Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...

Ambient curing is typically only used for small diameter pipes (e.g., laterals) and is sensitive to climatic
conditions. The slow rate of curing reduces productivity and increases the sewer’s out-of-service time
making its use in sewer mainlines uneconomical. Hot water curing is the original curing method for CIPP
and can be used in the curing of liners for the full range of host pipe diameters. Steam curing provides a
more rapid cure than hot water, and thus increasing job site efficiency. It involves less process water, but
increases safety issues. It is only used in the small to medium diameter range because the evenness of
curing conditions is harder to control in large diameter pipes and over long installation lengths. The
steam has less “thermal mass” which makes the curing more susceptible to circulation problems whereby
either insufficient heat is provided to allow a complete cure of the resin or excess heat from the resin
exotherm is not removed causing a resin boil. Also, the formation of condensate pools in the liner invert
needs to be avoided as this can also lead to inadequate curing of this region of the liner. In both cases,
temperature measurements are taken as the liner cures to track the exothermic reaction and to ensure
complete cure of the resin. The installation procedures and QA/QC requirements will change according
to the curing method chosen.
Smaller mainline CIPP liners are typically prepared to the appropriate
diameters and impregnated (“wet out”) with resin in the factory. They are
then shipped in a refrigerated truck to the job site for insertion and curing.
Lateral liners (3- to 4-in. diameter) are frequently impregnated by hand onsite.
Large-diameter liners are also wet out onsite using special wetout facilities.
Care needs to be taken that a liner does not begin to cure before or during the
installation process.
2.2.7 Ultraviolet Light Cured Liners. UV light cured liners were
developed and used in Europe by Inpipe from 1986 (Downey, 2011). A
German company, Brandenburger GmbH, later became a widespread provider
of resin pre-impregnated, UV-light-cured laminates for sewer rehabilitation.
In 1997, Brandenburger began promoting its technology outside Germany.
Its U.S. licensee, Reline America, Inc., was established in 2007 to distribute
this UV-cured, glass-reinforced CIPP liner to licensed contractors. In this
product, a seamless, spirally wound, glass-fiber tube is impregnated with
polyester or vinylester resins. The seamless liner has both an inner and outer film; the outer film blocks
UV light. The inner film is removed after curing. The shelf life of the impregnated liner is approximately
6 months. The liner is available in diameters from 6 in. to 48 in. and can be used in circular, oval, and
egg-shaped pipes. Reline America reports that up to 60-in. liners will be available in the near future and
that individual installation lengths of up to 1,000 ft are possible. The liner tube is winched into the
existing pipe and inflated with air pressure (6 to 8 pounds per square inch [psi]) and then cured using a
UV light train (see Figure 2-4). For QA/QC purposes, in addition to CCTV inspection of the line before
and after curing, a record of the liner’s inner air pressure during curing, the curing speed (ft/min), and
resin reaction temperatures (infrared sensors) are all monitored. Other vendors of UV-cured CIPP include
BKP Berolina, LightStream, and Saertex.
2.2.8 Emerging and Novel CIPP Technologies. One of the latest glass-reinforced CIPP liners to
enter the U.S. market is Berolina Liner ® from BKP Berolina Polyester GmbH in Germany. CIPP
Corporation is the U.S. licensee. The liner was first used in Europe in 1997 and outside Europe beginning
in 2001. At the time of this report, there have not been any U.S. installations, but the liner has been used
in Canada (Hamilton, Ontario). The liner is composed of glass fiber and/or polyester webs impregnated
with polyester or vinylester resin. Uniquely, the layers are overlapped and staggered giving the tube
variable stretching capability. After placement of a protective film sleeve covering the lower half of the
host pipe, the liner is installed by pulling it in place, which can be accommodated by the axial strength of
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Figure 2-4. UV Light
Curing Train