Page 269 - Trenchless Technology Piping Installation and Inspection

Pr oject Considerations for Pipe Replacement Methods 233

New Hydraulic
HDPE power

Expander

Pin joint
tooling

Blade set or
ductile slitter
Direction of bursting
FIGURE 6.3 The static pull bursting. (Source: HammerHead ® .)

inserted through the existing pipe. The cone transfers the hori-
zontal pulling force into a radial force breaking the existing pipe
and expanding the cavity, providing space for the pipe, as shown
in Fig. 6.3. The steel rods, each about 4 ft in length, are inserted into
the existing pipe from the pulling shaft. The rods are usually screwed
together. When the rod string reaches the insertion shaft, the bursting
head is connected to the rods and the new pipe is connected to the
rear of the head. A hydraulic unit in the pulling shaft pulls the rods,
one rod at a time, and the rod sections are unscrewed and removed.
The process continues until the bursting head reaches the pulling
shaft, where it is separated from the HDPE pipe. If cable is used
instead of rod, the pulling process continues with minimum inter-
ruption, but the tensile force of a cable compared to a rod section is
limited.
Pipe splitting is a form of static pipe-bursting method for breaking
and replacing cast-iron or ductile iron pipes by longitudinal slitting.
At the same time, a new pipe of the same or larger diameter may be
drawn behind the splitting tool. This method has a splitting wheel or
cutting knives that slit the pipe longitudinally at two more lines along
the side of the pipe.

6.3 Pipe Removal Systems
Pipe removal (also known as pipe eating) is a replacement tech-
nique based on horizontal directional drilling (HDD) technology
(more common), the microtunneling boring machine (MTBM), or
horizontal auger boring (HAB) technology. This method excavates
the existing pipe in very fine particles and removes them rather than
displaces them into the surrounding ground, as it would be for