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Pr oject Considerations for Pipe Replacement Methods 231
(a) (b)
FIGURE 6.1 The pipe bursting operation. (a) Insertion Shaft, and (b) Pulling Shaft.
6.2.1 Pneumatic Bursting Systems
Currently this method, the most common pipe-bursting method is
the pneumatic system (see Fig. 6.2). The bursting tool is a soil dis-
placement hammer driven by compressed air and operated at a rate
of 180 to 580 blows per minute. It is similar to a pile-driving opera-
tion, but in a horizontal orientation. The percussive action of the
hammering cone-shaped head is also similar to hammering a nail
into the wall; each hammer pushes the nail a short distance. With
each stroke, the bursting tool cracks and breaks the existing pipe. The
expander on the head, combined with the percussive action of the
bursting tool, push the fragments into the surrounding soil, provid-
ing space to pull in the new pipe. The expander can be front end
(attached to the front of the hammer) for pipes smaller than 12 in. or
back-end (attached to the back of the hammer) for pipes larger than
12 in. The front-end expander allows withdrawing the hammer
through the new pipe after removing the expander from the existing
manhole or the pulling shaft. The tension applied to the cable keeps
the bursting head aligned with the existing pipe and pressed against
the existing pipe wall, and pulls the new pipe behind the head. An air
pressure supply hose is inserted through the new pipe and connected
to the bursting tool. The bursting starts once (1) the head is attached
to the new pipe, (2) the winch cable is inserted through the existing
pipe and attached to the head, and (3) the air compressor and the
winch are set at constant pressure and tension values. The process
continues with operator supervision until the head reaches the pull-
ing shaft at which point it is separated from the new pipe and
retrieved.
6.2.2 Hydraulic Bursting Systems
In the hydraulic bursting system, the pipe bursting process advances
from the insertion pit to the reception (pulling) pit in sequences, which