Too many liners still do not meet all four of the test criteria. They may pass individual criteria, but only those samples that pass all four can be considered really good.

For the fourteenth year running, IKT ‑ Institute for Underground Infrastructure is pleased to present its annual LinerReport. This sets out the results from over 2,100 liner samples taken from rehabilitation sites for quality control purposes in 2017 and tested by the IKT CIPP Liner Test Centre.

Download LinerReport 2017 here

Determining target performance for samples

As in previous years, the modulus of elasticity, flexural strength, wall thickness and water-tightness have been determined for each sample submitted (for details, see box titled ‘Overview of liner test and inspection criteria’). Pass/fail was assessed for each sample by comparison of results against its target performance, derived either from the liner’s DIBt (German Institute for Building Technology) approval specification (Netherlands: KOMO Certificate; Switzerland: QUICK Guidelines) or as specified by the client (e.g. structural-analysis calculations).

Modulus of elasticity test – 2017 results slightly weaker

On average, 97.4% of the liners reached their required modulus of elasticity. This result was 1.5% lower than 2016 and 1.7% lower than 2015, the year when the highest score was achieved in any of the previous IKT LinerReports. However, this does not necessarily indicate a trend. Fifteen out of the 25 rehabilitation companies in this year’s survey achieved 100% for this test, one of them for two different liner systems.

Flexural strength test – 2017 results also weaker

The flexural strength test results were similar to the Modulus of Elasticity, with the average result lower than in both previous years (-0.8% and -1.7%, respectively). Fourteen rehabilitation companies achieved a score of 100%, but the results were much more broadly distributed. The lowest-scoring company passed only 70% of the tests.

Wall thickness test – wide variation in results

On average, the results of the wall thickness test were lower than for the two previous years: -1.7% compared to 2016 and -0.9% compared to 2015. The distribution of results for wall thickness was much greater than for the modulus of elasticity and flexural strength, with the lowest-scoring company passing 60% of the tests.

Water-tightness test – similar high results to last year

The water-tightness results remained at the same high average level as the previous year, with 99.1% of samples passing. This was the highest average score of all four test criteria. Seventeen rehabilitation companies passed all of the water-tightness tests.

Importance of passing all four tests

Ideally, each liner sample should meet all four test criteria (modulus of elasticity, flexural strength, wall thickness and water-tightness). It is not sufficient for a sample to pass less than four criteria. This is especially important because the DWA-M 144-3 (ZTV rehabilitation – Supplementary Technical Contractual Conditions) explicitly uses these criteria for quality assessment. This ZTV is now a widely accepted standard, and is used as the basis for most rehabilitation contracts.

The proportion of the liner samples tested in 2017 that actually met all four test criteria was 63% (previous year: 61%; see Diagram 1). While it is good that this rate has slightly improved on last year, it must be noted that more than one-third of the liner samples failed to meet one or more test criteria. Thus they do not meet the standards for high-quality sewer rehabilitation.

The top performing contractors in the ‘100% Club’

The quality standards for liners are only met if samples pass all four test criteria. In 2017, 9 out of 25 rehabilitation companies achieved this goal (previous year: 5 out of 22), scoring 100% for all their samples. One company even achieved this top result for two different liner systems.

The nine rehabilitation companies made it into the 2017 ‘100% Club’ are:

• Diringer & Scheidel Rohrsanierung, using the RS CityLiner
• Geiger Kanaltechnik, using the Alphaliner
• Hamers Leidingtechniek, using the Alphaliner
• Jeschke Umwelttechnik, using the Alphaliner and Brandenburger Liner
• Kanaltechnik Agricola, using the iMPREG Liner
• Koßmann Kanal- und Umwelttechnik, using the SAERTEX Liner
• KTF Kanal-Technik-Friess, using the iMPREG Liner
• LTS – Lilie Tief- und Straßenbau, using the SAERTEX Liner
• Max Bögl Stiftung, using the Brandenburger Liner

In summary: there is still room for improvement

The goal of the material tests on liners is for a sample to meet all four test criteria – modulus of elasticity, flexural strength, wall thickness and watertightness. Only 63% of the 2,152 liner samples tested by IKT in 2017 met that goal, while 37% failed one or more tests. The worst results were for wall thickness, which is especially important for structural stability.

This means a significant proportion of the liner samples did not achieve all of the target performance values established for them by certifications, structural calculations or the clients‘ stated requirements. In those cases, the goal of the lining process – to rehabilitate old pipes in such a way that they will last for decades – was only partially achieved.

The fact that this goal is achievable is shown by the nine rehabilitation companies that managed to meet all four criteria for all of their samples. Three of them have been able to consistently achieve this top result five years in a row. So it is not impossible.

What does that mean for the other rehabilitation companies? It means that there is still room for improvement. And for the clients? It means continuing to focus on quality assurance and to insist that all four test criteria are fulfilled, otherwise the permanence of the rehabilitation measures undertaken is questionable.

Download LinerReport 2017 here

View all IKT-LinerReports

IKT Test Centre for CIPP liners

Contact

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

 

For all of you who are coming over to Germany in May for IFAT 2018, the world’s largest trade fair on sewage, we are warmly inviting you to also use this opportunity to visit IKT on Friday, May 18 for our IKT International Day at our laboratory in Gelsenkirchen.

We are holding this get-together for all of our present and future international friends to meet our team, to show you our unique labs and testing facilities and to present our on-going and upcoming projects. We’d also like to talk with you about your plans and ideas, and ways to co-operate. So, take this unique opportunity, come to see us at the institute, learn about what we are doing and let’s talk how we can work together in the future!

The day will start at 10 am. We can advise you on local travel and accommodation. For more information please contact:

Dipl.-Ök. Roland W. Waniek
waniek@ikt.de

Non-destructive testing in sewers using the MAC system provides dependable data for structural assessment and, where necessary, selection of a rehabilitation method.

by Martin Liebscher, Mark Klameth, Stefan Bretz and Henning Winter

There is a need for rehabilitation of large interceptor sewers for three reasons: hydraulic capacity, leak tightness and stability. If the hydraulic performance of a sewer is not in order, it gets noticed. When groundwater ingresses, it gets seen. When wastewater egresses it can often be observed. But, failing stability of the fabric holds the threat of really serious problems.

In the field of stability “safety” is the most important topic and there can be no compromises. When checking on stability, it is necessary to gather as much dependable data as possible. This requires assessing both the condition of the pipe itself and that of the surrounding soil system as accurately as possible and, if there is a need for action, taking well founded decisions on the solutions to be implemented.

Dig it out or leave it in place?

So what are the options with large-diameter sewers? Do you dig them out and install new ones? Would an improvement of the fabric be enough? Is no action required as everything in good order? If only we could look into the pipe wall … or through the pipe, into the embedment …

There is a method which is capable of accurately determining the condition of both the pipe and the embedment by non-destructive in-situ testing and subsequent calculations. This is the MAC (Mechanical Assessment of Conduits) system, which was first developed by Eau de Paris, the water authority for the French capital. IKT ‑ Institute for Underground Infrastructure has modified this system for use in smaller diameters from DN 1000 upwards, and then further developed and partially automated the control and instrumentation technology used.

“Our system enables system operators to implement sewer rehabilitation strategies that are rational both ecologically and economically”, asserts Dipl.-Ing. Martin Liebscher, project manager at IKT. “This method provides benefits for the assessment of the stability of large-diameter sewers and for quality control inspection of completed rehabilitation work”.

MAC examines stability of the embedment

The MAC system allows you to examine stability beyond the pipe into the embedment and enables testing of the stability of concrete and masonry sewers with nominal diameters of between DN 1000 and DN 3000. It makes it possible to determine whether a sewer length has any weaknesses and where they are located. Follow-up analysis can identify the nature of such weak points – is the pipe wall too thin, or is the embedment no longer in good order?

Controlled force applied

The MAC system exerts a controlled force on the pipe wall in the sewer using a hydraulic press to generate a minimal ovalisation of the sewer cross-section. The deformation allowed and the force applied are kept sufficiently small, by a precalculation, to prevent any damage to the sewer structure.

Calculations produce results

The tiny, localised deformations to the pipe wall that result are measured using position sensors and are entered into a computer simulation. A three-dimensional Finite Element (FE) model of the sewer, complete with the corresponding test data, is generated and the condition of the pipe and the bed is determined at each inspection point using sophisticated variation of parameters. The results provide reliable input data for structural analysis and for indicating effective rehabilitation procedures.

Using the MAC system

There are five main stages when investigating pipes with problematic stability and applying a solution:

• Location of any weaknesses
• Identification of the best repair solution
• Elimination of weakness
• Checking of the success of the repair
• Assurance of the long-term effectiveness of the repair

The procedure for assessing the performance of rehabilitation using the MAC system is, from initial determination of condition to long-term quality checking. The MAC system operators first obtain an initial impression of how to conduct the inspection by entering the sewer. Parameters relevant for the MAC inspection are recorded (e.g. changes in cross-section width and height, connections, inflows and reinforcing components). A measurement matrix and the location of measuring points for the MAC inspection are determined, and the MAC inspection is then performed.

Setting up the MAC in the sewer

The MAC unit can be easily disassembled into modules, so it can be lowered into the sewer via a standard manhole shaft. The system is then reassembled in the sewer ready for use.

Operation of the MAC

During the testing, a high-pressure cylinder is used to apply sufficient force to the walls, at specified intervals along the length, to move them under control a few tenths of a millimetre apart without causing damage to the sewer. Fine sensors measure the resulting deformation in the vicinity of the hydraulic ram and at distances of around one metre ahead and behind it. This very slight deformation is sufficient to permit derivation of the condition of the pipe and of the soil, on the basis of the deformation pattern and the force exerted.

An initial control calculation is performed on a computer, prior to the measurements being taken, to determine the expectation range in which the measured data should lie. Deviations are then immediately apparent. In case of doubt, a second measurement can then be made at the relevant points. Where deviations are then confirmed, those points in the sewer can be further investigated (e.g. by the taking of drilling cores or undertaking an exploratory drilling operation).

Detection of weak points

Following the survey with the MAC unit the overall stiffness of the pipe-embedment system at the points of measurement is determined. The measured data can then be used for classification of the entire sewer length into zones of identical pipe/soil stiffness. Potential weak points can then be directly located and the locations that require more detailed investigation can be systematically specified.

Computer-assisted calculations

The in-situ measurements provide the general reaction of the pipe/soil system to the pressure applied by the MAC unit. These figures are purely mathematical variables and are dependent on the test apparatus and the sewer structure. Further analysis is necessary to derive data which can be entered into a structural analysis, which is undertaken by simulation of the entire pipe/soil system the form of a three-dimensional FE model. To do this calculation the geometry of the sewer (its shape and its wall thickness) must be known (e.g. from sectional drawings and construction documentation).

These measurements and calculations, provide detailed results and open up previously undreamed of possibilities for sewer assessment. “We can use the supporting FE computations to determine, for example, whether a pipe is cracked longitudinally or transversely, and we can also differentiate between Old Pipe Condition I and II”, states Dr.-Ing. Mark Klameth, expert in FE calculations at IKT. “This is important in deciding on the rehabilitation method. Or we will find, on the basis of the specific deformation pattern, a weakness in the embedment. The MAC procedure can also be used to check the condition of a length of sewer at regular intervals, to permit periodic inspections“.

Input data for structural analysis

The MAC inspections and FE calculations make up an overall package. The measured data from the test and the moduli of elasticity calculated from the FE analysis permit statements to be made concerning the uniformity of the pipe/soil system across the entire length of sewer examined. The calculated moduli of elasticity are reliable input data for calculation of a pipe structural analysis. A structural analysis in accordance with DWA-A 127 or DWA-A 143-2 can be performed where detailed planning documentation is available and/or where wall thicknesses and strengths have been determined on the basis of drilling cores.

Basis for decision on rehabilitation

Where a need for action is apparent, the large amount of data obtained provides a reliable basis for stipulating rehabilitation targets. The results of the MAC inspection and of the FE calculations can then be used for specifying these targets. For this purpose, the sewer can be subdivided into different rehabilitation zones according to criteria such as: water tightness, improving hydraulics and the retention and/or improvement of the existing system fabric. In improving the system fabric, rehabilitation work may be systematically focused around particular weak points (e.g. using shotcrete linings or renewal of brickwork pointing for structural rehabilitation of the pipe; or grout injections for improvement of the embedment).

Quality assurance for rehabilitation projects

Later in a rehabilitation project, the MAC system can be used again for quality assurance assessment of the completed rehabilitation work, or for the periodic re-inspection of critical zones for structural analysis. Direct before/after comparisons and also trends against time can be measured and recorded using the MAC system. Consequently, the immediate and long-term effects of rehabilitation provisions can be directly determined.

Further applications of the MAC system

This procedure can also be used for checking correct installation and embedment for new sewer construction projects. In this case the planned boundary conditions are known and so “target values” can be specified for subsequent in-service inspection. The use of the MAC system for quality assurance of new pipes could result in considerable savings for inspection of large-diameter pipes.

Just as the MAC system works for inspecting old or new pipes, it can also be used whether they are installed horizontally or vertically. Consequently, manhole stability can also be inspected using the MAC system. This application has been refined by testing stability as part of IKT “manhole-shaft coating” product testing. During these, manhole shafts were inspected using the MAC system in new condition, in cracked and unrepaired states, and then following rehabilitation using various methods.

Advantages of the MAC system

The advantages of the MAC system become particularly apparent when compared to the traditional procedure. Up to the present time, the assessment of the stability of large-diameter sewers has generally been labour and cost intensive, involving low potential for success and high risks of failure.

A view into the depths

The results of condition assessment are of great importance for subsequent selection of the rehabilitation method. The optical or visual inspection that is usually practised supplies inadequate information on the condition of a sewer, since only the immediate interior surface of the sewer can be assessed in this way. Faults located behind a “normal” looking surface remain concealed.

The MAC system, on the other hand, makes it possible to “look” deeper into the pipe wall and beyond into the embedment, making it possible to detect more than simply weaknesses that are apparent on the surface.

Systematic core drilling

Assessment of the zones behind or in the sewer wall, of the soil located above them, and of any overlying roadway structure, is necessary for appraising stability. Therefore, as part of the investigation, drill cores are usually taken at points where problems are apparent, or on a random basis. In particular, wall thicknesses and material strengths can be determined by random sampling.

Using the MAC system, measurements are made along the length of the sewer at defined intervals (generally every five to ten metres). Drill cores can then be taken extremely systematically if weak points are revealed. And, if no indications of weakness are found, there is a significantly greater probability that there really is no problem, thus potentially saving unnecessary expenditure on rehabilitation costs.

Relevant information for soil investigation

Classically, exploration of the surrounding soil has generally been conducted by means of boreholes drilled from the surface. However, this method is used only very sporadically, since such holes are both expensive and require a cross-section free of other utilities’ pipes and conduits.

The MAC system makes it possible to make statements concerning the condition of the embedment of the sewer along the length of the sewer. Where measured data indicates inadequate embedment (e.g. as a result of scouring), the areas affected can then be systematically examined in greater detail.

MAC supplies a basis for decision making

The classical procedure for assessing sewer stability can result in significant misinterpretations concerning structural condition and the need for rehabilitation. It only allows reliable assessment of stability and well-founded selection of the best rehabilitation method to a limited extent. In addition, the classical procedure does not afford the option of re-inspection of the repaired pipe/soil system.

The MAC system provides broader data for the selection of rehabilitation methods and a basis for the sewer system operator to make well-informed decisions. The MAC system also permits direct before/after comparison following the completion of a rehabilitation project. Comparative assessment of the measured data before and after the rehabilitation work provides certainty as to whether the provisions implemented have been effective or not.

Complexity and costs

The costs of using the MAC system and the subsequent calculations applying the Finite Element Method are below the annual replacement value costs for large-diameter sewers. Estimated annual replacement costs are 30 euros per metre, assuming construction costs of around 1500 euros per metre and a fifty-year depreciation period.

A MAC inspection costs around 18 to 25 euros per metre, which includes: delivery using the MAC deployment vehicle; assembly and disassembly of the system; performance of the inspection; and the costs of the FE calculations. These costs do not include: traffic control provisions, ensuring non-hazardous access to the sewer (cleaning, cordoning off, ventilation, etc.); and, any core drillings. The actual costs per metre of sewer of using the MAC system are dependent on the number of measurements to be performed (e.g. at 5m or 10m intervals) and on other conditions, such as accessibility and time of day when testing can be performed.

Daily rates of inspection, under optimum conditions, are around 200 to 300 metres, assuming a measuring interval of 10 metres. This rate can be increased during multi-day deployments if the MAC unit can be left in the sewer overnight, so eliminating setting-up time.

Use of the MAC system

IKT has already used its MAC system in a number of large and medium-sized German cities, such as Hamburg, Düsseldorf, Schwerte and Worms. For Wessex Water, a water and wastewater network operator in South West England, the MAC system was shipped over to investigate pipe and the soil stability of sewers in Bournemouth, on the Channel coast, and in Weston-super-Mare, near Bristol.

The network operators in these cities now know the condition of their large-diameter sewers and their rehabilitation options.

Contact

IKT Test Center
Dipl.-Ing. Martin Liebscher
Tel. ++49 (0)209 17806-23
liebscher@ikt.de

At their first web conference members of IKT’s newly formed International Contact Group (ICG) met recently to make contact and to discuss current issues concerning sewer systems. The participants, from eleven countries on four continents, identified major topics for further action through more detailed exchange of ideas, seminars or joint projects.

The options and opportunities for joint initiatives were discussed at this first online meeting of the international partners and friends of IKT. Five topics have been identified to take forward for joint actions:

• CIPP and quality control
• Sewer pressure pipes: operation and rehabilitation
• Liquid soil/flowable backfill material
• Sustainable management/asset management of sewer systems
• Flushable wipes and sewer blockages

The results and suggestions for further action are summarized in this paper.

Each of these actions will be supported by an International Advisory Board (IAB) that IKT is recruiting. If you are interested in participating in one or more of these actions please let us know.
The project coordinator for all of these is Thomas Brüggemann of IKT.
brueggemann@ikt.de
+49-209-17806-18

Worldwide connections

Participants from Algeria, Austria, Belgium, Finland, Germany, Italy, Luxemburg, the Netherlands, Singapore, United Kingdom, and the USA joined the web meeting. Other Group members from seven other countries (Brazil, Canada, France, India, Japan, Niger, and South Korea) were not able to attend this time.

International experts gave short presentations on current projects and issues of importance:

• Thomas Ertl, University Boku Vienna, Austria
• Ang Chee Meng, CH2M, Singapore
• Mandy Fletton, UKWIR, United Kingdom

The next meeting of the International Contact Group will be held on November 21 2017, 8:00 UTC (approx. 60 minutes). Please check your local time, UTC is relevant. (3 am New York – 8 am London – 9 am Berlin – 4 pm Singapore – 5 pm Tokyo)

The agenda will follow and will include short updates on the five major topics. Guests are welcome.

Be a part of it!

The International Contact Group is open to new members – experts from network operators, authorities, and associations, as well as scientists. If you want to take part in our regular exchange of thoughts and knowledge join ICG!

For any questions please don’t hesitate to contact us.

Contact

Bert Bosseler
T: +49-209-17806-0
E: bosseler@ikt.de
Thomas Brüggemann
T: +49-209-17806-18
E: brueggemann@ikt.de

 

There were excellent CIPP liner results for the individual test criteria, but only one in four of the rehabilitation contractors succeeded in a 100% pass on all tests conducted on their samples. However, five years ago this figure was only one in five, so the overall trend is upward.

IKT – Institute for Underground Infrastructure presents its 13th annual LinerReport. This is based on 1,845 CIPP liner samples taken on sites for Quality Control purposes during 2016 and tested by the IKT CIPP Liner Test Centre.

Download LinerReport 2016 here

The “100% Club”

In the past five years, in particular, it has become apparent that a number of rehabilitation contractors achieve optimum performance. These companies meet all four test criteria with all their liner samples and thus constitute what we are calling the “100% Club”. Therefore, they are entirely fulfilling the requirements of the German “ZTV Material Test” (Supplementary Technical Contractual Conditions) and the expectations of their customers. Only five of the twenty-two companies are included in this Club in 2016 (in 2015 it was 9 of 24), and only few contractors maintain such high performance over several years.

Five contractors at the top

The 2016 results for the individual test criteria do exhibit high average success rates, but the overall quality of a liner is satisfactory only if it passes all four test criteria. The five companies that achieved this in 2016 and the liner systems they used were:

• Arkil Inpipe (D), using the Berolina liner
• Hamers Leidingtechniek (NL), using the Alphaliner
• Jeschke Umwelttechnik (D), using the Brandenburger liner
• Kanaltechnik Agricola (D), using the iMPREG liner
• KTF Kanal-Technik-Friess (D), using the iMPREG liner

Modulus of elasticity was very good

The modulus of elasticity is an indication of the load-bearing capacity of liners. The average score per contractor for samples that passed the test was 98.9%, only slightly below the 99.1% achieved in 2015. Most contractors achieved extremely good results for this test with thirteen achieving 100%. However, five companies performed less well than in the previous year.

Slightly poorer performance on flexural strength

The average for tests passed for flexural strength – the point at which a liner fails due to excessive stress – was 0.9 % percentage points (%P) lower than in the previous year. However, at 98.4% the average remains at a very high level. A total of sixteen companies achieved 100% pass, while three contractors had lower scores than the previous year.

Improvement in wall thickness, but wide variation in contractor performance

Among the four test criteria, wall thickness traditionally produces the poorest test results. 2016 was no exception, with an average of 96.2% of the liner samples passing this test. Nonetheless this was a small rise, of 0.8%P, compared to the previous year. Seven companies passed all tests 100%. Among the four test criteria, the range of scores between the best and the poorest performing contractor is widest for wall thickness at 23.2%P.

Liners are watertight

The average for the water-tightness test criterion in 2016 was 99.1% (+0.5%P on 2015) and is thus closely approaching the 100% mark. Fourteen of the contractors examined succeeded in achieving this maximum and passing the test 100% with all their liner samples. Only three companies performed less well than in the previous year. Overall, the 2016 test results demonstrate that CIPP liners are watertight.

Conclusions

Three conclusions can be drawn from the data presented here for the 2016 IKT LinerReport:

• Firstly, the quality of CIPP liners has improved significantly in recent years. Around 60% of all site samples submitted meet all four test criteria completely satisfactorily. This, conversely, also means that this has not been achieved in 40% of all cases.
• Secondly, only few rehabilitation contractors manage to maintain the “100% passed” level consistently over several years. For most contractors, meeting customers’ requirements in all of their samples, i.e. 100%, is obviously an extremely demanding target. Quality fluctuates from year to year.
• Thirdly, the slight downturn in quality in also means that the trend is not necessarily always upward. It can dip downward again, and an upward trend is therefore not a matter of course.

The liner manufacturers and the rehabilitation contractors need to assign importance in the coming years to achieving even better, and constantly high, quality. The aim must be that all liners, and not just around a quarter as in 2016, meet the quality criteria 100%.

However, there is also an obligation on the majority of municipal clients and water companies: they must insist on quality from the contractors, and must consistently have samples from each CIPP liner site tested.

Download LinerReport 2016 here

View all IKT LinerReports

More information on CIPP liner testing

Contact

Barbara Grunewald, M.Sc.
T: +49 209 17806-40
E: grunewald@ikt.de

 

This Master Course is for international specialists, product and service providers who want to refresh their knowledge. It uses core elements from a university master course by Professor Bert Bosseler, Scientific Director of IKT, supported by case studies from international standardization at CEN and ISO. You will have the opportunity to meet and network with attendees coming from all industry sectors: clients, contractors, designers, consultants, suppliers and manufacturers.

Overview of major issues

Get the experts‘ overview of the major issues in sewerage and their technical background, refresh your existing knowledge, and get an update on international developments – at the IKT Master Course “Sewers and Pipelines – Construction, Operation and Maintenance”. Attend the Master Course in Amsterdam or Paris or book up for an in-house training!

Contact

Dr. Sissis Kamarianakis
Phone: +49 209 17806-42
E-mail: kamarianakis@ikt.de