Corrosion Under Insulation (CUI) remains a persistent and expensive challenge in the process piping industry. In refineries, petrochemical plants, and offshore platforms, insulation often conceals degradation until it is advanced, posing safety risks, impacting reliability, and driving up maintenance costs. Asset owners and inspection teams need reliable methods to screen for CUI without the time, labor, and expense of full insulation removal.
Real-time radiography is one method that supports efficient screening of insulated piping. It enables inspectors to identify early signs of corrosion with minimal disruption, using portable X-ray systems that provide immediate imaging feedback. This post outlines how the method works, where it fits into inspection programs, and what to consider during implementation.
Understanding Real-Time Radiography for CUI
Handheld real-time radiography systems use a low-energy X-ray source and a digital detector to provide a live view of internal piping. The display updates dynamically as the operator moves the device, allowing continuous scanning. Operators can capture video or still images for documentation.
Unlike traditional radiography, this method does not require film processing or large-scale setup. The image output can be viewed using wired monitors, integrated glasses, or wireless displays.
Inspection Workflow and Operator Tasks
Real-time radiography is used as a first-pass screening tool to identify corrosion-susceptible inventory (CSI) across long runs of insulated piping. Systems like OpenVision™ DX allow technicians to move quickly along the pipe surface, visually identifying signs of corrosion such as blistering, internal scale, or insulation deformation without removing insulation.
The basic workflow includes:
- Select the target pipe section based on accessibility, visual cues, or inspection history.
- Adjust the system to the pipe’s diameter by collapsing the C-arm and positioning the handles for comfort.
- Initiate scanning after a 5-second countdown and safety alert, allowing the operator to move the device across the pipe’s surface while observing the real-time image.
- Visually assess for signs of CUI, such as internal blistering, corrosion product buildup, or wall thinning indicators.
- Capture images or video as needed. Data is saved to local storage (e.g., USB) for post-inspection analysis or reporting.
Where Real-Time Radiography Fits in the Inspection Process
Corrosion under insulation is typically assessed using multiple non-destructive testing (NDT) methods. Each has specific use cases, advantages, and limitations. The most common methods include:
- Ultrasonic Testing (UT): Measures remaining wall thickness. Typically requires removal of insulation at the inspection location for accurate probe contact [1].
- Pulsed Eddy Current (PEC): Measures wall loss through insulation using electromagnetic signals. While effective for localized screening, PEC can be slower than real-time radiography for long piping runs due to scan time per point [2].
- Guided Wave Testing (GWT): Long-range screening along bare or partly stripped pipe. Useful for inaccessible areas [3].
- Traditional Film Radiography: Provides high-resolution internal imaging. Requires more setup time and radiation safety precautions.
- Visual Inspection: Performed after insulation removal. Identifies surface damage or water ingress.
- Thermography: Detects thermal anomalies that may indicate moisture or insulation defects. Not specific to corrosion.
Real-time radiography is used early in the process to screen large areas efficiently and identify where other tools should be applied. While it does not provide quantitative data, it helps prioritize follow-up inspections where more precise measurements are needed [2] [3]
Implementation Considerations
When deploying real-time radiography, consider the following:
- Radiation Safety: Operators must be trained and follow site protocols. Visual alerts and timed activation help maintain compliance.
- Portability: Systems should be easy to use in the field, including elevated or congested areas. Ergonomic design improves operator performance.
- Data Management: Images and video must be stored, archived, and tied to specific asset locations.
- Operator Training: Users must understand what CUI indicators look like in real-time imaging and how to document findings correctly.
- Integration: Real-time radiography should be used in combination with other NDT methods to provide a complete assessment of asset condition.
Conclusion
Real-time radiography is a practical screening method for identifying corrosion under insulation across insulated piping systems. It allows inspection teams to cover large areas quickly, detect signs of damage without removing insulation, and determine where further testing is required.
This method should be integrated into a structured inspection strategy that includes clear procedures for data capture, follow-up evaluation, and training. When used alongside other NDT tools, real-time radiography helps prioritize inspection resources and supports more efficient CUI management.
Sources
[1] Inspectioneering. (1996). Inspection Techniques for Detection of CUI. Inspectioneering Journal, November Issue.
[2] ASNT. (2015). Nondestructive Testing Handbook, Volume 5: Radiographic Testing. American Society for Nondestructive Testing.
[3] API. (2014). API RP 583: Corrosion Under Insulation and Fireproofing (CUI/F). American Petroleum Institute.
