Underground Infrastructure - July 2023 - 29

and have been widely used throughout the industry for decades
with immense success. A brief overview of those technologies
that migrated from gravity to pressure pipe applications is provided
here, followed by a deeper investigation into a relatively
new application known as flexible fabric-reinforced pipe (FFRP).
Cement lining, SIPP
A traditional method of protecting pipeline interiors is the
factory application of a cement or mortar lining. In terms of
trenchless rehabilitation, this method has evolved into sprayin-place
lining or spray-in-place-polymer lining (SIPP).
SIPP is versatile in that it can be used to add a protective
layer combating corrosion or physical deterioration, as well as
restoring structural integrity to a pipeline. Depending on the
desired structural performance required, this method can be
applied in a thin layer (Class I), or in multiple layers (Class II
and III), and can also be incorporated with a fiber mesh within
layers (Class IV).
SIPP improves the hydraulic characteristics of the pipeline,
eliminates the need to excavate tees or service lines, and is completed
quickly relative to dig and replace. Challenges associated
with this method include the need to shutdown and dewater
the pipe for the duration of the application, extensive cleaning
to allow for proper adherence of the material to the host pipe,
removal of appurtenances throughout the rehabilitation span,
and proper design of the applied material. Limitations also include
an inability to repair more than minor corrosion holes
and joint gaps and the fact that it requires diligent QA/QC
throughout the application process.
Pressure pipe CIPP
Cured-in-place-pipe (CIPP) liner is an impregnated reinforced
felt or woven polymer fiber hose with epoxy or vinyl ester thermosetting
resin. This method is used extensively in gravity sewer
applications and was one of the first trenchless technologies
adopted on a large scale.
The resin-saturated liner is inverted into the host pipe with
air or water and has traditionally been cured with hot water or
steam but has now evolved into newer systems being cured with
UV lighting. Properly executed UV-cured CIPP lining reduces
wrinkles and other imperfections in the finished product, waste
material and off-gassing of the curing resins.
trenchless rehabilitation methods are also inherently ecologically
and socially friendly, especially when compared to traditional
open cut pipe replacement.
For these reasons, trenchless technologies for rehabilitation
continue to grow and evolve in the pressure pipe sector
with immense benefits to the end-user. Shorter downtimes,
less disruption to the environment, less economic impact
to businesses and surrounding communities are readily observable
effects of the development and improvement of
trenchless technologies for pressurized water and wastewater
pipelines. Perhaps most importantly, these variables have a
considerable impact on the bottom line: cost.
Some trenchless methods for pressure pipes are well-known
Depending on the application, CIPP can be classified as a
class III or class IV pipe. Today, CIPP lining has been successfully
applied in pressure pipe rehabilitation applications.
Benefits of this method include fully structural rehabilitation
capabilities, moderate internal diameter loss (compared
to some other rehab methods), ability to span larger corrosion
holes and joint gaps, ability to line long distances in a single
day, elimination of pipe joints, and quick installation when
compared to dig and replace (a theme likely recognized by this
point with trenchless methodologies).
Challenges faced with pressure pipe CIPP lining include
dewatering and cleaning the pipeline, removal of valves and
other appurtenances throughout the rehabilitation span, laterals
and other connections must be internally reconnected
UndergroundInfrastructure.com | JULY 2023 29
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Underground Infrastructure - July 2023

Table of Contents for the Digital Edition of Underground Infrastructure - July 2023

Underground Infrastructure - July 2023 - 1
Underground Infrastructure - July 2023 - 2
Underground Infrastructure - July 2023 - 3
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