Codes and Specifications for Mitigating Corporate Risk

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One customer site survey revealed that as many as 20-30% of MTRs did not match the actual chemistry. Also, reports can be lost or misfiled and material may be labeled incorrectly. Different heat numbers – identification numbers assigned by a mill for the melting of metal to make a new product – with the same material chemistry have been reported. This is where positive material identification (PMI) enters the equation and “trust but verify” should become the focus.

Today, the methods used to manufacture metal—as well as the various countries in which the foundries are located—present the fabricator, supplier and owner/user of these products with numerous challenges when it comes to quality assurance and control of manufactured materials. This was pointed out by the Pipeline and Hazardous Materials Safety Administration (PHMSA) in a Plains Justice report, “Use of Substandard Steel by the U.S. Pipeline Industry 2007 to 2009.”

The report advises pipeline operators of material problems and inconsistent chemical properties (yield and tensile strengths) that have been found in micro-alloyed, high-strength line pipe grades, generally grade X70 and above. Some pipe material did not meet the requirements of the American Petroleum Institute (API) Specification for Line Pipe 5L (API 5L), 43rd edition, for the specified pipe grade even though the pipe supplier provided documentation that the pipe meet these minimum standards. It suggests that pipeline operators closely review manufacturing specifications for the production and rolling of steel plate. A number of pipe mills provided pipeline suppliers from India, Ukraine, Korea, China and Mexico with sub-standard (API 5L X70 standard) pipe, specifically low and variable yield and tensile strength and chemical composition properties in high strength line pipe. Material verification reported low or no manganese, vanadium, niobium, molybdenum and titanium.

This problem was caused by a combination of three factors: improper steel chemistry; improper rolling of steel plate; and improper segregation of various grades of steel slabs at the steel mills.

Metal manufacturing and processing requires precision at the elemental level, but with globalized trade in scrap metal, the rise in counterfeit metals, and the possibility of inaccurate MTRs, all participants in the metal industry—suppliers, distributors, inspectors and industrial consumers—are at risk of alloy mix-ups. Incorrect or out-of-specification alloy grades can lead to potentially catastrophic equipment failures.

The importance of positive material identification

In order to mitigate corporate risk, operations and construction personnel need to verify that they are using the correct materials. The material verification process compares the data in MTRs per line pipe and components, so that the heat number from the steel fabricator’s MTR is qualified and confirmed at the start of the project. Performing this level of verification also provides comprehensive records of material chemistry verification for a construction quality program.

Such actions are considered “recognized and generally accepted good engineering practice” (RAGAGEP). By definition, API RP 578 is: “Engineering, operation, or maintenance activities based on established codes, standards, published technical reports or recommended practices (RP) or a similar document. RAGAGEP details generally approved ways to perform specific engineering, inspection or mechanical integrity activities, such as fabricating a vessel, inspecting a storage tank, or servicing a relief valve (See CCPS [Ref. 33]).”

These actions also offer a cost/loss benefit ratio because they increase pipeline safety and reduce the chances that incorrect material might enter the construction process and the finished product. They provide proof to regulators that the pipe, valve, components, fittings, welds, and the entire pressure containing envelope material’s MTR chemistry is verified as required by project quality programs and owner requirements.

Understanding X-ray fluorescence technology

X-ray fluorescence (XRF) analyzers play an important role in any industry where positive material identification (PMI) and elemental chemistry are critical.

Using handheld XRF spectroscopy technology, nondestructive PMI testing of piping and components can be done in situ without shutting down process equipment or sending material samples off site. Analyzers can instantly verify the quality and composition of metals at the point of delivery, on the production line, or at finished product inspection points. With lab-quality results delivered in seconds rather than the days or weeks it can take for a traditional testing laboratory, production delays can be avoided, safety compliance achieved, and customer expectations met.

XRF spectroscopy technology, which was first used in the 1950s, analyzes the composition of a sample by measuring the spectrum of the fluorescent x-rays emitted by the different elements in a sample when it is bombarded with high-energy x-rays. Each of the elements present in a sample produce a unique set of characteristic x-rays that is a “fingerprint” for that specific element.

Over the years, improvements in XRF technology have led to the development of the current handheld instruments that use x-rays emitted from a miniaturized x-ray tube.

“When the operator pulls the trigger on an XRF analyzer, the x-ray tube powers up and sends a primary x-ray beam into the sample,” says Debbie Schatzlein, R&D staff scientist, portable analytical instruments for Thermo Fisher Scientific. “The primary x-ray beam impinges the sample – in this case metal alloy- then a spontaneous process occurs at the atomic level releasing energy in the form of fluorescent x-rays,” she continues.

These fluorescent x-rays are measured by the detector, which can both identify the element (x-ray energy is specific for individual elements) and quantify it (based on the intensity of those specific energies).

“The calculated concentrations of the individual elements are also compared to an on-board alloy library, so that the instrument not only displays the concentration of elements but also immediately identifies the alloy as well,” Schatzlein adds. The newest developments in handheld XRF analyzer technology incorporate an x-ray source, detector (silica drift detector, or SDD), digital signal processor (DSP), central processing unit (CPU), and a data storage device.

Using various spectral processing algorithms, the CPU mathematically analyzes the spectral data to produce a detailed composition analysis. For metal alloy samples, the resulting data is then compared against an internal alloy library of minimum/maximum specifications to determine an alloy grade (or other designation) for the tested material. The composition data and any resulting grade identification is then displayed on the instrument screen and stored in memory.

The technology is capable of simultaneously identifying 30 of the most common elements, and can detect elements as light as magnesium (atomic no. 12) to those as heavy as uranium (atomic no. 92).

Conclusion

There are not always shortcuts to verifying material chemistry, but breakthroughs in technology have made the process more efficient for QA/QC project managers. The most critical steps for verifying material chemistry include:

• “Trust but verify” MTRs by checking the material chemistry with x-ray fluorescence (XRF) technology on all valves, pipes, components, etc. before they are manufactured or installed in the field.
• Compare the MTRs per line pipe and components to confirm the heat number for the mill’s MTR (random per heat number).
• Provide complete records of material chemistry verification for construction quality program and operations.
• Verify correct materials to mitigate corporate risk.
• Improve and ensure the quality and performance of the XRF operator by applying the API 578 PMI certification to requirements.
• Consider what the cost/loss benefit ratio would be because of increased pipeline safety and reduced chance of incorrect material entering the construction process or finished product.
• Provide proof to regulators that pipe MTR chemistry is being verified as required by project quality programs and owner requirements.

Maintaining this disciplined approach through a PMI program can help reduce risk and increase productivity – both critical components to a company’s overall success.

Author Information
Don Mears is an API-certified training provider for Analytical Training Consultants, author of the API 578 PMI Certification Course and an oil & gas consultant. Mark Lessard is market development manager, portable analytical instruments for Thermo Fisher Scientific.

Photos courtesy Thermo Fisher Scientific.  

BONUS: Pipeline Networks in the United States

PMI of piping material is an integral component to maintaining the structural integrity of oil and gas pipelines, and XRF technology allows operators to meet various challenges, as well as the newest recommended practice from the API.

More than 190,000 miles of liquid petroleum pipelines traverse the United States. They connect producing areas to refineries and chemical plants while delivering the products American consumers and businesses need. Pipelines are safe, efficient and, because most are buried, largely unseen. They move crude oil from oil fields on land and offshore to refineries, where it is turned into fuels and other products, then from the refineries to terminals where fuels are trucked to retail outlets. Pipelines operate 24 hours a day, seven days a week.

Natural gas is delivered directly to homes and businesses through local distribution lines from local distribution companies. Large distribution lines, called mains, move the gas close to cities. These main lines, along with the much smaller service lines that travel to homes and businesses, account for the vast majority of the nation’s 2.4-million miles of underground pipeline system.

The focus on testing and verifying piping material as it relates to pipeline safety, specifically in vintage pipelines and components, is a priority for API. XRF technology can play a critical role as pipeline operators adhere to the newest standard – API RP 1173 – which was rolled out in July 2015 as a joint endeavor by the Department of Transportation (DOT) Pipeline and Hazardous Materials Safety Administration (PHMSA), NTSB, PHMSA and other entities.