Positive Material Identification (PMI)
Positive Material Identification (PMI) is the analysis of a metallic alloy to establish composition by reading the percentage quantities of its constituent elements. The object of this nondestructive testing method is to identify metal alloys in place using a portable X-Ray fluorescent analyzer that determines the elemental composition of the material.

Southern Inspection applies PMI:

1.   To test ferrous and non-ferrous metallic materials, stainless steels, Monels, Inconels, Hastelloys,
      Aluminum alloys, nickel based alloys, exotic materials
2.   While verifying material compliance in power and petrochemical industries
3.   To inspect valves and valve components, pipe, fittings, machined parts, castings, forgings, bolts
      and stock items
4.   To inspect welds and weld overlays
5.   To verify compliance of new and in-service pressure vessels, plate material, and structural steel

ADVANTAGES
  • Rapid and accurate analysis
  • Highly portable digital technology, can be used on site
  • Certifies components requiring NACE MR0175/ISO 15156
  • Leaves no trace of testing on test sample
  • Care must be taken to ensure that the surface of the test specimen is representative of the material as a whole
  • The instrument must be able to maintain surface contact with the material
LIMITATIONS
  • The depth of penetration of the x-ray for most elements is less than one thousandth of an inch in steel.  Care must be taken to ensure that the surface of the material being analyzed is chemically representative of the whole.
  • Surface of the item must be accessible and subject to satisfactory cleaning and visual inspection
  • Analyzers are limited to identifying only those alloys that are listed in the manufacturer’s library for the analyzer
  • Material verification cannot be performed where the material temperature is in excess of approximately 200°F, unless specialized equipment and techniques are used
  • Identification of small amounts of a specific element in an item can be difficult
  • Carbon, sulfur and phosphorous cannot be identified with x-ray fluorescence
PMI FUNDAMENTALS

Typical methods for PMI include X-ray fluorescence (XRF) and optical emission spectrometry (OES).  IRISNDT carries out PMI using the latest portable analyzers.  All analyzers have a margin of error that varies by element and activity of the radioactive source. The identification of small amounts of a specific element in an item can be difficult. Test results are summarized in an inspection report.



   

 

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