:: Set
up, Boring, and Fusing ::
Directional drills are relatively compact with a small footprint,
allowing them to get into tight spaces and situate on the
side of the road without impeding traffic. A small crew is
required: a drill operator, mud mixer/vacuum operator and
a tracking equipment operator. The tracking operator electronically
tracks the progress of the drill head beneath the surface
using a hand held tracker. He then gathers data from the sonde
located in the drill head just behind the drill bit. The sonde
gathers data such as location, depth, roll angle, pitch, and
temperature to help the driller adjust the direction of the
bit and control the bore path.
To prepare for the installation, the drill operator must first
calculate the route, or bore path, of the pipe along a shallow,
underground arc. The operator must also estimate the load
applied to the pipe during pullback and select an appropriate
pipe for the project. As he bores the path, a bentonite polymer
mix is injected into the hole to stabilize the hole, remove
cuttings, reduce torque, lubricate the pipe, and cool the
bit.
When the pilot hole has been bored and the bit emerges in
the exit pit, the drill bit is removed. A reamer is placed
on the end of the pipe string and pulled back to enlarge the
borehole. Generally the reamed hole is about 50% larger than
the pipe.
Lengths of polyethylene pipe are then fused together. The
pipe is heated and the molecules are transformed into a crystalline
state that enables a seamless joining of the pipe. The end
result is a fusion joint that is as strong or stronger than
the pipe itself. Strong fusions are essential, as service
pipe is subject to soil loads without side support from the
surrounding hole. This load requirement is a major difference
between HDD pipe and pipe installed in a trench. The Henniker
Directional Drilling crew is certified in pipe fusion.
“Henniker Directional Drilling completed a connection between our home and our town’s municipal water supply
in November, 2001. We probably could not have completed this job by conventional trenching methods, since
the town water main was located approximately 400 feet away, and access required crossing a state highway
as well as traveling up a secondary road. We never received an estimate for conventional trenching and
hookup but were informed that the cost would be very high, at least $ 25,000 and probably more.
The job was completed by Jeff Martin and his crew in a timely fashion and cost less than $10,000. Jeff and
his crew were courteous, professional, and caused no disruption in our daily lives. We would gladly work with
Jeff again and in fact consulted him about another project recently. We happily refer potential residential
and commercial customers to Jeff and the rest of the Henniker Directional Drilling team.”
- Molly & Ted Hardenbergh, Hopkinton, NH
|
: History
of HDD ::
Directional drilling has traditionally been applied in telecommunications,
electric installations, oil, forced water, sewer lines and
gas distribution. More recently, HDD has been applied to
horizontal environmental wells and geothermal systems. Contractors
are developing new HDD applications every day.
The directionally controlled horizontal drilling process
was developed in the U.S. and is commonly used for crossing
under natural or manmade obstacles, especially river crossings.
This method has revolutionized complicated river crossings
for pipelines, which were initially done by conventional
dredging methods or were rerouted through long distances
and crossed over at a bridge location.
This method is an outgrowth of the oil well drilling technology,
developed in the early seventies by Titan Construction,
Sacramento, California, U.S.A. The first installation was
accomplished in 1971 for Pacific Gas and Electric Company,
which involved the installation of approximately 600 LF
(180 m) of 4-inch (100 mm) diameter steel pipe under the
Pajaro River near Watsonville, California. Prior to 1979,
the method was limited to the installation of short lengths.
Since 1979, the method has advanced tremendously, enabling
long crossings with a wide variety of pipe sizes.
:: Problems
HDD Solves ::
Traditionally, installation of underground utilities involved
open trenching. The contractor had to excavate around existing
utilities to get to the depth required to install conduit.
Costly sidewalks, pavement, brick paving, sod and other
surfaces had to be open cut and replaced. There was always
a risk of hitting existing underground utilities during
excavation. Additionally, the excavation usually causes
interruption of traffic and inconvenience to nearby businesses.
:: Advantages
to HDD Over Other Methods ::
HDD equipment requires a relatively short set-up time; a
mini rig can be set up and start boring within an hour.
Labor requirements are minimal, as it only takes a small
crew to operate a small drilling rig.
The need for traditional excavation during horizontal directional
drilling is minimal or non-existent. In crowded urban areas,
horizontal directional drilling is increasingly viewed as
"the preferred technology" because:
- HDD eliminates the need for removal, restoration and long-term costs associated with trench settlement
- In open areas, horizontal drilling provides an efficient method for crossing obstacles such as rivers,
highways, rail tracks or an active runway
- Surface disruption is minimized
- Less negative impact on residents and businesses
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| The Vermeer 50x100 |
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| The Tulsa TR40 |
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| The Tulsa TR14 |
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