The trenchless method of horizontal directional drilling (HDD) is used to install subsurface pipelines, cables and conduits under waterways, roadways, densely built areas, difficult terrain or other surface obstacles.

The technology was originally developed in the US, with its roots going back to the 1960s/70s and Martin Cherrington widely recognised as an industry pioneer. Today it is known as a commonplace installation method in underground construction, and since the late 1980s, the technology and equipment involved have developed significantly.

At the centre of the HDD process is the directional drilling rig, which is used from the surface to bore a horizontal pilot hole in a shallow arc along a prescribed path to an exit point, and then to enlarge the hole by pulling a reamer back through it. Lastly, the pipeline is pulled through the finished borehole.

Today the evolution of HDD rigs is being propelled forward by increasing demand in the marketplace, particularly with regard to improved infrastructure that has kept utility contractors, fleet managers and manufacturers busy over the past few years.

Municipalities and similar customers are increasingly demanding that electrical wires, telecommunications lines and other utilities go underground for aesthetic and practical reasons.

"Whether we're talking about advanced technology in energy sources such as natural gas, wind and solar, or connectivity technology such as telecommunications, DSL and fibre-optic installations, directional drills have become an extremely popular solution in connecting infrastructure, and this demand has dictated a need to provide premium HDD solutions," explains Mike Brugh, part of the international siteworks business at the Toro Company.

"Traditionally, trenching has been less expensive, but with other factors, including road closures and geographic features, impacting the overall functioning of the locale, HDD becomes more cost-effective in the long run," adds Damian McCabe, business-development manager in the trenchless-equipment division at McCloskey International.

Recent requirements

As the industry landscape has become more competitive, HDD equipment has undergone significant improvements as a result of practicality and necessity to suit contractor needs.

HDD contractors are demanding flexible HDD systems that allow for a maximum range of applications at high speed yet low operational cost, guaranteeing a high return on investment. In addition, very few utility companies have the ability to keep multiple units of multiple sizes of rigs in their inventory, so manufacturers are now developing rigs that can perform cross-class functions.

"Contractors aren't just staying loyal to brands that they have used for decades. Instead, we are seeing contractors and fleet managers do more research on the features and benefits of HDD equipment to make sure they're using the best solution for each job. In short, higher levels of productivity are being expected from contractors, who are looking at their equipment selections to help make up the difference," says Brugh.

Customer needs have become more specific and refined. The market has changed, and the aspects customers care about now were often not of crucial concern to them ten years ago.

"One example is sound," says Jon Kuyers, underground global product manager at Vermeer. "Contractors want quieter drills for the comfort of their crews and the people in the area around a job site.

"Another example is the technology found on drills. Previously, technology was sometimes seen as being synonymous with complexity, but actually it has allowed us to simplify many things."

Contractors are always searching for ways to improve the efficiency of their equipment, and job sites have increasingly become residential zones.

"Underground construction companies are designing powerful drills that decrease surface disturbances by riding on turf-friendly tracks or utilising shorter drills in order to set up in tight spaces: systems that can help maximise the life of pipe joints and increase productivity," says Seth Matthesen, senior HDD product manager for Ditch Witch.

HDD technology has also seen various developments regarding automation, ecological machine design and drilling tools in recent years. And rigs that employ the latest wireless technology allow for enhanced communications and diagnostics to and from the machine.

"Modern HDD rigs provide several features easing and speeding up the drilling process, such as automatic drill-rod exchange or even complex bore automatics that relieve the operator from routine functions and shorten drilling times. High-capacity bentonite HP pumps on board the drill rig supplying great drilling fluid volumes accelerate the drilling process as well," says Tracto-Technik's Dr Hans Joachim Bayer.

According to Matthesen, the largest change for HDD over the past five to seven years has been in accommodating Tier 4 engine requirements. This not only changes the overall size and weight of the unit, but in many cases the cooling and hydraulic packages.

"CAN systems and distributed computing are new innovations that were not available even ten years ago. These innovations give the operator more feedback from the drill unit, which in turn can increase production and operator comfort," he adds.

Utility contractors are looking for HDD rigs that have highly intuitive controls. Operators of varied skill levels will potentially be using directional drills on site, and contractors can help mitigate any risk by selecting equipment that is easy to operate and understand.

Contractors also want to keep their crews safe, so a number of features are being integrated in premium machines to help increase safety on the job site, including, for example, stabilisers and an exit-side lockout system.

Latest designs

Here selected key HDD rig manufacturers introduce their main products and newest models.

Ditch Witch

Contractors increasingly find themselves working on utility projects, such as fibre-optic installation. These projects require efficient, powerful HDD rigs that meet the specific challenges of shallow installation projects.

Designed to ensure the most efficient utility installation possible, according to Ditch Witch, its JT9 is the most powerful HDD rig in its class. The rig offers 9,000lb (40kN) of pullback force and includes many of the advanced features of larger drilling rigs, such as a heavy-duty anchor system, open-top vice wrenches and an integrated remote display.

The Ditch Witch JT60 and JT60 All Terrain directional drills are efficient and productive in larger utility projects, matching 60,000lb (267kN) of thrust with a durable, customer-driven design. Unique to the JT60 is the patented, two-pipe all-terrain drilling system that provides more power to the bit than any other rock-drilling system in its class, improving productivity in the widest range of ground formations, Ditch Witch claims.

"We have seen a steady demand for each Ditch Witch All Terrain rig," Matthesen adds.

Herrenknecht

Commenting on HDD rig evolution, Herrenknecht's senior product manager for pipelines, Michael Lubberger, says: "On one hand, rigs have got equipped with more powerful and efficient rotary drives, more safety features and more features for the acquisition of data. On the other hand, we reduced the fuel consumption and the weight of the rigs and designed them to be robust and modular for job sites that are difficult to access. For example, modular rigs with single-piece weights under 10t for helicopter transport into the jungle."

Herrenknecht's latest innovations include the new Full Face Hole Opener, with which pilot holes can be enlarged in a single step. If a Down Hole Jet Pump is installed directly behind it, the borehole can be cleaned during the same step.

"Advancements and innovations in HDD downhole tooling such as these will make the use of HDD rigs with higher torques more efficient as the capability of the drill pipes is also increasing steadily," says Lubberger.

As communication systems become more advanced, it will be possible to access and control the rig, including data, camera and communication systems, from anywhere in the world. The advantages for service and trouble-shooting are evident.

Furthermore, Herrenknecht has developed SDD (slant directional drilling) rigs for steeper drilling angles based on HDD technology.

McCloskey International

Based on customer feedback following its introduction in 2014, the McCloskey D15 has undergone a number of key design enhancements and has evolved into its second generation, better able to accommodate a diversity of climates and conditions.

At the front of the drill, the augers have been placed in a more vertical orientation for enhanced transfer of power. At the rear, two foot plates add stability, anchoring the rig to the ground in uneven terrain.

A transfer bridge on the D15 houses the hydraulics away from the drilling area and features a manual control override should it be required. The operator's station also underwent significant changes, with enhanced sightlines for the control panel, joysticks angled for comfort and the placement of the grease bucket on the mast for easier access.

According to the company, safety was a key factor in the redesign, and the D15 has three E-Stop buttons. The 25gpm (1.58L/s) mud pump features one of the largest flow rates for a drill in its size category, and a large fuel tank allows for all-day projects without refuelling. An oversized oil cooler allows for better operation in high ambient conditions.

Understanding that particularly in urban centres a drill with a small footprint is not only preferred, but necessary, the D15 also has reconfigured augers to allow greater manoeuvrability in small spaces. The operator's station has been reconfigured.

The Toro Company

Powerful thrust and pullback, combined with a relatively small machine footprint, really pay dividends for utility contractors across the globe. Contractors are also looking for their HDD rigs to be increasingly versatile.

Toro's DD2024 is designed for short-range applications, but is powerful and versatile enough for mid-range projects as well, the company claims. Additionally, the Toro DD4045 is a mid-range drill, but can be used on both short-range and long-range projects.

Although Toro has been in business for over a century, underground directional drill equipment is still a relatively new product category for it. Operators of Toro HDD equipment appreciate the flexibility to choose either single- or dual-joystick operation, the ability to use cruise control while back-reaming and the ability to monitor all machine functions from the colour LCD display.

The two Toro HDD rigs are focused on productivity, with a two-speed floating carriage to decrease cycle time. The DD2024 drill combines a compact design with 20,000lb (89kN) of pullback force and 2,400ft-lb (3,254Nm) of rotary torque.

The DD4045 packs 40,000lb (178kN) of thrust and pullback, and 4,500ft-lb (6,101Nm) of rotary torque within a small footprint (85in wide). Drilling-fluid flow up to 70gpm (4.42L/s) and tool rotation speed of 225pm give the DD4045 the versatility to perform a wide range of installations.

Both rigs utilise a quad rack-and-pinion carriage design that spreads carriage load evenly and ensures smooth and efficient travel. The gear track is welded to both sides of the thrust frame for added reliability. The track is propelled by forward-mounted track-drive motors with planetary gears, which deliver greater traction in all ground conditions.

Tracto-Technik

The latest HDD rig models provide maximum power yet require comparably little space for both transportation and drilling.

A rack-and-pinion drive allows for precise control and adjustment of the thrust and pullback forces. Engines run with eco-friendly bio-diesel at low consumption, and noise and exhaust fumes meet the latest EU standards.

Major progress has been made in the development of drilling tools that enable versatile HDD applications in the most complex soils, including hard rock.

Equipped with special rock-drilling tools, modern HDD rigs can accomplish successful bores in very rough and rigid topographic and geologic conditions.

"A perfect example is the Grundodrill 18 ACS (All Condition System), which works efficiently in alternating soils as well as in hard rock at distinctively reduced operating costs and construction times compared with similar drilling rigs," says Bayer.

The 18 ACS works with a twin-tube drill rod consisting of an inner tube with plug-in connector and outer tube with Elicon thread.

For bores in rock, the Rockbreaker steering head with roller chisel is applied. When drilling, the outer tube steers the Rockbreaker and the inner tube, which is connected to the roller chisel, transfers a torque of 2,500Nm up to 350rpm directly onto the chisel. Only a small quantity of bentonite is required, reducing the costs for purchase, treatment and disposal.

Due to the 126kW diesel engine consuming less than 10L/h and a thrust and pullback force of 180kN, standard fluid-assisted bores up to 400m long and rock bores up to 300m with a diameter of 20in can be established economically, the company says.

Having a working width of 2.3m and an axis-centre distance between drilling axis and obstacle of only 1m, the Grundodrill 18 ACS is also suitable for application in limited spaces.

Vermeer

"Today, Vermeer horizontal directional drills are a lot more efficient and powerful - particularly in terms of thrust, pullback, rotational torque and horsepower - in the same or smaller footprint than in the past," explains Kuyers.

"Improvements in technology have also enhanced the capabilities and efficiency of drills by reducing cycle times and improving speeds. Also, improving and standardising controls and lowering noise levels have enhanced operator comfort."

The D23x30 S3 Navigator HDD was released this summer and will be followed by the D24x40 S3 Navigator and the D40x55 S3 Navigator. Vermeer's S3 generation of drills offers enhanced speed, simplicity and sound.

According to Vermeer, its midsize rigs continue to be very popular with contractors due to the flexibility to install many product types of various sizes and in a wide range of soil conditions, whether a crew is pulling fibre cable on a 600ft (182.3m) shot or pulling a 12in (30.5cm) steel pipe.

"With our recent product launches, we've had a lot of positive feedback from customers. For example, with the D23x30 S3, we've heard people comment on how quiet it is and how comfortable their operators are in it," says Kuyers.

"At the annual Vermeer Customer Conference in June, customers kept wanting to throttle up the D23x30 S3; they didn't think it was running because of how quiet it is."