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

Liner is custom made with an outside diameter smaller than the host pipe’s inside diameter and is
available in either PE3408 (80) or PE4710 (100) resins with diameters from 2 to 52 inches (50 to 1,320
mm). An insertion length of up to 2,600 feet (800 meters) has been achieved.
PolyFlex
Another example of a roller die tension based system, which also
incorporates some of the features of a compression based system
is the new PolyFlex product offered by Insituform Blue.
PolyFlex’s introduction in 2008 was primarily targeted at the
potable water industry, as PolyFlex is an NSF 61 certified
material. However, PolyFlex has also been considered for use on
sewer force mains (Regina, SK in Canada). After butt fusing the
sections of PE pipe into a continuous line, the pipe is both pushed
and pulled through the roller reduction unit. The outside diameter
of the pipe is reduced up to 20% by the roller reduction unit
(Figure 3-11). The pipe can be pulled through lines with up to
22.5 degree bends. After the line is in place the tension is released
and the pipe radially expands back to its original diameter. PolyFlex is available in diameters from 4 to
63 inches (100 to 1,600 mm). PolyFlex is made from PE4710 (100) resin, which has improved toughness
and better crack propagation properties than PE3408 (80). Consequently, the hydrostatic design basis
(HDB) is higher too. Unfortunately, the higher HDB is not yet recognized in the current AWWA C906
standard so, in the strictest sense, this improvement cannot be fully capitalized on yet. PolyFlex can be
either a semi or fully structural liner with pressure rating up to 150 psi (10.3 bar) in the smaller diameters.
Compression Based (Roller Die) Symmetrical Reduction
Figure 3-11. Roller Reduction
Unit for PolyFlex
In a compression based system, the PE pipe is pushed through a die consisting of a series of concentric
concave rollers (see Figure 3-12). The diameter reduction is associated with a thickening of the pipe wall
rather than an increase in length. The majority of the diameter reduction is retained after passage through
the reduction equipment. After insertion of the liner, it is reverted to its original diameter using water
pressure. The advantages of the compression system is lower winch loads, possible separation of the
reduction and insertion stages, more tolerance of obstructions in the host pipe, ability to stop and start the
insertion process, and minimum residual tension in the installed liner. The equipment for compression
reduction can have a high capital cost, especially given its diameter specific nature.
Figure 3-12. Illustration of PE Pipe Compression
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