Positive Material Identification (PMI) is a term that refers to the analysis and identification of materials through various nondestructive methods. PMI is able to determine the alloy composition of materials, and is a well-established technique that can either be performed in the field using handheld devices or in a laboratory.
PMI is an effective tool in situations where, for whatever reason, the material certificate for a component has been misplaced, destroyed, or is otherwise missing. It can be used in any situation where there is uncertainty about the material composition of a component.
There are several nondestructive examination (NDE) methods that can be used for PMI. Two of the more popular are X-Ray Fluorescence (XRF) and Optical Emission Spectroscopy (OES).
XRF works by exposing the material to be tested to an X-ray, causing the material to emit its own secondary X-rays in response. The levels of X-rays emitted by any particular material are always consistent based on the composition of that material. Thus by analyzing the secondary X-rays it is possible to determine the chemical composition of any unknown material. However, it should be noted that XRF cannot distinguish between material grades in certain elements such as carbon and silicon, among others.
OES works by exposing the material to an electrical spark and an electrode, often in an atmosphere of Argon. This spark works in a similar way to the X-rays in that it forces the material to emit light, which will differ in color and intensity based on the material that it is emitted from. It tends to offer a more complete view than XRF, and is the only method that can distinguish between levels of carbon in a material. While OES is considered a nondestructive method, it requires grinding the material for surface preparation and the process does cause slight burning on the surface as well.
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September/October 2018 Inspectioneering Journal
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The best approach for better inspection confidence and long term asset integrity is to conduct baseline inspections upon receipt of an asset. Baseline inspection can save millions by providing accurate baseline information for later comparisons and preventing safety incidents caused by critical oversights during the construction phase. |
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March/April 2016 Inspectioneering Journal
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March/April 2015 Inspectioneering Journal
By Paolo Torrado at Engineering and Inspection Services, LLC.
An issue that arises frequently in the oil and gas industry is poor or missing documentation of pressure vessels. It is common in the industry to repurpose old equipment, bring equipment back into operation after a long period of time out of service, or rerate equipment due to debottlenecking of process units. |
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Blog
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November/December 2013 Inspectioneering Journal
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January/February 2011 Inspectioneering Journal
By John Reynolds at Intertek
In the first article in this series entitled How to Put It All Together - Guide to Organizing a Successful PEI Program, (1) I provided an overview of the necessary Management Systems (MS) for a successful program to achieve excellence in pressure equipment integrity (PEI). This is the sixth article in that series. |
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November/December 2004 Inspectioneering Journal
By John Reynolds at Intertek
Unfortunately there is a recurring theme of pressure equipment integrity incidents in the hydrocarbon process industry which has been identified by the API and that is leaks and fires caused by the inadvertent substitution of materials of construction in piping systems - the so called positive materials identification (PMI) incidents. |
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July/August 2004 Inspectioneering Journal
By John Reynolds at Intertek
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May/June 2000 Inspectioneering Journal
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September/October 1995 Inspectioneering Journal
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