Even though horizontal directional drills (HDDs) were commercially available in the late 1980s, says Richard Levings, underground products manager for Ditch Witch, manufacturers spent the first years in the industry’s infancy simply explaining the HDD process to skeptics—its application, benefits, and costs—before the light finally dawned.
Today, more often than not, HDD is the first choice for installing underground product, especially in developed urban areas. Plus, the selection of HDD machines has never been as broad, with choices ranging from units with 5,000 pounds of pullback force that work comfortably on the lawn of small home, to pipeline rigs with a million or more pounds of pullback that routinely install 6,000 feet of large-diameter pipe in one shot.
HDD’s climb to near universal acceptance as the preferred method for underground installations, however, has not been without its valleys. After a slow initial start in the late 1980s, the demand for HDD machines soared beyond anyone’s expectation about a decade later with the fiber-optics boom. But when that industry declined, so did the fortunes of the HDD industry.
“When telecommunications was going through the roof,” says Gaylord Richey, regional sales manager for Astec Underground, “sales people were just order takers; everyone wanted to get into the drilling business. When that market fell off, there were probably a lot of people in the drilling industry who didn’t belong there, and HDD was tarnished by poor performance on the part of some of these people.”
Since then, the implementation of the HDD process and the sale of HDD machines has been more or less a steady upward pull that has gained momentum for a number of varied reasons, including refinement of the drills themselves, refinement in down-hole tools and tracking equipment, expanding traditional markets, new markets, and, generally, an increasing recognition of HDD’s capability and efficiency.
But not to be overlooked as a factor in HDD’s wider application is the acceptance and development of “HDD-friendly” materials, such as wider acceptance of fusible HDPE (high-density polyethylene) pipe. Such products have, so to speak, taken the cuffs off many designers, says Levings, allowing a choice of HDD-friendly materials that meet project specifications.
Markets: expanding and new
Most HDD manufacturers agree that the expansion of conventional utility markets (let’s arbitrarily say telecommunications, electrical, water, gas and sewer rehab) is a significant factor for brisk sales of both new and late-model used machines, especially units with rated pullback capacities between 15,000 and 50,000 pounds.
In the telecommunications industry, the demand for “broadband” services will potentially require making a fiber-optic connection to millions of homes. According to the FTTH (Fiber To The Home) Council, about 18 million U.S. households now have access to a fiber-optic connection, and only some 4 million connections have been made. These connections, says the Council, typically are 55 percent aerial (from a pole) and 45 percent underground. FTTH installations, then, represent significant potential for small HDD units, even though the pace of installation could be moderated if FTTH providers divert resources to expand wireless networks.
Also on the rise are geothermal installations, a long-time, so-so market for HDD machines. In its early days, says Levings, the industry attempted to establish the HDD process for geothermal installations, but was only marginally successful. But energy costs and environmental concerns have prompted greater interest in geothermal and the equipment to install these systems.
“In the past three or four years,” says Levings, “the geothermal market has solidified and will have a subsequent positive affect on the HDD industry.”
Although HDD machines in geothermal installations typically are limited to horizontal bores, Vermeer’s new D20x22FX Series II Flex-Angle machine, introduced some 18 months ago, is capable of both horizontal and vertical bores. The machine can drill from entry points that vary from 18 to 90 degrees. According to Vermeer engineer Tod Michael, the FX is designed primarily for vertical and steep-angle geothermal-loop installations, but also functions as a conventional HDD unit. The machine’s design, he says, allows higher fluid flows (as much as 100 gpm at 300 psi) to “create velocity in the bore” for carrying cuttings to the surface.
HDD machines also are being used increasingly for gravity-sewer installations, assisted by technology that simplifies drilling at the correct grade. The Ditch Witch OnGrade system, for example, establishes the sewer’s grade with an above-ground laser reference between the entry and exit pits. Tracker electronics allow the HDD operator to match the reference grade underground by maintaining a constant distance between the drill string and laser beam.
Not-so-common applications for HDD rigs these days, says Vermeer’s Michael, include installing cathodic protection along pipelines and soil stabilization in mountainous or sandy areas. Contractors involved in these markets generally are tight-lipped about their techniques, he says.
Also on the pipeline side of the HDD industry, where the largest rigs typically are employed, the shale-gas industry is becoming a significant market. Extracting the gas involves using HDD machines to establish collection wells, which are initially used for hydraulic fracturing (“fracking”), a process using high-pressure fluid to create a network of fissures in the rock to liberate the gas. (Some have concerns, however, that drilling fluid might leak into aquifers or that fracking liquids might seep to the surface and cause environmental damage.) Once the gas is flowing, pipelines ranging from 4 to 24 inches in diameter are needed to transport it long distances, often through environmentally sensitive areas where HDD is the preferred installation method.
Levings makes the further point that energy demand in developing nations is forcing increased pipeline installation, much of which is being placed with HDD. The pipeline segment of the industry may never have been busier, he says.
Product refinement
Vermeer’s Michael sums up recent design improvements in HDD machines by saying that manufacturers generally are striving to make these units more operator friendly, with such features as common control interface across the product line and easier pipe-makeup systems. Also on the list of refinements, he says, are more robust electronics and reduced noise and vibration.
According to Herrenknecht’s Max Hinterberg, “electronics and mechatronics” are allowing partial automation of the drilling process, permitting the machine to automatically maintain pre-set drilling and pullback parameters. Easier-to-operate machines, says Astec Underground’s Richey, are a welcome development for contractors attempting to accomplish more bores per day—as are safety devices that help the operator coordinate drill functions with less chance of mishap.
Richey also makes the point that machines are becoming more efficient—capable of installing larger product from a smaller machine footprint and better able to balance hydraulic-horsepower demand for the drill’s four basic functions: push; pull; rotate; and pump. Expanded diagnostic systems are helping drilling contractor reduce downtime, says Richey, and plug-in manual controls (such as Astec Underground’s Life Jacket system) allow critical operations to continue should an onboard processor falter.
Related refinements include those in down-hole tools and tracking electronics. The range of down-hole tools now available allow HDD machines to function effectively in virtually any ground condition. A fairly recent development is the use of air-hammer-type tools for drilling in extremely hard rock. Two developing trends in the use of air hammers, says Vermeer’s Michael, are to make these systems faster (higher air pressures and flows) and to use them on smaller drills.
Tracking systems, says Michael, have been refined with more intuitive user interfaces, and down-hole portions of tracking systems are more resistant to vibration and more reliable. Levings adds that tracking systems generally are more accurate and that lithium batteries in sondes promote greater durability and reliability. He notes that a recent innovation in Ditch Witch tracking electronics is the capacity to do “off-set” locating—finding the underground signal when an obstruction prevents standing directly overhead.
Also, says Vermeer’s Michael, innovation in wire-line systems (which use a signal-carrying wire in the drill string) have the potential to simplify electrical connections when making up the drill string, such as the CableLink system developed by DCI (Digital Contol Inc.) and Vermeer. Michael says that wire-line systems are used on most HDD machines with more than 200,000 or 300,000 pounds of pullback, but that these systems are being used increasingly on small units when conditions at the site cause interference with conventional wireless tracking systems.
Taking the long view, Levings sums up: “There are challenges in the HDD industry that must be overcome, but indications are that growth will continue and that the HDD method will be even more widely applied. It’s still the best way to install product and not disturb the surface.”
