Page 270 - Trenchless Technology Piping Installation and Inspection

234 Cha pte r S i x

HDD, MTBM, or HAB methods. Pipe removal is further divided
into several methods as follows:
• Pipe reaming and impactor methods: These techniques use a spe-
cially designed variation of the HDD process to excavate the
existing pipe in fragments and remove them rather than dis-
place them, and pull a new pipe to replace the existing pipe.
• Pipe eating: This technique consists of a microtunneling
machine, which has been specially adapted to allow the exist-
ing pipeline to be broken up, and removed. The MTBM has a
larger diameter than the existing pipeline. In the United States,
due to the high cost of microtunneling for this application, this
equipment rarely has not been used for this application. Hori-
zontal auger boring equipment has successfully been experi-
mental in several projects.
• Pipe ejection or pipe extraction: These techniques remove the
existing pipe as whole from the ground, by pushing and/or
pulling it toward a reception pit where it is broken and
taken out.

6.3.1 Pipe Reaming
Pipe reaming is a pipe replacement technique that uses an HDD
machine with minor modifications. After pushing the drill rods
through the existing pipeline and connecting the rods to a special
reamer (see Fig. 6.4), the new pipe string is attached to the reamer via
a swivel and towing head. As the drill rig rotates the drill rod string
and simultaneously pulls it back, the existing pipe is pulverized and
replaced by the new pipe. Removal of the existing pipe is accom-
plished by mixing the ground material with the drilling fluid and
transferring it to an exit point for collection via a vacuum truck. Direc-
tional drilling contractors can add inexpensively modified reamers of
various types for different pipe materials and ground conditions.
Pipe reaming is limited to nonmetallic pipeline replacement. The pat-
ented InneReam System can accomodate the surrounding environ-
mental conditions (groundwater, sand, rock, concrete encasement,
and the like) with certain modifications. Contact Nowak Pipe Ream-
ing Inc., for more information.

Direction of reaming

FIGURE 6.4 Pipe reaming method. (Source: Nowak Pipe Reaming Inc.)