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

On-Site Expandable PVC Close-Fit Lining
Duraliner
Duraliner from Underground Solutions is a patented, stand alone structural liner (Class IV) made of PVC
and available in diameters of 6 to 30 inches (150 to 760 mm). Duraliner is NSF 61 certified, so it also is
acceptable for potable water applications. Duraliner is a PVC pipe that meets all of the requirements of
AWWA C900 and C905 prior to modification by expansion. The final product meets the requirements of
AWWA C909.
The outside diameter of the starting PVC pipe stock is sized smaller than the inside diameter of the host
pipe. Sections of the Duraliner pipe are then butt-fused together forming a continuous pipe. The pipe is
then inserted into the cleaned and previously inspected host pipe. Special end caps are fitted to the ends
of the pipe along with temperature sensors. The PVC pipe is heated with steam, and then pressure is
applied to expand the material tightly against the walls of the host pipe. It takes approximately 90
minutes to fully expand the stock pipe. After cooling, the end fittings are removed and the expanded new
pipe cut to length and reconnected to the system. Insertion lengths ranging from 700 to 1,500 feet (213 to
457 meters) are possible. The liner can even navigate through a 45° elbow. The expansion of the PVC
reorients the molecular chain in the circumferential direction, thereby increasing the tensile strength.
Underground Solutions states that the HDB increases from 4,000 to 7,100 psi (276 to 490 bar). This more
than compensates for the reduction in wall thickness caused by the expansion. Molecularly oriented
polyvinyl chloride (PVCO) pipe has been used in Europe for over 20 years.
3.4.4 Cured-In-Place Pipe. The first installation of a CIPP product was in a 70 m length of
1,175 × 610 mm brick sewer in Hackney, East London. It was installed in 1971 and a small number of
other projects were undertaken by the inventor Eric Wood, and his partners Doug Chick and Brian
Chandler, who formed Insituform Pipes and Structures, Ltd. before they licensed Edmund Nuttalls, a civil
engineering contractor in 1973. Nuttalls Permaline Division performed approximately 380 projects
before they were bought back by Insituform Group in 1986. It is estimated that about 40,000 miles of
CIPP liners have been installed worldwide, perhaps 25,000 by Insituform companies.
It is by far the leading method for the rehabilitation of gravity sewers. With the expiration of the original
patent on CIPP, many new variants have been introduced. Figure 3-17 highlights the main differences
based on tube construction, method of installation, curing method, and type of resin.
The original CIPP product was a needled felt tube, impregnated with polyester resin, which was inverted
into a sewer through a manhole and cured using hot water. Insituform still markets this product today for
gravity sewers. Interestingly, the developer of the original CIPP product was actually trying to develop a
liner for rehabilitating pressure pipes. However, they found it easier to get trials in gravity sewers so the
pressure aspect was forgotten until some 20 years later. Now, a multitude of new CIPP products can be
classified as either semi-structural or fully structural for pressure applications. A few also have an NSF
61 listing and can be used for potable water.
For this report, discussion of the relevant technologies is organized into non-structural, semi-structural,
and fully structural CIPP as outlined below. The tube construction, installation method, cure method, and
resins used are discussed for each CIPP technology.
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