Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...
Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...
Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...
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does not <strong>in</strong>clude work on the behavior <strong>of</strong> <strong>in</strong>ternally pressurized l<strong>in</strong>ers for water ma<strong>in</strong> or force ma<strong>in</strong><br />
renovation.<br />
Research on the appropriate external load<strong>in</strong>gs to be designed for CIPP <strong>in</strong>stallations has also been carried<br />
out, <strong>in</strong>clud<strong>in</strong>g Spasojevic et al. (2004), Spasojevic et al. (2007), Law and Moore (2007), and Moore<br />
(2008).<br />
If the types or ratio <strong>of</strong> res<strong>in</strong>s are an area <strong>of</strong> concern, QA/QC us<strong>in</strong>g nuclear magnetic resonance test<strong>in</strong>g can<br />
be carried out to make this determ<strong>in</strong>ation. Research on the properties <strong>of</strong> res<strong>in</strong>s used for CIPP <strong>in</strong>cludes<br />
Kleweno (1994), Hayden (2004), and Bruzzone et al. (2008).<br />
2.3.3 Environmental Issues. The pr<strong>in</strong>cipal issue rose about the environmental impacts <strong>of</strong> CIPP<br />
materials and their <strong>in</strong>stallation has been the release <strong>of</strong> styrene <strong>in</strong>to the process water (or other water<br />
present <strong>in</strong> the host pipe) and <strong>in</strong>to the air. This has been a significant issue <strong>in</strong> Europe encourag<strong>in</strong>g changes<br />
<strong>in</strong> the way that CIPP is manufactured and supplied and the switch to UV-cured l<strong>in</strong>ers for smaller diameter<br />
CIPP rehabilitation. UV-cured l<strong>in</strong>ers (such as the German Brandenburger l<strong>in</strong>er) use gas-tight membranes<br />
to m<strong>in</strong>imize the release <strong>of</strong> styrenes dur<strong>in</strong>g storage and <strong>in</strong>stallation and the UV-cure process does not<br />
require water or steam <strong>in</strong>to which styrenes could leach before cur<strong>in</strong>g. Papers and reports discuss<strong>in</strong>g this<br />
issue <strong>in</strong> the U.S. <strong>in</strong>clude Lee (2008), Donaldson (2009), and Kampbell (2009). In most areas <strong>of</strong> the U.S.,<br />
styrene-based CIPP res<strong>in</strong>s with thermal cur<strong>in</strong>g are still <strong>in</strong> use, but closer attention to reduc<strong>in</strong>g gaseous<br />
styrene emissions and captur<strong>in</strong>g water/condensate conta<strong>in</strong><strong>in</strong>g styrene is generally be<strong>in</strong>g practiced. The<br />
smaller quantities <strong>of</strong> liquid water present dur<strong>in</strong>g steam cur<strong>in</strong>g means that water contam<strong>in</strong>ation is more<br />
easily handled <strong>in</strong> steam cures than <strong>in</strong> water cures (Kampbell, 2009).<br />
There is very little <strong>in</strong>formation concern<strong>in</strong>g the environmentally-caused degradation <strong>of</strong> CIPP. Two<br />
references identified on this topic are Sever et al. (2005) and Potv<strong>in</strong> et al. (2008). In the evaluations <strong>of</strong><br />
the oldest CIPP l<strong>in</strong>ers from the current study (see Sections 4 and 5), it was noted that the coat<strong>in</strong>g layer on<br />
the <strong>in</strong>terior <strong>of</strong> the polyester res<strong>in</strong> was degraded or miss<strong>in</strong>g <strong>in</strong> the areas exposed to flow. This coat<strong>in</strong>g<br />
layer was used to isolate the polyester res<strong>in</strong> from the environment dur<strong>in</strong>g impregnation, <strong>in</strong>stallation, and<br />
cur<strong>in</strong>g. Once cured, the layer had essentially served its purpose. Long-term exposure to water caused the<br />
polyurethane film used <strong>in</strong> early <strong>in</strong>stallations to breakdown due to hydrolysis, a process <strong>of</strong> slow but<br />
temperature-dependent dissolution. In newer l<strong>in</strong>ers, both improved formulations <strong>of</strong> polyether<br />
polyurethane (which has good resistance to hydrolysis) and PE are used as a coat<strong>in</strong>g material. The<br />
longevity <strong>of</strong> both coat<strong>in</strong>g materials is expected to be greatly improved over the orig<strong>in</strong>al form <strong>of</strong><br />
polyurethane coat<strong>in</strong>g.<br />
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