Avoiding Failure: Positive Material Identification - SGS

36 Positive Material Identification
Avoiding fAilure
Richard Ritchie, Director at SGS Industrial Services says improved positive material
identification is a cost effective way to avoid small problems with huge effects
Richard Ritchie,
Director at SGS
Industrial Services.
As the common wisdom says, prevention
is better than cure. Asset Integrity
Management Programs not only enable
facilities to keep operating, but also can
extend the life time of assets and facilities.
Systematic inspection, detection and correction
of failure conditions before they occur, or before
they develop into major defects, can avoid
unplanned downtime or even catastrophic
disasters, as well as help reduce maintenance
costs.
Improved Positive Material Identification
(PMI) allows plant operators and
maintenance experts to make informed
decisions on non-conforming
components. In most cases, an effective
PMI approach can generate savings far
beyond the cost of the program.
What is PMi?
Positive Material Identification (PMI)
is the determination, with certainty, of
the material in use and the
confirmation that it is the correct
material for the service. Missing or unclear
material certificates, or incorrect materials used
in a service, can increase risk, impacting
maintenance, safety and operations. Each
component material in the wrong service
represents a near miss. PMI is the solution. It
identifies the wrong material in service by
determining the alloy composition of materials
such as stainless steel and high alloy metals.
This can be accomplished either before
beginning plant operation, or after start-up of
operating units. In the latter case, the process
takes place years after commissioning and is
also known as Retro-PMI.
The benefits of Retro Positive Material
Identification assessment are substantial
reduction in the risk of catastrophic failure in
operating facilities, protection of employees and
the surrounding community against risk to
health or safety and finally, avoidance of lost
profit due to unscheduled outages.
There are two methods of Positive Material
Identification: X-ray refraction and Optical
Emission Spectrography. With the X-ray
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Fluorescence (XRF) principle, the fact that each
chemical element emits X-rays at a unique
energy is applied. The XRF equipment contains
radioactive sources, or a low voltage x-ray
generator, which sends out radiation. The
exposed material then temporarily emits
element specific radiation back, generating a
different energy level for every element. This
energy is detected and measured, thus
identifying the alloy elements. The disengaged
radiation is very low and extra safety measures
are not necessary. The important advantage of
the XRF-method is that it can be executed in
service without damaging the material. The
results are available directly after the inspection.
The other method is called Optical Emission
Spectrography (OES). The spectrography
equipment consists of a probe which releases a
spark that is used to vaporize a small amount of
the material being analyzed. The atoms and
ions in this vapor produce a spectrum which
can be optically detected and measured for
calculations to determine the components of
the material. OES instruments are larger in size
and use Argon gas to improve accuracy. It is,
however, the only reliable way to measure
carbon outside of the laboratory.
What are the benefits of improved PMi?
A traditional PMI approach faces several
challenges. It is usually conducted fully or
partially manually, with attendant probability of
human mistakes during the data collection and
data processing. As PMI testing technology has
advanced, improved instrumentation has
become more common, which is generally
combined with software developed specifically
to address PMI issues.
PipeWrxTM for instance is a new and
revolutionary software system meeting the need
for plant operators to detect, record and present
clear and precise information about the asset
integrity. It makes the identification, analysis
and tracking of every single component in every
unit possible, unlike the traditional approach
where only a fraction of components can be
evaluated.
In addition to the productivity improvements
such software provides, the quality and the
reliability of the data processing can be
optimized. Usually every component which
does not meet requirements should be replaced
after identification. However, in some cases,
practice has shown that not all critical
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Positive Material Identification
“ImpRoved posItIve mateRIal IdentIfIcatIon
(pmI) allows plant opeRatoRs and
maIntenance expeRts to make InfoRmed
decIsIons on non-confoRmIng
components”
RIchaRd RItchIe, dIRectoR at sgs IndustRIal seRvIces
components call for corrective action. A
material may not meet the engineering
specifications written years ago, but still can
prove to have fitness-for-service.
The fit-for-service assessment is a special
type of appraisal carried out to determine if the
product or installation can fulfill its stated
purpose - typically until the next shutdown - or
if repair or replacement is needed in order to
continue service as specified. When applying
the fit-for-service approach, all potential failure
modes are identified and an assessment is
conducted to ensure that the conditions for
failure are not reached during the intended
operation of the asset. In this way critical
components can be classified as: OK for current
operating conditions, requires monitoring,
replace and flagged for engineering review
Experience reveals that the number of
components needing replacement is
surprisingly low compared to the total amount
of critical components. In some cases corrosion
monitoring must be strengthen or the
engineering specifications must be revised. For
example, a recent retro-PMI assessment
allowed the operator to replace only 3% of the
7% non-conforming components which
represented significant cost and time savings.
An improved PMI approach, in light of
prescribed operating parameters and goals
clearly affects the reliability of the data
collected. It can reduce both the effort needed
for the identification and the cost of remedying
discovered discrepancies by categorizing
discrepancies for corrective action.
The positive contribution of electronic data
management is not limited to data collection
and analysis. Once discrepancies are classified
as to corrective action needed, actionable
reports can be generated. PipeWrxTM enables
improvements in communication, reporting
and assessments to support improved and
actionable decision making to enhance safety,
productivity and profitability.
With state-of-the-art applications which also
can be integrated into standard industry
software, plant operators and maintenance
experts can easily manage inspection and
maintenance planning and reduce the costs
and the effort required for these activities.
PMI is the determination, with certainty, of the material in use and confirmation that it is the correct material for the service.
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