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 KeySpans Angelo Fabiano, Principal Engineer
Operations Research, the growth in the gas industry drives
the development of new and more efficient installation technologies.
He said, "Were growing.
Through mergers and acquisitions, our territory continues
to expand. We are doing a lot of conversions; and thats
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
The most recent piece of trenchless
technology that KeySpan is utilizing promises to have a great
impact on the gas industrythe worlds first truly
steerable pneumatic piercing tool.
designed sonde within the Grundosteer's tapered head
provides pitch and roll information to an above-ground
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 tools 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
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 differenceit
can be steered. Sensors on the tool provide pitch and roll
information to the operator. An above ground locator is used
to track the tools 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 tools 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 tools 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.
the Grundosteer is
accomplished by rotating a wire-reinforced air hose
with a hydraulic tensioning unit called a torquer.
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."
unit can be surface launched by hand or pit launched,
as a conventional piercing tool can.
Mattson and the KeySpan crew dug
a small launch pit. The Grundosteer was launched in the 6
oclock 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 oclock 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 Grundosteers
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 oclock.
The tool began to arc slowly and surfaced 15 feet from the
95-ft. bore drops slightly for the first 15 ft. and
then travels up hill at 55% grade for 50 ft. The grade
then changes to 15% for the last 30 ft.
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 Grundosteers air hose.
As the air hose was removed, the new MDPE was pulled into
Fabiano said, "This tool will
let us do some things we werent 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 cant.
It can also do things that a conventional piercing tool cant.
And its 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,