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

more layers of absorbent non-woven felt fabric, with some fiberglass added for enhanced properties. The
outside layer of the tube is coated with an impermeable, flexible membrane that contains the resin. The
reported physical properties are impressive, with a flexural modulus of 940,000 psi (64,828 bar), flexural
strength of 16,000 psi (1,104 bar) and tensile strength of 16,000 psi (1,104 bar). However, NOVOC
reported a burst pressure in an 8 inch sample with a 6 mm (0.24 inch) wall of 230 psi (16 bar). This only
equates to a hoop tensile strength of 3,833 psi (264 bar), far lower than the 16,000 psi (1,104 bar)
claimed. Prior to installation of the liner, the host pipe must be well cleaned using mechanical scrapers or
power boring. The liner can either be installed by inversion or pulled into place by a winch. With
inversion, the liner is cured using hot water. If pulled into place, the liner is inflated with air and then
steam cured. Thermocouples are used in either case to monitor the exothermic reaction. The liner can be
installed through an elbow of up to 45°. After cure, the liner is allowed to cool down to 100°F before
relieving any pressure and then the ends are cut and sealed using Weko-Seals, or an equivalent. Service
connections can be reinstated robotically, but all large connections and fittings must be excavated and
reinstated using mechanical fittings. Depending on diameter, the maximum renewal length would be
1,000 feet (305 meters). In addition to CCTV inspection, pressure testing to 120% of the working
pressure is recommended after completion of the lining.
Insituform RPP (Reinforced Pressure Pipe)
Insituform RPP was first introduced by Insituform Technologies in 1998 and, since then, 19 miles of the
custom engineered CIPP product has been installed. RPP is designed to restore the structural integrity to
distressed pressure pipes and prevent internal corrosion and/or erosion. It is a fully structural (Class IV)
liner capable of carrying the full internal pressure and external load. Insituform RPP is available in
diameters of 8 to 72 inches (200 to 1,800 mm), with thicknesses up to 1 inch (25 mm). RPP is not
suitable for potable water applications. Insituform RPP has been used on several sewer force main
projects. The datasheet in Appendix A contains information on two force main installations. A
maximum pressure of 80 psi (5.5 bar), diameter dependent, is recommended by Insituform Technologies.
The design of Insituform RPP is predicated upon ASTM F1216, Appendix X1.3.2 for the fully
deteriorated pressure pipe condition. The initial tensile strength of the liner is 6,000 psi (414 bar). For
internal pressure design, a long-term tensile strength equal to one third of the initial value is used, along
with a factor of safety of 2. Insituform Technologies has carried out some limited long-term pressure
regression testing, but has not yet met the ASTM log time distribution requirements. The CIPP tube is a
sewn tube consisting of two or more layers of absorbent non-woven synthetic fiber combined with glass
fiber reinforcement. The outside layer of the tube is coated with a translucent flexible plastic material for
visual inspection during resin impregnation. A vinyl ester resin is used. The interior must be very clean
with no protrusions. Inversion lengths of 200 to 1,000 feet (61 to 305 meter) can be achieved and elbows
of up to 45 o negotiated by the liner. After curing, the ends are cut and sealed using expandable stainless
steel bands and elastomeric seals. A pressure test of twice the operating pressure, or operating pressure
plus 50 psi (3.5 bar), whichever is less is recommended. The limit on make-up water is 20 gallon/inch
diameter/mile/day.
Nordipipe
Nordipipe was first introduced in Sweden in 2002, later in Hong Kong, and then more recently in Canada.
Through 2008, there have been no installations in the US. Norditube Technologies, the US promoter of
Nordipipe, is a subsidiary of Sekisui-CPT Company. It is estimated that about 12 miles of Nordipipe are
being installed each year. Nordipipe is a fully structural CIPP product that incorporates a glass fiber
reinforced layer (chopped strand mat) between two non-woven felt layers. The tube is impregnated with
either epoxy (potable water) or vinylester resin. A PE coating is on the interior, which allows Sekisui to
have an NSF 61 listing for potable water applications (BNQ in Quebec) when used in conjunction with
the epoxy resin. The vinylester resin is roughly half the price of the epoxy. Nordipipe is available in
diameters from 5 to 48 inches (125 to 1,200 mm), with thicknesses from 0.18 to 0.94 inches (4.5 to 23.5
mm). The pressure rating of the liner is dependent on diameter and ranges from 250 psi (17.2 bar) for a 6
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