State of Technology Report for Force Main Rehabilitation, Final ...

Figure 3-9. Summary of Close-Fit PE Technologies
The installation of a close-fit liner is similar to sliplining in that the liner is pulled or pushed into the
existing pipe except with close-fit liners additional stages are needed for the diameter reduction prior to
insertion and then reversion after insertion. Also, the host pipe needs to be more extensively cleaned than
for ordinary sliplining given the close-fit of the liner. Some additional potential issues can occur during
installation of these relatively thin liners as follows:
• Accuracy in the alignment of pipes for butt fusion welding is more critical
• Tensile forces during pull in of the liner need to be monitored and controlled
• Limiting surface damage to no more than 10% of thickness during installation is more
difficult to achieve with a thin liner.
Despite some of these concerns, the use of a close-fit liner can be one of the more cost-effective ways to
rehabilitate a partially deteriorated sewer force main. As Figure 3-10 illustrates, a PE liner is capable of
bridging significant gaps in the host pipe. As an example, a 36-inch (900-mm) diameter SDR 50 PE liner
(t = 0.71 inch) in a system with an operating pressure of 150 psi (10.3 bar), can span a hole of 9 inches
(225 mm) in diameter in the host pipe.
MAX HOLE SPAN (d)/PIPE DIAMETER (D)
0.60
0.50
0.40
0.30
0.20
0.10
0.00
L
6 8 10 12 14 16
OPERATING PRESSURE (BAR)
Figure 3-10. PE Close-Fit Liner Hole Spanning Capabilities
23
SDR Ratios
80
70
60
50
42
32.5