The New Guided Piercing Tool Steering the Gas Industry in the Right Direction

With a customer base of over 2.6 million people, KeySpan, Energy Delivery needs to remain as efficient as possible to meet the needs of its customers. One way that KeySpan has increased its efficiency is through the use of new technology for service installations and conversions. According to KeySpan’s Angelo Fabiano, Principal Engineer Operations Research, the growth in the gas industry drives the development of new and more efficient installation technologies.

He said, "We’re growing. Through mergers and acquisitions, our territory continues to expand. We are doing a lot of conversions; and that’s one of the reasons for this need for new technology and trenchless applications. Trenchless installation methods have become an integral part of the gas industry. And in many ways, the gas industry has prompted growth in the trenchless equipment industry."

The most recent piece of trenchless technology that KeySpan is utilizing promises to have a great impact on the gas industry–the world’s first truly steerable pneumatic piercing tool.

The Guided Mole

Development of the steerable piercing tool began in 1992. The Gas Research Institute (GRI), Chicago, Ill. identified a need in the industry for an installation tool that had similar capabilities to a directional drill, but required a smaller crew and could operate in areas that a conventional drill rig could not. Through the coordination of the GRI, the engineering firm of Foster Miller, Inc., Waltham, MA, created a design for the tool.

Trenchless equipment manufacturer TT Technologies, Aurora, Ill., was selected to build and market the guided mole under the trade name Grundosteer®. Digital Control Inc., location and tracking equipment manufacturer, Renton, WA, was chosen to produce the tool’s guidance system. Finally, several large gas utilities, including Brooklyn Union Gas (now part of KeySpan), were selected to put the Grundosteer through rigorous field-testing.

Specifications and Operations

After several years of development and testing, the partners have arrived at the final tool design. Like conventional piercing tools, the Grundosteer is pneumatically operated and is powered by a piston inside of a casing. It can be surface launched by hand or pit launched from a starting cradle.

The 3-inch diameter tool can bore up to 200 feet. In all respects it operates and functions like a regular piercing tool with one big difference–it can be steered. Sensors on the tool provide pitch and roll information to the operator. An above ground locator is used to track the tool’s position and movement.

Depending on soil conditions, the tool can be steered at a maximum 85-foot radius. The operator can make adjustments to the tool’s course by rotating the air hose with a hydraulic tensioning unit called a torquer. A specially designed tapered steering head rotates accordingly then sets the tool’s course.

According to TT Technologies Piercing Tool Specialist Brian Mattson, the tool is ideally suited for the gas industry. He said, "It is not always practical to use a directional drill rig for difficult service installations. Conventional piercing tools are not always the right choice either. The Grundosteer combines the best of both methods." Those abilities were recently put to the test in the challenging service area of KeySpan Energy Delivery.

On the Job

Conversions, installations and system upgrades occur on a daily basis within the KeySpan service area, including the area once known as Brooklyn Union Gas. KeySpan maintains two full time directional drilling crews in the New York area and many other service crews are equipped with piercing tools. For one particular conversion in Long Island, neither a directional drill nor a conventional piercing tool would be practical. The Grundosteer would have to overcome several challenges.

Fabiano said, "The Long Island job called for the installation of a 1-inch MDPE gas service from a 4-inch steel gas main, running parallel to the roadway, to the house located 95 feet away. From the launch pit, the bore path dropped slightly for the first 15 feet then traveled up hill at 55% grade for 50 feet. At that point, the grade of the bore changed to 15% for the last 30 feet until reaching the exit pit located next to the house."

In addition to the challenging grade, the soils in that area are not very piercing tool friendly. Mattson explained, "Sandy soils are some of the most difficult soils to bore in for any piercing tool. The lack of ground resistance can cause the tool to ‘swim.’ In this case we encountered sandy and rocky soil conditions and had to run the tool at 1/3 power to prevent it from swimming."

The Shot

Mattson and the KeySpan crew dug a small launch pit. The Grundosteer was launched in the 6 o’clock position at 34 inches deep. The crew let the tool travel downward to match a small drop in grade before reaching the base of the hill. At approximately 15 feet, the crew rotated the air hose and positioned the tool head in the 12 o’clock position. At this point the tool began to climb the hill.

Mattson said, "Mapping the bore path out before the shot is very important, especially in a situation like this. The tool was at its shallowest during the first 15 feet of the bore. Given the distance we had to work with, we knew that after the tool turned to climb the hill, it would not be able to match the 55% grade before it reached the surface. Therefore, it would continue to gain depth throughout a majority of the bore.

However, we did not want to be deeper than 70 inches at any point during the bore. We needed to determine what grade we could achieve given the Grundosteer’s rate of turn and the bore length; how deep that grade would take us; and where would the tool be when it crested the hill."

After traveling the first 15 feet and making the turn upward, the tool eventually achieved a 35% grade climb. At that grade, the tool never exceeded 70 inches deep at any given point during the bore. At the 50-ft mark, the grade of the hill lessened dramatically to 15 percent. When the DigiTrak Receiver from Digital Control, showed the tool beginning to shallow, the crew rotated the hose once again and positioned the tool head back at 6 o’clock. The tool began to arc slowly and surfaced 15 feet from the house.

After the Grundosteer surfaced, the KeySpan crew trenched the final 15 feet to the house. The new 1-inch MDPE pipe was installed by attaching it to the Grundosteer’s air hose. As the air hose was removed, the new MDPE was pulled into place.

Fabiano said, "This tool will let us do some things we weren’t previously able to do. It is definitely another tool in our arsenal. As far as saving money goes, it takes a smaller crew to operate than a directional drill rig and can go places where a directional can’t. It can also do things that a conventional piercing tool can’t.

And it’s trenchless. And trenchless methods are designed for minimizing public disruption and lowering restoration costs. I look forward to seeing the tool reach its full potential."

GAS UTILITY and Pipeline Industries, October 2000