Our latest IKT Compare technology evaluation is examining the performance of lining systems for the trenchless rehabilitation of pressure sewers. The aim is to support sewer network operators in the selection of suitable systems and to provide them with certainty when developing tender documents, overseeing installation, accepting the work, and monitoring quality. There is still the opportunity for sewer network owners from other countries to join a partner project to contribute to and benefit from this research.

The issues with pressure sewers

For the past couple of decades sewer network owners and suppliers of liner technologies have been focused on addressing the rehabilitation of gravity sewers. For pressure sewers the focus has been on dig down and repair or excavate and replace. Pressure sewers are made from a range of materials, many are approaching the end of their service life or developing faults and there is an increasing requirement for rehabilitation, repair or replacement.

Trenchless rehabilitation techniques are usually the solution of choice for repairing damaged sewers, as they minimise disruption in the road and have economic and environmental advantages over open cut methods. However, sewer network operators cite a range of difficult issues for pressure sewers that limit the application and performance of trenchless solutions, such as lack of access points (for inspection or repair), bends up to 90°, unknown pipe layouts, and small nominal diameters in some cases.

Although the first rehabilitation techniques for sewage pressure pipes are now being offered on the market, sewer network owners have realised there is a considerable need to investigate their applicability and limitations. On the one hand, there is a lack of neutral and independent information on installation requirements, application range, performance and application limits of the available processes and products. On the other hand, there is currently very little experience to draw on when considering rehabilitation measures for pressure sewers.

For the planning process there is a particular need to understand how to select remediation techniques tailored to the specific application, and for the installation there are issues of implementing quality assurance and for flood protection during installation.

Achieving the objectives

The objective will be achieved through comparative evaluation of the techniques available in the market. Working with the project steering group of sewer network operators, the typical damage scenarios encountered with pressure sewer pipes are being defined and a testing concept developed.

What is available?

A market review of available technologies, products and suppliers is being undertaken and, from this, the project steering group will be selecting eight products for evaluation that are representative of the available technologies. This review is also considering the current status of applicable standards and regulations.

Evaluation

1:1 scale laboratory testing is being devised that will result in test rigs being installed in IKT’s large-scale test facility comprising pumped pressure pipes in which typical damage scenarios have been created.

The selected rehab products will be installed and tested under identical conditions which will include assessing their ability to withstand the typical pressure changes experienced in live pressure sewers. To support the laboratory evaluation, in-situ evaluation will be undertaken on the same techniques installed in sewer pressure pipes at the network operators’ sites. In addition to their performance the quality assurance provisions for the products will be evaluated.

Whilst, for practical reasons, the 1:1 scale testing will be undertaken on pipes between DN100 and DN400, the project will also be assessing in the field the rehabilitation of pressure pipes <DN100. The findings will provide information on the potential and the limits of rehabilitation methods for pressure pipes, and statements on their technical performance, that can be used as a basis for investment decisions. This will be supported by recommendations for quality assurance in tendering, award of contracts, construction supervision and acceptance.

As with all IKT Compare projects the members of the Project Steering Committees additionally benefit from the exchange of knowledge and experience with other network operators.

Additional partner projects

Core funding for this project has been provided by the Ministry of the Environment of the State of North Rhine-Westphalia, and supported by the participating German sewer network owners. A partner project alongside this main project in Germany is being undertaken with the City of Arnhem, The Netherlands, to examine pressure sewer inspection techniques. Another partner project is in development with sewer network owners from other countries that will include consideration of the application of lining to larger diameter pipes.

If you are a sewer network owner and would like to find out more about the project or consider joining a partner project please get in touch.

Contacts

• Dipl.-Ing. Markus Gillar
  IKT Senior Research Fellow
  phone: +49 209 17806-46
  email: gillar@ikt.institute
• Dipl.-Ing. (FH) Serdar Ulutaş, MBA
  IKT Senior Research Fellow and Head of IKT Compare
  phone: +49 209 17806-32
  email: ulutas@ikt.institute
• UK: Dr Iain Naismith
  phone: +44 (0) 7983 605219
  email: naismith@ikt.institute

 

Sewers and tree roots—this gets the alarm bells ringing for pipe network operators, because with root ingress, for example into sewers is something they are struggling with almost daily. In other networks, such as district heating, gas or drinking water, the roots around pipes are more problematic, as they can transfer enormous loading during storms, for example. You don’t want roots in the pipe trench and especially within the pipes. 

But, you don’t want to start chain sawing the green infrastructure of the city. Fortunately, there are innovative products and processes that may help keep the roots away from the pipes. Whether they can really do this is currently being investigated by IKT in an international project together with partners from The Netherlands. Passive measures to protect pipes from root ingrowth such as plates, low-porosity backfill materials, mats and special pipe joints are being tested in a test setup that is unique in the world.

This open-air test area was set up by IKT in cooperation with IKT Nederland, the city of Almere and the RIONED foundation in The Netherlands. This project investigates how effective ecologically sustainable concepts for resolving conflicts between urban green areas and underground pipelines can be.

Watching the roots grow

Five trees have been planted along two sewer pipes in a new development area in the City of Almere, near Amsterdam, whose roots are now under observation, in the truest sense of the word, because glass panes were installed at two points so that you can actually watch the roots grow.

Explaining research in an understandable way

In order for residents and passers-by to understand what the system is all about, an information board has been set up to explain the project and its goals in a comprehensible way. Leo Bloedjes from the city of Almere, IKT project manager Mirko Salomon, IKT Nederland branch manager Sebastiaan Luimes and IKT managing director Roland W. Waniek inaugurated the experimental set-up and the information board.

24 systems under test

24 systems made of various materials were installed on the sewer pipes and in the pipe trenches of the test facility to provide passive protection against root ingrowth. These include special pipe connections, low-pore backfill materials, plates and mats. The products and processes that are being evaluated were selected by the client, i.e. they are the systems of particular interest for the city of Almere.

Safe lines under the green city

In this international research project, the effectiveness of the installed systems is now being investigated over a period of several years. The first excavations to examine their performance are planned for Floriade 2022, the International Horticulture Exhibition Expo that takes place in The Netherlands every 10 years, and in 2022 has the Theme Growing Green Cities. Almere is hosting the Expo and experimental set-up is near the exhibition grounds and the participants think that this is really a good fit with that theme.

After the excavations, the barrier function of the systems against growing tree roots will be analysed for the first time. The researchers will then derive initial recommendations and guidance from the results, which support network operators in selecting suitable root protection measures. In addition, these long-term performance considerations can also provide valuable information for the development or optimization of products and systems for root protection of pipes.

Keeping roots and pipelines at a distance

Underpinning this is the fact that underground pipes and the roots of the city trees share the same ground space and repeatedly clash. Due to high groundwater levels in Almere, the space conditions under the roads are particularly cramped. Underground sewers have to be installed in Almere at depths of only about one meter below the ground level. In the past, to avoid later root ingrowth where new underground pipelines were being installed, individual trees were felled as a precautionary measure. In times of climate change, this is a very unpopular measure, which one absolutely wants to avoid in the future. Therefore, the Gemeente Almere is very interested in new concepts that combine a green city and optimal protection of the pipes against root ingrowth.

Do systems work in the long term?

The aim here is either: to make the bedding area of the pipes as unattractive as possible for roots (low-pore backfill materials); to direct root growth into harmless areas (using plates and foils); or to prevent the roots from growing into the pipe (casing pipes and using root-resistant joints). Whether these measures can keep the roots away from the pipes over a long period of time and effectively prevent roots from growing around or into the pipes has hardly been researched to date.

With this international research project, the participants want to make a contribution to a better urban environment, greener cities and safer sewer operation. And contribute to better relations—between pipe network owners and tree owners as well as between neighbouring countries.

And for the people visiting the test facility there is already something to see: The first roots have appeared behind the viewing panes.

Web guide

IKT Nederland
City of Almere
RIONED foundation

Contact

Mirko Salomon, M.Sc.
Project Manager
tel.: 0209 17806-25
e-mail: salomon@ikt.de

 

For more than ten years, the performance of CIPP liners continuously improved. But, in recent years the annual test results have sometimes been poorer. Is this a sign of a reversal in that trend?

Fifteen years ago, IKT published its first LinerReport and has repeated this exercise every year since. Altogether, these reports include the test results from some 23,000 samples taken from installed Cured In Place Pipe (CIPP) liners in sewers. This represents sampling from an estimated 2 to 2.5 million meters of lining installed in rehabilitated sewers.

The samples used for the LinerReport are taken at sewer rehabilitation sites shortly after the installation of a CIPP lining and are then tested at IKT’s two materials testing laboratories, in Germany and in The Netherlands (since 2013). Four test criteria are applied: modulus of elasticity, flexural strength, wall thickness and water tightness.

2018 results

The latest IKT LinerReport includes more than 2,100 liner samples, taken at installation sites in 2018 for quality control purposes and examined by the IKT testing laboratories. As in previous years, the modulus of elasticity, bending strength, wall thickness and water tightness were determined for each site sample. In each case performance has been determined by comparing the test results with the expected target values derived for each sample from the relevant product approval (Germany: DIBt Approval; The Netherlands: KOMO certificate; Switzerland: QUIK guideline) or client information, e.g. static design calculations.

Download LinerReport 2018 here

The average proportion of passed tests results for the four test criteria remained at a high level in 2018 (mean values: 98.9%; 97.5%; 97.4%; 94.1%), similar to the previous year‘s level, with a very small improvement in the modulus of elasticity and very small declines in the other three criteria. 2018 was a good year overall for liner quality.

Samples passing all four test criteria

For about two thirds of the liner samples tested by the IKT testing laboratories in 2018, required target values for all four criteria were available. Only if all four target values are known, can a complete evaluation of the sample against all criteria be made. At least one target value was missing for one third of the samples. Of the total of 1,366 samples with all four nominal values, 90% met the requirement for all four test criteria. So, one tenth failed at least one test criterion.

Members of the “100% Club“

Five lining companies managed to achieve a 100% pass for all four test criteria with all their samples in 2018. They are:

• Bluelight GmbH with PAA-F-Liner
• Hamers Leidingtechniek B.V. with Alphaliner
• ISS Kanal Services AG with Alphaliner
• Jeschke Umwelttechnik GmbH with Alphaliner
• Kanaltechnik Agricola GmbH with Brandenburger Liner

Conclusions: Preventing loss of quality

The IKT LinerReport has been reflecting the development of quality assurance for CIPP sewer lining since 2003/04. Looking back over the last 15 years, we can see a clear trend of improving quality, over about a decade until 2013/15, before stabilising. Since 2015, there has been a slight tendency for a decline in performance against the mechanical test criteria. Has the long-term improvement in CIPP sewer lining quality assurance ended?

A sign of declining quality assurance?

This claim seems premature at this time. However, the slightly declining average test results of the last three to four years indicate that it is not a given that a high level of quality can be maintained once it has been achieved. This could be interpreted as a sign of a possible reversal in the trend. There could be several reasons for this: an intensive struggle by the lining companies for market share in a market that is still very price-competitive, the development of new machinery and plant capacities, the entry of new market participants and, last but not least, the much-discussed shortage of skilled workers, which is particularly noticeable in the commercial sector. Much of this is speculative, so it remains to be seen how the markets develop.

Sewer network owners must ensure quality assurance

In order to maintain a high level of CIPP liner quality, customers should make it clear to suppliers that quality is important to them and that they take the requirements of the relevant standards and regulations very seriously. In their function as network owners, they should commission independent testing themselves and insist on consequences in the event of negative test results.

Clients should make sure that they have CIPP liner installation checked so that there are no quality loopholes, which can prove to be very expensive in later years. Finally, they should pay much more attention to acceptance warranties, because then they will still have some control in the event of inadequate renovation work.

Download LinerReport 2018 here

View all IKT-LinerReports

IKT Test Centre for CIPP liners

Contact Persons

• Barbara Grunewald, M.Sc.
  T: +49 (0) 209 17806-40
  E-mail: grunewald@ikt.institute
• Iain Naismith, PhD
  T: +44 (0) 7983 605219
  E-mail: naismith@ikt.institute

 

Today, Roland W. Waniek, Managing Director of IKT, celebrated his 20th job anniversary with IKT. He said: “These have been 20 exciting and intensive years. I would like to thank all employees and the Board Members for such good and successful collaboration over that time! And I look forward with confidence to the future.” Then he cut the cake.

Prof. Dr.-Ing. Bert Bosseler, IKT’s Scientific Director, who worked with Roland for the past 18 years, thanked him and praised his commitment and foresight. For IKT’s Supervisory Board, Hans-Joachim Bihs delivered greetings and a bouquet of flowers.

 

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IKT is building a globally unique test facility for heavy rainfall and urban flooding. The project, which costs around 11 million euros, is funded from the EU’s and North Rhine-Westphalia’s joint Fund for Research Infrastructures. NRW Environment Minister Ursula Heinen-Esser now visited IKT and presented the million-dollar funding decision. Overall objective: Preventing flooding from local heavy rainfall and protecting people and buildings.

More frequent heavy rainfall

There has been more heavy rain in recent years than ever before. Heavy rains in Wuppertal, Münster, Dortmund and numerous other cities have been bad experiences. They led to catastrophic local flooding with extensive damage to private and public buildings. Even people were harmed.

IKT Managing Director Roland W. Waniek: “Our research question is: How can damage caused by heavy rain be mitigated or even prevented in the future? The existing sewer systems are not designed for these water masses, for justified reasons. Therefore, new approaches, new techniques and new urban planning concepts are needed.”

Computer simulation is not enough

Because of the complex urban conditions and mixtures, especially in the inner cities, it is very difficult to develop solutions on the computer alone. The dynamics of rainwater and its flow behaviour in urban areas quickly push even the best simulation models to their limits.

New test rig on a scale of 1:1

For this reason, IKT has designed a new test rig which simulates realistically on a scale of 1:1 how rainwater flows off roads, residential and commercial areas. The new facility will enable IKT researchers to replicate entire road sections, including all the associated installations such as kerbstones, gutters, gullies, manholes and pipes as well as state-of-the-art rainwater retention equipment. Even road gradients of up to 10 percent can be created.

Water from below, from above and from the side

The experimental setups will then be exposed to heavy rain masses of 1,000 litres per second and hectare. This could be used to flood a football pitch ankle-deep in a good quarter of an hour. In addition, large-scale flooding of streets and squares can be simulated with a water surge of 250 litres per second. This could fill two bathtubs in one second.

In a water cycle driven by powerful pumps, flooding can be simulated again and again to observe the behaviour and performance of the road and drainage system and its protective effect on people and property.

Results for on-site practice

The research results from IKT will allow conclusions to be drawn for the future rainproof design of roads, footpaths, cycle paths and underpasses. It will also show how buildings can be better protected. Above all, the Institute aims to provide local authorities with practical insights that can be used in a targeted manner on site. Also the environmental regulators can see which technical regulations and legal requirements make sense and which may need to be changed.

International Heavy Rain Research

The new IKT test facility will also have a control station with which measurement data and video images of the tests can be visualised in real time and transmitted via the Internet. This will enable scientists worldwide to observe and comment on the experiments being carried out in Gelsenkirchen. Research on heavy rainfall and urban flooding will be internationalised, as heavy rainfall does not only exist in Germany.

Contact

Iain Naismith
phone +44 1491 712707
e-mail naismith@ikt.institute

Short liners are often the first choice for repairing local damage in house connections. But, can they deal with seriously damaged pipes? The results of the new IKT-Compare project “Short Liner for House Connections” are now available.

IKT institute has found in its most recent IKT-Compare project that in principle short liners (also referred to as patch or point repairs) can make good quality repairs to house connection pipes, even when the pipe is severely damaged. Eight short liner systems were tested and achieved scores ranging from “VERY GOOD” to “SATISFACTORY”. The evaluation did find significant differences in performance between the systems that were examined.

Twinbond Liner was the best performer with a score of VERY GOOD (1.2). Second place went to epros DrainPacker (Trelleborg) also graded VERY GOOD (1.4). Bodenbender Point-Liner-System (1.7), Berolina Repair System (2.5), Cosmic TopHat system (2.5) and MC Konudur LM-Liner (2.5) each received a GOOD grade. Alocit short liner (2.7) and I.S.T. Spot Repair System (2.9) were graded SATISFACTORY.

The project has been undertaken in co-operation with twelve sewer network operators which wanted to understand the strengths and weaknesses of this widely used technology. It has been funded by the North Rhine-Westphalian Ministry of the Environment and the network operators.

Download table of results
Download product test report (German)

Tough testing of short liners

A rehabilitation using a short liner should be able to restore the structural stability of a pipe, secure its hydraulic performance and seal a damaged area. For this reason, the IKT Compare team and the network operators involved placed particular emphasis during testing on the water tightness, operational reliability and structural stability of the rehabilitation. The particular focus was resilience external water pressure.

Test set-up damage scenarios

For this project IKT built eight identical 1:1 scale rigs, in its large-scale test pit (15m by 6m by 6m), into which suppliers installed their short liners. Each rig comprised a length of sewer to which were attached one house connection pipe on the same level as the sewer pipe and two house connection pipes from a higher level. The house connection pipes were prepared with defined areas of damage, including milled patterns of cracks, the removal of some or all of the joint seals and broken sections. A total of 64 damage patterns were produced – eight in each of the eight test rig setups.

These patterns of damage were arranged as follows:

• Test Setup I (the lower house connection pipe, to which a 2m head of external groundwater was subsequently applied): cracks, a broken joint, a radially displaced joint and a joint displaced at an angle
• Test Setup II (the two higher house connection pipes, to which a 1m head of groundwater pressure was subsequently applied): a defective change of pipe material, defective change of pipe diameter and material from cast iron DN 150 to PVC DN 125, a defective change of pipe diameter and material from clay pipe DN 150 to PVC DN 125, and a break in the joint of a 45 degree bend

Following installation of the eight different short liner systems into separate test rigs, an extensive testing programme began, starting with initial visual inspection and leak tests. This was followed by short-term and long-term external water pressure tests, high-pressure jetting at different pressures and using different types of nozzle, simulated backing-up of water, changing groundwater levels, and cleaning with rodding devices.

Frequent visual inspections and leak tests were undertaken as the programme progressed. Finally, when the test rigs were exhumed from the test-pit, the cross-section reduction was measured and the adhesive tensile strength and ring stiffness of the installed liners were assessed.

Grading of performance

In addition to physical tests, the QA/QC procedures were examined. The laboratory results were validated through in-situ observation of the same systems being installed at actual construction sites. The final scores in this IKT Compare test are based on these three evaluations. The range of grades applied is from VERY GOOD (score of 1.0) to INSUFFICIENT (score of 6.0).

Weighting of scores: Water Tightness counts for the most

To derive the final scores the results of the 1:1 scale testing system tests were given a 85% weighting and the results of the QA/QC evaluation 15%. For the 1:1 scale test score, the three test criteria were weighted as follows: “water tightness” (60 percent), “operational reliability” (20 percent) and “structural stability” (20 percent).

The assessment of QA/QC comprised five criteria: the installation manual, the available training courses, the system’s DIBt (German Government’s approval body) approval, external production monitoring, and a comparison between the installations observed in the laboratory and in the field. The results for each criteria were given a 20% weighting in the final QA/QC score.

In addition to the test criteria used to derive the comparative scores of the systems, supplementary information was collected and presented that would be of interest to the end user. These include results from internal pressure tests undertaken after the rigs were excavated and the adhesive tensile strengths of the liner bonding to the host pipe. The preparatory measures undertaken by the installer, such as initial inspection, substrate preparation and cleaning, were documented. Also presented are: the number of on-site working days, the number of installation staff, the time required for preparatory work and installation, and the costs.

What the systems can do

In this IKT Compare project, the system suppliers demonstrated that serious damage to house connections can be reliably sealed using short liners, including breaks, cracks, misalignments and deflections. In particular, the Twinbond and Trelleborg systems proved to be the most reliable under permanent groundwater load, jetting, simulated backflow events and changing groundwater levels. For this they were deservedly awarded the score of 1.0 for water tightness.

Special Challenges

In principle, it was also shown to be possible to seal the changes in nominal diameter and pipe material in Test Setup II. However, four of the systems came up against their performance limits here, showing weak points, which led to infiltration. In one case, gushing water was visible immediately after installation. Therefore, changes in diameter and material require special attention during installation.

Results of Test Setup I

All eight short liners showed very good to satisfactory results for the four damage patterns in Test Setup I: cracks, broken joint, radially displaced joint and joint displaced at an angle. No infiltration was observed during the whole test period. However, about half of the systems showed visual abnormalities in the form of moisture and/or discoloration at some locations, but without the formation of droplets.

Structural stability assured

The structural stability testing of the short liners showed that they basically have reliable adhesive and load-bearing performance. For products with full-surface bonding of the liner to the host pipe, hardly any abnormalities were observed, i.e. no crack formation, no excessive deformation, no stability failure nor large-surface loosening of the adhesive bond. Five systems showed partial loosening of the adhesive bond at points of changing diameter or pipe material, albeit without any consequences.

The Cosmic system is not intended to bond over the full-surface, only at the start and end of the liner. However, the supplier was able to submit a static proof which confirmed the structural stability of the short liner observed in the test.

Operational activities

The test scenarios simulating sewer operation, such as high-pressure jetting, water backing-up in the pipe, and changing groundwater levels, had no significant effects on system performances.

Good QA/QC

There were no issues with quality assurance: seven out of the eight systems fulfil all the criteria for quality assurance and receive a grade of 1.0. The Cosmic system does not have a DIBt approval and so gets a grade of 2.0.

Conclusion

In conclusion the IKT Compare project “Short Liners for House Connections” has demonstrated that short liners can renovate even severely damaged sewer pipes. However, changes in diameter and material require special attention during installation as they might cause serious problems. It is important to select the right system for the task, to understand the limitations of individual systems, and apply the necessary QA/QC before, during, and after installation.

Download table of results
Download product test report (German)

Contact

IKT ‑ Institute for Underground Infrastructure, Germany
Serdar Ulutaş, MBA, Dipl.-Ing. (FH)
phone: +49 209 17806-32
email: ulutas@ikt.institute