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

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Once the liner materials, liner cross section, curing method, and installation procedure have been decided, the project execution can occur. Most CIPP liners are impregnated with resin (also known as “wet out”) in a factory setting. Typically, a vacuum impregnation process is used to allow the resin to flow more easily into the liner fabric and to more fully saturate it. Prior to 2001, this vacuum impregnation process was covered by a separate Insituform patent and, hence, other CIPP lining companies often used modified procedures to work around the patent. After wet out and during transport to the site, thermally-cured liners are kept in refrigerated storage or in a chilled condition to avoid premature curing of the liner. Small diameter liners (e.g., for sewer laterals) and very large liners can be wet out at the site. For small liners, this can be for convenience and is facilitated by the relative ease of handling a small diameter liner during wetting out. For large diameter liners, the large liner thickness coupled with the large host pipe diameter means that the lay-flat liner becomes too heavy or too wide to transport when wet out. However, on-site wet out puts an extra burden on QC for the impregnation process. When the impregnated liner is ready, it is introduced into the host pipe to be relined. This can be done by inversion of the liner along the host pipe using water or air pressure or by pulling the liner into place and then inflating it to a close fit using water or air (see Figure 2-2). Figure 2-2. CIPP Installation Options: Liner Pull-in (Left) and Liner Inversion (Right) (Courtesy Insituform Technologies, Inc.) Once the uncured liner is in place and held tightly against the host pipe, the liner is cured using hot water, steam or ultraviolet (UV) light causing the liner resin to become a cross-linked and solid liner material. The curing procedures (e.g., time and temperature curves for thermal curing and UV light intensity and advance rate for UV curing) are important in making sure that the full thickness of the liner becomes properly cured and that thermal or other stresses are not introduced into the liner in a partially cured state. Following the full curing of the liner and removal of any accessory installation materials, the restoration of lateral connections can be carried out. These are typically simply restored by cutting openings at the lateral connection. A dimpling of the liner can aid in the identification of the position of the connection, but such dimpling is less identifiable in liners with higher strength fabrics. If the CIPP liner has a significant annular space and if the connection is not grouted or sealed to the sewer lateral, then this connection can be a source of continued infiltration into the mainline sewer. Research into the magnitude of this effect can be found, for example, in Hall and Matthews (2004), Bakeer et al. (2005), and Bakeer and Sever (2008). 8
Figure 2-3 highlights the main differences in CIPP technologies available today based on tube construction, method of installation, curing method, and type of resin. The original CIPP product was a needled felt tube, impregnated with polyester resin that was inverted into a sewer through a manhole and cured using hot water. This product is still used for gravity sewers. Figure 2-3. Summary of Common CIPP Technologies The following sections describe the major generic technology variants for CIPP rehabilitation in terms of the tube construction, choice of resin, cure method, and insertion method. Appendix A in the companion EPA report (Sterling et al., 2010) contains datasheets provided by some of the most established vendors for specific products representing these variants. Due to the wide range of manufacturers and contractors offering CIPP rehabilitation, it was not possible to represent all products with individual datasheets in that report. 2.2.3 Installation Method: Inversion or Pull-In. From the first installation of CIPP in 1971 until 1973, the installation method involved a pull-in-and-inflate procedure. In this method, the uncured liner is pulled into position directly as shown in Figure 2-2. An outer layer confines the resin during impregnation and pull-in. This layer remains between the cured CIPP liner and the host pipe, which reduces the potential for interlock between the resin and the host pipe, but fully confines the resin, thus avoiding the potential for blocked laterals and washout of the resin by high groundwater inflows. Either an internal hose (called a calibration hose) inflates the liner within the host pipe and holds it under pressure until the liner is cured, or the ends are tied or plugged and the liner is simply inflated while curing. In 1973, coated felt was introduced allowing the liner inversion process to be used (see Figure 2-2). In this process, the impregnated but uncured liner is forced by water or air pressure to turn itself inside out along the host pipe section to be lined. Since there is a sealing layer outside the felt tube, this liner can be 9
Page 1 and 2: EPA/600/R-12/004 | January 2012 | w
Page 3 and 4: DISCLAIMER The work reported in thi
Page 5 and 6: ACKNOWLEDGMENTS This report has bee
Page 7 and 8: samples had a flexural modulus valu
Page 9 and 10: CONTENTS DISCLAIMER ...............
Page 11 and 12: 4.3.10.2 Upstream Sample ..........
Page 13 and 14: 9.2.2 Recommendations for Developme
Page 15 and 16: Figure 5-27. Raman Spectra for the
Page 17 and 18: ABBREVIATIONS AND ACRONYMS AMP Asse
Page 19 and 20: 1.0: INTRODUCTION This report forms
Page 21 and 22: 1.2 Organization of the Report Foll
Page 23 and 24: Some sections of a sewer system may
Page 25: • The depth of the pipe below the
Page 29 and 30: The most commonly used resins are i
Page 31 and 32: the glass fiber. The tube, which is
Page 33 and 34: 3.0: DEVELOPMENT OF CIPP EVALUATION
Page 35 and 36: • The municipality would be willi
Page 37 and 38: • Measurements and/or physical sa
Page 39 and 40: Table 3-3. Laboratory Evaluation an
Page 41 and 42: 4.1 Introduction 4.0: CITY OF DENVE
Page 43 and 44: Figure 4-1. Images of the Recovered
Page 45 and 46: Sample ID Figure 4-4. Soil Grain Si
Page 47 and 48: Location Table 4-5. Denver 8-in. Li
Page 49 and 50: Profile Plot Red - Steel tube Green
Page 51 and 52: Table 4-7. Results from Flexural Te
Page 53 and 54: 35 Table 4-9. Comparison of Test Da
Page 55 and 56: 4.2.12 Buckling Test. A steel mecha
Page 57 and 58: Figure 4-18. Pressure Gage and Pres
Page 59 and 60: 4.2.13 Shore D Hardness. Durometer
Page 61 and 62: Figure 4-24. Barcol Hardness Readin
Page 63 and 64: increases and the heat of cure decr
Page 65 and 66: In summary, CCTV inspection of thre
Page 67 and 68: Figure 4-28. Thickness for Denver 4
Page 69 and 70: 4.3.6.2 Downstream Sample. Seven sp
Page 71 and 72: Figure 4-34. Flexural Stress-Strain
Page 73 and 74: Table 4-18. Flexural Test Results f
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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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Figure 5-16. Tensile Stress-Strain
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5.2.15 Buckling Test. A mechanical
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Figure 5-24. Localized Leak on the
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Figure 5-26. Barcol Hardness Readin
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5.3.3 Visual Inspection of Liner. I
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Figure 5-32. Ultrasonic Testing for
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Table 5-13. Geometric Data for Flex
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Figure 5-38. Shore D Hardness of Co
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6.1 Introduction 6.0: REVIEW AND CO
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Overall, the liners appear to be ho
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age difference between the liners i
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Looking for correlations to the low
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A significantly lower range of Shor
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7.0: RECOMMENDED TEST PROTOCOL FOR
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combining this broadly available in
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Table 7-3. Overall Structure for a
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Table 8-2. CIPP and Other Rehabilit
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Table 8-5. Rehabilitation Specifica
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113 Table 8-9. Process Verification
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Göttingen Stadtentwässerung: Göt
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experience and quality, and do not
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km of pipe and 50-year-old pipes ar
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methods are detailed in the Guide t
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The business of pipeline rehabilita
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• Destructive testing (but will n
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In Denver, in CCTV inspections of n
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9.2 Recommendations for Future Work
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Falter, B. 1996. “Structural Anal
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Lehmann, M.A, J.P. Schroeder and C.
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APPENDIX A LIST OF TEST STANDARDS R
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The following table lists the non-A
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B.1 Introduction This study was con
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Mean thickness values for each cont
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APPENDIX C INTERNATIONAL STUDY INTE
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The original Insituform liner insta
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However, the figures published by O
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exfiltration and infiltration. Any
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STW uses CIPP for virtually all of
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method. Top hat repairs to junction
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All design and construction supervi
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Process verification test samples a
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consultant born out of the corporat
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BW continues to use CIPP, mainly in
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East, but has not yet had marked su
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