Underground Construction - June 2020 - 36

THE RIDDLE OF PIPES, PACP
AND REMAINING USEFUL LIFE
®

By NASSCO TAC Chair Christopher Garrett, P.E., Brown and Caldwell
NASSCO's Technical Advisory Council (TAC) has been fielding a number of questions recently
about defining Remaining Useful Life (RUL) of gravity pipe assets based solely on grades per the
Pipeline Assessment Certification Program (PACP). This question is not without merit, and PACP has
responsibility for the confusion. To clear the air and provide guidance on the issue, the TAC will be
authoring a series of articles that address the different facets of this question: What is the relationship
between PACP and RUL? As an introduction to the topic, this article examines the relationship and
the current recommendation for prioritizing assets for inspections and renewal.
Since its introduction by NASSCO in 2002, PACP has continuously improved its coding, grading
and analysis of captured information to promote a fairly objective standard that tracks system
condition over time. This continuous improvement process included the introduction of an Asset
Management protocol in Version 7 (May 2015) for defining criticality as Consequence of Failure (CoF)
and Likelihood of Failure (LoF). These are asset management parameters that define a RUL corollary
based on risk. Consequently, the short answer to the PACP vs RUL question is that there is no
measurable direct relationship; however, NASSCO recommends an asset management strategy that
is documented in Appendix D of the PACP manual.
Some of the confusion for users may relate back to PACP manual versions prior to Version 6 (2010).
These earlier versions presented a guideline relationship between PACP grades and RUL under the
condition grading system discussion. A qualifier was included in the discussion that the mechanisms
and rate of pipe deterioration were dependent on local conditions, and that the guidelines needed
verification by research. The guidelines are summarized in the following table.

PACP Observation Descriptions Prior to Version 6 (2010)
GRADE DESCRIPTION
5

Immediate
Attention

4

Poor

3

Fair

2

Good

1

Excellent

DEFINITION
Defects requiring immediate attention

RUL: Pipe has failed or will likely fail within the next 5 years

Severe defects that will become Grade 5 defects within the
foreseeable future
RUL: Pipe will probably fail in 5 to 10 years

Moderate defects that will continue to deteriorate
RUL: Pipe may fail in 10 to 20 years

Defects that have not begun to deteriorate

RUL: Pipe unlikely to fail for at least 20 years

Minor defects -RUL: Failure unlikely in the foreseeable future



Underground Construction - June 2020

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Contents
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Underground Construction - June 2020 - IFC
Underground Construction - June 2020 - Contents
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