Over the past 20 years, pipebursting has become firmly established as a primary method of replacing underground pipe infrastructure past its useful life.
The process is relatively straightforward: a bursting tool is inserted into the pipe to be replaced and pulled through the pipe, shattering or splitting it. An expander behind the head displaces fragments or pieces of pipe as new pipe is pulled in behind it.
Two types of bursting tools are available: pneumatic bursting heads use percussive action to crack pipe; static heads are equipped with blades that cut or split the pipe.
Key benefits of the method are reduced excavation requirements that allow new pipe to be installed in urban areas where restoration would be costly and disruptive, and the ability to increase the size of new pipe.
The pipebursting industry changed significantly in 2005 with the expiration of British Gas/Advantica pipe bursting patents, opening the market to new manufacturers and allowing contractors to perform pipebursting without paying licensing fees.
Advances in bursting equipment have significantly changed the types of pipes that can be replaced and new pipe that can be installed by the process.
“Initially, pipebursting was primarily used in the replacement of friable-type pipe materials that would crack or shatter to allow for insertion of a replacement pipe material,” says Gerry Muenchmeyer, P.E. president of Muenchmeyer Associates, LLC. Muenchmeyer has pipebursting experience both as an engineer and a contractor, and serves as NASSCO’s Technical Director. He is also the former president of the International Pipe Bursting Association, a division of NASSCO.
“In subsequent years,” he continues, “pipebursting technology has advanced to include the replacement of such materials as ductile iron, steel and plastic pipes using the pipe splitting technique.”
Wide choice of materials
Not only has pipebursting technology advanced, says Muenchmeyer, but choices for the replacement pipe now include such materials as vitrified clay, FRP, ductile iron, PVC and steel, in addition to polyethylene which has the longest history as replacement pipe using the bursting methods.
“The ability to install different pipe materials has opened up significant opportunities for sewer and water pipe replacement as well as for other related industries,” Muenchmeyer says. “The installation of new clay pipe, using the static bursting technology has demonstrated that in addition to continuous pipe, segmented pipe can also be effectively installed one section at a time using this technology.”
Pipebursting technology can be applied to a variety of existing pipelines including: water mains and service connections, sewer mainlines and laterals, gas mains and services, telecommunications ducts and industrial pipelines.
Collins Orton, TT Technologies product specialist, says rapid advances have occurred after the British Gas/Advantica pipebursting patents expired.
“That opened the market not only to contractors who no longer had to purchase licenses, but to manufacturers who could develop new products without patent restraints,” he says.
Today, Orton explains, pipebursting and splitting equipment can be used to displace about any kind of existing pipe to install most any type of standard pipe used in wastewater, potable water, and natural gas industries, both for transmission and distribution.
“Equipment manufacturers have made advances in cutting and splitting blades to accommodate different types of pipe, ” says Orton. “Bursting tools fracture old pipe and push pieces into the surrounding soil. Pipe splitting tools have expanded the bursting technique to pipe that cannot be burst or broken apart by the conventional bursting process. Splitting heads have multiple blades of various heights and roller cutters that get progressively larger that slice or split flexible pipes in one or several places and expanders push pieces into the soil around the pipe.”
HDPE pipe has been widely used as the new pipe installed by pipebursting, but project owners who do not need or want to introduce HDPE into their systems have other choices. Restrained joint PVC and ductile iron pipes, clay pipe, and most recently fused PVC pipe are being used on many bursting projects, and manufacturers of these pipe products are actively promoting them for trenchless applications.
“Project owners,” says Orton, “have the option to install many types of pipe by the bursting process, and it is a challenge for manufacturers to recognize what types of pipe project owners want to use in their systems and develop the equipment and pipe to satisfy their requirements. The cartridge loading method of installing pipe lengths one at a time, rather than fusing a string of pipe, provides another way for contractors to make installations.”
Orton says one of the most recent advances in pipebursting technology is the ability to burst small diameter pipes.
“Over the past five years,” he says, “we have introduced equipment to burst small diameter copper pipe to replace gas services which has introduced a whole new bursting application. Developing specialized tools and methods of attaching cutters to pull through half inch diameter pipe has been extremely challenging, and now that technology also is being applied to the water market. There is a very large number of gas and water services that need replacement, either because of age, type of material such as polybutylene pipe, or mandate, and pipebursting now is an option.”
Together these advances have contributed to the steady growth of the pipebursting industry with footage increases estimated to average 20 percent a year and in some years, as much as 30 percent, says Orton.
“Even so,” he adds, “there still are project owners and consulting engineers who do not completely understand the process and its capabilities. Education still is in its infancy.”
Alan Goodman, Hammerhead manager of burst and ram sales for North America, says that pipebursting, along with other trenchless methods of construction, minimizes excavation and surface disruption, making it especially suitable for use in areas with existing surface improvements.
However, it offers other important advantages.
“Pipebursting,” he stresses, “is a fast, clean, and environmentally neutral technology that does not involve chemical processes. Pipebursting replaces damaged and leaking pipe with new, uncompromised pipe, rather than a lined, repaired old pipe. In addition, pipebursting has the unique advantage of being able to maintain or increase pipe flow capacity and to provide longer life expectancy compared to other methods such as linings.”
Continuing equipment refinement
These basic advantages are enhanced by improved equipment designs that are more productive, can handle more difficult jobs, install a wider range of pipe materials, and improve the ability to upsize new pipe, believes Goodman.
Other factors contribute to the increasing use of pipebursting.
“Larger and better designed bursting machines with more power have been developed,” Goodman says. “Improvements and more power extend the range of bursting jobs and increased power puts less stress on the equipment. The capability of installing a wider range of material has expanded bursting to non sewer projects of water and gas pipes, electrical conduit and other applications. Pipebursting also is effective in existing pipes that were previously lined.”
Also, Goodman says, there is a constant evolution of tooling, providing better, more effective accessories to increase the likelihood of success that in the past would not have been attempted by pipebursting.
“An example,” he says, “is the pilot-tool a tapered attachment that leads the burst head, keeping the burst head centered to stay on path in old pipe and decrease friction as the bursting process begins.”
What about the future of pipebursting?
From an engineer’s perspective, Muenchmeyer believes pipebursting can become a significant tool used in the potable water industry, in the U.S., as it gears up to renew or replace its water infrastructure.
“With multiple pipe replacement materials,” he says, “pipebursting should be positioned as one of the technologies of choice for not only the water industry but also for the growing lateral sewer replacement market.”
Pipebursting And Asbestos Cement Pipe
Asbestos cement (AC) pipe was widely used for potable water, sanitary sewer and storm drain pipelines from the 1940s through the 1960s, but documentation of health issues related to asbestos restricted the use of asbestos in most products, and U.S. production of AC pipe stopped more than 30 years ago.
However, much AC pipe remains in the ground today in active water and sewer systems – as much as 630,000 miles of it says a report presented by Kent Von Aspern at the 2008 UCT show. Von Aspern is a senior project manager, HDR Inc., an architectural, engineering and consulting firm. Much of this pipe is at or near the end of its useful life and needs to be replaced.
The composition of AC pipe – Portland cement, water, silica or silica containing materials, and asbestos fibers – is well suited to pipebursting. However, fragments of AC burst pipe could appear to fall in the category of regulated waste that would cause the project area to be classified an active waste disposal site.
Von Aspern says the U.S. Environmental Protection Agency has surveyed the industry to learn more about pipebursting and pipe reaming to determine whether burst fragments would be a health hazard and are evaluating current restrictions to determine if clarifications or modifications are needed.
Because federal regulations are considered by many to be unclear, some entities are issuing clarifying documents. The bottom line: Von Aspern recommends checking with appropriate regulatory agencies in the area where projects are located to see what restrictions apply to bursting AC pipe.