Underground Construction - March 2022 - 35
EDITION 72 | MAR 2022 | NASSCO.ORG
cure initiator package optimized for that
particular wavelength.
Most standard light cured liners are
made out of layers of fiberglass fabric.
Fiberglass has a similar refractive index to
the polyester and vinyl ester resins which
allows for more efficient light penetration.
There are, however, limits to how far
the light can penetrate the liner, which
will determine the maximum thickness
that can be installed (unless used in
combination with other heat-activated
initiators). The fiberglass reinforced liners
have a very high flexural modulus which
allows for thinner liner designs. Fiberglass
reinforced liners also generally have better
long-term creep retention properties which,
again, contributes to thinner design values.
Fiberglass and resin manufacturers have also
developed new products which improve the
ability to cure through thicker laminates. This
has become increasingly important as light cure
manufactures have significantly expanded the
diameter range available in the production of
these liners. Fillers are typically not used with
light-cured resins, with the occasional exception
of alumina trihydrate (ATH), which also has a
reactive index that is a close match to the resin
and fiberglass. The ATH will, however, have
some impact to the thickness that can be cured.
LED cure systems are most widely used in
smaller dimeter applications. Their flexibility
and smaller footprint make them ideally suited
for use in lateral applications where you need
the ability to handle bends and transitions.
These systems typically use woven or needle
punched liners which have significantly more
flexibility than a glass-reinforced liner. Traditional
polyester needle punched felt liners, or glass/
felt hybrid liners are also now being installed
using an air inversion or a pull in process and
then cured with the same metal halide light
train systems used for glass-reinforced liners.
These felt liners will have a little lower thickness
limitation compared to an all-fiberglass liner.
The use of felt liners can provide a lower cost
compared to a glass reinforced liner, however
thicker liners will need to be installed due to the
lower flexural modulus of these systems.
The light cure CIPP market continues to see
good growth year after year and has picked
up additional market share around the world.
The suppliers, equipment manufacturers, and
installers also continue to innovate new products
and procedures to help continue this trend.
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35
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Underground Construction - March 2022
Table of Contents for the Digital Edition of Underground Construction - March 2022
Contents
Underground Construction - March 2022 - Cover1
Underground Construction - March 2022 - Cover2
Underground Construction - March 2022 - Contents
Underground Construction - March 2022 - 4
Underground Construction - March 2022 - 5
Underground Construction - March 2022 - 6
Underground Construction - March 2022 - 7
Underground Construction - March 2022 - 8
Underground Construction - March 2022 - 9
Underground Construction - March 2022 - 10
Underground Construction - March 2022 - 11
Underground Construction - March 2022 - 12
Underground Construction - March 2022 - 13
Underground Construction - March 2022 - 14
Underground Construction - March 2022 - 15
Underground Construction - March 2022 - 16
Underground Construction - March 2022 - 17
Underground Construction - March 2022 - 18
Underground Construction - March 2022 - 19
Underground Construction - March 2022 - 20
Underground Construction - March 2022 - 21
Underground Construction - March 2022 - 22
Underground Construction - March 2022 - 23
Underground Construction - March 2022 - 24
Underground Construction - March 2022 - 25
Underground Construction - March 2022 - 26
Underground Construction - March 2022 - 27
Underground Construction - March 2022 - 28
Underground Construction - March 2022 - 29
Underground Construction - March 2022 - 30
Underground Construction - March 2022 - 31
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Underground Construction - March 2022 - 33
Underground Construction - March 2022 - 34
Underground Construction - March 2022 - 35
Underground Construction - March 2022 - 36
Underground Construction - March 2022 - 37
Underground Construction - March 2022 - 38
Underground Construction - March 2022 - 39
Underground Construction - March 2022 - 40
Underground Construction - March 2022 - 41
Underground Construction - March 2022 - 42
Underground Construction - March 2022 - Cover3
Underground Construction - March 2022 - Cover4
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