Underground Technology: Principles of Pipe Bursting

A pipe bursting system is made up of numerous components that work together to replace existing fracturable (clay, concrete, etc.) or non-fracturable (ductile iron, steel, etc.) pipe. A tapered bursting head is forced through the existing pipe, cracking it and pushing the fragments into the surrounding soil, while new pipe is simultaneously pulled back through the enlarged hole.

The two most common methods of pipe bursting are static and pneumatic. Static pipe bursting systems are typically comprised of a hydraulic pulling unit, hydraulic power unit, rods and expander or pipe splitter, depending on the type of pipe to be burst. "The hydraulic unit, just with brute hydraulic force, pulls the bursting rods and expander/splitter through the existing pipe and fractures or splits the pipe," says Collins Orton, TT Technologies.

Pneumatic systems operate on a principle similar to pneumatic piercing tools. "It's the same principle, just on a bigger scale," says Alan Goodman, Hammerhead.

The system typically includes a pneumatic hammer, expander, cable winching system (10- or 20-ton pulling capacity) and air compressor, which serves as the power source. A cable is hooked to the bursting head to guide it and provide constant tension.

"You need the winch (cable) for two purposes: for constant tension to always continue pulling, and also to eliminate pipe friction (collapse of the hole onto the pipe) on the back side," Goodman points out.

As the head moves through the host pipe, it fractures it using dynamic energy. "The pneumatic hammer exerts high impact forces with each stroke," says Orton, "and fractures the existing pipe."

Static systems can be used to burst fracturable and non-fracturable pipe and can tow in a variety of new pipe types. Pneumatic systems are best suited for fracturable pipe, and are more limited in the types of pipe they can tow back through the hole.

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