Positive Material Identification (PMI) is the analysis of a 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).
The need to use PMI has dramatically grown over the last 10 years to the point where in many refinery’s and Petrochemical plants 100% alloy material verification is now carried out.
If Inspectors are correctly trained to carry out PMI it ensures that the correct material has been used and we therefore have a greater assurance that failure should not occur due the wrong material being used.
What are the responsibilities of an individual who carries out PMI?
An individual certified to PMI Level 2 has demonstrated competence to perform NDT according to PMI procedures. Within the scope of the competence defined on the certificate, Level 2 personnel may be authorised by the employer to:
- Select the PMI technique for the test method to be used;
- Define the limitations of application of the testing method;
- Translate NDT codes, standards, specifications and procedures into NDT instructions adapted to the actual working conditions;
- Set up and verify equipment settings;
- Perform and supervise tests;
- Interpret and evaluate results according to applicable standards, codes, specifications or procedures;
- Prepare PMI written instructions
- Carry out and supervise all tasks at or below Level 2;
- Provide guidance for personnel at or below Level 2, and
- Report the results of PMI test
PMI training at IEQS GROUP covers the following:
- The factors to be considered when using PMI
- Selected Definitions
- The XRF Principle
- Radiation safety
- Radiological Controls
- Incorrectly using the analyser
- XRF Control Measures
- Materials to be tested & Detectable elements
- Why use PMI
- Using a XRF analyser
- Operational Pitfalls
- Analysis of results
- Proper Inspector training is required to ensure that not only can equipment be used correctly but to ensure that meaningful results are collated.
- Training has to be documented and the syllabus open to external audit.
- There has to be evidence available to show that all trainees have understood the training and are now competent to carry out PMI.
- To this end an end of course examination must be successfully passed so that certification can be provided to prove competence.
Examinations for PMI are based around the employer based scheme SNT-TC-1A.
The PMI Level 2 examination includes a theory paper, specific paper, and a practical exam.
The requirements for Level 2 PMI are: 12 hours training, previous to the exam, and 1 month supervised work experience to be obtained.
Once the above requirements have been obtained, the certificate will be issued.
To be eligible for the Level 2 examination, an eye test must be passed (near vision and colour).