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

3.4.3.1 Symmetrical Reduction Close-Fit Lining – PE
Tension Based (Static Die, Roller Die) Symmetrical Reduction
In the tension-based, symmetrical-reduction process, the diameter of the PE pipe is temporarily reduced,
while maintaining a circular cross section, by pulling the pipe through a static die or simultaneously
pushing it through a series of concentric rollers. The advantages of a tension based close-fit PE liner are
its quick installation and relatively low cost. However, winch loads can be very high, and, with insertion
clearances relatively small, the process is susceptible to jamming at obstacles (e.g., an offset joint). Local
obstacles can lead to incomplete reversion and high residual tensile stresses that can create problems for
fittings. Also, the liner pipe must be pulled into the existing pipe all at one time without stoppage or
release of tension. If the pipe reverts during installation, there is no way to move it.
Swagelining
Swagelining was originally developed by British Gas for rehabilitating gas mains and is now offered by
Advantica. It is one of the original symmetrical-reduction PE pipes using the static die method. The
starting PE pipe, made of PE 3408 (80), initially has a larger outside diameter than the inside diameter of
the pipe to be lined. After sections of the PE pipe are butt fused together to form a continuous pipe, the
PE pipe is pulled through a reduction die to temporarily reduce its diameter. This reduction is maintained
by the tension exerted from the pulling cable. After the pipe has been pulled through the existing pipe,
the pulling force is removed and the PE pipe returns to its original diameter. Swagelining has been used
for diameters from 3 to 44 inches (75 to 1,100 mm) and in diameter ratios (DRs) from 11 to 42. With the
lower DR products, the resulting close-fit PE liner can be considered a fully structural liner for pressure
applications. The pressure class of PE pipe, based on the current AWWA standard C906-07, is given in
Table 3-4. As most sewer force mains tend to operate at pressures well under 80 psi (5.5 bar), a DR 21
PE pipe is probably the thickest that would ever be considered for a rehabilitation project. The pressure
rating of PE pipe is sensitive to the maximum operating temperature that the system will experience. For
operating temperatures between 81 to 90 o F, the pressure class is derated 10%, and for 91 to 100 o F a 20%
derating is applied. The pipe manufacturer should be consulted for adjustments above 100 o F.
Table 3-4. Pressure Class of PE 3408 based on AWWA C906 at 80 o F
Pressure Class
Dimension Ratio psi kPa
32.5 51 352
26 64 441
21 80 551
17 100 689
13.5 128 883
11 160 1,103
Note: Based on AWWA C906 at 80 o F
Tite Liner ®
Tite Liner was introduced into the US in 1985 and, since then over 8,000 miles of the PE liner has been
installed. Tite Liner is marketed by United Pipeline Systems, a division of Insituform Technologies. Tite
Liner is a symmetrically reduced PE liner where the continuous pipe made up of previously butt fused
sections is pulled through a roller reduction unit which radially compresses the liner outer diameter. Once
the liner is in place, the tension is released and the Tite Liner expands radially to fit the inside of the
existing pipe. Tite Liner has primarily been used in the oil and gas industry to provide internal corrosion
protection and abrasion resistance to steel pipes. In the case of the water and wastewater industry, Tite
Liner has been used as a semi-structural (Class III) liner given its relatively thin wall thickness. Tite
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