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Integrity Evaluation 1 Copyright © PIMS of London Ltd
Summary Integrity Evaluations perform a critical role within the Integrity Management cycle –they aim to precisely identify,
locate & quantify features & patterns of threats. They shape the decisions you take to manage risk & maintain
performance within your system.
PIMS works with you to ensure that the evaluations provide appropriate information to support the correct
remediation & response decisions. We do this by building a “functional specification” for the features you need
to find, then determining which method/s that may best meet that specification. We help you fully exploit this
information, beyond your immediate requirements, using it to strengthen the basis upon which subsequent Risk
Assessments are performed.
If you are unfamiliar with evaluation technologies & techniques, or you are resource-constrained, PIMS can
project manage integrity evaluations on your behalf. Beyond standard pressure testing techniques, we have
personal track record in managing thousands of kilometres of in-line inspection (ILI: metal loss, crack detection
& geometric); we can set-out the structured process required to ensure you get value out of direct assessment
(DA: external corrosion, internal corrosion and stress corrosion cracking). Alternatively, we can locate &
supervise those contemporary evaluation techniques that are appropriate to your pipeline or facility.
Once the integrity evaluation information has been captured, PIMS’ support is invaluable. We can take this
information and, combining it with other relevant data, perform immediate integrity assessments to determine
critical corrective actions that must be executed as a priority. With these priorities met, we can then extend
study focus to produce future integrity assessments. Not only does this give you a further, business-case
justified, schedule of corrective actions over time, it also identifies preventative actions that you can take to
maintain sustainable system improvements. Within the clear path set-out to ensure the fitness-for-purpose of
your pipeline or facility, we then propose recommendations for re-inspection intervals and techniques.
Our goals-led approach, framing each task within your overall integrity management objectives, ensure that you
are empowered with an Integrity Evaluation that helps to make your business better.
Integrity Evaluation 2 Copyright © PIMS of London Ltd
Objectives that can be Achieved Provided that the type of threat in question is one that can be detected by an Integrity Evaluation, the
information required to support correction of that threat before it causes failure can be provided by an Integrity
Evaluation. Furthermore, all information arising from an Integrity Evaluation can be used to ensure that
subsequent Risk Assessments performed are increasingly robust and fed from more quantitative data.
Potential Consequence of Improper Execution In themselves, Integrity Evaluations do nothing to prevent failure. Only when supported by a subsequent set of
corrective and preventative actions, do Integrity Evaluations prove to be of value in reducing Risk. Furthermore,
Operators must understand the precise capabilities of each Integrity Evaluation method in order to safeguard
against false assurance on Threats that may not be detected by that particular method.
Selecting the most appropriate Integrity Evaluation method When determining which methods are to be applied for the pipeline Integrity Evaluation, it is essential that
operators consider a “functional specification” for the features they wish to detect and characterise and then
challenge which method may best satisfy that specification. The evaluation methods seek to identify features on
a pipeline that are symptomatic of a particular threat or threats being present.
With regard to the threats that are to be evaluated (or the features that are symptomatic of that threat being
present) the following evaluation methods may be considered:
Evolutionary Threats (Time-related)
• Corrosion
• Stress-corrosion Cracking (SCC)
• Fatigue - an accelerant to failure, eg, after a dent has been inflicted.
• Product-related - threats such as Hydrogen Induced Crack (HIC) and Blistering
Inherent Threats (Stable/Binary)
• Fabrication Defects - during the manufacture of the pipe itself.
• Welding or Construction Defects - during the pipe-laying process.
• Out-of-Specification Ancilliaries
Event-led Threats (Time Independent)
• Mechanical Damage
• Operational Aspects
• Climatic & External Force
Integrity Evaluation 3 Copyright © PIMS of London Ltd
Deployment of the selected Integrity Evaluation technique In-line inspection
Before performing a pipeline in-line inspection, the requirement must be documented to ensure that the
equipment, staff, processes and software that will be part of the inspection are qualified to achieve the desired
specification as set out in the Integrity Evaluation Programme. This documentation must include consideration
for at least the following items:
• The goals and objectives to be achieved, and the accuracy required in the inspection.
• The physical and operational characteristics, and pipeline restrictions.
• The requirements and criteria established in the specifications or standards the department,
organization or company has set to that purpose. In the event that such standards or
specifications are not available, the criteria established in NACE-RP-0102-2002 should
apply.
• The selection of an appropriate inspection tool, based on the inspection requirements and
on the equipment capacities.
The in-line inspection involves the passage of a tool (commonly referred to as a pig) through the pipeline
segment. The tool gathers information on pipeline characteristics during the passage or run. There are three
main categories of inspection tool:
I. Metal Loss tools
- - Magnetic Flux Leakage: Both Standard & High Resolution tools
- - Ultrasonic Wall measurement (Straight Beam)
II. Crack Detection tools
- - Ultrasonic Crack Detection (Angle Beam)
- - Magnetic Flux Leakage: Transverse Flux tools
III. Geometric tools
- - Internal profiling and calliper tool
- - Inertial mapping unit Geopositioning tool
Pressure test (including Hydrotest) Pressure testing – whether conducted using water (fluid), air (gas) or product - must be used as a substitute to
the In-line Inspection method, or in combination with the In-line Inspection method if In-line Inspection is not
practicable. Pressure tests enable the localization of the following features when they result in a loss of enough
magnitude to be recorded by the pressure record tools installed:
a) Localised total metal loss (external/internal)
Integrity Evaluation 4 Copyright © PIMS of London Ltd
b) General total metal loss (external/internal)
c) Stress Corrosion Cracking (SCC)
d) Manufacturing defects (seal or defective metal)
e) Defective girth weld
Acceptable test methods, minimum necessary equipment and other additional requirements of pipeline
hydrotest shall observe the criteria established in the standards or specifications the department, organization
or company has set to that purpose. In the event that such standards or specifications are no available, the
criteria established in standard API-RP-1110-1997 should apply.
Direct Assessment (DA)
Direct Assessment is an integrity evaluation method that can be applied to buried pipelines to consider defects
that are related to some time-dependent threats (internal corrosion, external corrosion, stress corrosion
cracking). The Direct Assessment method should be applied in pipeline systems where pressure testing or the
available internal inspection technologies are not adequate or cost-effective. The Direct Assessment constitutes
a structured process that should not interrupt pipeline operation. Thus, it may be used when the pipeline
operational schedules and product flow rate limit the use of other methods.
Direct Assessment can be used as a solo evaluation method or in combination with other assessment methods.
As a solo evaluation method, it can be used to address external corrosion threats in liquid and gas pipelines,
internal corrosion threats in gas pipelines, and may be considered as an option to understand SCC threat
susceptibility in liquid and gas pipelines.
Other methodologies of Integrity Evaluation
Where In-line inspection, Pressure testing and Direct Assessment cannot be applied, alternative methods of
proven and equivalent technology will be used to evaluate integrity.
Integrity Evaluation report format Regardless of the methodology utilised – be it through In-line inspection, pressure testing, direct assessment or
other methodology – it is important that results are reported in a consistent manner.
The first element that requires consistency is that of the pipe tally. A consistent pipe tally enables an efficient
approach to be taken towards all pipe segments. It also enables alignment of data from disparate sources or
different Integrity Evaluation techniques on any particular segment.
The second element that requires consistency is that of Integrity Evaluation technique accuracy and confidence.
The purpose of expressing accuracy and confidence in a consistent manner enables a degree of span to be
Integrity Evaluation 5 Copyright © PIMS of London Ltd
applied to risk assessments. It also prevents operators from unnecessarily discounting a threat should that
feature lie beyond the reporting threshold.
The third element that requires consistency is that of feature classification. Though feature classification is well
documented with regard to Metal Loss and Cracks, it is important to ensure that other features such as dents or
even pipeline fittings are described in a consistent manner.
It is up to the operator to determine whether the Integrity Evaluation report should include recommendations on
stages to be followed to mitigate the risk represented by features identified as being beyond acceptable limits.
Should this element be required, it is important that the operator determine the manner in which acceptable
limits are defined.
Post Evaluation Assessment The primary purpose of an Integrity Evaluation is to identify what immediate response is required to prevent
imminent pipeline failure resulting from the presence of critical defects.
As with the criteria for the Integrity Evaluation technique itself, it is important that the operator clarifies the exact
purpose of the Post Evaluation assessment. This clarification must be geared towards the manner in which the
information gathered from the evaluation and the Post Evaluation assessment will be used to determine:
• Corrective actions to address a present and identified threat before it causes failure
• Preventative actions to either eliminate consequence or remove the possibility for a threat
to re-occur.
• Reactive actions scheduled as a last line of defence to limit consequence should failure
occur
Though the Post Evaluation Assessment in itself forms a conclusion of a Predictive action, to monitor and
model threat occurrence and location, it is quite likely that the results of such an assessment will also identify
the type and frequency of subsequent evaluations that may be considered appropriate for that pipeline
segment.