How Retroactive PMI Supports Safer Plant Maintenance in Clean Energy Sectors

By Samudrapom DamReviewed by Laura ThomsonOct 16 2025

Positive Material Identification (PMI) is a non-destructive testing method used to determine a material’s elemental composition. Using tools like handheld X-ray fluorescence (XRF) analyzers, PMI ensures materials meet quality and safety standards. Safety and regulatory compliance are paramount in clean energy sectors like hydrogen plants, solar farms, biorefineries, and nuclear facilities. Retroactive PMI, critical in this context, identifies unknown/undocumented materials in existing infrastructure.^1-3

This is important for older facilities/when maintenance records are incomplete. By verifying materials retroactively, engineers can detect mismatches, prevent equipment failure, and ensure compliance with industry standards. This improves operational safety and reliability of clean energy plants and their compliance with environmental and safety regulations.^1-3

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Why Retroactive PMI Is Essential for Clean Energy Infrastructure

Clean energy infrastructure, such as large-scale grid-connected photovoltaic (PV) power plants, continues to expand, which increases the risks of legacy components and inadequate material traceability. Over time, degraded labeling, outdated documentation, and unknown alloys compromise the safety and reliability of critical equipment.

In PV plants, operations and maintenance are distinct but complementary activities, where documentation control and incident reporting play a central role. Failures in inverters, combiner boxes, and pressure-retaining components have already led to internal shutdowns of clean energy facilities, indicating the need for rigorous material verification. Retroactive PMI provides a non-destructive approach to address these concerns.

PMI ensures that metallic components, especially those containing alloying elements like chromium, nickel, or molybdenum, have the correct chemical composition to meet design expectations like corrosion resistance and mechanical strength.^1,2,4-7

This includes pressure-retaining parts, alloy bolting, welds, cladding, and overlays. Undetected alloy mismatches/degradation accelerate corrosion/cracking, leading to ruptures in pressurized systems/unexpected operational failures.

Failure and degradation mechanisms in PV modules, such as corrosion, highlight the importance of identifying material vulnerabilities.

Unknown alloys become a greater risk with evolving module materials and system complexity. Retroactive PMI addresses this by verifying materials before failure, enabling timely repairs/replacements during scheduled maintenance windows. This prevents unplanned shutdowns and costly emergency interventions. Moreover, industry standards such as the American Petroleum Institute (API) Recommended Practice 578 define PMI as a validated material verification program, particularly in the reinstallation of alloy components during maintenance. Techniques such as Handheld Laser-Induced Breakdown Spectroscopy (HHLIBS), as cited in API 578’s third edition, further enhance PMI accuracy.^1,2,4-7

Common PMI Techniques Used

Handheld XRF, LIBS, and optical emission spectroscopy (OES) are the most commonly used PMI techniques.^1,8

XRF analyzers are used for non-destructive elemental analysis of solid samples of all sizes when the surface is clean and free of coatings, grease, or contaminants. The technique cannot detect carbon and some light elements like phosphorus (P), sulfur (S), and silicon (Si). It directs a beam of low-energy X-rays generated by an isotope source or X-ray tube onto the sample. This excites inner-shell electrons in the atoms, causing them to emit secondary or fluorescent X-rays as they return to a stable state. These emitted X-rays are characteristic of specific elements, effectively serving as "electromagnetic fingerprints." The resulting spectrum is analyzed qualitatively, identifying which elements are present, and quantitatively, determining their concentrations, making XRF a reliable tool for PMI.¹

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Arc spark emission spectrography is used to determine the elemental composition of metal alloys. It works by creating a spark between a sample and an electrode, exciting the atoms in the sample. This excitation causes the atoms to emit light at characteristic wavelengths, which is then analyzed to identify and quantify the elements present. The sample must be clean, free from coatings or contamination, and have a flat, ground surface.

The emitted light is transmitted to an optical system, dispersed into spectral lines, and compared against calibration curves for accurate analysis. OES provides qualitative and quantitative results with high precision. It is commonly used in PMI for quality control, ensuring materials meet industry standards. Safety protocols must be followed during testing to ensure the accuracy and reliability of results. OES and XRF are key tools in materials verification processes.¹

XRF instruments have transformed chemical analysis in the field but require radiation safety training, as they emit X-rays. They also cannot detect low atomic number elements such as lithium due to technical limitations. Portable LIBS has emerged as a powerful alternative, capable of qualitative and quantitative analysis, particularly for alloys. It can detect light elements such as silicon, lithium, potassium, and beryllium, which are beyond XRF’s capabilities. LIBS uses a high-energy laser pulse to create plasma, atomizing and exciting the sample surface. Unlike XRF, LIBS does not emit ionizing radiation, simplifying transport and use. However, safety precautions are still necessary due to potential risks from the near-infrared laser, which is invisible and highly focused.⁸

For in-situ retroactive use, portable XRF offers rapid, non-destructive analysis but is limited by its inability to detect light elements and the need for radiation safety compliance. OES provides highly accurate results, including carbon detection, but requires flat, prepared surfaces and is less portable. Portable LIBS excels in detecting light elements and offers greater portability without ionizing radiation, though it requires careful laser safety measures and may need matrix-specific calibration for accuracy.^1,8

Examples

In a typical PMI application within a solar power or hydrogen production facility, the process is used to verify that installed alloy components match the specified materials required for high-pressure or corrosive environments. For instance, during maintenance or system upgrades, technicians use PMI to confirm material composition in critical piping or pressure systems. This ensures that incompatible/substandard materials are not used, preventing premature failure or system leaks. Through early detection of issues, PMI helps avoid unexpected breakdowns, supports uninterrupted operation, and reduces costly downtime. The process facilitates regulatory compliance by confirming that all materials adhere to industry codes and specifications.^5,6,9,10

Commercial and Technological Landscape

Leading companies providing PMI services and equipment include Thermo Fisher, Bruker, Hitachi, and Shimadzu. Recent innovations in XRF and OES technologies have enhanced the speed, portability, and accuracy of material verification, with many new tools designed for real-time, on-site analysis. These advancements support broader adoption across clean tech industries. Green hydrogen production has embraced PMI to ensure material compliance, structural integrity, and long-term reliability in demanding operational environments.^7,9,11,12

Future Outlook

The future of retroactive PMI is closely tied to its integration with digital twins and predictive maintenance platforms, which will enable real-time material verification across clean energy infrastructure. As regulatory demands for stricter material traceability continue to grow in the clean energy sector, reliable, on-site verification is becoming more critical.

Advancements in portable and remote PMI tools are boosting field efficiency, while the rise of automated PMI in alloy production is helping streamline quality assurance throughout the manufacturing process.

References and Further Reading

1. Velu, S. (2024). Positive Material Identification (PMI) https://www.academia.edu/118860955/POSITIVE_MATERIAL_IDENTIFICATION_PMI
2. Retroactive Positive Material Identification (PMI) [Online] Available at https://www.azom.com/article.aspx?ArticleID=21873 (Accessed on 13 October 2025)
3. How Non-Destructive Testing(NDT) Helps Energy Infrastructure [Online] Available at https://gridinta.eu/how-non-destructive-testingndt-helps-energy-infrastructure/ (Accessed on 13 October 2025)
4. Iftikhar, H., Sarquis, E., Branco, P. J. (2021). Why Can Simple Operation and Maintenance (O&M) Practices in Large-Scale Grid-Connected PV Power Plants Play a Key Role in Improving Its Energy Output? Energies, 14(13), 3798. DOI: 10.3390/en14133798, https://www.mdpi.com/1996-1073/14/13/3798
5. Guidelines for Positive Material Identification (PMI) [Online] Available at https://www.piping-world.com/guidelines-for-positive-material-identification-pmi (Accessed on 13 October 2025)
6. Abdulla, H., Sleptchenko, A., & Nayfeh, A. (2024). Photovoltaic systems operation and maintenance: A review and future directions. Renewable and Sustainable Energy Reviews, 195, 114342. DOI: 10.1016/j.rser.2024.114342, https://www.sciencedirect.com/science/article/pii/S1364032124000650
7. Highlights on Positive Material Identification (PMI) [Online] Available at https://www.bruker.com/ko/applications/industrial/metals/positive-material-identification-pmi.html (Accessed on 13 October 2025)
8. Schlatter, N., Freutel, G., & Lottermoser, B. G. (2022). Evaluation of the Use of field-portable LIBS Analysers for on-site chemical Analysis in the Mineral Resources Sector. GeoResources, 2, 32-38. https://www.researchgate.net/publication/362090852_Evaluation_of_the_Use_of_field-portable_LIBS_Analysers_for_on-site_chemical_Analysis_in_the_Mineral_Resources_Sector
9. Harju, A. (2024). Project execution performance development in valve availability in renewable power and green hydrogen production industry to meet customer delivery time requirements. https://lutpub.lut.fi/handle/10024/167309
10. Overview of API RP 578 - Material Verification for New and Existing Assets [Online] Available at https://inspectioneering.com/tag/api+rp+578 (Accessed on 13 October 2025)
11. Positive Material Identification Market Size & Share Analysis - Growth Trends and Forecast (2025 - 2030) [Online] Available at https://www.mordorintelligence.com/industry-reports/positive-material-identification-market (Accessed on 13 October 2025)
12. Positive Material Identification Market [Online] Available at https://www.reanin.com/reports/global-positive-material-identification-market (Accessed on 13 October 2025)

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