Andes Construction, Inc. :: Pipe Bursting

The Pipe Expanding process allows a new polyethylene pipe to be pulled through an old pipeline of equal or smaller size. This is possible because the Pipe Expanding head shatters the old pipeline as it is pulled through, and pushes the pieces out into the surrounding soil.
The old pipeline may be made of any type of fracturable material, such as iron, clay, or concrete. Because pipelines can withstand tremendous external pressures, many people have the erroneous idea that tremendous pressure must be exerted on the Pipe Expanding head to pull it through a pipeline and shatter the pipe. Actually, that is not the case. Fractural pipelines can withstand much greater external pressure than internal pressure. As a result, a pulling pressure of one or two tons is usually sufficient to shatter an old pipeline and pull in hundreds of feet of polyethylene pipe.

Because the broken pieces of the old pipeline are pushed back into the surrounding soil, the new pipe can be the same size, or several sizes larger than the pipe it replaces. Some people have the misconception that the new polyethylene pipe is stretched as it is pulled through the old pipeline, but it is not. The tow cable is only connected to the Pipe Expanding head. As a result, all of the stress is on the cable and head. The polyethylene pipe is simply along for the ride.
New, Seamless, Jointless Pipeline
The design characteristics of polyethylene pipe have been well established for many years. It is manufactured to AGA, ASTM, AWWA, and API standards, so it has known physical properties and an established service life. Typically, 20- to 40-foot sections of polyethylene pipe are electrofused together at the jobsite. Electrofusion melts the PE until molecules of the two pieces flow together so there is no physical difference between the two pieces. As a result, the joint disappears, and the pipeline becomes one continuous whole. Of course, polyethylene pipe has other advantages over old, jointed pipe. polyethylene pipe is much smoother, more resistant to abrasion, and it will not be damaged by microbiologically-induced or chemical corrosion.

Pipe Expanding can be used to replace 3-inch through 30-inch pipes. As the Pipe Expanding head shatters the old pipe and pushes it back into the surrounding soil, it also pulls in a new polyethylene pipe. While most pulls average about 350 feet, single installations as long as 900 feet have been accomplished. The new pipe is protected from stress during this operation because the tow cable is connected to the Pipe Expanding head, not the polyethylene pipe. Since the head expands the diameter of the hole slightly, friction on the new pipe is not significant.

New, Water-tight Service Connections
Most trenchless technologies cannot achieve a water-tight seal at lateral service connections. Without water-tight service connections, ground water which had previously infiltrated the sewer through joints, cracks, and missing sections simply migrates to the service connections. As a result, main line rehabilitation seldom reduces infiltration by more than 50%. However, with trenchless pipe expanding, new, water-tight fittings are installed at every lateral connection, thus stopping all infiltration except through manhole walls and service lines on private property. Trenchless pipe expanding, while a trenchless, does involve a slight amount of digging in the street to perform the lateral connections, something that CIPP liner does not involve, but even with the trenches being dug, the amount of time and money to replace sewers and storm drains is reduced by approximately 50%.