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Construction and Inspection for Cur ed-in-Place Pipe 283

“moderate,” and “severe” are meant to take into account the overall
severity as well as frequency of defects affecting the entire pipe.
In another method, inspected pipelines can be assigned Catego-
ries A, B, C, and D on the basis of their unit scores, as listed in the
“Defect Score” column of Table 7.4. Category E defects can be identi-
fied solely on the presence of critical defects noted during the closed-
circuit television (CCTV), or other inspection methods. The defect
score is not applicable for Category E pipelines.
The National Association of Sewer Services Companies
(NASSCO)–Pipeline Assessment Certification Program (PACP),
defines, in detail, each defect category and provides a program to
train CCTV operators to identify these defects in a common
descriptive language uniform for the United States and Canada.
The condition data identified by the CCTV operator are then com-
piled and, through the use of a rating system, a priority level for
renewal is assigned. This condition assessment will allow the
designer to select the most applicable technology to accomplish the
renewal. Based on NASSCO guidelines, Table 7.5 presents different
types of defects that will impact CIPP installations. Figures 7.1, 7.2,
and 7.3 represents the structural, operational and maintenance,
and construction defects respectively.

7.3 Main CIPP Characteristics
As said previously, the primary components of CIPP are a flexible
fabric tube and a thermosetting resin system. For typical CIPP appli-
cations, the resin is the primary structural component of the system.
These resins generally fall into one of the unsaturated polyester, vinyl
ester, and epoxy generic groups, each of which has distinct chemical
resistance and structural properties.
Unsaturated polyester resins were originally selected for the first
CIPP installations due to their chemical resistance to municipal sew-
age, good physical properties in CIPP composites, excellent working
characteristics for CIPP installation procedures, and economic feasi-
bility. Unsaturated polyester resins have remained the most widely
used systems for the CIPP processes for over three decades.
Vinyl ester and epoxy resin systems are used in industrial and
pressure pipeline applications, where their special corrosion and/or sol-
vent resistance, tensile strength, and higher temperature performance
are needed. These systems can also be used in sanitary sewer sys-
tems. In drinking water pipelines, epoxy resins are required.
The primary difference between heat cured and UV light cured
resins is how the resin cure is activated and the workable life of
the resin catalyst mixture (time from when the resin is first mixed,
or catalyzed, until it cures at a specified temperature). Heat acti-
vated resins are designed to cure when a heat source is applied for