Horizontal Directional Drilling (HDD)
Horizontal directional drill is a trenchless technique forming a bore hole through the ground for installation of water mains, sewer & drainage pipeline, gas, cable TV, or phone service; in order not to cause disruption of service for long periods of time and create inconveniences for commercial and private interests.
Horizontal directional drill machines will bore under or around obstacles with planned drill path. The shape of a drill bit on the drill head allows an operator to control the direction of drill path direction during a bore.
The drill head is equipped with a transmitter that sends signals to an above ground receiver and the head’s location will be tracked during a bore in order to provide steering position information to the HDD operator.
Horizontal Directional Drilling System
Drill Rig
Horizontal directional drilling machines are available in many sizes. Regardless of a machine’s size, it has three main functions — rotation, forward thrust/pullback and fluid flow.
HDD Process
Horizontal directional drilling machines will bore under or around obstacles. Once the drill path is planned, an underground pilot bore is performed utilizing a series of drill rods connected to a drill head. After the pilot bore is completed, a back reamer is attached to the drill string that enlarges the drill path to accommodate the product that will subsequently be pulled into place. Vermeer NAVIGATOR horizontal directional drilling machines can install product under roads, buildings, railroad tracks, streets, rivers, creeks and in congested underground areas.
Steering
Steering refers to control of the direction of a drill path. The shape of a drill bit on the drill head allows an operator to change the drill path direction during a bore. When an operator points the drill bit downward to the 6 o’clock position and pushes the drill head forward, the drill head goes deeper. When the drill faces the 12 o’clock position, the drill head will rise. Pushed to the 9 o’clock position, the head goes left. Pushed to the 3 o’clock position, the head goes right. If no change in drill path is needed, the drill head and rod are rotated while thrusting.
Locating
Prior to starting a bore, the drill head is equipped with a transmitter that sends signals to an aboveground receiver during the bore. The drill head’s location will be tracked during a bore in order to provide steering position information to the HDD operator. The depth and position information is displayed on the locator screen.
Back Reamers
When a pilot bore is complete, the drill head exits the drill path and a back reamer is attached. Utilizing drilling fluid and the drill string, the back reamer is pulled back through the path to enlarge it to accommodate the product that will be pulled into place. Sometimes pre-reaming is performed to incrementally enlarge the drill-path wall. The installation product is then attached to the drill string and pulled into place. Many back reamer styles and sizes are available for different ground conditions and product sizes.
Mud Flow
Mud flow is an important component of the HDD process. Mud flow is created by pumping a combination of water and specialized drilling fluid additives through the drill rod and head (or backreamer). The drilling fluid then mixes with soil in the drill path and creates a flowing slurry back out of the path as the product pipe is pulled into place. Mud flow cools the transmitter housing in the drill head, suspends cuttings to help prevent product pipe from getting stuck during the bore and seals the bore to help prevent fluid loss and bore wall collapse.
Working Procedure
Stage 1 – Launching Pit & Receiving Pit
Stage 2 – Setting Up of HDD Drilling Rig
Stage 3 – Install Pilot Drill Rod
Stage 4 – Install Pilot Drill Rod to Receiving Pit
Stage 5 – Fit Reamer Head at End of Drill Rod
Stage 6 – Enlarge the Drillhole by Reamer and install Product Line
Stage 7 – Install Product Line Completed
General HDD Site Operation Procedure
- Site Survey
- General site survey to ensure suitability of machine set-up and new pipe launching pit location,
- Mobilization, site storage as well as other areas requiring authority approval.
- Underground Utilities
- Utility survey to ascertain buried location and depth;
- Ensure general situation is suitable for cable conduit installation under utilities.
- Bore Path Planning
- Design bore path;
- Ensure spacing between the three (3) cable conduit meets the designed requirement;
- Ascertain set back distance from covered drain at HDD equipment side;
- Locate drill rod exit position (cable conduit launching pit) and ensure sufficient space behind pit for laying out continuously fused cable conduit before insertion;
- Operation
- After final inspection of HDD, tooling and ensuring all safety requirements checked and certified, the HDD operation is ready for commencement;
- HDD drill out to exit pit location — tracking against planned bore path to ensure accuracy and make necessary directional changes where necessary;
- After drill rod string arrived exit pit, remove drill head and sonde housing and assemble suitably sized back reamer to rod string and towing the continuously fused 160mm PE cable carrier pipe;
- HDD pull rod string towards itself, creating a larger bore hole using the back reamer and installing the cable conduit simultaneously;
- Suitable mud (bentonite) should be used during the drill out, pull back and conduit installation process;
- After installation the first conduit, the HDD is set-up again for the second bore and conduit pull back operation;
- Repeat the operation for the third cable conduit installation;
- Finishing up
- Inspect installed conduits;
- Demobilize from site;
- Hand over installed conduits for further activities
Get Started with SKK Works Pte Ltd HDD Services
Whether you have a project involving utility installations, pipeline crossings, or any HDD application, SKK Works Pte Ltd is here to provide the trenchless solutions you need. Contact us today to discuss your project requirements, request a quote, or schedule a consultation with our experts. Let us be your trusted partner in achieving precision and efficiency through Horizontal Directional Drilling.
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