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Working Through Challenges, Clay Pipebursting Project Exceeds Expectations
The bursting equipment was a TT Technologies Grundoburst 2500G static bursting machine with a pulling capability of up to 315 tons. The machine utilizes Quicklock rods between the machine and the expander, sized for the pipe being installed. For this project, rods were connected to a special 24 inch outside diameter expander sized for the 18-inch VCP. The expander had an internal socket arrangement for the lead piece of VCP to butt against.
Launch and receiving pits were constructed at new manhole locations at intervals of approximately 400 feet. Trench boxes were used to stabilize the walls of the pits to provide a safe working environment and allow ample room for equipment and pipe. The bursting equipment could easily be rotated 180 degrees in the launching pit to launch bursting pipe from the opposite direction.
A technical paper prepared by Project Engineering Consultants, the city of Phoenix Water Services Department, National Clay Pipe Institute and TT Technologies, states:
“The bursting equipment for this project was designed and assembled for the specific purpose of bursting the existing VCP and towing in the new non restrained joint jacking VCP. Because the pipe sections are compression fit joints, a bursting system was built to push each pipe joint "home" as well as to keep the column of assembled pipe sections in compression during bursting. A ride-along hydrostatic machine (cylinder pack) attached to bursting rods inside the new pipe sections kept the column of assembled pipe segments in compression as the bursting progresses. The pipe sections were lowered into the pit and the pipe joints were pushed home with the cylinder pack via pressure plate. The cylinder pack provided 40 tons of force to keep the assembled pipe segments in compression and rods in tension as the bursting head is pulled toward the static pipebursting machine. As the bursting head is pulled forward, fracturing the existing VCP and expanding the fragments into the surrounding backfill, the rear cylinder pack pressure plate keeps the assembled pipe sections in compression,” the summary states.
“As the pull progressed, additional rods were added, followed by the pipe sections which were slipped over the rods. A cylinder rack with three pressure plates was then employed and pinned to the rods. Next, the plate was hydraulically energized to serve two functions: to push the newly added pipe joint fully into place, and hold the entire jacking pipe train in compression as the pipe bursting expander was pulled forward by the 2500G machine.