Switzerland Contractor Handles All Types of HDD Work
By Jeri Lamerton Sep 19, 2013
Drilljet AG is a utility contractor in Switzerland specializing in installation of underground utilities for a broad range of clients, including telephone and power companies, regional gas providers, city governments, and general contractors.
Depending on job requirements, work is completed using open-cut excavation, horizontal directional drilling (HDD), pipe bursting, pneumatic piercing tools, and rod pushing equipment.
Based in Moosleerau, Switzerland, about one hour away from Zurich between Zurich and Bern, all of the company’s work is in Switzerland.
Drilljet evolved from Hans Hunziker AG, established in 1997 to provide high-end civil engineering services. When work required houses to be connected to utilities, the company manufactured a compact rod pusher that pushed a rod through the ground to make a hole through which pipe was inserted, thereby avoiding the need trenching through surface improvements. As demand for this type of work expanded, the company acquired larger, more powerful Ditch Witch hydraulic rod pusher equipment.
When projects required that larger pipes be installed in the ground for longer distances, the first horizontal directional drill was acquired in 2000, said Philip Hochuli, horizontal directional drilling project manager.
HDD technology allows several types of pipes to be installed without the need for extensive excavation, reducing surface damage and the costly restoration necessary after digging.
“HDD is a proven technology that is well accepted by project owners and general contractors in Switzerland,” said Hochuli. “As demand for HDD increased, the decision was made in 2003 to start a new directional drilling company, Drilljet.”
Drilljet specializes in underground utility construction exclusively, and today operates three HDD machines: one Jet Trac (JT) 3020 AT, a 156-hp model producing 30,000 lbs of pullback, 4,000 ft-lbs of torque, and spindle speeds to 225 rpm; one JT2720 with 113 hp, 27,000 lbs of pullback, 3,200 ft-lbs of torque, and a maximum spindle speed of 225 rpm; and one JT820, a compact 35-hp model with 7,000 lbs of pullback, 850 ft-lbs of torque, and spindle speeds to150 rpm.
A challenging recent project was making a 230-ft long bore to install 10-in. diameter PE water pipe in the mountains in Southern Switzerland at Grosse See in the canton of Valais. The pipe is for an artificial snow system in wintertime and a water power system in the summer. Water flows through turbines down into the valley.
Drilljet worked for the project’s general contractor, Sportbahnen Unterbäch AG..
“The pipe had to be placed 23 ft in the ground in extremely difficult rocky soil conditions, which ruled out any possibility of digging,” said Toni Hochuli, who operated the JT3020 AT for this project “In addition to the rock, digging was not possible because there would be a risk of water from a nearby lake entering an excavation.”
Because of the rocky conditions, a JT3020 All Terrain system was used for the project. Even though the machine is relatively compact, the dual pipe mechanical drilling system enables it to effectively bore and steer through hard rock.
The logistics of getting the drilling unit, support equipment, and materials to the work site was not easy.
The highway into the mountains was good, but as the Drilljet truck towing the machine neared the set up location, it had to leave the highway and came to an old wooden bridge that had to be crossed.
After crossing the bridge, the truck continued another 20 miles on secondary roads. Then to reach the location for beginning the bore, a JT3020 AT had to be driven across very rough terrain. A large excavator was brought to the site to clear a path for the drilling unit. Mounted on rubber tracks, the JT3020 AT can move across open country, as well as paving and landscaped surfaces with little damage.
Hochuli said it took from 9 a.m. until 4 p.m. to get the drill unit to the set-up location.
Support equipment also had to be brought to the location.
After leaving the highway, a Ditch Witch MM9 fluid mixing system was pulled on a trailer by a four-wheel drive quad vehicle, then taken by helicopter to the final location. Installation materials were lifted by helicopter directly to the work site.
Supplies and the three-person drilling crew were taken to the location daily by fully-loaded quads, said Hochuli.
“There were mixed soil conditions, mostly hard rock,” Hochuli said. “There was clay at the beginning, many big stones and different types of rock and stone mixed in. Some of the rock was measured at 50,000 psi.”
A 5.5-in. tricone bit was used to drill the pilot hole which was complete in one day.
The hole was enlarged in two backreaming passes: first to 10 in., then to 12 in. with the fused length of pipe pulled in behind the Kodiak backreamer on the second pass.
Pullback of pipe was completed in a half day. After the pipe was in place, connections were made at the lakeside exit point by Drilljet and at the other end by Sportbahnen Unterbäch AG.
The exclusive, patented Ditch Witch AT (All Terrain) system makes it possible for compact equipment such as the JT3020 AT to complete installations in rock impossible for conventional HDD equipment to make.
Conventional HDD equipment uses a single drill stem and a slant-face drilling head to control steering. However, AT models use a mechanical, dual-pipe system that delivers maximum downhole horsepower. An inner rod drives a rock bit, and the outer pipe steers the downhole tool for drilling pilot holes and provides rotary torque for the hole opener during backreaming. The AT system enables simultaneous drilling and steering through rock and rocky soil. AT equipment required no more drilling fluid than convention equipment.
In addition to the 30,000-lb pullback JT3020, there are 40,000-lb pullback and 100,000-lb pullback Ditch Witch All Terrain models.
Drilljet AG is served by DWL Baumaschinen GmbH, Triengen, Switzerland.
Jeri Lamerton is public relations manager for The Charles Machine Works Inc., Perry, Okla.