It is a rapid, non-destructive method. Positive material identification is performed on a wide range of components and assets, and provides a semi-quantitative chemical analysis. It is used for both material verification and identification.
Why PMI is required?
The most frequent cause of industrial accident
is failure of mechanical integrity. Examples of this includes refinery
explosion, stress corrosion cracking, flow accelerated corrosion mainly in power/nuclear
plant technology and insufficient strength of welded joints.
PMI testing means that companies can makes sure
that every single part in their system meets specification. Critical
replacement parts are the right alloy grade and all bought in materials are exactly
what they should be. This important step can be the key difference between
seamless operations and catastrophic safety failures.
What is Positive Material
Identification?
PMI
is the analysis of a material, this can be any material but is generally used
for the analysis of metallic alloy to establish
composition by reading the quantities by percentage of its constituent elements. Typical methods for PMI include X-ray fluorescence (XRF) and optical emission spectrometry (OES).
PMI
is a portable method of analysis and can be used in the field on components.
X-ray fluorescence (XRF) PMI can
not detect small elements such as carbon. This means that when undertaking
analysis of stainless steels such as grades 304 and 316 the low carbon 'L'
variant can not be determined. This however can be analyzed with optical
emission spectrometry (OES).
Positive
material identification is performed using either of the two techniques below:
- X-ray Fluorescence (XRF) analyzer: This is the most
common method and the portability of the hand-held equipment allows
Intertek to perform PMI on-site at our customers’ premises. The device
scans the metal material and identifies its key elements. However, it
cannot detect carbon and some lighter elements and is not suitable for
identification of pure carbon steel materials.
- Optical Emission Spectroscopy (OES): This method can detect almost all types of elements including carbon and lighter elements and carbon steel. Although not as portable as XRF analysers, the equipment can be transported to sites and used at high elevations with proper lifting arrangements.
One another method
is also used which is Laser Induced Breakdown Spectroscopy. LIBS is an
analytical technique that has been used in laboratories. Most handled LIBS
analyzers are used for fast sorting of alloys in scrap yards, alloy
identification and analysis in various application in metals industry.
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