As much of the world’s underground infrastructure has reached the end of its design life, many cities are aware that they have a major problem lurking under their streets. Some of these cities have been compelled to take action. Many others are not doing much until there is no other alternative.

Although these problems cannot be resolved completely, pipe bursting offers an economical solution to repair damaged pipes. According to estimates from Advantica in 2002, the pipe bursting method has become the most widely applied trenchless pipe replacement method with more than 50,000 kilometres (31,000 miles) rehabilitated worldwide.

The defective or under-dimensioned pipe is cracked with a burst head and then displaced into the surrounding soil. This creates space for the new pipe of the same or greater diameter. The pipe bursting technique allows the replacement of defective pipelines in the same path without any substantial influences on soil and groundwater. Open trenching, which requires the breaking up and repairing of valuable surfaces, is thereby almost entirely eliminated. Pipe bursting is an environmentally friendly and cost-effective alternative.

Pipe bursting has a long history, but would never have been so successful or even imaginable without piercing tool/impact moling technology and horizontal steel pipe ramming. British Gas and UK based engineering company DJ Ryan first developed the concept to replace pipes by bursting. In the early 1980s the company applied soil displacement hammers (impact moles) and horizontal ramming machines on a large scale for trenchless installation of pipe and cable. In 1981 British Gas and DJ Ryan applied for the first basic method and equipment patents in the UK, more patents followed in Europe, US, Japan and South America.

Some contractors with self-made equipment had been using the process as far back as 1975. The term pipe bursting was not used at this time; however contractors were performing this process in some locations, including within the United States and Germany.

The reason for the technological development in the UK was the King Report, according to which there was an urgent need to replace thousands of miles of defective cast iron gas pipes installed in 1977. These replacement programs were put into practice in the early 1980s and have been carried out ever since.

During the first years, the wider application of pipe bursting outside the UK progressed quite slowly. This was caused by the fact that the technology was patented by British Gas and DJ Ryan, and British Gas required a technical transfer licence fees from manufacturers and royalties for each installed metre using this technology. Only a few manufacturers with an eye to the future were willing to commit and to sign licence agreements, which, under these circumstances, sometimes caused significant additional operating costs.

As the pipe bursting process began to develop in the US, the market that took hold was the replacement of sanitary sewer piping. The long term neglect of sewer system assets in the US prompted the US Environmental Protection Agency (EPA) to require some major cities to embark on long term sewer replacement/rehabilitation projects.

To the best of the author’s knowledge the pipe bursting technique has been used in the following countries since:

In general, it has to be decided whether repair, renovation or pipe renewal (replacement) is required. A pipe replacement is necessary:

* When repair or renovation is technically or economically inappropriate; * When the hydraulic capacity needs to be improved by a greater pipe diameter; * When repair or renovation offers only a short term solution with a pipe replacement being inevitable; * When there is request for a long lasting pipe durability and or a higher product life span; and * When the static loading capacity of the defective pipe would be otherwise negatively affected.

As with any technology, pipe bursting also has its limitations. At this time, the application range is limited to circular existing pipes, and if necessary, the host pipe has to be taken out of service during the bursting process (not necessary for mains, drainage pipe replacement). The course of the host pipe must be usable for the new pipeline (for example inclination). Heavily encrusted pipes must be cleaned so that bursting rods can be pushed through (static bursting) or respectively the winch rope can be pulled in when (dynamic / pneumatic pipe cracking).

The soil surrounding the host pipe must be displaceable and house connections have to be installed using pits. This, however, guarantees a professional and safe integration. Furthermore, sharp bends, flanged joints of steel and ductile iron pipes, depending on selection of bursting tools, require intermediate pits, pipe slumps (sags) cannot be removed however may be reduced and a minimum distance has to be kept away from existing parallel or crossing pipes as well as an adequate cover depth,

However, the application of the pipe bursting method also offers all advantages of a modern, trenchless installation method. Pipe bursting is the installation of new, industrially produced pipes, which may be compromised when installed by open cut methods. Pipe bursting gives a considerable reduction in excavation and road works with almost no traffic disturbance, no annoyance of the public or noise and dust pollution, reduced construction time and the reduction of indirect costs. High daily output up to 150 metres (490 feet) gives a cost effective replacement and considerable cost savings compared to open cut and almost any pipe material available for trenchless installation methods can be installed by pipe bursting, including plastic, ductile iron, steel, glass reinforced plastic and even vitrified clay and polymer-concrete pipes However, new plastic and ductile iron pipes are most commonly installed with pipe bursting.

Pipe bursting allows the replacement of almost any host pipe material (with some limitations) and can be applied for any kind of pipe damage as long as the bursting rods can be pushed in (static bursting) or the winch rope can be pulled in (dynamic / pneumatic pipe cracking). There is no reduction of pipe diameter; up-size of pipe diameter is also possible and the preparation of the host pipe, like high-pressure cleaning, removal of debris and blockages are not necessary (but may possibly be necessary for specific reasons).

Pipe bursting means there is considerably less likelihood of unintended ground settlement compared to open cut, the method is applicable for pipes in sloped areas and areas with trees and garden. Installing short pipes, bursting is possible from manhole to manhole (manhole diameter minimum 1,000 mm / 39 inch), pipe bursting can also be used for the replacement of laterals and is controlled and described by worldwide standards, norms and regulations.

Pneumatically and hydraulically driven pipe bursting systems were already known from the very beginning of the technology development. Pneumatic machines had been originally known as “PIM machines” (PIM = Pipe Insertion Method).

* A cone shaped head to create the channel with the diameter of the protection pipe to be installed; * A head cone with moveable blades to be activated externally via hydraulic system to burst obstacles like pipe fittings and repair collars; and * A rear part with direct towing attachment for the protection pipe as an integral part of the machine.

A further characteristic component of this technology is a winch to guide the PIM machine and to assist the bursting process.

During the first half of the 1980s individual pipeline sections to be replaced with the PIM machine were already up to 100 m (330 feet) in length, whereas – dependent on soil conditions – a bursting process up to 0.5 m/min (1.6 ft/min) could be achieved. It was already possible to replace cast iron pipes up to ND 150 mm (6 inches).

The development of a purely pneumatic Grundocrack bursting hammer considerably improved the efficiency of the PIM machines. This technology became known as pipe cracking.

Grundocrack pipe bursting cracking hammers are based on the principle of horizontal ramming machines. These hammers had a slotted head upon which a bursting blade was attached. This tool configuration was successfully used for replacement of cast iron pipes. The winch assists the bursting hammer by pulling it, with constant tension, against the host pipe. This enabled a direct force transmission of the percussive piston into the host pipe and therefore led to greater efficiency, even when bursting joints and pipe repair clamps. Since then, it was also possible to replace pipelines up to 150 metres (490 ft) and up to ND 300 (12 inch) with bursting replacement times of 1-2 m/min (3-6 ft/min).

The first hydraulic pipe bursting machines were equipped with hydraulically expandable and contractible heads in order to displace the host pipe into the surrounding soil – called “˜static pipe bursting machines’. Currently, this term should be reviewed as these machines were “˜static pipe bursting machines without bursting rods’. Since they relied on pipe material, they could only be applied in brittle sewage pipes. Among others, these machines were known as “˜Clearline Expandit’, “˜KM Pipe Bursting’ or “˜exPress Pipe Bursting’.

While the first applications in the UK were limited to cast iron gas pipes, the application range extended very quickly to water and sewage pipes. Already polyethylene pipes had been used as replacement host pipes. However, they were often installed into PVC-protection pipes. For the replacement of supply pipes in shallow depths, the bursting systems could be launched and retrieved from small pits. The winch was positioned at the exit pit. The PE-pipes were welded to a pipe string and pulled into the protection pipes after the bursting had been completed.

Pipe bursting is also becoming common on sewer lines at deeper levels as the new technology allows much smaller and less costly pits, or has even made pits obsolete. With increasing requirements, the pipe bursting technology made enormous progress. For example, in order to save manholes in sewage networks, a technology combining pneumatics and hydraulics was developed, which adapted to these conditions and allowed short pipes to be gradually installed into the damaged pipeline.

In the 1990s the pipe bursting technology range was improved by a modern variation, the static pipe bursting method with bursting rods. In the beginning, the technology was applied with standard round screw threaded bursting rods such as the Clearline Maxiburst or TT UK’s Grundoburst TX. Shortly thereafter, TT Group (Tracto-Technik) developed a ladder shaped bursting rod with a quick connection which could be connected by a simple click instead of being screwed together. These so-called “˜QuickLock’ bursting rods offer many technical and economic advantages.

QuickLock rods have no threads, therefore they are not screwed together. This saves the need to grease the threads each and every time. The QuickLock connection remains stable both when pushing or pulling and is quickly achieved by clicking the male and female end connections together. Years of job-site experience has shown that productivity can be increased by up to 40 per cent using QuickLock rods in comparison to screwed threaded rods.

Also, the ladder-type recesses also take some weight away from the QuickLock rods, making them easier to handle and simple to work with. Due to the design of QuickLock connections, the flexibility of these rods is increased in their couplings so they can also follow a radius to some degree, which is particularly useful under full tensile load.

During the static pipe bursting process with QuickLock rods, a hydraulically driven bursting rig firstly pushes the rods through the existing host pipe. After arriving in the exit pit, bursting tool, expander and new pipe are connected to the QuickLock rods. The bursting process and pipe installation is started by pulling back the rods. Rigs developing a pulling force up to 2,500 kN (275 US tons) are available. In 2004, Grundoburst 2500G (Figure 8) received the Top 100 Award in the US, an annual award for innovative products in the range of construction machines and accessories.

Currently pipe bursting is mainly applied from ND 50 (2 inch) to ND 800 (31 inch) for gas and water pipes as well as from ND 50 (2 inch) to ND 1,000 (39 inch) for sewage pipes. The number of pipelines repaired is increasing worldwide.

Pipe bursting, with its different variations and decades of applied experience, is a comprehensive trenchless renewal option for a large proportion of the world’s damaged fluid, gas supply and sewer pipelines. This amounts to enormous potential for economic savings when carrying out the inevitable pipe rehabilitation programs. Especially, in times of critical financial situations, the cities and municipalities can hardly afford to simply give away this potential as a result of technological conservatism. All in all, we can surely look to pipe bursting to be a preferred technique as by now there should be more than 70,000 kilometres (approximately 43,000 miles) of supply and sewer pipelines worldwide have already been “˜cracked’, “˜burst’, “˜split’ and replaced with new pipes.

1. Hoeper, G, Jonas, K.: Rohrnetzsanierung in Essen, Germany 3R International Edition January / February 1986 2. Rameil, M.: Handbook of Pipe Bursting Practice, Vulkan Verlag Essen, Germany 2007

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