Pressure swing adsorption (PSA) vessels create and separate gases using a high degree of pressure. The PSA process can be implemented across a large range of applications and is commonly utilized by oil and gas refineries to purify hydrogen.
With this process, gases and impurities are filtered from the feed stream by being adsorbed onto solid surfaces at high pressure levels and desorbed at lower pressures. The higher the pressure, the more gases are adsorbed. While high pressure increases operational efficiency, it also increases the risk of structural issues that can lead to catastrophic failures and dangerous explosions.
Learn about some of the common damage mechanisms found in PSA vessels and what can be done to identify and address problem areas to optimize safe, reliable operations.
Understand and Mitigate Risks for Seamless Operations
Having knowledge of vulnerabilities and potential issues in facility infrastructure is critical in maintaining safe, uninterrupted operations. In an attempt to help mitigate risks and disruptions, many facilities develop risk based inspection (RBI) programs.
As defined by Inspectioneering, a risk based inspection is a process that, “requires qualitative or quantitative assessment of the probability of failure (PoF) and the consequence of failure (CoF) associated with each equipment item, piping circuits included, in a particular process unit. A properly-implemented RBI program categorizes individual pieces of equipment by their risks and prioritizes inspection efforts based on this categorization.”
This method helps in optimizing maintenance plans through improved risk management, enabling sites to maximize their resources and investments in the assets that have the highest probability for failure. The evaluation considers several different factors, including an asset’s safety, health, financial, and environmental risks to effectively construct inspection and maintenance strategies.
Once assets have been categorized and assigned a risk value, the site can begin prioritizing its next steps. The equipment that poses the highest risks will be addressed first in an attempt to reduce the number of failures and unplanned outages. PSA vessels are often prioritized assets in risk based inspections due to their extremely volatile nature.
Common Damage Mechanism in Pressure Swing Adsorption Vessels
In determining an asset’s operational risk, a site will evaluate the known and potential damage mechanisms, and then estimate the consequences of a failure due to the identified damage mechanisms.
Fatigue cracking, which is caused by cyclic or fluctuating stress over an extended period of time, is a common damage mechanism found in PSA vessels due to the cyclic nature of a swing adsorber. It’s common for fatigue cracking to occur near a stress riser, like the junction point between the weld metal and base metal.
Once a fatigue crack forms in the material, continued exposure to cyclical stress can magnify the issue and cause the crack to grow. Additionally, environmental factors, like thermal conditions, corrosion, or hydrogen embrittlement, can also contribute to the acceleration of fatigue cracking and crack growth.
PSA vessels experience repeated pressure cycling and have exposure to high-purity hydrogen gas which can aggravate fatigue cracking, causing cracking and crack growth to occur all too often. If left unidentified or unaddressed, cracks can lead to major structural integrity problems for the asset and even explosions, presenting dangerous safety risks for facility personnel.
Expand Visibility into Asset Health to Detect and Monitor Damage
Routine inspections contribute to the overall safety, sustainability, and reliability of assets. Due to the inherently dangerous nature of the hydrogen production and separation processes, PSA vessels should be inspected thoroughly and on a routine basis for ongoing monitoring.
To make that possible, it is important to implement an inspection solution that enables in-depth data gathering to establish a current baseline of asset health and accurately track progression in subsequent inspections. Accurate, consistent, and repeatable inspection procedures will help in building an effective RBI program, ensuring individual assets are safe for continued use.
However, not all inspections are created equal. Traditional manual inspection methods often require sites to construct scaffolding to reach areas of the asset, which adds extensive time, resources, safety risks, and costs to a project.
Manual ultrasonic testing (UT) captures one reading per distance or grid, making it difficult to find localized corrosion or defects. Only collecting data from select points provides sparse coverage, which may not accurately identify the full extent of damage mechanisms or may completely miss them altogether. Not only do these methods lack data quality, but they are extremely time consuming to conduct. With reduced coverage, accuracy, and time efficiency, many companies turn to automated ultrasonic testing (AUT) solutions.
By design, robot-enabled AUT has the mobility to access hard-to-reach and hazardous areas, eliminating the need for scaffolding while expanding the amount of data coverage. This provides a more comprehensive assessment with a holistic view of asset conditions for confident RBI analysis and decision making.
A robust amount of data is gathered, which increases the quality and probability of damage detection. Continuous readings are captured across the asset rather than specific, predefined points that can leave gaps in coverage. Also, robots use encoders to determine their location on an asset, making it easy to conduct the same inspection again in the future to monitor the progression of damage.
Robot-enabled AUT inspection techniques provide better visualizations for more confident RBI assessments because of their advantages related to access, coverage, efficiency, and data quality. Phased Array Ultrasonic Testing (PAUT) is an optimal method for inspecting PSA vessels, inspecting both sides of welds and heat-affected zones simultaneously to provide in-depth data at speeds significantly faster than conventional AUT. By utilizing automated PAUT, sites can gain visibility into the health of all weld seams, heat-affected zones, flanges, and any other areas prone to cracking or other damage mechanisms. Due to its comprehensive data capture, the probability of detection is drastically improved over traditional methods.
To complement PAUT, Rapid Automated Ultrasonic Testing (R-AUT) can also be performed for generalized or localized corrosion mapping of the asset. R-AUT provides high-density phased array UT data for in-depth analysis, collecting over 94,000 thickness readings/ft2 (1 million readings/m2) at speeds 5x faster than conventional AUT.
Pairing inspection technologies like PAUT and R-AUT results in high-quality, spatially dense data to create corrosion maps and weld scan data visualizations to easily identify and track damage without putting humans in harm’s way.
Increase Confidence in Your Inspections and Operations
Leveraging best-in-class inspection technologies will provide unprecedented data insights that empower impactful decision making. When choosing an inspection method, make sure to select a solution that is repeatable and provides ample data coverage to reduce costs and safety risk factors while improving reliability and operational uptime. By gaining a data-rich, in-depth understanding of asset health, you will confidently achieve your RBI program goals and maintain seamless operations today and in the future.
Download this case study to discover how a leading petroleum company avoided extremely dangerous outcomes by performing thorough, proactive robotics inspections of their PSAs.