Tightening Inspection Standards for In-Service Riser Bolt Inspection

Introduction

Bolts, threads, and other fasteners are critical components across various industries, including oil and gas, power generation, aerospace, and manufacturing. While often small relative to the overall asset, their integrity is paramount for safe operation. This application note focuses on non-destructive testing (NDT) for fasteners, specifically riser bolts, and highlights how encoded phased array ultrasonic testing (PAUT) enhances inspection efficiency, reliability, and provides essential data for post-analysis and comparative monitoring.

Key Aspects

• The Challenge: Inspect riser bolts without time-intensive removal or unnecessary downtime.
• The Solution: In-service phased array ultrasonic testing offers cost-effective, reliable, and improved riser bolt inspection.
• The Benefits: Traceable and repeatable inspection data enables efficient fitness-for-service analysis and proactive decisions.

1. The Challenge

Factors such as metal type, manufacturing processes, and environmental exposure contribute to riser bolt degradation, leading to flaws like cracks, corrosion, and thread loss. These issues compromise fastener strength over time. Bolt removal is not only time-consuming but can also weaken the bolt and surrounding area, potentially leading to costly failures. Asset owners require reliable "in-situ" inspection methods that overcome the limitations of conventional techniques, such as standard ultrasonic testing or phased array ultrasonic testing, which can struggle with complex geometries like threads and signal interpretation. Current solutions often lack permanent data recording or precise positioning information.

[Image Description: A photograph showing large industrial pipes, likely on an offshore platform, with prominent yellow and blue color schemes, illustrating the operational environment for riser bolts.

2. The Solution

Eddyfi Technologies provides a dedicated solution combining a manual scanner with a portable phased array instrument, TOPAZ®. This system utilizes high-frequency ultrasonic sound waves to detect anomalies in riser bolts. The technology enhances characterization and sizing of indications through data visualization and provides a permanent digital record.

The purpose-built manual scanner features an efficient cable management system and encoded rotation for operator assessment. Its radial probe position is adjustable, and the probe is spring-loaded for optimal coupling. This design accommodates various bolt types and hex nuts.

The TOPAZ® device is a high-performance portable phased array ultrasonic testing instrument. It supports up to 64/128PR, two conventional ultrasonic channels, multiple probes, and 2D matrix array onboard capabilities, eliminating the need for external software. The integrated instrument, powered by onboard software tools, delivers reliable data for in-service riser bolt inspections.

[Image Description: A set of images showing the Eddyfi Technologies inspection system. One image displays the TOPAZ® portable phased array ultrasonic testing instrument connected to a scanner. Another image shows a close-up of the manual scanner with its probe. A third image shows the TOPAZ® instrument itself, a compact handheld device with a display screen.

Technique and Test Results

The inspection technique involves using a 1D linear array, 5 MHz, 32 elements, performing an azimuthal scan. Longitudinal wave beams are generated and focused on the bolt's outer diameter surface in a "projection" mode. Refracted angles are selected via ray-tracing for adequate coverage of the area of interest. The probe is guided and rotated to cover the bolt's complete circumference.

[Image Description: A diagram illustrating the ultrasonic testing technique. It shows a probe positioned on a bolt, with lines representing ultrasonic wave beams propagating into the bolt. The diagram includes labels for "Depth", "Index", and "Scan", indicating measurement parameters.

The test results demonstrate the system's capability to identify predetermined defects. The example shows a riser bolt with several notches indicating flaws. These notches are characterized by their depth and position. For instance, Notch 1 is 0.75" x 0.25", Notch 2 is 0.75" x 0.125", and Notch 7 is 0.5" x 0.06".

[Image Description: A diagram showing test results on a riser bolt. The bolt is depicted with several numbered notches representing defects. Each notch is labeled with its dimensions (e.g., "0.75" x 0.25" (L x d)") and its position is indicated on a scale. The diagram includes "Depth (inch)" and "Scan (deg)" axes.

Figure 3 shows that Notches 1 and 2, located near the bolt geometry echo, are well resolved using the linked B-Scan view, which is more effective than A-scan detection alone.

Figure 4 illustrates that Notches 3, 4, 5, and 6, situated in the threaded area, with depths ranging from 3.17 to 9.52 millimeters (0.125 to 0.375 inches), are clearly detected and resolved from the thread signals.

Figure 5 highlights that Notch 7, only 1.52 millimeters (0.06 inches) deep and close to the back wall, can also be clearly resolved from the geometry.

Figure 6 showcases 3D imaging of phased array ultrasonic testing data applied to a riser bolt CAD model. This visualization, generated with UltraVision Classic 3D software, significantly aids data interpretation for end-users.

[Image Description: A 3D model of a riser bolt, rendered with detailed thread geometry. The model is overlaid with colored representations of ultrasonic data, highlighting simulated flaws or indications within the bolt structure, demonstrating advanced data visualization.

3. The Benefits

This easy-to-deploy and comprehensive solution offers significant time savings. By providing increased reliability and efficiency, it equips operators with the necessary tools for setup through reporting. This empowers asset owners to make informed decisions regarding the longevity of riser bolts and their surrounding areas in relation to overall asset health.

Implementing an advanced non-destructive testing solution to optimize inspection programs is a sound investment. Eddyfi Technologies' phased array ultrasonic testing solutions can enhance riser bolt inspection processes and more.