Inspecting Beyond the Curve with IRIS

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Industrial boilers have been integral to various applications for over a century, providing steam for propulsion systems in ships and other vessels. However, the harsh working environment exposes boiler tubes to factors such as wall thinning, which can compromise their integrity. The Internal Rotary Inspection System (IRIS) has proven to be an effective inspection technique for assessing boiler tube conditions. Nonetheless, conventional IRIS components face limitations when inspecting complex tube designs, such as those featuring S-shaped vertical tubes. This application note explores the challenges associated with inspecting vertical boiler tubes with elbows and presents an innovative solution using a flexible IRIS probe.

The Challenge

To employ ultrasonic testing through an internal rotary inspection system to assess the straight sections of vertical boiler tubes that include elbows.

Boiler tubes are subject to high temperatures and the potential presence of sulfur oxides under normal operations. Over time, these conditions can lead to the development of damage mechanisms such as inner erosion or outer corrosion, which can pose significant problems. While internal rotary inspection system inspection is known for providing accurate thickness measurements, the shape of boilers that feature vertical tubes with bent sections limits the use of this technique. This makes them impossible to scan using conventional IRIS probes. Furthermore, the accessibility to the boiler tubes may be restricted, limiting the inspection to the lower end only. This presents a set of interconnected challenges that need to be addressed: negotiating the bends to inspect the straight sections of the tube, providing local immersion of the steam turbine during inspections from the lower end of the vertical tubes, and ensuring proper turbine centering to avoid signal loss caused by a misaligned IRIS probe.

The Solution

A flexible internal rotary inspection system probe capable of passing through elbows with a specified bend radius for two specific tube lines.

To achieve the goal of inspecting the straight parts of the boiler tubes, a significant challenge is encountered when the probe needs to pass through sharp elbows. Not only does the new solution need to travel through these elbows, but it also must provide better coverage at the bend vicinities. The image provided demonstrates that only a 50-millimeter (2-inch) section before the bend is unable to be inspected because the turbine and centering device are shorter than standard components.

In response to these challenges, we developed a flexible internal rotary inspection system solution that incorporates a centering device integrated with the turbine. This petal-shaped centering device offers the rigidity necessary to keep the turbine properly centered while providing the flexibility required to negotiate bends smoothly. In addition to this feature, the shortened transducer and turbine head prevent the tips of the turbine from rubbing against the tube’s inner surface, ensuring better centering closer to the bends. The versatility of the flexible IRIS probe kit is enhanced by interchangeable centering devices, allowing the inspection of different inner diameter tubes. This probe has been designed to pass through two tube lines featuring a 120-mm (4.7-in) bending radius with a 75-degree elbow. More specifically, this probe can operate in a 31.8-mm (1.3-in) outer diameter (OD) tube with an inside diameter (ID) ranging from 19.8 to 21.2 mm (0.78 to 0.83 in) and a 38.1-mm (1.5-in) OD tube with an ID ranging from 26.1 to 27.5 mm (1.03 to 1.08 in).

Similarly, two interchangeable foam-loaded holders are used to retain water as the vertical tubes are inspected from their lower end. Just like a standard IRIS probe, the turbine spins as water flows through it. Because of the holders, water collects and floods the tube at the turbine’s location. This simple yet efficient design quickly immerses the probe head and further aids in centering the probe accurately.

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  • Enhanced flexibility and bend negotiation for inspecting challenging boiler tube configurations with elbows.

The tailormade IRIS solution offers the capability for ultrasonic testing of boiler tubes that are typically challenging to access due to their severe bends. This solution enables efficient inspection of such tubes that would otherwise be inaccessible. Specifically, it provides internal rotary inspection system local immersion for vertically oriented tubes to ensure thorough examination of the tube surfaces. Moreover, the design improvements result in good coverage at the bend vicinities, where potential issues are commonly found.

This innovative redesign of the existing IRIS technique not only overcomes the limitations posed by tube bend configurations but also establishes a path for internal rotary inspection system inspection in new tube lines. By successfully addressing the challenges associated with negotiating bends, providing local immersion, and ensuring proper centering, this tailored solution contributes to enhanced inspection capabilities, improved safety, and increased efficiency in industrial boiler operations.

For tailored learning opportunities focused on IRIS probe and other tube testing inspection techniques visit the online Eddyfi Academy. Contact our experts for more information or visit the eStore to build a custom quote today!