Operating principle at a glance:
HDD Rigs in operation
With horizontal directional drilling technology from Herrenknecht, pipelines can be installed rapidly, economically and with minimized impact on environment and existing infrastructure. Later application of the pipelines include the transportation of oil & gas, sewage water, district heating, high-voltage power lines, cable bundles for telecommunication and more. HDD Rigs are highly adaptable in diameter and lenghts of the borehole and used mainly in stable, loose soils and rock.
Simple but functional
With HDD (Horizontal Directional Drilling) pipelines are installed in three steps. First of all, the HDD Rig drills a pilot bore from the launch point toward the reception point. The rotating drill rods are precisely guided along the desired alignment by a surveying system located directly behind the drill bit. During drilling, mud pumps supply a bentonite suspension directly through the drill rods to the jets in the drill bit. In soft geologies, the soil is excavated hydraulically using high pressure, while in rock, excavation is done mechanically with the help of a mud motor. The bentonite mixes with the excavated material and flows back to the starting point through the annular gap between the drill rods and the borehole wall. A separation plant separates the liquid from the solid components and supplies the recycled suspension back to the bentonite circuit.
The pilot bore is followed in a second step by reaming. After exiting at the reception point, the pilot drill bit, including the surveying system, is removed from the drill rods and replaced by a reamer. Using excavation tools and bentonite nozzles, the soil is excavated both hydraulically and mechanically while pulling back the drill rods through the pilot borehole. The water-bentonite mixture in the borehole supports the expanded borehole, removes the soil, and at the same time cools all the components. Reaming is usually performed in several passes until the final borehole diameter is achieved – which is about 30 to 50 percent larger than the actual pipeline diameter. In a third step, the pipeline is installed by connecting the prefabricated pipeline to the drill rods. Lifting the front end of the pipeline creates a so-called overbend and the entry angle of the pipeline is adjusted to match the entry angle of the borehole – also maintaining the minimum bending radius. Then, the pipeline is attached behind a smaller reamer to ensure a clean borehole and a swivel joint, is pulled back to the entry point by the HDD Rig until it reaches its final position. During this process, bentonite minimizes the friction between the pipeline skin and the surrounding soil.
Additional power for long crossings
The traditional HDD method may reach its performance limits when dealing with extremely long crossings, large pipeline diameters, or difficult ground conditions. Therefore, Herrenknecht has developed the Pipe Thruster for such demanding projects. It provides an extra thrust force of up to 750 tonnes at the exit point when installing pipelines. Due to the simultaneous pull by the HDD Rig and thrust by the Pipe Thruster, high installation forces can be applied gently and safely.
A drill bit excavates the soil in a pilot hole; subsequently, a reamer widens the borehole
Hydraulic support using bentonite suspension
Hydraulic conveyance of the excavated material through the annular gap using a bentonite suspension
The carriage thrusts the rotating drill rods forward and pulls them back during reaming
The right rig for the job
HDD Rigs developed by Herrenknecht can be delivered in five different standard configurations. All models have a control cabin, as well as their own power supply pack powered by a diesel or electrical engine, in sound-insulated container or onboard. Depending on the application, the attached power packs have an output ranging from 328 to more than 940 kilowatts and is engineered to the customer’s requirements.
Combinations of all types are possible and one of Herrenknechts' strengths. Fusions of Trailer and Modular Rigs or Compact and Crawler Rig merged with an electrical power unit are often made and jobsite approved. Herrenknecht Rigs are defined by their pulling forces, which are betwen 80 and 600 tonnes (800 and 6,000 kN).
Frame Rig: Their low weight and easy transport make Frame Rigs a reliable and economical solution. Without its own transport or motion system, the Frame Rig reaches the jobsite on a regular truck trailer. A standard crane is sufficient for loading and unloading and for aligning the rig on the jobsite.
Trailer Rig: The great advantage of Trailer Rigs is their extreme flexibility. Due to their low-weight design, they can be transported with standard semi-trailer trucks. A crane is not required, neither for setup and demobilization, nor for alignment and commissioning. This makes Trailer Rigs particularly suitable for projects in which long distances in between several crossings are to be covered.
Crawler Rig: On jobsites in rough “off-road” terrain not accessible to trucks or cranes, Crawler Rigs offer considerable advantages. Their robust and mobile crawler with its caterpillar tracks enables mobility and maneuverability on difficult terrain.
Modular Rig: To be able to use HDD Rigs in remote regions, Herrenknecht has developed another innovative solution. Modular Rigs can be dismantled into two or three modules and transported in standard freight containers. On site they are re-assembled. An optional, remote-controlled crawler adds further mobility on the jobsite.
Compact Rig: Short and compact designed rig optimized for smaller projects and inner city applications. Using range 1 (6m/20ft) drill pipes and optionally equipped with onboard control cabin and high pressure Mud Pump, the rig serves all customer needs.
Special solutions for special projects
Target-oriented implementation of customer-specific requirements is part of Herrenknecht’s daily business. References from successfully completed projects are HDD Rigs operating in ambient temperatures of down to -20° Celsius, a specially designed rig for a project on an Australian island where the focus on nature and wildlife preservation was of utmost importance, or corrosion-proof equipment for sea outfall projects directly along the coastline. Other specialized rigs can even be dismantled in such a way, that they can be transported by helicopter. Pipelines are successfully installed worldwide using powerful HDD Rigs from Herrenknecht. The geological application range of the proven trenchless HDD method covers everything from soft loose soils to hard rock. Ancillary HDD equipment such as high pressure mud pumps, bentonite mixing equipment, separation plants, drill rod storage, mobile break-out units, or bentonite pumps are part of the Herrenknecht portfolio.