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Big Burst in the Sunshine State
PUCC Takes On 36-inch Force Main In Tallahassee
Finally, the winch system is integral to the pneumatic pipebursting process. The winch needs to provide constant tension at variable speeds. That is especially important for projects with point repairs or, in the case of the Tallahassee project, pipe couplings. When the bursting tool reaches a repair it slows down as it works its way through. After the repair is burst, there is less resistance and the tool speeds up quickly. The constant-tension, dual-capstan, twin-motor winch will compensate for this change in speed and prevent slack from developing in the line.
For the pilot burst and ultimately the entire project, a 24-inch diameter Grundocrack Taurus pneumatic pipe bursting tool with a 20-ton constant tension Grundowinch was used. A Grundomud bentonite mixing and delivery system provided lubrication for the bursting process.
On the job
With everyone pleased at the result of the pilot burst, the remaining project was given the green light. The project was divided into three sections: two sections of pipebursting, 1,750 feet and 5,005 feet, as well as 930 feet of direct bury. The force main was located in the vicinity of the median of Capital Circle, a six-lane highway. Limited lengths of the force main edged out in to the outer lanes of the Northbound and Southbound carriageways from the median.
Launch and exit pits were strategically positioned at existing plug valves, existing air release valves, the ends of existing steel casings plus connections to DIP separating work packages and every 300 to 400 feet otherwise. PUCC was required to adjust the number and location of the pipebursting pits to minimize the number of pits required based on the maximum length of bursting that could be achieved. Pits averaged 20-feet long by 10-feet wide.
Portland Utilities’ crews overcame numerous challenges throughout the completion of the project. Bursting down the center of one of the busiest roads in Tallahassee made safety and traffic management top priorities. The size and weight of the equipment and pipe also added a level of complexity to the project. Because of its size, the pipe was difficult to stage and move. With bursting lengths up to 484 linear feet, the fused sections of ASTM 4710 36-inch HDPE pipe weighed in at just less than 68 tons.
The main pipe bursting operation began in November 2009 and was completed in February 2010. Crews worked five days a week, 24 hours per day with the exception of a two-week mandatory shut down period between Christmas and New Year.