Application

Positive Material Identification

Positive Material Identification

Positive Material Identification, or PMI, is an integral part of process safety management in many industries including the petroleum refining and petrochemical. Whether the need is quality control, sorting of scrap material, or even failure analysis, materials testing to provide verification of metal alloy grade and composition is crucial to the success of many businesses.

In response to a series of accidents resulting from material mix-ups, many companies have instituted stringent Positive Material Identification programmes. Industry organisations have also worked to develop guidelines to assure that the nominal compositions of all alloy components in a process system are consistent with design specifications.

Since their introduction in 1998, Niton analysers have become the industry choice for Positive Material Identification and material testing. A combination of performance, portability, ease of use, and unparalleled attention to customer needs has made Niton the number one supplier of Positive Material Identification instrumentation. This attention to customer needs is the driving force behind the design of all our instruments.

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Thermo Niton XRF analysers can be used as a key part of the PMI needed to comply with API RP 578

Positive Material Identification | XL2
Positive Material Identification | XL5

What is API Recommended Practice (RP) 578? (Don Mears, Analytical Training Consultants (ATC) )

  • General — The purpose of this recommended practice is to provide the guidelines for a material and quality assurance system to verify that the nominal composition of alloy components within the pressure envelope of a piping system is consistent with the selected or specified construction materials to minimize the potential for catastrophic release of toxic or hazardous liquids or vapours. This recommended practice provides the guidelines for material control and material verification programs on ferrous and non ferrous alloys during the construction, installation, maintenance, and inspection of new and existing process piping systems covered by the ASME B31.3 and API 570 piping codes. This practice applies to metallic alloy materials purchased for used either directly by the owner/user or indirectly through vendors, fabricators, or contractors and includes the supply, fabrication, and erection of these materials. Carbon steel components specified in the new or existing piping systems are not specifically covered under the scope of the document.

  • Alloy Substitutions in Carbon Steel Systems - When determining the need to perform material verification on carbon steel systems; the owner/user should evaluate the effect that the process stream could have on substituted alloy materials. In some cases, the substitution of harden able alloy materials in carbon steel piping systems resulted in failure and loss of containment. Examples of such systems include hydrogen sulfide(H2S), hydrofluoric acid(HF), and sulfuric acid(H2SO4) services. Flow-Accelerated Corrosion or FAC is a well-known source of problems. FAC is a process in which carbon steel piping and components are degraded in the presence of flowing water or steam-water with low dissolved oxygen. See (Appendix Niton Application Bulletin). The research conducted has demonstrated that FAC is a complex process influenced by a number of variables. They include but are not limited to;

    • The composite of steel, principally the alloying elements of Chromium, copper and molybdenum.
    • The water chemistry in use, PH, dissolved oxygen, and temperature.
    • The flow variables including; fluid velocity, diameter, fitting geometry and upstream influences.

    According to PVP-Vol. 338, Pressure Vessels and Piping Codes and Standards, ASME 1996, of the variables listed above, both laboratory testing and plant experience have shown that the material composition, particularly the Chromium content, is the most important variable influencing FAC.

  • Roles and Responsibilities - A material verification program for piping systems may involve participation of several groups within the operating plant or the shop of a contractor, vendor, or fabricator. When establishing a material verification program. Consideration should be given to the roles and responsibilities that each group has within the specific organisation. These roles and responsibilities should be clearly defined and documented. Within the operating plant, this can include those groups responsible for purchasing, engineering, warehousing receiving, operations, reliability, maintenance, and inspection. Copyright © 2008 Analytical Training Consultants (ATC).