Pipe Bursting Overview
Pipe replacement by pipe bursting Pipe bursting is a trenchless method of replacing buried pipelines (such as sewer, water, or natural gas pipes) without the need for a traditional construction trench. “Launching and receiving pits” replace the trench needed by conventional pipe-laying.
An expanding device called an expander head, which may be either pneumatic or hydraulic, is introduced into the defective pipeline through a launching pit. As it travels through the pipeline toward the receiving pit it breaks the pipe into many small pieces, pushing the pieces into the surrounding soil. New pipe is attached to the back of the expander head, replacing the line immediately.
Pipe bursting may also be used to expand pipeline carrying capacity by replacing smaller pipes with larger ones, or “upsizing.” Extensive proving work by the gas and water industries has demonstrated the feasibility of upsizing gas mains, water mains and sewers. Upsizing pipe diameter is now well established, and pipes from 4″ to 60″ diameter and greater have been replaced.
There are five key pieces of equipment used in a pipe bursting operation: the expander head, pulling rods, a pulling machine, a retaining device, and a hydraulic power pack.
Today’s expander heads have a leading end much smaller in diameter than the trailing (bursting) end, small enough to fit through the pipe that will be replaced. The smaller leading end is designed to guide the expander head through the existing pipe; earlier models did not have this feature and lost course at times, resulting in incomplete pipe bursts and project failures.
The transition from the leading end to the trailing end can include “fins” that make first contact with the existing pipe. Using these fins as the primary breaking point is a very effective way to ensure that the pipe is broken along the entire circumference.
A winch is set in the receiving pit to pull the expander head and new pipe into the line. The head is pulled by heavy, interlocking links that form a chain. Each link weighs several hundred pounds. All of the equipment used in a pipe bursting operation is powered by large air compressors.