What is Flange PMI Testing ?
Positive Material Identification.
What is positive material identification (PMI) testing?
Positive material identification (PMI) testing is the examination of a material, usually a metallic alloy, to confirm the material is consistent with the user’s request. In general, this is done using one or more of three testing methods: Handheld XRF, Handheld LIBS, or Portable OES. These test methods determine the chemical composition of the metal and match the chemistry to an alloy grade library to provide an alloy grade ID as the result.
As a nondestructive testing (NDT) method for analyzing the composition of metals and alloys, PMI testing is the most efficient way to test large batches of material at all points of the metal supply chain.
PMI testing for metals and alloys
Determining the precise composition and grade of an alloy enables everyone in the supply chain to match specifications. People that come into custody of the materials along the supply chain include suppliers, distributors, facility workers, manufacturers, and other responsible parties.
Other properties that an alloy can be tested for are:
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heat resistance
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durability
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corrosion resistance
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surface contamination
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sensitization
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grain flow
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weld qualification
Depending on what the metal is going to be used for, other non-destructive and destructive tests can be conducted.
Alloy chemical compositions
It’s important to note that each alloy has its own recipe and there are literally hundreds documented in every alloy group.
The purpose of alloy groups is to categorize different compositions of metals. For instance, an alloy of nickel with one-third copper is known to resist corrosion from seawater, some acids, and many substances involved in chemical and petrochemical processing.
Here are some more examples of alloy groups:
- Heat-resistant alloys all contain nickel and chromium in order to withstand high operating temperatures.
- Corrosion-resistant alloys — like the one I mentioned above — are specifically intended for use in industrial chemicals, corrosive waters, pollution control, food and beverage processing, and more corrosive environments.
- Special alloys vary in composition and properties. They’re grouped together because their utility depends on mechanical properties (thermal, magnetic, electric) and not necessarily corrosion-resistance or strength.
The Unified Numbering System (UNS) for metals and alloys is the process for designating compositions to groups.
Why is positive material identification important?
it's about quality over profitability.
Proper PMI testing prevents fatalities
If just one defective metal part can cause an enormous fireball, think of the damage faulty metals can do on a larger scale.
When should PMI testing be conducted?
Ideally, positive material identification should be administered every time a metal switches hands throughout the supply chain.
The metal supply chain
Supply chains for all sorts of materials have become wildly complex. That’s why consumers have taken more interest in where their products or food originate from.
Metals are no different. Therefore, it’s crucial to perform PMI testing at every point on the supply chain.
Points of the metal supply chain can include:
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scrap to foundry,
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foundry to parts fabricator,
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fabricator to refinery or airplane,
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and inspection of in-service parts during maintenance or safety audits.
