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

4.2.9 Specific Gravity and Porosity. For this liner, the specific gravity and porosity of the liner
were measured using a mercury penetration test carried out by Micrometrics Analytical Services. The test
data indicated that the bulk density (at 0.54 pounds per square in. absolute [psia]) was 1.0731 g/mL, the
apparent skeletal density was 1.2762 g/mL and the porosity was 15.915%. The specific gravity was also
measured by TTC with a higher value reported (1.159 ± 0.93 compared to the 1.0731 value measured in
the mercury penetration test). The TTC value is closer to the specific gravity of 1.19 measured by
Insituform on a sample sent to them for parallel testing (see Table 4-9). The full Micrometrics test reports
for all the liners tested are included in Appendix C and the results are discussed further in Section 6.
4.2.10 Ovality. A profile plotter (Figure 4-7) was used to accurately map any deformation inside
the liner. The system features a linear variable displacement transducer (LVDT) connected to a motorgear
system that rotates around the inner circumference of the liner. An encoder system provides position
information regarding the location around the pipe at which the data is taken.
Figure 4-7. Profile Plotter Setup
The liner was placed inside a circular polyvinyl chloride (PVC) tube, as if it was inside a host pipe, and
careful measurements were taken to ensure that the liner center was aligned with the measuring device.
Next, the profile plotter was aligned with the center of the CIPP liner tube. Continuous readings were
taken around the circumference of three cross-sections spaced 1 in. apart and averaged. The liner was
found to be approximately circular with reference to its center (green line in Figure 4-8). On the spring
line to spring line plane, the liner had a slightly larger diameter than on the crown-invert plane, most
likely due to geometrical imperfections in the original host pipe. The percent ovality based on the ovality
definition in ASTM F1216 is 5.07%. The red and blue lines are shown in connection with the liner
buckling test that was carried out on this liner and which is described in Section 4.2.12. When a host
and/or liner are oval in shape, the larger radius of curvature in the flatter section of the oval liner reduces
the ability of the liner to resist external buckling pressures. This is taken into account in the design
equations for the liner in ASTM F1216. When pipe ovality exceeds 5%, the structural impact on liner
strength becomes more significant.
30