Guided moles making impact: the steering capability allows installation to be made a greater lenghts than with standard non-guided compaction boring tools and allows crews to guide the tool in a curved path or to adjust the grade of an installation. (Cover Story).
The steering capability allows installations to be made to greater lengths than with standard non-guided compaction boring tools and allows crews to guide the tool in a curved path or to adjust the grade of an installation.
"The tool is an excellent and economical way to make trenchless directional compaction boring installations of utility service lines without the need to use horizontal directional drilling equipment," says Chris Brahler, TT Technologies' president. "A Grundosteer does not require as much training as a directional drill, and crews familiar with standard piercing tools adapt quickly to its operation."
Guidance is achieved with a slant-faced tool head similar to those used on HDD equipment. Directional changes are made by repositioning the slanted face. This is accomplished by a crew member physically turning the tool's wire-reinforced air hose, using a specially-designed handle that clamps onto the hose.
Just as with HDD equipment, a radio transmitter in the tool head sends information about tool head location and drill face position to a walk-over receiver operated by a crew member directly above at the surface. A special housing isolates the downhole transmitter from vibration caused by the impact of the tool as it pounds its way through the ground.
To date, primary users of the tool are gas and electric utility companies, says Brahler.
"The product is meeting the standards of the utilities using it," he says. "Reports are that the tools are working very well with no mechanical or electronic problems. Average lengths of installations are between 70 and 150 feet, and as long as 190 feet."
On the job
Some of the first Grundosteer guided piercing tools to go into service are being operated by the Public Service Electric and Gas Co. (PSE&G), Newark, NJ.
"We now have 11 units deployed on the gas side of our operations," says George Ragula, distribution technology manager. "We use them both for gas mains and services, but primarily to install services 2 inches in diameter and smaller."
They are employed to install pipe under streets, paved parking lots and landscaped areas in order to avoid making surface cuts and in situations where access limits the use of large equipment.
The key to effectively using the tools, says Ragula, is careful planning to identify the right applications.
"If you plan and use the tools correctly," he explains, "it is possible to achieve substantial cost savings. However, it isn't just cost - there are customer satisfaction issues, as well. Limiting property damage and inconvenience caused by construction pleases our customers, and the customer element is very important."
Steering capability extends the useable range of piercing tools, continues Ragula. "It allows us to do all types of installations, make curves, change elevations - jobs that were the nemesis of standard tools."
Ragula also says the tools are relatively simply to deploy. "Our crews use standard piercing tools every day, so the only new element is tracking its path and steering. Direction changes are made by the way the drill head face is positioned, and that is a technology that is well established."
One of the more interesting and difficult installations undertaken with a Grundosteer tool was completed on Long Island, NY, by KeySpan Energy Delivery.
The project called for a 1-inch-diameter MDPE service line to be installed from a main running parallel to a road that extended 95 feet up a hill to connect to a home. The tool was launched from a small pit, and guided downward at a slight grade for approximately 15 feet to the base of the hill. The bore path then went upward at a 55 percent grade for 50 feet. The tool then was brought to the surface near the house. Pipe was attached to the air hose and pulled into the ground as the hose was removed from the bore hole. Average depth of the bore never exceeded 70 inches below the surface.
"This tool will let us do some things we were not previously able to do," says Angelo Fabiano, KeySpan principal engineer, operations research. "It can do things a conventional piercing tool can't. As far as saving money, it takes a smaller crew than a directional drill rig and can go places where a directional machine can't. And because it is trenchless, it minimizes public disruption and lowers restoration costs."
The Grundosteer tool can be surface launched, or the bore can be initiated from a small pit. Most of the crews using the first units seem to prefer pit launches, Brahler says, because they can start the bore at the necessary depth.
The 3-inch diameter tool is 87 inches long and weighs 85 pounds. It requires 35 cfm of air to generate 400 strokes per minute. Maximum effective bore length is listed as 200 feet.
Initial concept for the guidable tool was developed by Foster-Miller Inc. GTI (formerly the Gas Research Institute) conducted research and provided coordination. TT Technologies manufactures the tool and Digital Control Inc. is the manufacturer of the downhole electronics and the walk-over tracking receiver.
Since the tool was introduced, a stepped-head option for rocky soils and optional ribbed sleeve for sandy conditions have been made available.
While most of the first tools to reach the field are doing gas work, Brahler says that it will be equally effective for installing water services, as well as other applications within its range of operation.
"We see a solid future for the Grundosteer tool," concludes Brahler, "and we continue to invest in testing to offer a broader line of accessories for steering heads and pull back tools."