Page 220 - Trenchless Technology Piping Installation and Inspection
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184 Cha pte r F i v e
Rig side Pilot borehole Pipe side
Drill pipe Drill bit
Rig side Reaming Pipe side
Drill pipe
Reamer
Rig side Pull back Pipe side
Drill pipe Product
Swab
pipe
Swivel
FIGURE 5.1 Generic HDD installation. (Source: Trenchless Engineering
Corporation.)
intermediate to the Mini- or Maxi-HDD categories may utilize appro-
priate “Midi” equipment of intermediate size and capabilities.
Due to the high importance and large expense associated in accom-
plishing Maxi-, and possibly Midi-, HDD operations, such as major
river-crossings, experienced engineers are typically engaged to help
plan and design the overall installation, including use of appropriate
hardware and software programs and navigational equipment. Mini-
HDD is relatively a low-cost procedure, which typically does not
employ the services of professional engineers. Nonetheless, since
improper Mini-HDD procedures, including incorrect bore planning,
pipe loading, and equipment setup, can lead to problematic installa-
tions, including inadvertent return of drilling fluids and possible dam-
age to nearby buildings and facilities, the second portion of this chap-
ter (Secs. 5.4 and 5.5) presents relatively an easy-to-understand bore
planning guidelines and pipe loading calculations for such operations.
Same concepts can be utilized for Midi- and Maxi-HDD operations.
5.2 Method Description
Directional drilling methods utilize steerable soil drilling systems to
install both small- and large-diameter pipes. In most cases, HDD is a
two-phase process. Phase 1 involves drilling a pilot borehole of
approximately 2- to 6-in. diameter along the proposed design center-
line. In phase 2, the pilot borehole is enlarged by use of a backreamer
to the desired diameter to accommodate the pipeline. At the same