Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...

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composite. More research on identifying or developing a better NDT method or equipment for in-situ liner thickness measurement is recommended. 9.1.3.4 Flexural and Tensile Testing. The testing of flexural specimens for the structural performance represented by the flexural strength and flexural modulus is often carried out since it can be compared with the specified values in the ASTM F1216 standard. Tensile strength and tensile elongation at break also have been measured values when structural liner performance is investigated. In this study, other parameters such as the tensile modulus were also recorded. From the testing conducted so far, the flexural modulus tests provided the most useful values for interpretation but, of course, that may not be the case for all types of liner issues. The tensile elongation at break varied over a wide range in the tests conducted. Typically, when flexural and tensile testing is carried out, all the parameters mentioned above are easily measured and recorded and could prove useful in a larger data set for establishing correlations among types of liner defects and the test values for each parameter. 9.1.3.5 Surface Hardness Testing. Surface hardness testing was found to reveal differences between the hardness of the inner surface of a CIPP liner and its external surface and to reflect the low flexural modulus value and the variability of the tensile elongation at break value of the Denver 48-in. upstream liner sample. While few conclusions can be drawn from the surface hardness data collected to date, this type of testing appears to hold promise for evaluation of liner properties – either as-installed or their degradation over time. As a non-destructive test that could potentially be deployed in pipelines of 8-in. diameter (and larger), such a test could provide a quantitative non-destructive measure of great value and it is recommended that further investigations of data correlations and test adaptations to in-pipe measurements should be pursued. 9.1.3.6 Material Composition Testing. It is considered very important in the assessment of liner deterioration to find a test or set of tests that will shed light on chemical or physical changes occurring in the liner material over time. Tracking the rate of such deterioration (in conjunction with other liner and site characteristics) would provide important information in projecting the lifetime of a liner. In the pilot study, no evidence of liner deterioration was seen in the Raman spectroscopy and differential DSC testing that was carried out. This is either due to the lack of deterioration in the samples tested compared to the virgin resins tested or because the test is not sensitive to any type of deterioration that may, in fact, be occurring. It is recommended that these tests and/or similar forms of material testing be applied to deliberately aged liner specimens to establish the signatures of particular forms of deterioration before they be applied in a wider context for tracking liner performance in the field. 9.1.4 Recommendations for National Data Compilation and Management. The ultimate goal of carrying out retrospective evaluations is to be able to provide better guidance to municipalities on the long-term performance of the various rehabilitation technologies available to them. Table 7-3 provided a summary of an overall structure that could be used for a database to accommodate the differences in the types of technologies used and the specifics of those technology applications. It is suggested that the categorization of the city experiences be able to be as detailed as the city data would allow, but would also allow information capture at a broader level when only that level of information was available. As discussed in Section 7.3, broad interpreted data from agency records, CCTV inspections, and condition assessment databases need to be accessed in addition to well characterized, quantitative data from retrospective liner testing or the use of specific NDT approaches to liner evaluation. However, it is not intended that the database would attempt to include all of the individual CCTV or condition assessment data that cities are collecting. Rather, the database proposed would contain the interpreted results from agencies of the performance of rehabilitation technologies plus specific physical or NDT that addresses liner performance or degradation. 128
9.2 Recommendations for Future Work 9.2.1 Recommendations for Continued Retrospective Evaluations on Retrieved Samples. The expected life of rehabilitated sewers is critical to the effective asset management of sewer systems and yet very little quantitative study has been made to determine the performance and/or degradation of rehabilitation technologies with time. This pilot project examined five CIPP liners at four sites in two cities. The results are very promising for a life of CIPP liners that will meet or exceed the 50 years which has been taken as the nominal life expectancy for such liners. The results, however, cannot be taken as representative of the tens of thousands of miles of rehabilitated sewers that have already been installed using many variations of CIPP and other rehabilitation technologies. It is recommended that the pilot studies and retrospective evaluation program be extended to cover the following activities: • Additional CIPP sample retrieval in other cities with a wider variety of site and sewage flow characteristics. • Pilot studies of other sewer rehabilitation technologies – focusing initially on those with the greatest number of years of service. As with the current CIPP study, the pilot study would seek to identify the most useful quantitative tests that could be used to evaluate performance, degradation, and expected remaining life. • A broader survey to capture the locally interpreted data from a wide range of cities on their experiences with rehabilitation technologies. • An effort to encourage sewer agencies to keep as-installed material test data for later comparison with follow-up testing. This should include working with the most widely used database and asset management systems to make sure that such information can readily be incorporated and identified using their software. • Additional research on root cause analysis of CIPP failures. 9.2.2 Recommendations for Development and Calibration of NDT Protocols. The alternative to obtaining large physical samples for quantitative testing is to use NDT to obtain meaningful data, which was also recommended by the utilities participating in this study, and/or to test small physical samples that are easily retrieved robotically from inside the pipe and easily repaired. This project has tested several quantitative liner characterization tests that could be expected to be developed for robotic deployment within sewer mainlines of 8-in. diameter and larger. It is recommended that additional research be carried out to develop and characterize the most promising NDT protocols. 129
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EPA/600/R-12/004 | January 2012 | w
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DISCLAIMER The work reported in thi
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ACKNOWLEDGMENTS This report has bee
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samples had a flexural modulus valu
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CONTENTS DISCLAIMER ...............
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4.3.10.2 Upstream Sample ..........
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9.2.2 Recommendations for Developme
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Figure 5-27. Raman Spectra for the
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ABBREVIATIONS AND ACRONYMS AMP Asse
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1.0: INTRODUCTION This report forms
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1.2 Organization of the Report Foll
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Some sections of a sewer system may
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• The depth of the pipe below the
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Figure 2-3 highlights the main diff
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The most commonly used resins are i
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the glass fiber. The tube, which is
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3.0: DEVELOPMENT OF CIPP EVALUATION
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• The municipality would be willi
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• Measurements and/or physical sa
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Table 3-3. Laboratory Evaluation an
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4.1 Introduction 4.0: CITY OF DENVE
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Figure 4-1. Images of the Recovered
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Sample ID Figure 4-4. Soil Grain Si
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Location Table 4-5. Denver 8-in. Li
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Profile Plot Red - Steel tube Green
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Table 4-7. Results from Flexural Te
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35 Table 4-9. Comparison of Test Da
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4.2.12 Buckling Test. A steel mecha
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Figure 4-18. Pressure Gage and Pres
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4.2.13 Shore D Hardness. Durometer
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Figure 4-24. Barcol Hardness Readin
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increases and the heat of cure decr
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In summary, CCTV inspection of thre
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Figure 4-28. Thickness for Denver 4
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4.3.6.2 Downstream Sample. Seven sp
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Figure 4-34. Flexural Stress-Strain
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Table 4-18. Flexural Test Results f
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4.3.8.2 Upstream Sample. Specimens
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4.3.10 Barcol Hardness 4.3.10.1 Dow
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4.3.11.2 Downstream Sample. The Ram
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5.1 Introduction 5.0: CITY OF COLUM
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April 16, 2010 The specimen was rec
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The resulting gradation curves are
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Table 5-4. Soil pH at Designated Lo
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Figure 5-8. Average Thickness at Di
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5.2.12 Flexural Testing. Specimens
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Figure 5-14. Flexural Stress-Strain
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Page 103 and 104: 5.3.3 Visual Inspection of Liner. I
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Page 107 and 108: Table 5-13. Geometric Data for Flex
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Page 111 and 112: 6.1 Introduction 6.0: REVIEW AND CO
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Page 119 and 120: A significantly lower range of Shor
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Page 129 and 130: Table 8-5. Rehabilitation Specifica
Page 131 and 132: 113 Table 8-9. Process Verification
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Page 149 and 150: Falter, B. 1996. “Structural Anal
Page 151 and 152: Lehmann, M.A, J.P. Schroeder and C.
Page 153 and 154: APPENDIX A LIST OF TEST STANDARDS R
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Page 163 and 164: The original Insituform liner insta
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Page 169 and 170: STW uses CIPP for virtually all of
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