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

3.4.4.2 Semi-Structural CIPP Liners
Hot Water/Steam Cured
Insituform PPL ® (Pressure Pipe Liner)
PPL was first introduced in 1995. Since then, 44 miles of PPL has been installed in the US. The
interactive liner is available in diameters from 8 to 60 inches (200 to 1,500 mm), with the ability to span
over small holes and gaps in a host pipe for pressures up to 200 psi (13.8 bar). Insituform has a special
epoxy resin that is NSF 61 certified for potable water, otherwise vinylester is used. The tube is made of
Insituform’s standard non-woven felt tube, but with some special glass reinforcement included for added
tensile and flexural properties. The initial flexural modulus of PPL is 250,000 psi (17,241 bar) and
flexural strength is 6,500 psi (448 bar). For spanning over holes, the flexural strength is reduced to one
third of the initial value for long-term performance. In addition, a factor of safety of 2 is utilized. The
PPL sock is saturated either in the factory or on site. The tube is then positioned in the existing pipe
using water pressure to invert the tube inside out and to form a close-fit. PPL can be installed in lines
with bends up to 90 o . Typical renewal lengths are from 200 to 1,000 feet (61 to 305 meters). After
positioning, the tube is cured with circulating hot water. After curing, the liner is allowed to cool down to
90 o F. The ends are cut and sealed using expandable stainless steel bands and elastomeric seals. After
installation, the liner is CCTV inspected for any abnormalities. Samples are collected and tested to
confirm that the physical properties meet the design assumption. Also, a pressure test to twice the
operating pressure, or operating pressure plus 50 psi (3.4 bar) (whichever is least), is recommended.
National Liner ®
National Liner was introduced in 1995. National EnvironTech Group, the technology supplier for
National Liner, reports that over 200 miles of liner have been installed, with most of that for gravity sewer
applications. National Liner has only been used for pressure pipe installations in the past few years. Two
of the nationally licensed contractors have both reported using National Liner for sewer force main
applications. National Liner does not have a NSF 61 listing, so it is not suitable for potable water.
National Liner is available in diameters of 6 to 120 inches (150 to 3,000 mm), with wall thicknesses
ranging from 4.5 to 33.5 mm (0.18 to 1.34 inches) with the standard felt tube. Greater thicknesses are
reportedly possible. The liner is made of a non-woven, needled polyester felt that is shop or site
impregnated with a polyester resin. For pressure applications, a vinylester resin is used. National
EnvironTech Group offers a maximum operating pressure of 50 psi (3.4 bar) with its standard felt tube,
but higher pressures with a new glass fiber composite tube are reportedly under development. The liner
with a felt tube would be considered a semi-structural liner (Class II/III), and, with the glass fiber,
considered a fully structural liner (Class IV). National Liner is installed using the inversion method, with
either a column of water or pressurized air. Either hot water or steam is used for cure depending on the
method of inversion. Any excess resin mechanically locks the tube to the host pipe by filling in cracks.
3.4.4.3 Structural CIPP Liners
Paraliner PW and Paraliner FM
A relatively new product, Paraliner was introduced by NOVOC Performance Resins, LLC in October
2007. Approximately 10,000 feet (3,049 meters) of potable water mains were lined with Paraliner PW in
2008. The liner is available in diameters of 6 to 96 inches (150 to 2,400 mm) and with thicknesses from
0.18 to 2.07 inches (4.5 to 52 mm). Paraliner PW or FM is impregnated by the installation contractor
with a 100% solids NOVOC vinyl ester resin that contains no styrene. The “green” solution has no EPA
reportable components and is NSF 61 certified (by Underwriters Laboratory [UL]) for use in potable
water. As a result of no styrene, curing times are reduced 30% to 50% over conventional CIPP liner.
Minimal shrinkage due to 100% solids also ensures a tight fit to the host pipe. The tube consists of one or
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