A Guide to API Recommended Practice 578, 3rd Edition

In February 2018, the American Petroleum Institute (API) released its third edition of Recommended Practices (RP) 578, titled, “Guidelines for a Material Verification Program for New & Existing Assets.” Almost two years later, the new guidelines are still not widely known despite substantial modifications and updates that help make sure oil and petrochemical companies have implemented an appropriate asset integrity program.

Since an “asset” is any metal used in oil and gas, these recommended practices apply to practically all of the oil and gas industry, making API 578 a crucial part of business operations.

Material Verification

Most significantly, it is evident from the latest edition that it is now a requirement for all oil and petrochemical systems owners/users to implement an effective Material Verification Program (MVP). It also advocates Positive Material Identification (PMI) for ferrous and non-ferrous alloys during the construction, installation, maintenance, and inspection of new and current process equipment.

It is applicable to metallic materials bought for use either directly by the owner/user or indirectly through contractors, distributors or fabricators, and includes the supply, fabrication, and installation of these materials. Guaranteeing the integrity of all oil and gas assets, not only alloy piping systems, reduces corporate risk by further limiting the release of hazardous substances that can occur with nonconforming construction materials.

API RP 578 identifies seven areas of consideration and general concern in material verification, mainly relating to the systems that are most vulnerable to corrosion. Knowing which assets are in danger of corrosion and what elements ought to be tested are vital parts in establishing an effective MVP that utilizes the latest and most appropriate PMI technology.

Technology

Alloy substitutions for carbon steel, carbon steel substitutions in low alloy steel systems, residual elements in carbon steels in hydrofluoric acid alkylation units, and process units susceptible to sulfidation are all at high-risk for heightened corrosion rates.

Optimizing these systems relies upon which alloy is used, which can be hard to determine as, to the human eye, all of them look identical. PMI technology can distinguish different alloys, detect carbon content and identify residual elements.

To be able to carry out PMI, testing can be conducted with any of the three analytical technologies referenced in API RP 578: Laser-Induced Breakdown Spectroscopy (LIBS)X-ray Fluorescence (XRF), or Optical Emission Spectroscopy (OES).

Laser-Induced Breakdown Spectroscopy (LIBS)

Included in the third and latest edition of API RP 578, LIBS is a powerful analytical technique that utilizes a laser to ablate the surface of a sample, which causes it to emit characteristic wavelengths of light that the analyzer can detect and indicate the elemental content of.

While this process may sound complicated, LIBS analyzers are simple to use and available as a portable handheld device. It is seen as a minimally destructive technique, requiring little sample preparation, and delivers results in seconds. Some LIBS analyzers can also detect carbon content in various alloys.

X-Ray Fluorescence (XRF)

XRF analyzers utilize X-rays to excite the surface of a sample, which then emits fluorescent X-rays that are unique to each element. XRF analyzers are simple to use thanks to their point and shoot capability, they are non-destructive and provide immediate results. However, unlike LIBS, XRF analyzers can’t detect carbon content.

The latest XRF analyzers are fitted with silicon drift detectors (SDD) that allow it to sense light elements, including sulfur, aluminum, magnesium, phosphorus and silicon. The third edition of API RP 578 stipulates that these devices should be used, especially for refractory instillation units (anchors) which at one time were not possible to test at all.

Optical Emission Spectroscopy (OES)

The third technology included in API RP 578 is OES. OES utilizes electricity to excite the sample to create a reading, which means it is necessary to obtain a hot work permit and in bad weather, it cannot be used outside. The technique is also destructive as it melts the surface of the sample a small amount. OES, similar to LIBS, can sense carbon, but unlike LIBS and XRF, a handheld instrument version is not available, and it needs greater expertise to operate. OES is usually housed in a sizable system that must be carried in a large backpack or moved via pushcart, which can be hard to use in the field.

Of every available technology, XRF analyzers are a user’s primary PMI tool, due to their mobility and simplicity to use. However, LIBS can and should be employed wherever carbon detection is necessary as it doesn’t sacrifice portability or simplicity. These are complementary technologies that enable oil and petrochemical systems owners/users to guarantee the integrity of all their assets.

Trust, But Verify

Verifying the integrity of every asset is becoming more critical in a globalized market as numerous businesses are buying material from overseas and from vendors they may be working with for the first time. Undependable or inexperienced contractors occasionally try to save money by not carrying out PMI or by using an external testing lab to validate the material they ship out. This means their accompanying Mill Test Reports are not always precise and a “trust but verify” approach is required to verify the chemical makeup of the alloy.

Employing API Recommended Practice 578 will aid oil and gas asset owners and users in implementing and maintaining a reliable MVP as part of their overall asset integrity management system. With new analytical technology, such as LIBS and XRF analyzers, it is possible to efficiently follow these guidelines, help reduce corporate risk, ensuring employee safety and highly efficient business operations.

Acknowledgments

Produced from materials originally authored by Don Mears, Oil and Gas Specialist from Thermo Fisher Scientific.

This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific – Handheld Elemental & Radiation Detection.

For more information on this source, please visit Thermo Fisher Scientific – Handheld Elemental & Radiation Detection.

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