A new trench-digging machine that uses supersonic jets of air to loosen dirt will protect the operator by minimizing the risk of damage to buried electrical cables or gas lines.

Developed by Battelle and Concept Engineering Group Inc. for the Electric Power Research Institute (EPRI), the "Soft Trencher" (patent pending) uses air jets, instead of the hard-cutting teeth of conventional excavators, to crumble the soil. The soil is captured by a vacuum air stream and placed on a truck or deposited along the trench.

"The supersonic air jets effectively break up the porous soil, but they are harmless to utility pipes and cables," said Tom Rodenbaugh, Manager of Cable Operations and Software Development. "The vacuum system also replaces the conventional method of mechanically scooping up the dirt. This eliminates another chance to cut the utilities and harm the operator."

Gary Brawley, Battelle project manager, said the Soft Trencher has advantages over traditional excavation equipment, which can easily damage buried cable or pipe. "The down force from this machine is significantly reduced and is better by virtue of its cutting principle," Brawley said. "Currently, the Soft Trencher is undergoing tests and demonstrations by Concept Engineering Group in Pittsburgh."

The Soft Trencher can be maneuvered from the operator's seat or a tethered remote control box to allow maximum visibility. The operator can easily see exposed utilities to guide the excavation head around them. This feature eliminates the slower and more costly, labor-intensive hand-digging around the utilities.

The system has a minimum trench width of one foot to a maximum of about six feet with multiple passes. On a single pass, the excavation head removes two to five inches of soil, depending on the soil type, and can also pick up and pass rocks as large as about seven inches in diameter.

CEG is also researching modifications to the Soft Trencher so that it could be used for environmental waste site cleanup, bulk material handling and loading, railroad grade cleanup and material recovery.

"An offshoot of the machine developed for EPRI has real applications for digging up buried waste," said Richard Nathenson, President of CEG.

For environmental waste cleanups, it's possible that the Soft Trencher could be modified with a heating source inside its vacuum hopper to separate contaminates from the soil. It could also have a radio-controlled remote and vision system added to the machine to replace the tethered controls that now exist. This would allow the operator to be safely isolated from a hazardous site.

In bulk material handling and loading, the Soft Trencher would replace a conveyor system and a loader in a gravel yard. For railway cleanup and material recovery, the soft trencher could be adapted with rail wheels for low speed operation along the tracks. It could be used for ballast cleaning between rails and tunnel operations. Also, the on-board conveyor makes it suitable for direct recovery of materials.

The Soft Trencher has been selected by R&D Magazine as one of the 100 most technologically significant new products of 1994. The Soft Trencher and its technology are currently available for license.

Additional information on the Soft Trencher is available by calling Gary Brawley, Battelle, (614) 424-4581; or Tom Rodenbaugh, EPRI, (415) 855-2306.

Battelle serves industry and government by developing, commercializing, and managing technology. With a wide range of scientific and technical capabilities, Battelle puts technology to work for clients in 30 countries.

Concept Engineering Group, Inc. [(412) 826-3191] is a multidisciplinary engineering company located in Pittsburgh that specializes in safe excavation technology using supersonic air jets and pneumatic vacuum transport. CEG's capabilities range from initial research and development to prototyping, field testing, and commercialization.

EPRI, founded in 1972, manages technical research and development programs for the U.S. electric utility industry to improve power production, distribution and use. Some 700 utilities are members of the Institute.