HORIZONTAL DIRECTIONAL DRILLING (HDD)

Introduction

Horizontal Directional Drilling (HDD) is a trench less methodology that provides an installation alternative that can offer a number of benefits over traditional open-cut. HDD can be implemented with very little disruption to surface activities, requires less working space, and may be performed more quickly than open-cut methods. Also, it can simplify or eliminate certain permitting processes. This type of installation of underground infrastructure systems has seen a dramatic increase in recent years.

Procedure

• HDD is a trench less construction method that involves drilling a small pilot hole, using technology that allows the drill to be steered and tracked from the surface. The pilot bore is launched from the surface at an angle between 8 and 20 degrees to the horizontal, and transitions to horizontal as the required depth is reached. A bore path of very gradual curvature or near-straight alignment is normally followed to minimize friction and to stay within the allowable joint deflection and the allowable curve radius for the pipe. This minimizes the chance of getting the pipeline “hung up” in the soil or damaging the pipe.

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• The pilot hole is enlarged by pulling back increasingly larger reamers, or reaming heads, from the pipe insertion point to the rig side. To achieve the appropriate bore path size it may be necessary to perform several reaming operations. Generally, all reaming procedures prior to the actual product installation are referred to as pre-reams, and the final ream to which the product pipe is attached is referred to as the back ream. After the pre-reams, the pulling head and connecting product pipe are attached to the reamer using a swivel, a device that isolates the product pipe from the rotation of the HDD drill pipe. The product pipe is then pulled behind the final reamer back through the horizontal directional drill path to the exit pit on the rig side.

Pipe Bursting

• Utilizes a heavy-duty winch to pull a cracking head that breaks the soil or other material into pieces
• Pipe is simultaneously pulled into the formed void
• Allows use of larger diameter pipe
• Excavation limited to entrance and exit pits as well as lateral connections
• Can also be used to replace lower lateral

Pipe Reaming

• Utilizes a horizontal directional drilling machine and modified cutter head
• Grinds existing pipe into smaller pieces that are carried out with other excess materials by drilling fluid to exit pit
• Pipe is simultaneously pulled into place
• Allows use of significantly larger diameter pipe to replace existing pipe
• Excavation limited to entrance and exit pits

Horizontal Direction Drilling

• Utilizes a horizontal directional drilling machine to install a new pipe where no pipe currently exists
• Process starts with pilot hole drilled to desired grade
• Hole is then enlarged by back reaming while pipe is simultaneously pulled into place
• Utilizes a horizontal directional drilling machine to install a new pipe where no pipe currently exists
• Process starts with pilot hole drilled to desired grade
• Hole is then enlarged by back reaming while pipe is simultaneously pulled into place

Advantages

• NAVIGATOR Horizontal Directional Drilling units work by first drilling a pilot bore underground Different drill heads are matched to the soil conditions and rock formations. A "sonde" transmitter and receiver can be used for greater accuracy, allowing the operator to steer the drill to avoid other utilities or objects such as tree roots. Once the pilot bore is complete a back reamer is attached to the drill string and pulled back , enlarging the bore opening to accommodate the conduit or pipe that is subsequently pulled into place. No digging trenches. No Excavation. Minimun disruption!
• The HDD method is extremely protective towards the environment, causing no ecological damage at all. Minimal damage to the area is only caused within the vicinity of the unit. Several reasons also speak for the application of the directional technique in central town areas.
• The normal course taken by the drilling operation is described in the following: 1.Planning,preliminarysurvey
  2. Selecting the drilling units and drilling tools
  3. Pilot bore and detection
  4. Back reaming (s) or upsizing bore(s)
  5. Pulling in the pipe.
• The high demands and expectations towards the quality of the drilling job waiting to be done require precise localization and steering. Localization is carried out following the transmitter-receiver principle. One operator follows the course of the bore head all the time. All measured values are taken to protocol; directional corrections are passed on to the machine operator via radiophone. It is also possible to directly store the data found in this way, printing them with the help of a PC or Laptop later on. Directional control works according to the "clock-hand principle" via slanted surface of the head; the head changes its direction in correspondence with the clockwise direction.

Conclusions

• In case of canals and rivers it works very gently with out disturbing the water bed.
• An other rule which is to be considered that every bore angle will be accurate enough that it will change its direction (horizontal) after the specified standards, after a specific distance, by the irrigation authority.