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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The ma<strong>in</strong> defects noted dur<strong>in</strong>g <strong>in</strong>spections after 1 to 2 years are bulges and deformations caused by<br />
buckl<strong>in</strong>g failure <strong>of</strong> poorly impregnated or cured sections and delam<strong>in</strong>ation <strong>of</strong> coat<strong>in</strong>gs.<br />
TW operates a Dynamic Asset Condition Model based on the performance <strong>of</strong> a group <strong>of</strong> sewers <strong>in</strong>itially<br />
<strong>in</strong>spected around 1989 and re<strong>in</strong>spected periodically. Most sewers <strong>in</strong> the model focus have been <strong>in</strong>spected<br />
at least three times s<strong>in</strong>ce <strong>in</strong>ception. The rate <strong>of</strong> deterioration is described as not significantly different<br />
from the rate <strong>of</strong> error <strong>in</strong> identification <strong>in</strong> the survey. Over the course <strong>of</strong> the exercise, term<strong>in</strong>ologies and<br />
classification s<strong>of</strong>tware have changed. TW used an <strong>in</strong>ternal classification scheme SRS2 at the outset and<br />
moved to Exam<strong>in</strong>er s<strong>of</strong>tware and is currently transition<strong>in</strong>g towards Infonet. It is hoped that some historic<br />
data can be reclassified us<strong>in</strong>g the improved system. Generally, the f<strong>in</strong>anc<strong>in</strong>g method discourages capital<br />
ma<strong>in</strong>tenance, concentrat<strong>in</strong>g on <strong>in</strong>vestment <strong>in</strong> new works which enhance pr<strong>of</strong>itability, pipe l<strong>in</strong><strong>in</strong>g is<br />
undertaken on an as-needed basis, particularly where assets are identified as at risk <strong>of</strong> collapse with<strong>in</strong> five<br />
years.<br />
TW has proposed a type test for CIPP systems that is applied to demonstrate water tightness (see Figure<br />
C-2). CIPP systems satisfy<strong>in</strong>g this test may be selected for small diameter sewers, up to 375 mm (14.8<br />
<strong>in</strong>.) exhibit<strong>in</strong>g serious <strong>in</strong>filtration. The test (developed by WRc as a collaborative project CP308 -<br />
<strong>in</strong>filtration reduction properties <strong>of</strong> CIPP l<strong>in</strong><strong>in</strong>gs) <strong>in</strong>volves sett<strong>in</strong>g up an array <strong>of</strong> five 1 m (3.28 ft) long,<br />
pla<strong>in</strong> ended clay pipes such that the gradient is not more than 50 mm (2 <strong>in</strong>.) over the length <strong>of</strong> the test<br />
l<strong>in</strong>e. The central pipe is fitted with a lateral connection through which the l<strong>in</strong>e may be filled to test<br />
<strong>in</strong>filtration through the l<strong>in</strong>er wall. The pipes are jo<strong>in</strong>ted us<strong>in</strong>g mechanical coupl<strong>in</strong>gs with jo<strong>in</strong>t gaps set at<br />
3 and 25 mm (0.12 and 0.98 <strong>in</strong>.). Each coupl<strong>in</strong>g is fitted with top and horizontal ferrule connectors. The<br />
top ferrule connectors are fed from a header tank so as to provide a 5 m (16.4 ft) water head, the test l<strong>in</strong>e<br />
is plugged and restra<strong>in</strong>ed before pressure test<strong>in</strong>g for leakage under the 5 m head for 15 m<strong>in</strong>utes.<br />
Figure C-2. Setup for CIPP Water Tightness Test Used by TW<br />
The l<strong>in</strong><strong>in</strong>g is <strong>in</strong>stalled under a 3 m (9.84 ft) <strong>in</strong>version or <strong>in</strong>flation head and cured <strong>in</strong> accordance with<br />
manufacturers recommendations. Mechanical or hydrophilic seals which are deemed part <strong>of</strong> the system<br />
may be fitted. The l<strong>in</strong>ed pipe is subjected to an external head <strong>of</strong> 5 m (16.4 ft) for 30 m<strong>in</strong>utes us<strong>in</strong>g the<br />
horizontal and top ferrule connections as valves <strong>in</strong> comb<strong>in</strong>ation to simulate various conditions <strong>of</strong><br />
C-5