Static Bursting Systems
The second most common method of pipe bursting is the static pull system. In the static pull system, a larger tensile force is applied to the cone-shaped expansion head through a pulling rod assembly or cable inserted through the existing pipe. The cone transfers the horizontal pulling force into a radial force -- breaking the old pipe and expanding the cavity providing space for the PE pipe as shown in the figure below. The steel rods, each approximately four feet long, are inserted into the old pipe from the pulling shaft. The rods are connected together using various types of connections. When the rods reach the insertion shaft, the bursting head is connected to the rods and the PE 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 removed. The process continues until the bursting head reaches the pulling shaft, where it is separated from the PE pipe. If cable is used instead of rod, the pulling process continues with minimum interruption, but the tensile force of a cable compared to a rod section is limited.