Most replacement techniques involve destroying or removing the existing service in-situ and pulling in a new service in the void so created. Known generically as pipe bursting, the most common technique currently used for this type of project is the rod or cable based system. Here a rod or cable is fed through the old service between manholes or access pits. A ‘bursting head’ is attached to the end and the rod or cable is pulled back towards the pulling unit. The bursting head is designed to fracture or split the old service, pushing the broken pieces aside into the surrounding ground as it advances. The new service is pulled in behind simultaneously. Correct design of the bursting head, expander shell and pulling capacity of the machine does allow the old service to be up-sized if required and if the ground and adjacent services allow.
One of the newest entrants into the pipe bursting market is Ditch Witch which launched three new systems to work in the pipe replacement market. The new Ditch Witch PR50, PR75, and PR95 pipe bursting systems are designed to fracture or cut most types of existing pipe including water, sewer, or utility, and pull in new pipe with 50, 75, or 95 t of pullback force, respectively. Other standard features include quiet, fully enclosed power packs and load-sensing hydraulics that automatically shift the unit to high speed when there is no load, and downshift the unit when a load is introduced to increase machines productivity.
If replacement is either not an option or not required, then the next choice is that of renovation.
Renovation
Recently one lining technique that has been introduced by Tracto-Technik is the new Tight-In-Pipe method (TIP) which installs new Polypropylen (PP-HM) pipes between manholes or shafts that fit very closely to the old pipe wall. As the outer diameter of the new pipe is only slightly smaller than the inner diameter of the old pipe, there is no necessity for annulus filling. The difference in cross-section is small enough to allow house connections to be remade.
An essential advantage of the Tight-In-Pipe technique is that during installation small to medium sized off-sets in the old pipe, such as tears, leaks, deformations up to 20% of the pipes’ cross-section, misalignments, tree root infestation etc, can be evened out by means of a patented guiding sleeve.
Looking at the more conventional CIPP lining sector, one of the more interesting developments is the emergence of lining systems designed specifically for use in gravity pipelines experiencing high groundwater infiltration. Several companies have been involved in almost simultaneous development of such systems such as Insituform Technologies, Onsite and epros (now part of the Trelleborg Group). Each of these companies have undertaken a rigorous testing regime, organised for WRc in the UK according to the requirements of Thames Water, which was instrumental in establishing the need for such systems, to establish the systems’ suitability for purpose. The new liners are designed so that once installed the curing process does not cause the liner to shrink away from the host pipe inner wall, leaving an annulus which would allow migration of the infiltration water to another, possibly untreated section of the pipe, or to put it simply, transferring the problem further down the line.
Another development in the CIPP family has been the progressive emergence of Steam cure and UV light cure lining systems more into the mainstream. Both systems offer advantages over traditional hot water or ambient cure systems both technically and environmentally. Steam for instance offers a curing system that offers reduced cure times and is also very controllable and allows linings to be heated to over 100°C. The advantage of this becomes apparent when it is understood that resins cure twice as quickly for every 9°C rise in temperature. Furthermore, there is no hot water to circulate, heat or dispose of once curing is completed. The use of steam curing also creates less in the way of styrene levels and odours and as a consequence the potential for pollution in the sewer system is greatly reduced, as are customer complaints.
In terms of the UV systems, they offer greatly reduced site footprint, curing times and again no hot water to dispose of. Also, provided the liner and resins, which are normally factory impregnated, are protected from the daylight, the shelf life of an impregnated liner is much longer than that of a conventional system.
By way of support equipment for CIPP lining operations there has also been an up-turn in the demand for inversion drums. Inversion drums allow liners to be installed into a pipeline without the need for scaffold towers, so improving not only the site footprint once again but also reducing potential safety concerns with operators working at height. One manufacturer currently launching such inversion drums onto the market is Trelleborg-epros which offers a Mini-type drum and the System 5 drum. The Mini-type drum can operate on pipes of 150mm diameter for installations of up to 11m long, at a liner wall thickness of 3mm. The System 5 drum is designed to be able to handle some of the more ‘heavy duty’ installations on pipes of up to DN500 over distances of up to 100m, with liners of up to 10.5mm wall thickness.
Away from the CIPP lining systems Insituform Technologies has been working on, and in the past year launched, a new range of what are commonly known as Fold & Form linings for pressure pipe renovation operations. Known commercially as PolyFlex and PolyFold the systems have been under development by the company’s new water targeted division, Insituform Blue, since early 2006.
PolyFlex is designed to answer current lining requirements in the water supply industry, the system drives circular Polyethylene (PE) pipe through specially designed rollers. The rollers reduce the liner pipe diameter (by about 10%), allowing it to pass into the host pipe being lined. Once fully installed in the host pipe, the liner ends are expanded out and fitted with end connections. The liner is then filled with water and pressurised, causing the liner to revert towards its original diameter inside the host pipe and achieve a close fit. The PolyFlex product is currently designed to operate in host pipes from 100mm diameter up to 450mm diameter.
In parallel to this development, Insituform Blue developed PolyFold, which is appropriate for work in larger diameter pipes over longer distances. As the name suggests, this system forms PE liner pipe by folding it into a ‘U’-shaped profile to reduce its effective diameter for easy installation into the host pipe. To do this, the pipe passes through a specially designed ‘folding’ rig. On this rig a hydraulic pushing machine advances the liner pipe through guide rollers and pipe folding wheels. The end of the liner is attached to a winch at the reception pit which guides it through the host pipe during installation process.
To ensure that the liner does not revert in the host pipe until required, the folded pipe is strapped as it exits the folding rig. This strapping holds the folded liner in its ‘reduced diameter’ profile until the lining pull-in is completed. Once the pull-in is complete the liner ends are opened out using air bags and end connections are fitted. The liner is then filled with water and pressurised to burst the banding and re-round the liner, again achieving a close fit lining of the host pipe. PolyFold can be utilised on pipe diameters from 300mm up to 1,400mm
As well as full lining systems, there have over the years been developed a number of different systems which do not utilise a lining material as such to affect a repair. The Sanipor ‘flood’ renovation system is one such technique. Using two liquid components the Sanipor system first pass Solution 1 into the damaged pipeline and allows it to impregnate the faults and surrounding ground. This solution is then quickly removed and Solution 2 is pumped in. The two solutions react to form an effective seal of the defects in the pipe over the whole length into which the solutions have been used, including any lateral pipelines that have been filled during the process. Whilst this system has been around for many years, it is only in the last 18 months that the system has undergone rigorous testing through WRc and been awarded WRc Approved status so gaining industry recognition.
Patch up
Localised repair or patching is also an area in which there has been some significant development in recent months.
One significant development has been the production of a new sealing gel for use in resin injection operations on pipe experiencing infiltration problems. Previous sealing gels have always had the potential problem, particularly where, in certain circumstances, if ground water levels fall, the drying of the commonly utilised Acrylate product may have the potential to cause failure.
So working closely together the contracting arm of Wessex Water (one of the UK’s main water companies), Wessex Engineering & Construction Services (WECS), Sdi-unistride Ltd, one of WECS’s contractors and De Neef UK an international sealing and resin products manufacturer, undertook a development programme for a new sealing gel that would not exhibit this potential tendency. Ultimately the collaboration produced and fully laboratory and field tested product known as SewerSeal JF. Now accepted by Wessex Water’s Technical Committee and the material of choice for WECS on joint sealing projects, the new gel has recently been involved on its first commercial both for WECS and in other parts of the UK. The new gel offers the facility to increase life expectancy of joint seals considerably whilst being installed using the same technology as was used with the previous resins
So, to summarise, whilst the ‘sexy’ end of the industry might still get much of the attention and glory with its high-tech, photogenic machines, there is a great deal of work in both the development and application of pipeline replacement and renovation systems which cannot be overlooked in the increasing success story that is trenchless technology.
The PR95 pipe bursting unit from Ditch Witch The Insituform steam cure lining system in the process of curing on one of the Thames Water designed/WRc witnessed infiltration test rigs The Insituform steam cure lining system A pipe line before and after the application of a UV cure lining system, in this case on a project carried out by contractor DBI using Saertex lining with a Prokasro light train Before… A pipe line before and after the application of a UV cure lining system, in this case on a project carried out by contractor DBI using Saertex lining with a Prokasro light train …After The Mini type and System 5 inversion drums from Trelleborg-epros Installing a PolyFoldliner on a project in London, UK Installing the new SewerSeal JF joint sealing gel on its first commercial project at Montacute, Somerset, UK Installing the new SewerSeal JF joint sealing gel
