Sheet Metal · 2021年11月2日

How to use trenchless process to replace pipeline

The technology of replacing pipeline with burst pipe is not a new technology, but it is more and more popular because of the high cost and large interference of other replacement technologies. By digging old pipes (possibly water supply pipes, gas pipes, industrial wastewater or sewer pipes) and laying new pipes to replace them, it means that roads must be dug and traffic must be interrupted. As the old pipeline runs under the new buildings, the open excavation method will have a negative impact on business and government institutions. The pipeline burst technology can avoid such complex problems. The technology is very simple to implement. Squeeze a new pipe into the old pipe to replace it, crush the old pipe and push its fragments into the surrounding soil. Miller pipeline produces a pipe burst system called xpandit.

The system is connected with a pipe splitting machine, which is hydraulically operated. It can provide vibration free power to expand the pipe, so as to form a large annular gap and push the debris into the surrounding soil. At this time, the new pipe is pulled into the annular gap. In order to increase the pipe diameter of a sewer in Nanaimo, Canada, from 355mm to 660mm, the pipeline burst device (hydrahaul h225) produced by TRS company uses about 115t burst force (about half the energy of the device). Bill Sims of Nanaimo’s Engineering Department estimates that “replacing the same length of pipeline with pipeline burst technology saves the city at least $1 million in direct construction costs than open excavation and trenching technology.” another benefit of the new pipeline is that the city will have a gravity system rather than a pumping system. In this way, Nanaimo can save the operation and maintenance cost of the water channel for a long time. Sims added: “our environment is also protected from the terrible impact of being dug a 12m wide trench and piled up a spoil pile next to a river with fish.” the replacement and sizing of sewer pipes with NUMA tools is a slightly different approach. This method is to use a auger to drive into the original broken old pipe, remove obstacles and cut off tree roots. The auger drills from the auger into the hole to the new pipe, and then install an impact head on the auger at the new pipe into the hole.

The impact head passes through the old pipe and breaks it, and the auger moves the debris to the auger into the hole. At the same time, The new pipe is laid into the new pipe trench. Ralph Leonard, general manager of NuMA company, especially mentioned: “one of the advantages of the technology we provide is that we remove the debris, and we don’t need to worry about the obstacles in the old pipeline. If we use other methods, we will face the arduous task of drilling through the obstacles.” don’t think that the pipeline burst technology can only be used to replace large-diameter pipelines, That is, the water supply and drainage main pipe of a complete neighborhood. When a sewer main is judged to be seepage, it is decided to replace it with trenchless technology, because the sewer is located under a boulevard with big trees on both sides. The consulting engineer also found that the serious seepage problem of the branch pipe is mainly caused by the tree root, and some are caused by the poor quality of the connection when the original pipeline is laid. There are 535 branch pipes to be replaced in this sewer. The contractor adopts pipe burst technology for long branch pipes and open excavation and trenching technology for short distance pipes. If the technology of open ditch is adopted to replace all branch pipes, 275 patches will be left on a relatively new road, and the road may be repaired due to irregular subsidence at the backfill in the near future.

The Contractor used the grundocrackmini atlas pipe cracking tool of TT technology. The equipment is designed to start from the access hole or small lead-in pit, so the road surface can be intact. The workers directly fired a pipe burst device at the old clay pipe (152.4mm in diameter). After the burst device pulled in the new polyethylene pipe with the same diameter, the old clay pipe burst. The excavation required for each pipe section replaced is only a small pit of about 1 square meter. Carola Schmitt of TT technologies explains: “The use of burst technology depends on the rock stratum and soil conditions. The most suitable project for pipeline burst technology seems to be the old pipeline originally laid with open excavation and trenching technology, because the backfill around the pipeline usually helps the pipeline burst. Soil such as sea sand can not maintain its expansion state, and there is enough time for the new pipeline to be laid.” Expanding the pipe diameter also depends on the soil conditions. Mike Schweiger of TT technology commented: “we encountered pure rock waste. The pipe trench is basically opened from the rock. The pipe is almost the same size as the pipe trench, and the whole pipe trench is backfilled. In this case, it is not feasible to increase the pipe diameter by using the pipe burst technology.”

When a new factory or business is opened near a small town, the population of the town and the need for sewers may increase sharply. In the case of senbury Town, the total number of immigrants accounts for one-third of the original 6000 population of the town. The people in the town know that there is a seepage problem in the sewers of the town, because whenever it rains, the sewage volume of the sewage treatment plant will double, resulting in pollution In order to demonstrate the advantages of pipeline burst technology, the contractor Darrell Moffitt chose a project to replace a 100m long pipeline as an example, in which the damaged clay pipe (203mm in diameter) is burst and polyethylene (PE) of the same diameter is used Pipe replacement. Before cracking the old pipe, Moffitt’s workers first assemble and fuse the required PE pipe, flush the pipeline, and use a special TV camera to determine the position of five branch pipes on the pipeline to be cracked. Dig out an inlet pit about 6m long and only 1m wide, and support it at the inlet hole. An air pipeline slightly longer than the new pipe (connected with the compressor) It is inserted into the new pipe. A pipeline is slid down to the original old sewer and connected with the cable of the winch of Vermeer hydro guide 8t, which is an integral part of the full set of Vermeer hammerhead burst system.

The hammerhead mole pneumatic impact device is inserted into the new pipe and connected with the air pipe line. Then the burst head (outer diameter about 254mn) It is fixed on the plastic pipe. Once these are ready, the pipe, burst head and its device are lifted by the winch into the inlet pit and aligned with the original sewer at a depth of about 1.5m. When the winch is tensioned, the burst device starts, passes through the whole old pipe to the inlet hole, punches the old pipe and bursts it. The next step surprised the contractor. When the new PE pipe of about 250mm is expanded Now in front of the hole, the winch cable is disconnected, the bursting device is reversed and disengaged from the bursting head. Then the device exits the hole through the new pipe and returns to the lead-in point. The contractor said, “this saves time for excavation and hole repair.” The contractor estimated that it would take only four days to replace the whole sewer in this small city, six days less than using trenching technology.

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