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Western Dam Engineering <br /> Technical Note <br /> <br /> May 2016 <br /> <br />13 <br /> Special care needs to be taken when pulling <br />the liner in place so it is not damaged due to <br />friction. <br /> Liners used for this type of installation require <br />a second inner calibration tube or bladder to <br />inflate the resin-impregnated tube. <br /> After the CIPP liner is in place, a calibration <br />hose is inverted inside the liner and water or <br />air is forced into the liner, expanding it, and <br />holding it tight against the existing pipe. <br /> The CIPP manufacturer determines the <br />minimum and maximum air or water pressure <br />required to push the CIPP liner tight against <br />the existing pipe without damaging the fabric <br />tube of the CIPP. <br /> Figure 4 – Pulled-in-Place Installation Method [2] <br />Post-Installation <br />The CIPP liner should be inspected by trained <br />personnel following installation. If the CIPP-lined <br />conduit is too small for man-entry inspection, video <br />inspection methods should be used. No dry spots, lifts, <br />delamination, pinholes, wrinkles, twists or infiltration <br />of groundwater should be present and the CIPP liner <br />should be in a fully expanded condition. Some <br />installation and curing systems, such as certain UV <br />systems, have provisions for video inspecting the <br />installation once inflated and prior to curing. This is <br />preferred as installation deficiencies can be corrected <br />prior to curing of the CIPP. <br />Liner Materials and Curing Methods <br />Curing of the liner refers to the process of hardening <br />the resin through polymerization induced by either <br />thermal or UV light exposure. Selection of the resin <br />and curing method are interdependent, as the curing <br />methods will dictate the resin to be used. The curing of <br />each liner utilizes a delicate balance of resin catalyst <br />level, curing temperature and time of exposure to <br />maximize the installed physical properties [6]. <br />Proper transportation of the CIPP lining materials is <br />critical, especially for thermally-cured resins in hot <br />climates. Care needs to be taken to avoid damage to <br />the fabric and prevent premature curing of the resin <br />while being transported. Most CIPP resin systems are <br />thermosetting and the resin starts to cure when <br />exposed to heat; therefore, it should be transported in <br />a refrigerated truck. Ultraviolet (UV) light can also be <br />used to cure CIPP and these liners should be <br />transported in light-tight packaging, but have a <br />significantly longer shelf life with no need for <br />refrigeration. <br />The common curing methods are heated water, steam, <br />ambient, and Ultra Violet light (UV). All curing methods <br />require an internal pressure to press the liner tight <br />against the host pipe before and during curing. <br />Recommended pressures should be maintained <br />throughout the curing process. The curing process <br />used will be based on available resources, access, <br />transportation distance, climate, and the <br />manufacturer’s recommendation for the specific resin <br />system. For thermosetting (steam/hot water) curing <br />methods, the CIPP should be cooled in a controlled <br />manner after the curing process is complete. <br />Circulating Heated Water <br />Cool water is used initially to invert the pipe to prevent <br />premature curing until the liner is fully installed, and <br />the water inside the liner is subsequently heated. As <br />the liner is inverted, a hose is inserted with the CIPP <br />tube and is subsequently used to circulate hot water