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Pre-Chlorinated Bursting: Cost Effectiveness On A Large Scale
Based on this information a reasonable burst length was determined, based on what could be completed in a normal work day and services reinstated at the end of the day. The preferred locations to access the existing pipe with the bursting tool are fire hydrants or gatewells with an exit pit serving as the entry pit for the next burst.
On the project, a typical burst will start at around 9 or 10 a.m. and be completed around 1 to 2 p.m. That leaves three to four hours for hydrants, gatewells and service installation. There has been sufficient space in neighborhoods to assemble pre-chlorinated pipe runs in accordance with EPA guidelines. Pipe is fabricated at nearby right-of-way areas that do not impact residents driveways and moved into place on burst day. Residents along the burst path typically are without water for one day from 8 a.m. to 4 p.m.
The equipment used to make the bursts is a HammerHead HydroBurst HB80 static pipe bursting system. The HB80 is powered by a 72-horsepower diesel engine that drives a 31 gpm variable displacement hydraulic pump developing 80 tons of pulling force. Available with an optional automatic rod spinner providing 16-second payout of 35 inch-long lengths of lightweight, heat-treated rod that is flexible enough to negotiate bends in the host pipe. Rod storage capacity is 148 feet. API-style joints effectively accommodate thrust loads encountered when pushing around sweeping bends and encrusted or collapsed pipes. A standard feature on Hammerhead static-bursting equipment is a rod-lock device that places constant tension on pipe string, eliminating rod rebound and increasing production. Optional hydraulic leveling and jacks adjust to place the machine on grade and aligned with the existing pipe. Adjustments can be made during the burst as conditions change without stopping the bursting process.
The installation by pipe bursting of pre-chlorinated HDPE water pipe -- pipe that is disinfected before placement in the ground -- is widely used in Europe, but is in its infancy in the United States.
“In this method, the pipe string to be installed is fabricated above ground,” explained Mark DiMichele, P.E., president of D & D Water and Sewer. “The assembled pipe is pressure tested, chlorinated and tested for bacteria by a state-certified lab.”