Sunday, June 23, 2024

Online Pipe Replacement Techniques

The first move into this area came in the 1990’s and utilised impact hammers that were guided through the original pipe using a winch cable to keep them on the existing route.

For the past 50 years, if not more, one of the biggest factors affecting underground works has been the highly, and increasingly, overcrowded nature of the subsurface with the various utilities and services that are already installed. This is particularly the case in urban areas where huge developments on communications technology are taking place, so adding to the plethora of pipes, cables and ducts that are found from just a few centimetres deep to several metres deep below the surface.

This led to a train of thought that meant clients and contractors went from simply looking at ‘putting in a new one’ when a service or utility needed to be replaced to ‘can we fix or replace the old one where it is’. Having previously looked at renovation and rehabilitation systems for repairing ageing and deteriorated pipelines back in our February issue this year, it is now time to look at another option, that of Online Pipe Replacement. Where a pipeline that is beyond repair or is of a material that is no longer deemed suitable for use, this family of techniques is able to utilise the original route of the pipeline or duct so as not to impinge on virgin ground that might first of all be used for some other utility or service, whilst affecting the replacement without the need for full length trenching.


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The first move into this area came in the 1990’s and utilised impact hammers that were guided through the original pipe using a winch cable to keep them on the existing route. The impact process of the hammer then broke down the fabric of the old pipe, provided it was of a material that could be fractured. The head of the hammer is fitted with a specially designed attachment that not only aided the fracturing of the pipe fabric in the ground but also pushed the shards of the now broken pipe outwards into the surrounding ground. This then created a void into which a new pipe could be pulled, normally fixed to the rear of the impact hammer so that the new pipe was installed as the hammer advanced through the old pipe. The surrounding ground also had to be sufficiently compressible. This technique has thereafter become know as Dynamic Pipe Bursting. The problem then arose that not all pipes that were in need of repair could be fractured in this way. Ductile Iron and steel pipes as well as plastic pipes do not usually fracture but need to be split or cut and they do not always respond well to the impact action of the hammers used.


A further problem with impact hammer technology for pipe bursting (also known today as ‘online pipe replacement’ because of the various different options now available), was that particularly in the urban environment having relatively heavy impact operations not too far below ground often led to complaints from local residents and businesses due to the vibrations that were being felt at surface. So other options were investigated. Several different approaches have become popular over the ensuing years with different ideas became commercially available and increasingly popular. One of the early options that is now not commonly used, if at all, was the expansion shell system. Similar to the impact hammer technique in some ways, the bursting head, instead of being more or less self-advancing through the original pipe, was drawn through the pipe on a winch cable. Depending on the diameter of the unit and the length of the head, this advance was made in unit length increments. At each stopping point the bursting head was expanded inside the pipe using hydraulic rams built into the unit, pushing the steel framework outwards against the pipe wall. In friable pipes, such as unreinforced concrete, clay, asbestos cement, pitch fibre etc., which are generally designed to be strong when under compression from the surrounding ground but which are less so under tension from internal pressures, the outward pressure broke the pipe relatively easily. The new pipe attached to the rear of the shell was drawn in as the system advanced.

The disadvantage here was that the minimum size of bursting head was limited by the need to have an effective shell expansion system within the body of the head, so the smaller pipe diameters were more difficult to replace using this technique. Both impact hammer and expansion shell systems could however be used to install a larger diameter new pipe if required and if ground conditions were sufficiently compressible to allow for the surrounding ground to be opened up to allow for the required larger void to be created. Where the surrounding ground is not compressible this does have an adverse effect on the potential to use pipe bursting options (of any sort) that utilise force from inside the pipeline outwards. Another factor that sometimes influenced the applicability of the impact hammer and expansion shell systems was the state of stability of the old pipeline. Because both systems required the installation of a winch cable before the process could begin, if the pipeline being replaced was in a serious state of collapse at any point along the route it might be impossible to position the cable required.


Despite being quite effective, both impact hammer and expansion shell systems had their disadvantages in terms of speed of operation and impact on the surroundings and nearby buildings, utilities and people. They do still have their place in the market but with the need to minimise local and environmental impact, many pipe bursting situations now use what is known as Static Pipe Bursting. With this system a rod pusher/puller machine is used to push a steel rod through the old pipe as a first stage. Often the lead rod is specially designed to negotiate its way around or through obstructions. Some systems even offer a rotational capability that enable a form of drill head to be used to negotiate through even the toughest and most blocked pipelines. Because the rod is a solid metal bar it is much easier to get the rod string through most obstructions in the pipeline, something that is not always possible when installing a winch cable. Once the rod string is installed a bursting head arrangement is attached to the rod string and the new pipe to be installed is usually attached to the rear of this head using a swivel.

The rod ‘pusher’ then becomes a rod ‘puller’ and the whole bursting arrangement is drawn back towards the start pit. The bursting head demolishes the old pipe, an expansion cone, which normally sits just to the rear of the busting head, pushes aside the broken pipe shards and expands the void to the required diameter thereby making room for the new pipe that follows along behind. The rods are removed from the machine as the process proceeds until the bursting head arrives at the start pit. The head arrangement is removed and the new pipe is connected to the existing pipe network. The rod systems can vary also.

In most cases the bursting rods are simple solid steel rods with screw fittings at the end that join the individual rod lengths together. In this case the pulling action is achieved using grips around the rod that either push or pull the rod string as required. There is a different rod system where the rods link together and are designed in a ladder format. Here the rods simply link together at the ends and the ladder design allows the pulling and pushing action to be achieved by a rack and pinion action. There are a number of different designs for static pipe bursting some of which will be highlighted later in this article. They vary in physical size and pulling power and each will be need to be selected by the end user to suit the varying installation scenarios. One of the disadvantages of these systems is that in the majority of cases there is a need for an often reasonably sized start and reception pit to enable the operation to take place effectively, although in the modern industry this is not now always the case. Where this situation arises, some manufacturers have brought to the market small footprint bursting systems that utilise a wire rope as a ‘pulling’ medium that provides the bursting forces required to complete the work. In many cases these systems can be either surface mounted with pulley systems that align the cable to the old pipe or which can be mounted within existing manholes so negating any need for start and reception pits with smaller dimension pipe being added to the pipe string as the burst advances so as to fit int the manholes being used. These cable-based machines again come in various designs and should be investigated by potential users to endure they are suited to the project in hand. Where old pipe materials are not conducive to simple fracturing, there has been a need to develop pipe splitter ‘bursting’ heads that do not so much break the existing pipe as cut it in a manner that will allow the remains of the pipe to again be pushed aside by the expansion cone into the surrounding ground. It should be noted that different old pipe materials react to different cutter heads in different ways and anyone looking to use any of these techniques should consult closely with their equipment provider to ensure that the right head is applied to the right job – otherwise it will simply not work and waste both time and money!

The development of the specialist cutter heads also had a significant impact on use of the systems for even friable pipe materials. As the use of the techniques has evolved and expanded, one problem that occurred early-on was that repair collars would not fracture even when the pipe itself could, usually because they were made of steel. The development of the new splitter heads did however in the main negate this problem as the repairs could also be split. Sometimes however the strength of these collars meant that the stresses/loads on the equipment required larger machines than necessary being used on projects.

The drive across many countries to reduce drinking water network leakage rates has meant most pipe replacements so far have utilised plastic, usually PE of uPVC pipes, as the replacement material, with leakage rates in many being reduced significantly over the past decade or so. But even now across Europe there is still a problem with, according to some, up to 20% of treated water leaking out of the various systems before reaching the customer. So, the move from gravity to pressure pipe systems in the use of pipe replacement techniques has been quite considerable.

A major advantage of both Static and Dynamic pipe bursting systems has been the facility, under the right ground conditions, to replace an old or deteriorated pipeline not just size-for-size but to upsize the pipe along its original route to offer increased capacity. This is an option which, with increasingly dense populations in existing urban areas, has major significance.


Over the years and given the many different situations in which there has been and is still a need for the replacement of deteriorated or undersize pipelines, it is no surprise that in particular the static pipe bursting and cable-based systems appear to have taken a lead in popularity amongst both contractors and clients looking at the replacement options available. This is largely because they are relatively easy to use and cost-effective which is a ‘must’ for all client operations in the modern world.

However, there are times when even the most popular systems do not provide the solution to the problem in hand. To answer these situations there have been other not always but possibly more costly but also highly effective solutions developed. Typically, these situations arise where due to ground conditions, proximity of other utilities or circumstances where it is not advisable or possible to leave the remains of the old pipe in the ground due to potential for contamination or other environmental reasons.

Two options have been developed for such circumstances. The first is what had become known as ‘Pipe Eating’. To replace a pipe using pipe eating normally requires the use of equipment that will not only fracture or fragment the old pipe sufficiently to install the new one but also one that will remove all traces of the old pipe from the site/route. This until recently has usually been achieved using either a microtunnelling technique or the use of a specialist cutting head on an HDD (Horizontal Directional Drilling) machine.

With the microtunnelling system, a shaft is sunk at the launch position at one end of the pipe being replaced. The cutter head is designed such that it will not only extract any ground around the old pipe but also grind or break down the pipe material itself. As the cutter head advances along the line and grade of the required replacement the old pipe is removed by the spoil extraction system of the microtunneller and the new pipe is jacked into position behind the microtunneller. One advantage of this system is that if the new installation is required to have a significantly larger diameter, then the surrounding ground does not have to be compressible just boreable. Also, should the alignment of the old pipe have altered over time due to ground movement, loadings etc., it is possible to realign the new pipe to the precise line and grade required.

Similarly with the HDD option, the drill string of the HDD rig is pushed through the old pipe until it reaches the reception end of the pipe line being replaced. A special cutter head is again fitted to the drill string and the new pipe attached via a swivel to the rear of the cutter head. The whole arrangement is then pulled back towards the HDD machine with cutter head demolishing the old pipe as it advances whilst installing the new one immediately behind the cutter head. The drilling fluid system for the HDD rig extracts the remains of the old pipe in a similar fashion to that used when reaming a pilot bore the correct size during a traditional HDD operation. Again, the diameter of the final pipe replacement can be adjusted by allowing the cutter head to not only remove the old pipe but also any surrounding ground, provided that other utilities will not be affected by such an enlargement.

A more recent adaptation of the pipe eating technique has been the use of an impact hammer that would normally be associated with the pipe ramming technique. Here, a new pipe was installed along the line of an existing pipeline with the new pipe being rammed by a hammer around the outside of the old pipe. At the leading end of the new rammed pipe a special arrangement was placed inside to fracture the existing pipe so that it could be removed along with spoil created by the ramming method.


At, usually, smaller diameters such as service pipe connection to houses or business premises there is also a need to replace ageing pipes. In many instances this is because, particularly in long establish and well-developed countries, many of the services still remaining in use are lead pipes. The requirement to renovate or replace these has become increasingly urgent as more becomes known of the effects of lead on the human condition and lead-in-water limits are decreased further and further with currently many of the developed world looking limits of lead at not more the 10 ppb (parts per billion) concentration. Where this situation arises the small diameter of these pipe makes it increasingly difficult to replace them using the more recognised technique covered earlier. This has led to the development of what are known as ‘Pipe Extraction’ techniques. In general, with pipe extraction techniques the old pipe is first isolated at both ends and a cable/wire rope is passed through the pipe. In some instances, this cable is fitted with ‘teeth’ that, when the cable is pulled back towards its launch point, expand and contact the inner pipe wall digging into the softer lead to gain grip along the rope length. As the cable is withdrawn the pipe is pulled out of the ground and wound onto the drum of the winch pulling the cable. The new pipe is usually attached to the free end of the winch cable and is drawn into place as the old pipe is removed. The technique is similar where instead of the ‘toothed cable’ the wire rope is ‘glued’ into place over the extraction length thereby enabling the extraction to be completed.

So, to summarise, what has tended to happen is that individual terms have come to be associated with specific types of pipe replacement technique of which there are number.

These include:

  • Pneumatic Pipe Bursting or Pipe Cracking or Dynamic Pipe Bursting
  • Expansion Shell Pipe Bursting
  • Rod-based Pipe Bursting or ‘Static Pipe Bursting’ and ‘Splitting’ using varying designs of bursting heads for friable and non-friable pipes
  • Cable/Rope-based Pipe Bursting smaller diameters difficult to access for rod systems
  • Pipe Extraction
  • Pipe Eating

Today, in many areas of the world, Static pipe bursting and Pipe Extraction seem to be taking a lead as the more popular options, but the other options still have their place and continue to be used where circumstances are favourable. MACHINE OPTIONS What follows is a small selection of the various machine types that are available from just some of the manufacturers in the pipeline replacement field. The popularity of the Static and Cable systems is reflected in the fact that almost all of the information provided by manufacturers in response to the information request for this article covers just these technologies. But it should be borne in mind that the other options are out there if needed but may be a little more difficult to source. Just do not forget they are there when considering project options. Who knows when they be just the right choice! HammerHead Trenchless Equipment: Hammerhead Trenchless, part of the Charles Machine Works Group is available worldwide through the Ditch Witch dealership chain. In the UK, Mammoth Equipment Ltd is the distributor of Hammerhead Trenchless Equipment in the UK and Eire. Based in Ely in Cambridegshire, Mammoth provides sales, support, service and training for the full range of Hammerhad Moles, Pilers, Rammers, Bursters and Winches

Pipe Bursting, has become a well excepted method of replacing failing gas, water and dirty water mains. Hammerhead offers a full range of bursters divided into four categories which include:

  • Portaburst Lateral Rope Bursting Systems – Developed to satisfy the rising demand for small diameter sewer line replacement in 3 in (75 mm) and 4 in (100 mm) diameter range at lengths up to 45 m, Portaburst provides a small footprint, low weight, high power solution that can be used in manholes in difficult access locations such as gardens and backyards. With 30 tons of pull back the Portaburst used a compacted steel cable rather than steel rods to ease installation in mains and also features special compact burst heads in 4 in (100 mm) and 6 in (150 mm) diameter sizes reducing bursting train length enabling retrieval in a manhole.
  • Hydroburst Static Rod Bursting Systems – Hydrobursts are available in 50, 100, 125 and 175 ton variants depending on the pipe size requirement, the systems utilise 1 m long screwed steel rods to pull back burst heads in existing mains from 2 in (50 mm) up to 24 in (600 mm) diameter with size-for-size or upsized new mains being installed. The Hydroburst HB125 and 175 units feature rod rotation as standard to enable the drilling through of in-pipe collapses that can often prevent the use of other types of bursting equipment
  • Pneumatic Pipe Bursting Systems – The original pipe bursting systems utilised small air hammers to crack and expand existing failed mains. The development of static rod bursting systems, especially for the water industry with pre-chlorinated pipe, revolutionised pipe bursting and replaced pneumatic bursting in smaller sizes. However, this was not the end for Pneumatic pipe bursting which in the dirty water industry is often seen as the preferred method over static rod burster due to rig size and the elimination of the requirement for fixing high tonnage burster in the ground.
  • Same Path™ Gas-Line Slitting – Whist pipe bursting is recognised as a cost-effective trenchless method to replace old metal gas pipes, the replacement of dated plastic pipe does pose some unique challenges. Static rod bursters can cause plastic to overheat, buckle and even jam up leading to multiple dig downs to free up the process. Hammerhead recognised this and has developed a Same Path™ gas line slitter for the replacement of 1½ in (38 mm) to 4 in (100 mm) diameter old PE plastic gas lines. The system uses specialist slitter heads and a Hammerhead Hydroguide winch to pull the head through whilst installing the new main.

Kobus: Kobus offers a range of Pipe Puller equipment for pipe extraction purposes. The Kobus Pipe Puller KPP300 is compact and easy to use. The modular construction allows ease of manual handling by 2 operators and is ideal when site access is difficult for pipe sizes from ½ in i.d. to 1¼ in o.d. (13 mm i.d. to 36 mm o.d.). The unit is driven by its own separate hydraulic power pack with power-on-demand, and manual control lever. The unit can be used for lead pipe and service pipe replacement and features Power-on-demand hydraulic power pack delivers controlled pulling, 10t pulling force at spool, modular construction allows for manual handling and ease of access in restricted areas. It also offers a compact foot section minimises size of excavations required, easy and quick to assemble on site for each pipe replacement, a dead man operating lever on power pack for safety, a robust safety cover to protect personnel and will fit in most site vans for ease of transportation. The KPP400 Kobus Pipe Puller is an all-in-one, excavator mounted unit for ease of moving around site. It mounts on most types of compact 2 t excavator. The Puller is driven from the auxiliary hydraulics of the excavator and is capable of generating up to 20 t of pulling force at the spool. The bottom foot section rotates to allow optimum positioning of the excavator for best access.

Attaching directly to a mini-excavator, there is less manual handling and no need for separate power pack. With a 360o rotatable foot to allow optimal positioning of excavator for access, the Puller offers 20 t of pulling force at the spool with male and female spool sections to allow automated removal of old pipe from the spool. Operating at lengths of up to 25 metre the unit can extract galvanised steel, lead, copper, poly and PE pipe and replace pipes with PE pipe of 20, 25 and 32 mm diameter.

Pipe Equipment Specialists Ltd (PESL): PESL offers two pipe bursting units, the Miniburst and the Maxiburst. The Miniburst is a portable pipe replacement system for small diameter pipes in limited access locations. The unit is designed to work usually with segmental PE pipe which also aids the installation in tight working spaces and can replace pipes from 4 in to 6 in (100 mm to 150 mm diameter. PESL’s other option the MAXIBURST Pipe Bursting System is currently capable of bursting 100 m of 4 in (100 mm) diameter pipe in less than 30 minutes. There are two models available, the MaxiBurst 40 and the MaxiBurst 70. The MaxiBurst 40 is suitable for pipe sizes from 3 in (75 mm) to 8 in (200 mm) diameter, whilst the MaxiBurst 70 can be used for all pipe sizes from 4 in (100 mm) to 14 in (350 mm) diameter. Both units have been designed with safety, reliability, speed and low operational costs as the primary objectives and have proved themselves to be rugged and reliable. Terra AG: Terra has been operating in the field of trenchless technology for many years having been established in 1975. It now offers equipment for HDD, geothermal and pipe replacement operations. The TERRA-HYDROCRACK HC 600 is one of the most productive Rod Burster for the replacement of old pipes 50 to 350 mm diameter made of cast iron, ductile, steel, clay ware or plastic. With a maximum pulling force of 60 tonnes at 235 bar new pipes up to 350 mm diameter can be replaced over a length of 150 m.

The pulling speed lays by industry leading 225 m/h. Powered by a proven 49 HP strong PERKINS Diesel engine it operates always at maximum performance. The TERRA-EXTRACTOR X 1000 is one of the most powerful Rod Bursters for the replacement of old pipes 100 to 600 mm diameter from cast iron, steel, clay ware or PE/PVC. With a maximum pulling force of 100 tonnes at 250 bar, new HDPE pipes up to 600 mm diameter can be replaced. Smaller pipes can be replaced over lengths up to 200 m. The operation speed is 96 m/h. Powered by a 142 HP strong JOHN DEERE engine, it fulfils the newest environmental emission norms Tier 4 interim (Euro 3B).

In the company’s cable burster family, the TERRA-EXTRACTOR X 400 is an extremely powerful and productive cable burster for your tough pipe bursting jobs. Powered by a proven 25 HP strong KUBOTA Diesel engine you get the power to get the job done quickly and the durability to be up and running burst after burst. The X 400 replaces 40 to 300 mm main lines with up to 40 tons of pulling force at 215 bar. New pipes up to 355 mm diameter can be replaced over length up to 150 m. Equipped with a 25.4 or 14 mm diameter cable the X 400 is ideal for the replacement of old pipes made from cast iron, ductile iron, steel, clay ware or PE/PVC.

The TERRA-EXTRACTOR X 300 C is an extremely powerful and compact cable burster for your tough lateral pipe bursting jobs. Equipped with a 22 or 14 mm diameter cable the X 300 C is ideal for the replacement of old pipes made from cast iron, steel, clay ware or PE/PVC. Pipe bursting with a TERRA cable burster provides a high degree of flexibility. Its compact footprint requires minimal excavation and the system is built to help you cut down on wasted time, maximising productivity. Its user-friendly, modular design makes it easy to operate, easy to set up and easy to transport. The TERRA-EXTRACTOR X 100 is an extremely powerful and compact cable burster for your tough lateral pipe bursting jobs. Equipped with a 13 mm or 8 mm diameter cable the X 100 is ideal for the replacement of old pipes made from PE/PVC, thin-walled steel and lead. Pipe bursting with a TERRA cable burster provides a high degree of flexibility. Its compact footprint requires minimal excavation and the system is built to help you cut down on wasted time, maximizing productivity. Its user-friendly, modular design makes it easy to operate, easy to set up and easy to transport.

TRACTO: As a pioneer in trenchless technology, No-Dig full-range supplier TRACTO offers the most comprehensive product range for underground pipe replacement in the existing pipe path applying either dynamic pipe cracking with GRUNDOCRACK or static pipe bursting with GRUNDOBURST. The major advantages of both pipe replacement methods are:

  • Applicable for almost all types of damage and old pipe materials • Long service life of new pipes from 80 to 100 years
  • Upsizing of pipe capacity by 1 to 2 nominal widths possible
  • Short assembly and setup times
  • No subsequent costs due to ground settlement, road damage etc.
  • Safe application according to latest rules and standards Using dynamic pipe cracking, old pipes made of brittle materials can be replaced with new PE pipes (long and short) or PVC-U pipes up to ND560 mm in quite a simple way. The air driven GRUNDOCRACK’s blade shatters the old pipe while advancing through the old pipe and radially displaces the fragments into the surrounding soil while pulling in the new pipe simultaneously. The pulling force of a winch supports the pipe cracker, guaranteeing safe guidance through the given pipe path. The machine’s heavy duty one-piece housing transmits dynamic energy optimally for maximum impact. The smooth machine body ensures easy recovery through the new pipe in confined spaces. In addition to pipe cracking, the GRUNDOCRACK system is also applicable for calibre pipe bursting and for the TIP relining method.

The static pipe bursting system GRUNDOBURST makes pipe replacement even along slight bends quick and easy. It consists of the bursting rig with hydraulic cylinders, a hydraulic power pack, the click shut QuickLock bursting rods with cutting tool and various diameter expanders for pulling in the new pipe. Using GRUNDOBURST, damaged long or short pipes with circular or oval profile up to ND1200 of almost any material (plastic, metal, GFRP or stoneware) can be replaced with new pipes up to ND1200 having identical or larger diameters. Five different GRUNDOBURST models with a pulling force 400 to 2,500 kN allow for application out of pits and/or manholes into pits and/or manholes. After pushing the QuickLock rods through the old pipe, a roller blade with expander and the new pipe attached are connected to the rod string. When pulling back the rods, the roller blade cuts the old pipe while the expander pushes its fragments aside and the new pipe is pulled in either from the pipe coil or as a welded pipe string. To simplify tool retrieval later, the roller blade and the expander can be pulled into the pit inside the extension frame of the rig. The GRUNDOBURST system is immediately ready to use and can be easily operated by only two people. Apart from the complete replacement of pipes, The GRUNOBURST rigs can equally be applied for partial repair or rehabilitation of damaged pipes applying calibre bursting, Tight-in-Pipe, pipe reduction or pipe relining. Whilst the foregoing is just a small sample f the range of online pipe replacement systems available, it should be stressed that these are not all there are. Anyone looking to enter the market for pipe replacement or expand their presence with new equipment should be sure to examine the full range of systems available before making their choice to ensure that the machine and equipment selected are suited to the likely conditions to be found on any projects they are to be used on.

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