Thursday, September 28, 2023

Rehabilitation Options For The 21st Century

Eric Wood developed the first embryonic Insituform Cured-InPlace-Pipe lining system back in the early 1970s

It has been almost 50 years since the first pipeline CIPP (Cured-In-Place-Pipe) renovation lining systems were introduced to the market by Eric Wood the inventor of the Insituform Process. During that time there have been various incarnations of the technology from hot water cured through assisted ambient cure and light cure systems.

There have also been several other pipeline rehabilitation options developed from spray lining techniques and hand applied linings through Sliplining and Modified Sliplining to Spiral Wound and Sectional Liners.

Whilst most of these options are fairly widely used across the globe, it is CIPP linings that appear to take much of the lion’s share of the market. We shall however take a quick look at the non-CIPP options first.

- Advertisement -


Where pipe deterioration is not too advanced or where the client/owner is trying to prevent deterioration, it is often not necessary to utilise structural liners. Here it is possible to use hand applied, sprayed, or mechanically applied (spray) coatings. These coatings can either cement mortar or resin based.

Hand applied coatings require a man-entry operation to install the liner. This can be achieved using either a trowel or a hand-held spray gun. More often these days a spray system is utilised to apply such coatings using pump-powered systems with specially design rotating spray heads that are moved through the pipe at a set rate to provide the thickness of coating required. This can be for both mortar and resin-based applications. The technique can be applied to most commonly used pipe diameters.

One recent development in this area has been the introduction of a brush-based resin coating application system. With this option a mechanical ‘miller machine’, such as the Picote Millers, provides the rotational impetus to a set of brushes within the pipeline is supplied with a resin feed. The resin is brushed against

the pipe wall to form the coating which can be up to 4 mm thick. One advantage claimed for this system is that whilst sprayed applications give a nominal thickness this does not always take account of pipe wall deformations and so may leave dimpling in the final coating.


There are several forms of what have commonly become known as ‘Slipining’ techniques. The simplest of these is where a new pipe is passed through the deteriorated host pipe. The diameter of the liner pipe is determined by the minimum diameter of the host pipe depending on any deformation that may have occurred as part of the deterioration process, ground movement of failure of the original pipe material.

By inserting a new pipe inside the old generally leaves an annulus between the liner and the host pipe which it may be necessary to grout to close off infiltration from the surrounding ground and prevent its transfer to another part of the network. The major problem here is the loss of capacity as compared to the original pipe, something that may be significant depending on the flows the renovated pipe is required to handle over time and as conditions vary.


Where a tight fit liner is required to minimise loss of capacity within the host pipe, various methods have been developed and these are generally known as Modified Slip Lining techniques.

One of the more common forms of Modified Slip lining is the ‘Fold & Form’ technique. Here the liner pipe may be either thicker or thinner walled depending on the application which again may be either a gravity or pressure pipe requirement.

The liner, which is originally circular, is chosen so that it will form a close and tight fit against the inner wall of the host pipe. The tight fit requirement normally means that the liner cannot be passed directly into the host pipe as in Sliplining, so the liner pipe is passed through a folding machine which uses a die to deform the liner pipe into either a ‘U’ or ‘C’ configuration. This action in effect reduces the liner pipe’s cross-sectional profile to one that is much smaller that the host pipe it is designed to line. The folding process can be done either on-site of off-site at the factory or depot before transportation. The advantages of either option vary depending on the application. Once the liner is installed over the length of pipe that is being renovated it is place under pressure using either compressed air or pressurised water.

One area where this fold & form technology has also taken hold is that of lining pressure pipes where for example Primus Line® offers a range of liners for just such a purpose. Primus Line® is a versatile liner system for the transport of liquid and gaseous media. The flexible liner, reinforced with aramid fabric, and the specifically developed connectors form a high-performance solution for the trenchless rehabilitation of pressure pipes or for setting up a robust independently placeable flexible line. The liner is supplied folded. That way Primus Line® can be installed even in pipes with the same nominal diameter. Adhesive tape keeps the liner in its U-shape until it is pressurised to about 500 mbar. This pressure causes the liner assumes its original round form once inside the host pipe.


Spiral wound liners come in both hand constructed and machine constructed types. Both generally utilise the same basic materials to form the liner. The liner is provided as a profile strip of PVC, steel reinforced PVC or HDPE plastic which comes loaded on a reel. To form the lining the profile plastic is pulled off the reel and fed to the construction crew in the host pipe or into a spiral winding machine located either within the host pipe or at the entrance to it, depending on how the machine operates.

The winding machine rotates to bring the flat plastic profile into a spiral so that the edges of the strips to interlock forming a pipe that becomes the water-tight liner. The host pipe diameter pays a significant part in selection of the process to be used. The in-pipe travelling winder can also be utilised for lining non-circular cross-sections.


Sectional liners are supplied as liner segments that are usually factory-manufactured to a specification that can be designed and made to fit any particular pipeline configuration including smaller linking segments to run around bends. They tend to be constructed of GRC, GRP or RPM materials and the liner dimension is normally restricted by the minimum internal dimension of the host pipe. Given the rigid nature of the

liner section the use of a flexible jointing material between adjacent section ends may be necessary particularly at bends. The technique may be labour intensive for the transport and positioning of the liners involved. There is also a need for confined space training and legislative requirements. Most if not all sectional lining installations usually require the annulus between liner and host pipe to be grouted and given the lengths involved in most projects this requires careful planning and execution to ensure that a fully grouted product results. Two of the most well-known names in the sectional liner field are Amiblu with its circular and non-circular liner options (more of which can be read elsewhere in this issue) and Channeline (which has featured in a previous issue of Trenchless Works).


As previously mentioned CIPP linings have been around for some 50 years and are available in various forms for a variety of diameters and using a number of curing techniques.

When CIPP began the most common curing technology was Ambient Cure, arguably the most utilised curing method in the CIPP industry. In this method the liner cures in the ambient temperature without any assistance from heat or other curing external influences. There are a variety of different resins available for Ambient Cure which can be manipulated by the user for longer or shorter curing times.

Due to the working time of the resin the liner must be impregnated by the engineer on site before being pulled or inverted into the host pipe This option does offer the advantage of a small on-site team and a small on-site footprint.

Ambient Cure can be incredibly cost-effective, with a relatively fast installation process and limited equipment requirement. It is however not practical for use on longer length, larger diameter jobs. It is generally recommended that Ambient Cure installations are not carried out on any diameter liner larger than 225 mm and longer lengths may be limited due to the time constraints of the resin cure.

Eric Wood’s CIPP technique was a Hot Cure method using heated water that was used to invert the liner into the host pipe. This requires using a hot water boiler to cure a liner. The Hot Cure method can be used for long length and large diameter installations and involves factory impregnation of the liner prior to delivery to site in refrigerated transport.

Hot Cure speeds up the cure speed of the liner and there are a variety of different resins available with the possibility of using some chemically resistant resins. More recently it has become possible to line Pressure Pipes. This technique does however have a relatively large installation footprint due to the requirement of a water source and tankers and the boiler system.

Over time the CIPP industry explored further curing methods such as Steam Cure. This involves the addition of steam, using a steam generator, to cure the liner once in the host pipe, passing steam through the liner until it is cured.

As with Hot Cure, Steam Cure liners are factory impregnated and delivered to site in refrigerated transport. This is a reasonably low-price methodology after the initial cost of the steam boiler and requires less water supply than Hot Cure as no tanker is required to dispose of wastewater, ultimately reducing on-site footprint and cost.

Steam Cure is suitable for liners up to 2,000 mm diameter but there is the added potential of ‘cold spots’ if there is pooled water within the pipe or laterals. On site health & safety guidelines must be stringent given the large quantity of hot steam being emitted from the boiler and a larger compressor is usually required compared to a hot water cure.


More recently there has been a significant move across the CIPP sector towards light curing techniques.

A completely different method of cure originated with the introduction of UV Cure. The liner is pulled through the host pipe using a winch and a UV light train is electronically pulled through the pipe, prompting the liner to cure. UV Cure is suitable for curing liners up to 1,600 mm diameter and is becoming a popular methodology due to its fast cure time and high strength characteristic.

Further to the development of UV Cure has come UV LED Cure, one of the latest cure methods in the CIPP industry. UV LED cure is a fast, safe, and simple curing process with a much smaller on-site footprint than all other curing methods. It is the only cure method on the market that has the capability to cure both standard UV glass reinforced liners and felt liners impregnated with UV LED resin. UV LED Cure uses styrene free resins meaning there is no odour on site. UV LED methods also dramatically reduce the time required for pipe rehabilitation. The lightweight and portable curing equipment means access to small working areas is achievable and less power is required than with traditional systems. UV LED is capable of curing liners both horizontally and vertically. There is however, currently a limit to the cure ability of UV LED to liners up to 600 mm diameter.

There has also been the introduction of Bluelight cure technology. The Bluelight PAA-F liners are available in diameters of DN70 to DN100, DN100 to DN250 with PAA-G liners up to DN400. The curing reels are far more reliable than removable heads due to the reduced handling of the equipment. There is also a patented cooling process which prevents moisture and contaminates coming into contact with any electronics and with zero moving parts in the head itself this PBF claims offers a greater reliability than other systems on the market.

The curing heads are available in 3 different sizes from the small light head for DN70 to DN125 and the ball light head for DN100 to DN200 and then the large light head for DN100 to DN400 the advantage of the small and ball light head is that it can negotiate 90o bends in the DN70 and DN100 liners. The smaller 40 m reels are better suited for difficult access areas where the liners are usually shorter.

For the more traditional UV market some figures are available, although these may be ‘ball-park’ estimates. Across Europe for example there seems to be something of an imbalance when it comes to the uptake of UV light cure lining systems with these figures showing that the:

  • UV share of CIPP in the UK is approximately 37%
  • UV share of CIPP across all of Europe (including the UK) is approximately 61%
  • UV share of CIPP in Germany is approximately 66% (note: Germany is believed to cover approximately 50% of the total European CIPP market)

UV share of CIPP across all of Europe including the UK but excluding Germany is approximately 55%

This would seem to indicate that in the European market the lion’s share of CIPP installations is now completed using UV light cured lining techniques. The UK is some way behind with just around 37% of its CIPP market being UV light cure-based. These figures do not however take account of any market share for LED or other systems installations.

Lately however with many authorities and governments providing guidelines and legislation that requires the removal of these noxious substances from the environment, there has been a drive towards reformulated resins that do away with the styrene base using an epoxy base.

One such example that was recently announced as about to hit the market is from InPipe in Sweden. Inpipe Freeliner as it is known is claimed to be the world’s first fiberglass reinforced liner that is free from both styrene and Bisphenol A, another chemical that is on the removal list.


Whilst light curing systems have been around for many years, the past few years have seen a significant push towards smaller more portable systems that care aimed at the smaller diameter end of the market and the smaller contractor, where more traditional curing techniques still proliferate but where the need for market change is becoming ever more apparent. Several companies are involved in the sector as follows:

BKP Berolina – The Berolina-Liner System is a cost-effective and efficient method for sewer pipe rehabilitation. Compared with other methods energy consumption is reduced significantly thanks to optimised production, transportation and installation conditions. Since 1997, BKP has successfully produced UV light-curing and glass fibre reinforced tube liners.

Different liner types are available to meet most requirements for sewers in need of rehabilitation including:

  • Berolina-HF-Liner for higher mechanical characteristics – Due to the special construction of the glass sheets and higher glass content, the Berolina-HF-
    Liner achieves higher mechanical characteristics resulting in a reduction of the structurally required wall thickness compared to the normal Berolina-Liner.
    The resulting lower weight allows easier handling. The Berolina-HF-Liner is also available with Integrated Enhanced Security (IES) which means a smooth slip film is no longer necessary for the pulling in with the result that installation time can be reduced by up to 60 minutes.

Berolina-LP-Liner for application in the low-pressure range – The Berolina-LP- Liner (LP=Low-Pressure) is used in wastewater pressure pipe rehabilitation. By using very resistant glass and the particularly favourable structural arrangement of the glass sheets, a maximum internal operating pressure of 3 bar is possible. The standard Berolina-Liner was modified and used for the low-pressure range under the name Berolina-LP-Liner in order to rehabilitate pressure pipes too.

Brandenburger – Brandenburger develops and manufactures pipe liners in-house for trenchless sewer rehabilitation. The pipe liners are hardened with UV light, forming a new pipe within the old one. As the dimensions, cross-sections and mechanical loads differ depending on the pipe to be rehabilitated, the company offers a suitable product for every situation combined with technical advice.

With liner wall thickness ranging from 3 mm to 5 mm, the various liners available from Brandenburger are applicable to pipes of diameter from DN150 to DN1600.

Brawo Systems – According to Brawo Systems, which has C J Kelly International
Ltd and S1E as distributors in the UK, the BRAWO Magnavity light curing systems
is Smart – Efficient – Powerful. These three attributes it is claimed stand for the innovative BRAWO® Magnavity system, which makes light curing even smarter, more efficient and more powerful. The system consists of a choice of two intelligent LED heads, a 50 m long combination hose with integrated energy and compressed air supply, a retraction unit and a control box. The innovative, unique design of the LED head allows it to be retracted simultaneously with the inversion of the liner. Curing is thus carried out immediately after installation of the liner, without the need for additional insertion of the eel. In this way, a complete work step is saved, and even with long pipes and ducts, one access point (e.g. inspection opening) is sufficient for the rehabilitation.

In addition to the already familiar Nano LED head with 96 high-performance
UV LEDs for use in pipe diameters from DN 70 to DN 250, there is now also the new, extremely powerful Mega LED head. Thanks to its 192 high-power UV LEDs and the associated greater light output, up to approximately 70 % faster curing is possible compared to the Nano LED head. The Mega LED head is suitable for rehabilitating the dimension ranges DN 125 to DN 300. From a pipe diameter of DN 150 upwards, pipes with bends can also be rehabilitated economically and efficiently.

Further to these developments, Brawo Systems has also recently introduced the new BRAWOLINER 3D DN 200-300, which now optimally complements the ever-popular 3D liner product range. This means that all nominal diameters from DN 50 to DN 400 can be served, even when there are dimensional changes in the pipe run. The BRAWOLINER 3D DN 200-300 is compatible with the Brawo I, Brawo III and BRAWO LR resin systems. Curing can be carried out as usual with steam, hot water, light or ambient temperature.

PBF Drainage – Bluelight is claimed to be the most developed system available with over 12 years of experience and that it is the only pure LED light cure equipment compared to the other systems which are UV LED. PBF Drainage (PBF) has been the UK agent for Bluelight since 2018 when it purchased what was believed to the first LED light curing equipment in the UK. Not long after the company set up its agency agreement with Bluelight gmbh.

The growing demand for Styrene free resins, has meant a vast growth in demand for LED curing equipment. Water companies are guiding contractors away from styrene especially in or around properties where the risk of exposure is greater. This has led to more and more contractors investing in modern high-quality equipment.

The Bluelight PAA-F liners are available in diameters of DN70 to DN100, DN100 to DN250 with PAA-G liners up to DN400. The curing reels are far more reliable than removable heads due to the reduced handling of the equipment. There is also a patented cooling process which prevents moisture and contaminates coming into contact with any electronics and with zero moving parts in the head itself this PBF claims offers a greater reliability than other systems on the market.

PBF is now impregnating Bluelight LED light cure liners in the UK utilising the most up to date impregnation system available, with automatic dosing, temperature-controlled impregnation, and calibrated roller gaps, it is possible recreate the high specification of materials used throughout Europe.

PBF can supply both the felt inversion liners and the glass liners both impregnated with its patented styrene-free vinylester resins, both types can only be cured using PBF’s own system working at 450 nm (nanometre) wave length which is proven to be the most efficient light wavelength.

ProKASRO – ProKASRO has been producing its KASRO UV curing systems since 2003 for the installation of CIPP pipe liners in an efficient manner. The KASRO UV CCU is applicable to pipe diameters from DN150 to DN1200 and is available with a curing cable length from 200 to 240m. The equipment is highly mobile, compact and equipped with four wheels so that pipeline rehabilitation can be operated within the narrowest of streets. The system operates as a complete control unit above an electrically-driven cable drum with the operation, display and datalogging being carried out via a 21 in (530 mm) Touchscreen PC. The systems can be installed in a vehicle and is inclusive of a device for tele maintenance via remote control. The KASRO light sources available include: 8 x 400 W; 8 x 600 W and 8 x 1000 W.

Various light sources are also available depending on the project being undertaken. These include the KASRO UV light source chain for DN150 to 500 pipes; the KASRO UV light core for DN550 to 1200 pipes and the KASRO UV light core for DN1000 to 1600 pipes.

Reline UV Group – The RELINE UV Group offers customised equipment, perfectly matched to the company’s Alphaliner product range to ensure successful renovation projects. The innovative UV technology has been developed and produced in-house. This system technology was developed from practice for practical applications. UV curing systems from the RELINE UV Group have what is claimed to be the highest curing performance on the market and are equipped with intelligent, permanent performance monitoring that automatically compensates for drops in radiation power of each individual emitter. The company offers two systems the REE2000 and the REE4000. Details of the Alphaliner systems can be found elsewhere in this issue.

RSM Lining Supplies – RSM offers the SPEEDYLIGHT+ which is a fast, UV LED curing systems for reinstatement of up to 70 m of 100 to 300 mm (4 in to 12 in) diameter pipe in one installation, featuring an innovative, patent pending, rotating UV LED design, delivering high energy density at the surface of the liner.

The system offers the facility to cure both felt and glass fibre liners; increased installation productivity; Interchangeable rotating curing heads; Deeper curing penetration; Two curing heads for different working diameters; negotiation of 90o bends and an All-in-One package with integrated power supply and no interconnecting cables.

S1E – S1E exclusively offers the Starlight UV curing system from IST with the capacity to rehabilitate smaller mainline and lateral pipelines from a single machine, with fast cure times. IST’s original NuVision UV curing system is in use in every continent in the world. The Starlight system takes NuVision’s technology further and offers a product for smaller-bore pipelines.

SAERTEX multicom – SAERTEX multiCom introduced what is claimed to be the world’s first GRP liner for trenchless rehabilitation of potable water pipes with UV curing in 2016. Today the company claims to be setting additional milestones in order to save even more CO2 with this environmentally-friendly technology and make its product range even more sustainable. Together with Scott Bader, one of its strategic partners, the company has now implemented a significant innovation in the sustainable production of GRP pipe liners known as SAERTEX-LINER® UPgreen.

UPgreen technology is a sustainable process optimisation in the production of glass fibre reinforced pipe liners. For impregnation of the SAERTEX LINER® carried out at the factory, SAERTEX multiCom® relies on unsaturated polyester resins (UP resins) from Scott Bader which are manufactured with a new, climate-friendly production method. Since the last quarter of 2020, 70% of the UP resins supplied have been produced with the new technology. As a result, in the last quarter of 2020 alone, 270,000 kg of CO2 have already been demonstrably saved with around 160,000 running meters sold. That corresponds to the CO2 footprint of 723 flights from Frankfurt am Main to New York.

UPgreen technology is used for all SAERTEX-LINERs in the product range that use UP resins. These GRP pipe liners are used for trenchless rehabilitation of municipal sewers and pipelines. The environmentally-friendly changeover of the UP resin system has no impact on the technical properties of the products. Therefore, customers do not have to take any technical changes into consideration for their projects. In addition, all further developments are in harmony with all globally-existing product approvals, so they remain valid. So far, SAERTEX multiCom® has launched the UPgreen technology in Europe. China and the USA will follow in the future.

The fact that increasing numbers of equipment offerings and wider ranges of installation options are now available give credence to the fact that light cure lining has yet to come fully of age, particularly in the UK – but it is getting there.

- Advertisement -
Trenchless Works bringing you balanced journalism, accuracy, news and features for all involved in the business of trenchless and no-dig from around the world

Related Articles

- Advertisement -
- Advertisement -
- Advertisement -