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 matches a given specification. 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 due to a wider variety of alloys that are indistinguishable to the eye.
Today, many major oil and chemical companies require that every pipe, flange, connector, valve and welding seam in critical parts of their facilities be measured to verify that materials match engineering specifications. In addition to compatibility issues, several other reasons can exist for material specification including design, corrosion resistance, and compliance to codes and standards such as the ASME Boiler and Pressure Vessel Code.