabilities.
Suitable for diverse soil conditions & surfaces (river crossings, roads, landscapes, etc.)
The horizontal drilling can work anywhere, from roads to the busy and crowded areas, without disrupting or destroying the surrounding area.
It enables deeper installations.
Causes minimal hazardous impact on the environment.
Maintenance cost incurred is quite less.
It not only works with the steel or iron pipes but also with the plastic and polyethylene pipes.
STAGES OF DRILLING PROCEDURE
Step 1:
Pilot Hole
Small diameter hole is drilled along a designed drill path.
Step 2:
Pre-reaming
Pilot hole is enlarged to 1.5 times the diameter of the product pipe.
Step 3:
Reaming/Clean Passing
Used for swabbing and cleaning the hole.
Step 4:
Pulling
Product pipe is attached behind the reamer and pulled into the enlarged hole.
DRILLING A PILOT HOLE
Cheaper than traditional techniques
The drilling head along with a transmitter fitted on it allows it to operate and control the drilling process.
A fluid is filled in the head to reduce friction and provide more stability to the bore hole.
Visual information about the position, angle and azimuth of the drilling head is shown on the locator display that receives information via the transmitter.
ENLARGEMENT OF PILOT HOLE (REAMING)
Conducted to enlarge the hole prior to pipe installation.
Reamers attached at exit point, then rotated and pulled towards the rig to enlarge the hole.
Reamers consist of a circular array of cutters and fluid jets.
Drill pipe is added behind the reamers as they progress towards the drill rig.
Ensures pipe string is always maintained in the hole.
Also possible to ream away from the rig.
PIPELINE PULLING
Prefabricated pipe attached behind reamer at exit point and pulled to rig.
Swivel/thrust bearing placed between pipe section & reamer to minimize torsion.
Pull section supported using a combination of roller stands and pipe handling equipment (side booms, cranes, roller cradles) to minimize tensile forces in pipe.
Laydown area needed beyond exit point must equal length of drill for continuous length of prefabricated pipe. Temporary ramps can be constructed for continuous pipe or split in half and welded prior to the day of pullback.
HORIZONTAL DIRECTIONAL DRILL SET-UP
