Ensuring material integrity in refining operations is critical for employee safety, regulatory compliance, and successful downstream oil and gas operations. As analytical techniques advance through modernization and research, so does the ability to protect downstream refining operations.
A key example is protection from corrosion in carbon steel piping. This is particularly a risk in the hydrofluoric (HF) alkylation units in refineries where hydrofluoric acid is used to create high-octane gasoline. Generally, iron fluoride scales protect the carbon steel piping from the acid. However, carbon steel’s residual elements of nickel, chromium, and copper can hinder that protection. If left undetected, corrosion can build up in the piping, leading to significant risk and potentially catastrophic damage.
Elemental analysis with handheld X-ray fluorescence (HHXRF) analyzers can help downstream facilities analyze the integrity of installed carbon steel piping and new piping from suppliers. Already installed piping in refineries may include residual elements from recycled materials used to create it before detection limits for nickel, chromium, and copper were reachable at today’s levels.
The properties of carbon steel
The exact chemical composition of carbon steel can impact its durability and performance; it’s often specifically formulated to ensure characteristics for the application that steel is anticipated to perform. Such formulations can impact the characteristics of steel, like its:
- Strength
- Ductility
- Corrosion resistance.
Residual elements refer to an unintended elemental composition from the raw materials that went into making the carbon steel. For carbon steel piping in HF alkylation units, the residual elements of particular concern include:
- Copper
- Nickel
- Chromium.
The American Petroleum Institute (API) recommends a general formula for keeping the sum of copper, nickel, and chromium in carbon steel piping for HF alkylation units below 0.15%. Any sum above that level can degrade the piping’s corrosion resistance and put both people and operations at risk. HHXRF analysis can help operators determine the integrity of installed piping or new supplies to determine the risk of corrosion. This is part of the positive material identification (PMI) work in oil and gas to ensure safety and operational success.
Of the three residual elements that can add up to put piping at risk in HF alkylation units, nickel is the most difficult to adequately detect at low levels, given that its elemental signature overlaps with iron. That means any PMI analysis to ensure the integrity of piping in HF alkylation units needs to be capable of detecting copper, chromium, and nickel at low levels to help ensure the sum stays below the 0.15% threshold.
Using XRF elemental analysis to measure residual elements
Even minor components in steel, such as a single elbow joint, can lead to significant problems.
Implementing modern elemental analysis techniques is crucial to mitigate risk. HHXRF analysis offers a nondestructive method to accurately detect and quantify the presence of copper, nickel, and chromium in carbon steel. HHXRF analyzers enable onsite elemental analysis, providing immediate insights into the piping’s composition and potential vulnerabilities.
By identifying critical levels of residual elements through XRF analysis, operators can make informed decisions regarding the following:
- Piping integrity and replacement
- Maintenance
- Operational safety
These choices enhance the overall safety and longevity of the downstream operations.
Ensuring operational safety
Adopting HHXRF analysis in refineries utilizing hydrofluoric (HF) acid in alkylation processes is not just a preventive measure against equipment failures. This is an integral part of ensuring the operational integrity and safety of the facilities.
HF acid’s corrosive nature can aggressively attack carbon steel pipes. The pipes might contain varying levels of residual elements, such as nickel, copper, and chromium. These elements can significantly alter the corrosion resistance of the steel, potentially leading to accelerated degradation.
Variabilities in the composition between different batches of pipes or at connected junctions can further complicate the issue. HHXRF analysis enables onsite monitoring of piping materials to confirm that they adhere to strict specifications. This helps manufacturers to avoid unexpected shutdowns, costly repairs, and environmental fines.
More importantly, HHXRF analysis enables refineries to predict equipment lifespans more accurately. This can help make informed decisions about maintenance and replacements, ensuring continuous and safe operation.
The future of managing residual analysis
There are numerous incidents that could be cited as examples of where ensuring material integrity for safety and reliability in the oil and gas industry could have improved or avoided adverse outcomes. Even when minor in concentration, residual elements in carbon steel can lead to significant problems if not properly managed.
Implementing HHXRF analysis for PMI is a step toward more robust regulatory compliance and safer operations.
Thinking about using handheld XRF analysis?
Analytical chemistry and solid-state analysis can help us uncover the elements that characterize different materials. XRF analysis plays a crucial role in numerous industries to ensure optimal material performance. HHXRF analysis can be used in industrial environments to more quickly ensure that materials are safe to use and meet identified standards.
References and Resources
- Philadelphia Energy Solutions (PES) Refinery Fire and Explosions. U.S. Chemical Safety and Hazard Investigation Board. https://www.csb.gov/philadelphia-energy-solutions-pes-refinery-fire-and-explosions-/. Accessed 19th February 2024.
- 2. API RP 751-2021 Safe Operation of hydrofluoric acid alkylation units, American Petroleum Institute, Washington, DC
- 3. API RP 571-2020 Damage mechanisms affecting fixed equipment in the refining industry, American Petroleum Institute, Washington, DC
- Video: Using XRF on carbon steel piping
- Application Note: Rapid analysis of residual elements in carbon steel piping from hydrofluoric acid alkylation units
- Visit our PMI web page to learn more about keeping your operations safe and successful: www.thermofisher.com/pmi.
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