Addressing Laminations in Pipeline Integrity: The NDT Global Approach

In the world of pipeline integrity, laminations present a unique challenge due to their often-misunderstood nature and potential to significantly compromise a pipeline's health. 

In this article, we’ll explore how laminations originate, the threat they pose to a pipeline's integrity, and the best techniques and methodologies for detecting them. We’ll also outline how NDT Global assesses, categorizes, and prioritizes different types of laminations using a combination of data-driven tools and the expertise of our seasoned professionals.

The Many Challenges of Pipeline Integrity Management

Increasing economic pressures on energy producers worldwide mean fewer new pipelines are being constructed. That’s forcing pipeline managers in the oil and gas industry to rely heavily on aging infrastructure while trying to find ways to improve and extend the life of these assets. 

Over time, ad hoc point repairs and improvements result in original pipeline infrastructures comprising a complex “patchwork” of varying pipe manufacturers and vintages, making it difficult to predict, assess, and detect anomalies—such as laminations—and other points of weakness.

Diverse physical environments only add to the complexity of pipeline infrastructure management. A single pipeline system may cross different terrains, temperatures, and elevations within the same run, making Inspection and maintenance extraordinarily complicated.

What are Pipeline Laminations and Why Can They Be Cause for Concern?

Laminations are planes of non-fusion within steel plates that typically occur during the pipe manufacturing process when discontinuities or porosities in the plate steel are rolled out and flattened. They are most frequently observed in older pipelines (pre-1980s) due to the less rigorous quality control mechanisms employed at the time, but it’s not impossible for them to be present in modern pipelines. 

Not every lamination represents a significant threat or risk, but some can create planes of weakness within the pipe’s interior that can compromise the pipe’s long-term health and viability. For this reason, it’s vital to identify laminations and assess their individual impact as well as potential interactions with other defects or anomalies as part of a robust pipeline integrity management strategy.  

Pipeline Laminations: Types and Risks

Laminations come in various forms, each with its own set of risks and implications:

  • Planar laminations lie parallel to the pipe wall, remain on a single plane across the middle of the pipe’s steel wall, and are generally stable.

  • Sloping laminations are inclined towards the interior or exterior surface of the pipeline, posing a higher risk.

  • Surface-breaking laminations connect directly to the internal or external surface of the pipeline, presenting a significant threat.

  • Bulging laminations protrude from the surface, indicating severe structural and integrity issues.

  • Hydrogen-induced blistering laminations have distinctive bubbles and circular patterns. Depending on their size and position, these laminations can significantly degrade the mechanical performance of pipeline steel.

  • Overlapping laminations are high-density layers that obscure inspection and assessment.

While planar laminations often don't require immediate action, most other types of laminations can significantly erode the thickness of pipelines and thus require urgent assessment and remediation.

What Technologies Are Available to Assess Laminations?

Two primary types of technology are used across the industry to assess pipeline laminations. 

Ultrasonic (UT) Metal Loss technology, which utilizes straight beam or compression wave UT, is the most common and effective way to identify and assess laminations and size metal loss

UT Crack technology, while not necessarily designed to detect and address mid-wall laminations, can also provide some value, especially when laminations have some form of radial component

NDT Global’s Approach to Detecting, Assessing, and Managing Laminations

At NDT Global, we approach laminations by uniting precision technology with deep analytical expertise. Here’s an overview of how we go about detecting, assessing, and managing laminations.

1. Detecting Laminations with UT Metal Loss Technology

UT Metal Loss technology is our primary tool for identifying and sizing laminations. 

UT Metal Loss technology provides detailed wall thickness measurements and detects mid-wall features like laminations with unparalleled clarity. It can identify planar laminations by their uniform shape and detect sloping and surface-breaking laminations due to the distinct wall thickness patterns they introduce.

As part of the assessment exercise, our teams leverage UT Metal Loss technology to take three critical measurements:

  • Reference Wall Thickness: The nominal wall thickness in the area of the lamination.

  • Slope of the Lamination: Measured at the start and end points of the anomaly.

  • Effective Length: The total length of the lamination across the pipe wall.

Using this data, they can map laminations precisely and accurately quantify reductions in wall thickness due to surface-breaking or sloping laminations. 

Addressing Complex Issues

Bulging laminations and hydrogen-induced blistering are more complex issues that our expert use of UT Metal Loss technology can detect and address effectively:

  • Bulging laminations are easily identified due to their distinctive oval patterns in wall thickness and a reduction in standoff measurements. 

  • Hydrogen-induced blistering produces circular patterns indicative of blistering within the pipeline material. Our team uses distinctive ultrasonic patterns to identify these anomalies accurately.

So, using UT Metal Loss technology allows us to not only clearly detect a wide range of laminations, but also to size them and perform the necessary in-depth assessments. 

2. Supporting Detection with UT Crack Technology

UT Crack technology (ShearWave) complements UT Metal Loss by honing in on any radial components present in sloping laminations. Sloping laminations that surface-break are particularly visible using this technology.

For instance, a sloping lamination that connects to the interior surface (ID) will produce a corner echo in the UT Crack data, signaling a surface-breaking anomaly. This echo allows our analysts to categorize the lamination appropriately and recommend appropriate remedial action.

"UT Metal Loss technology is the optimal technique to detect, identify, and size laminations. Our team's expertise ensures accurate data interpretation and actionable insights that empower better decision-making." - Ryan Sikes, Product Manager at NDT Global

Key Takeaways: Using UT Metal Loss Technology vs. UT Crack Technology
  • UT Metal Loss technology is the optimal technique for detecting, identifying, and sizing laminations. 

  • UT Crack technology should support UT Metal Loss technology in certain scenarios. For example, UT Crack technology can add significant value in cases where laminations have potential radial components—whether that's a surface breaking or an advanced sloping element. UT Metal Loss technology alone may not be able to detect radial components present in laminations.

  • It’s not possible, however, to accurately size laminations using UT Crack diagnosis technology, and any findings should be treated as informative only unless additional assessments or correlations with additional data sets are performed.

  • In cases where pipelines have dirty steel or where there’s a high prevalence of known laminations, we may recommend combining the use of these two technologies, i.e., Metal Loss technology to detect and size laminations and UT Crack technology to assess and/or eliminate the risk of associated radial components. 

  • By combining and correlating those two data sets, we can obtain a holistic view of all laminations present and perform a level of assessment that a single technology may not necessarily allow.

3. Comprehensive Categorization

Once the presence of laminations has been confirmed, and we’re clear on their nature and size, the next step is determining how they should best be addressed or if any action is required at all. (As we mentioned earlier, parallel or planar laminations don’t necessarily justify further action or assessment.)

In categorizing identified laminations (whether they were detected through the use of UT Metal Loss technology alone or in conjunction with UT Crack technology), we take into account various aspects, including:

  • The type and nature of the lamination

  • Its location and size/measurement

  • Its distance from or potential interaction with any other feature or installation

  • Whether it's manufacturing or hydrogen-induced

NDT Global’s integrity services specialists will then categorize laminations into three primary categories:

  • Category A (Insignificant): These laminations are typically planar, lie parallel to the pipe surface, and have no contact or interaction with welds or other features. As such, they don’t necessarily require additional assessment or action.  

  • Category B (Assessment Required): These laminations have varying depths—whether sloping or potentially surface-breaking—and have significant weld contact or adjoin to a weld. Additionally, any hydrogen-induced or blistering lamination would meet Category B assessment requirements. 

  • Category C (Immediate Action Required): Laminations interacting with other significant anomalies, such as metal loss or cracking.

Prioritizing Laminations

Next, let’s look at how we prioritize laminations that require additional assessment or immediate action (i.e., Those in categories 2 and 3.)

If we discover blistering laminations or those that interact with welds, we follow API 579 guidelines to assess them based on contact distance and prioritize action accordingly. Laminations within 25mm (1 inch) or twice the wall thickness of a weld are considered interacting. We then categorize these interactions into three priority levels:

  • Priority 1: Significant contact with welds requires immediate verification.

  • Priority 2: Intermediate contact, requiring verification if cracking is observed.

  • Priority 3: Clear separation from welds, considered acceptable.

The Power of Clarity™ in Action

As we’ve explored, assessing every pipeline lamination thoroughly and taking the appropriate action based on its type, category, and risk is a complex and multi-faceted endeavor.

By leveraging our "Power of Clarity" philosophy, NDT Global brings together UT Metal Loss and UT Crack technologies—and the best people—to capture the best diagnostic data. This provides pipeline operators with deep insights into their assets, empowering them to make the best decisions that ultimately ensure safety, business efficiency, and environmental stewardship.

Let us help you navigate the complexities of laminations and deliver the "Power of Clarity" for your pipeline's integrity

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