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Emergency Pipe Bursting Project In Alaska Uses Chain-Drive System
Remote Pipe Bursting
“To our knowledge, bursting a pipe within a pipe surrounded by foam had never been done,” said Jerry Currey, UCMC president. “Testing was conducted to determine whether pipe bursting would be successful. We obtained a 20-foot section of arctic pipe and set up a test burst at our storage yard. The test was successful, and the decision was made to proceed.”
The old CPVC pipe would be replaced by HDPE pipe pulled behind a bursting tool that would crack and break the old pipe.
YKHC made arrangements to purchase the pipe bursting equipment and materials that would be needed to replace the failed pipe, and planning proceeded to do the work when warm weather arrived. Lefferts said the investment in equipment ensures that it will be immediately available for future use.
Equipment used on the project was a TTS 40, a 40-ton system which included a TTS hydraulic power unit which was driven by a 30-horsepower gasoline engine, 360-linear feet of 3/4-inch anchor chain and links; and four- and 6-inch bursting heads. Currey explained that chain drive bursting equipment uses a hydraulic puller and chain to draw the bursting head and new pipe through old pipe being replaced, rather than rods employed by conventional pipe bursting equipment.
Currey said TTS chain drive bursting equipment with an hydraulic puller eliminates rods, constant make-up and break-out of threaded rod connections and bulky, expensive, low-powered winches.
“All equipment for this project had to be flown in,” said Currey. “The pipe was flown from Anchorage to Bethel to Pilot Station. All other materials were flown from Anchorage to St. Mary’s and then brought upriver to Pilot Station on skiffs. Larger planes can land in Bethel and St. Mary’s, making this the most cost effective method of transportation.”
The plan called for the 1,000-foot run of pipe to be installed in three separate pulls requiring four pits three-feet wide, 10-feet long, and four to five-feet deep. Pits were dug by a John Deere 310 rubber-tire backhoe. The second pit served as the exit pit for the first pull and starting pit for the second.
YKHC crew members fused lengths of the HDPE pipe while the launch pit was dug and bursting equipment moved into place and set up.
The first 330-foot pull had gone approximately 250 feet when the head pulled off the pipe, said Currey.