FlowMole Technology Helps Shape Guided Boring

Wed August 16, 2000 - Northeast Edition
Lori Lovely



Electronics comprise the most significant change in utility work since 1994, said George Taylor, vice president of operations and engineering with UTILX Corporation. And UTILX has been at the forefront of the developing technology.

In 1984 three engineers at the company’s research and development lab in Kent, WA, succeeded with an innovative drill pipe, signaling the beginning of widespread guided boring.

“Like cowboys bull-dogging in a rodeo, two guys wrestled with a hand-held frill motor while a third engineer braced the spinning drill pipe against his leg,” said Ken Fender, one of the original FlowMole research and development team. “We would push like crazy, stop, add a section of drill pipe, and then do it all over again. To everyone’s amazement, the damned thing came out of the ground exactly where we had steered it.”

The FlowMole technology has its origins in a research project initiated by the Electric Power Research Institute (EPRI) in 1978. EPRI hoped to develop new technology for the excavation, installation and replacement of underground electric utilities. They funded a limited partnership in 1983 to continue development.

The program manager, now CEO, John Potter said, The company had exactly two years and $10.4 million to develop a commercially viable product. He assembled a group of engineers to work on two major development projects: a cable follower for the replacement of underground cable, and a guided mole for boring along a specified path to lay utility distribution lines under irregular terrain.

Guided boring is among the least disruptive of the trenchless construction methods. FlowMole further minimizes disruption by facilitating setup in small areas and by its ability to reduce mess and noise by positioning the field power unit and spoils extraction truck up to 300 ft. away from the drilling site. Hoses feed fluids and power to the rig.

A group of scientists and engineers used EPRI’s finding that bentonite could be used to stabilize a horizontal borehole tunnel as a baseline. They focused efforts on the underground cable follower system. The cable follower was a shallow, sub-surface horizontal boring system that attached itself to a primary electric distribution cable. A rotating fluidjet cutting head inched its way along the cable, forming a hole through which a new cable could be pulled in as the old cable was being removed.

FlowMoles are powered by the 7400-M2 field power units, self-contained power and supply sources that feed the drill through hoses. Liquefied bentonite drilling fluid used for cutting through soils is stored on the FPU along with hydraulic, pneumatic and electrical supplies.

A second research team concentrated on the viability of a guided boring system. Engineers modified the 50,000 psi waterjet technology developed by one of Flowjet’s sister companies to pump drilling mud at 3,000 to 4,000 psi.

Using low volumes of drilling mud at moderate pressure, engineers were able to erode a small tunnel without the overcutting and surface subsidence typically required with water jetting.

The company continued to refine its process. One of the engineers realized that a small bore hole to allow the drill pipe to pass to the exit point was all that was necessary. A reamer could then be attached and pulled back through the hole to increase its diameter. The research team decided to try using a bent-axis drill, which bores straight as long as the drill pipe is spinning, but veers off in a specific direction when stopped.

“Someone got a piece of drill pipe, bent the end, attached a fluidjet cutting head, and started pumping drilling mud through it,” said Al Chau, a scientist with the group.

FlowMole crews completed their first project with a prototype guided drilling unit in June 1985, replacing 760 ft. of telephone cable for Pacific Bell in Stockton, CA. By November, the newly founded FlowMole Corporation acquired the rights to the guided drill technology. They introduced their first commercial-grade GuideDrill that year. The trailer-mounted unit was frequently used for work along front lot lines. Demonstrations for utility companies in Illinois, Pennsylvania, Virginia and California were in demand. Contracts were signed for replacing aging underground telephone and power cables.

The following year, in 1986, the company manufactured a highly maneuverable dolly-mounted unit. This 5-hp unit could drill up to 2-in. diameter bore holes and enter backyards through gates as narrow as 32 in.

As Taylor said, controlling the drill string is the important thing.

“It’s a big issue,” he affirmed. “There’s a lot of stuff already there — you need information about what’s down there. You have to know exactly where the drill head is. Very precise information is required — good electronics is the key.”

Chau said that winning the No-Dig ’86 award from the International Society for Trenchless Technology in 1987 “made all those long hours and sacrifices worth it.” The award honored the most notable advancement or achievement in trenchless technology worldwide.

In order to differentiate itself from copycat companies, FlowMole decided to provide the GuideDrill as a service in 1987, said Richard Brinton, vice president of business development in 1987. Four years later, the company renamed itself UTILX, reflecting its role as a “single-source solution for utility replacement.”

Demand for larger diameter guided bores for installation of pressure sewer, water lines and multiple conduits led to the development of drills with more capacity. “The Series F drill — with 33,000 lbs. of pullback force — combined with our highly experienced field crews, gives us a tremendous competitive advantage in the marketplace,” said Chau, vice president of research and engineering. “Anyone today can bore a straight tunnel through good soil, but if you can’t steer with a high degree of precision, it’s easy to damage underground cables or pipe. A damaged fiber optic line alone could cost in the hundreds of thousands of dollars to fix, and most utilities aren’t willing to risk extraordinary repair costs or disruption to their customers.” UTILX’s drilling units can bore to depths of 50 ft., steer around buried obstacles with a high degree of accuracy and exit exactly at the entrance to a vault or transformer.

UTILX has become one of the largest providers of guided boring services in the world. Now the company turns its attention to repositioning itself from a technology-driven company to a market-driven, customer-service oriented company.

In order to better respond to its customers, UTILX is adding locations. The company has operations in New Jersey, Virginia, Atlanta, Chicago and Denver, plus a number of smaller centers for service.

Another way in which the company has expanded its services to meet customer needs is the development of a method of cable restoration called CableCure. The process uses a silicone-based restoration fluid that is injected into underground electrical or telephone cables. The fluid purges all water from the cable, penetrates and eliminates water trees, and prevents future water intrusion. Developed in 1987, CableCure has restored 3 million ft. of underground electrical and telephone cable in North America and Europe.

Underground distribution has become the standard method of residential utility service across the country for 20 years. As the underground systems become older, they become more susceptible to outages through cable faults and deterioration. Replacing large expanses of buried cable can be extremely costly for utility companies.