Positive Material Identification (PMI) is one of the more specialised NDT methods. PMI serves critical roles in instances where material certificate is missing or it is not clear what the composition of a material is.
This method can be used on ferrous and non-ferrous alloys in order to identify, detect and quantitatively measure elements such as Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Zirconium, Selerium, niobium, Tin, Copper, Lead, Tantalum, etc. A PMI involves various methods such as XRF and Spark emission.
The PMI equipment contains low radioactive sources (isotopes) or x-ray tubes. The material analysed reflects the radiation, generating energy. Because every element has its unique atomic structure, this reflection will generate a different energy level for every element. This energy is measured and detected, thus identifying the alloy elements.
Spark Emission Spectrograph
Spectography is based on optical emission. The material being analysed is vaporized by a spark generated by the PMI equipment probe. The vapor produced consists of the atoms and ions which produce a spectrum that can be optically measured and then recalculated to determine the components of the material. The exposure of radiation is sufficiently low during PMI, thus, extra safety measures are not required.
We perform the test in accordance to ASTM 1476: Standard Guide for Metals Identification, Grade Verification, and Sorting