Nace CP 1, Course Manual

Page: 283 / 535

RP0169-2002
12 NACE International
5.2.3.7 Care shall be exercised when using
materials such as loose wrappers, nonconducting
urethane foam, and rock shield around pipelines
as protection against physical damage or for other
purposes, because these materials may create an
electrical shielding effect that would be detrimental
to the effectiveness of cathodic protection.
5.2.3.8 When a pipeline comes above ground, it
must be cleaned and externally coated, or
jacketed with a suitable material, for the prevention
of atmospheric corrosion.
5.3 Methods for Evaluating External Coating Systems
5.3.1 Established Systems Proven by Successful Use
5.3.1.1 Visual and electrical inspection of
in-service pipeline coatings should be used to
evaluate the performance of an external coating
system.
These inspections can be conducted
wherever the pipeline is excavated or at bell holes
made for inspection purposes.
5.3.2 Established or Modified Systems for New
Environments
5.3.2.1 This method is intended for use when
external coating systems will continue to be used
and are qualified under Paragraph 5.3.1, but when
application will be extended to new environments
or when it is desired to revise a system to make
use of new developments.
5.3.2.1.1 The use of applicable material
requirements,
material specifications,
standards, and recommended practices for
application,
as given in Table 1, is
recommended.
5.3.2.1.2 The use of applicable references in
Table 2 is recommended unless previously
covered in applicable references in Table 1.
5.3.3 New External Coating System Qualification
5.3.3.1 The purpose of this method is to qualify a
new external coating material by subjecting it to
laboratory tests appropriate for the intended
service.
After laboratory tests have been
conducted and indicate that the external coating
system appears to be suitable, application and
installation are conducted in accordance with
recommended
practices. In-service field
performance tests are made to confirm the
success of the previous steps. The steps of the
method are (1) laboratory tests, (2) application
under recommended practices, (3) installation
under recommended practices, and (4) in-service
field performance tests.
If good results are
obtained after five years, only Steps 2 and 3 are
required thereafter.
5.3.3.1.1 Applicable sections of Tables 3 and
4 are recommended for the initial laboratory
test methods.
5.3.3.1.2 Applicable sections of Tables 1 and
2 are recommended for conditional use during
Steps 2 and 3.
5.3.3.1.3 During a period of five years or
more, the use of the evaluation methods
given
in Table 5, Item 1 or 2 are
recommended. The test method in Item 3
may be used as a supplementary means for
obtaining data for correlation with laboratory
tests.
5.3.4 Method for Evaluating an External Coating
System by In-Service Field Performance Only
5.3.4.1 The purpose of this method is to qualify an
external coating system when none of the first
three methods given in Paragraph 5.3 has been or
will be used. It is intended that this method should
be limited to minor pilot installations.
5.3.4.1.1 The use of at least one of the first
two
methods given in Table 5 is
recommended on the basis of at least one
investigation per year for five consecutive
years.
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Section 6: Criteria and Other Considerations for Cathodic Protection
6.1 Introduction
6.1.1 This section lists criteria and other
considerations for cathodic protection that indicate,
when used either separately or in combination, whether
adequate cathodic protection of a metallic piping
system has been achieved (see also Section 1,
Paragraphs 1.2 and 1.4).
6.1.2 The effectiveness of cathodic protection or other
external corrosion control measures can be confirmed
by visual observation, by measurements of pipe wall
thickness, or by use of internal inspection devices.
Because such methods sometimes are not practical,
meeting any criterion or combination of criteria in this
section is evidence that adequate cathodic protection
has been achieved. When excavations are made for