Positive Material Identification (PMI) is one of the more specialized non destructive testing methods. With positive material identification the alloy composition of materials can be determined. If a material certificate is missing or it is not clear what the composition of a material is, then PMI offers the solution. Because specifications for materials used in industry are increasingly more specific, the need for PMI testing has been on an increase for the past several years. Periodic plant maintenance shutdowns are less frequent and consequently the materials used in the plant are in use longer. A wider variety of alloys that are indistinguishable to the eye are being used in process plants. When facility and inspection staff replace components, they must be able to guarantee that the new part matches required specifications. Recent industrial accidents have cost the lives of workers and heightened the awareness of the need for accurate and comprehensive PMI inspections.
The X Ray Fluorescence is one of the very useful methods for PMI. The equipment used in this method contain x-ray tubes or low radioactive sources (isotopes). The material, which is exposed reflects the radiation and generates energy. Each & every element has its own automic structure and this is why, the reflection generates different energy for each element. It is when this energy is measured and recognized, then the alloy elements are identified.
Spark Emission Spectrography is another method for PMI. This method is based on the optical emission. All the same, it is essential that the surface is uniform to the material. Coatings, Dirt and Oxides on the material will affect the identification results. Not only this, the surface should also be very smooth. By using the PMI methods, you can identify the elements like Cr, Mn, Nb, Mo, Co, Fe, Zn, Ni, Ti, V, Cu, Se.
Extra safety measures are not needed because the exposure of radiaiton is sufficiently very low. If you are dealing with preventive maintainence of technical installations and exploitation licenses, then the NDT / NDE (Non Destructive Testing and Examination) are indispensable techniques. These techniques also provides the necessary guarantees when business security, expense saving, quality and business safety is in order for both new and existing installations. Not only this, these techniques also decrease the risk of leakage as well as other defects. This increase the business safety and integrity within the installation and can save expenditure.
In today's times, all the prominent companies require that every flange, valve, pipe, connector and welding seam in critical parts of the plant be evaluated to confirm that materials match the engineering specifications. Apart from the compatibility issues, there are many other reasons that can exist for material specification consisting corrosion resistance, design and adherence to codes as well as standards like Pressure Vessel and ASME Boiler Code. It also finds applications in the below mentioned areas.