Small Diameter Pipes
The COBRA scanner on a 0.84 in. pipe with two A15 PA probes with an OmniScan X3 16:64 displaying two PA groups with sectorial scans and C-scans.
Overview
Small Diameter Pipes
The COBRA™ manual scanner, combined with the OmniScan® phased array (PA) flaw detector, is used to perform circumferential weld inspections on small-diameter pipes. The COBRA holds up to two PA probes for inspections on pipes with outside diameters ranging from 0.84 in. to 4.5 in.
With its very slim design, this manual scanner inspects pipes in limited-access areas where minimal clearance is required. Adjacent obstructions, such as piping, supports, and structures, can be as close as 12 mm (0.5 in.).
This scanner uses multiple links to quickly adapt to various pipe diameters (simply add or remove links). In addition, the retention mechanism is spring-loaded, allowing the scanner to securely clasp pipes. This unique feature also enables the scanner to be installed and operated from one side of a row of pipes when access from both sides is impractical.
The COBRA scanner is characterized by its smooth-rolling encoded movement, which enables accurate data acquisition. The COBRA scanner ensures stable, constant, and strong pressure, thus providing good UT signals and precise encoding around the full circumference of the pipe.
Different ultrasound techniques for different challenges
The COBRA® solution can be used with different probes, depending on the application. Phased array, TRL dual linear array, and TOFD ultrasound techniques can be performed using the following probe options:
This Olympus phased array solution uses low-profile A15 phased array probes with optimized elevation focusing, which enhances the detection of small defects in thin-walled pipes. Specially designed low-profile wedges that fit each pipe diameter covered by the scanner are available for a complete solution. |  |
The A25 dual linear array probe (DLA)* series is designed to inspect austenitic material that cannot be otherwise inspected using an A15 probe in pulse echo. The A25 probe features an innovative system that enables the two arrays to conform to the wedge roof angle. The latter is optimized according to the diameter of the pipe being inspected. |  |
The COBRA scanner is compatible with conventional UT probes with 3-mm diameter elements and a specially designed wedge to perform TOFD* inspection. |  |
*When using TOFD and a DLA probe, the height clearance is increased.
Applications
- Boiler tube
- Small diameter process pipe
General Techniques
Ultrasonic Weld Inspection Solutions
The OmniScan flaw detector has an established track record for reliable and cost-effective phased array (PA) weld inspections as an alternative to radiography. Olympus ultrasonic weld inspection solutions provide an affordable means to inspect welds in compliance with major code and manufacturing requirements. An ideal combination of acquisition unit, scanner, encoder, and software, these solutions can be put to work virtually anywhere. Continuously improved and supported software makes the inspection of welds even easier, allowing you to complete your entire workflow more efficiently.
The Olympus weld inspection solutions applies to welds made of carbon steel or corrosion resistant alloy such as austenitic.
General Benefits:
- Fast weld inspection of different diameters, thickness, and materials
- 100% volumetric weld coverage
- Adaptable to butt welds, circumferential welds, long seams, one-sided access configuration, and most common weld profiles
- Portable for in-house and field inspections
Combining Different Techniques for Full Weld Coverage and Improved Efficiency
Phased Array Pulse-Echo Technique Phased array technique is based on the capacity to electronically modify ultrasonic beams generated by probes that contain multiple small elements. When these elements are excited using different time delays (focal laws), the beams are steered at different angles and focused at specific depths. |  |
Conventional UT Pulse-Echo Technique This technique uses a single element transducer to generate an acoustic beam at a fixed angle. The echo coming back to the transducer is interpreted by the instrument to provide information on size and position. |  |
| Time-of-Flight Diffraction (TOFD) Technique Time-of-flight diffraction (TOFD) is an ultrasonic technique that relies on the property of defects such as cracks to diffract energy from their tips to the receiver probe when impinged by ultrasonic beams generated by the transmitter probe. TOFD technique uses a wide beam that provides good coverage and is independent of defect orientation. |  |
Transmit-Receive Longitudinal Wave (TRL) This technique uses separate transmit and receive probes to generate refracted longitudinal wave. The use of separate probes minimizes vulnerability to noisy material, which is especially beneficial for inspection of coarse grain alloy, such as austenitic and nickel. |  |
Surface Wave Technique The surface wave (creeping) technique is an ultrasonic test in which discontinuities are detected by the return of a creeping wave that tracks the surface of the component being tested. |  |
Ultrasonic Testing (AUT) in Lieu of Radiography Testing (RT)
Ultrasonic testing in lieu of radiography has proven very effective for pressure vessels, tanks, piping, and other weld configurations. Olympus ultrasonic weld inspection solutions features comply with ASME, API and other radiography replacement code requirements such as full raw data collection and the use of an encoder. Compared to conventional radiography, Olympus ultrasonic weld inspection solutions offer multiple benefits such as:
- No radiation safety hazards
- Eliminates work area disruption
- Real time digital archiving of inspection data
- Elimination of film archiving
- Improved productivity
- Improved probability of detection (POD)
Comparing the Indications
 |
|
Measurement Capabilities
| ID | Type of Defect | Ultrasound (AUT) | Radiography (RT) |
| 1 | Toe crack |
• Position X, Y, and Z
• Length sizing • Height sizing |
• Position X and Y
• Length sizing |
| 2 | Centerline crack |
• Position X, Y, and Z
• Length sizing • Height sizing | • No detection |
| 3 | Porosity |
• Position X, Y, and Z
• Length sizing |
• Position X and Y
• Length sizing |
| 4 | Incomplete root penetration |
• Position X, Y, and Z
• Length sizing • Height sizing |
• Position X and Y
• Length sizing |
Benefits of the Olympus Ultrasonic Weld Inspection Solutions
| Olympus Ultrasonic Solutions | Radiography (RT) | |
| Absence of Radiation hazard | Yes | No |
| Absence of restricted area | Yes | No |
| Ease of deployment on site | Yes | No |
|
Probability of detection (POD)
(Planar defects such as crack and lack of fusion) | Very good | Poor |
| Inspection throughput | Very good | Good |
| Depth sizing capability | High accuracy | Poor |
| Length sizing capability | High accuracy |
Good accuracy
|
Scanning Methods
Two-sided InspectionThe COBRA scanner with the OmniScan MX2 flaw detector is capable of two-sided inspection to cover both sides of the weld with only one pass for greater productivity. For these inspections, the scanner holds two phased array probes placed on either side of the weld; the distance between the probes can be adjusted to quickly adapt to different weld thicknesses.
| One-sided InspectionFor pipe-to-component inspections, the scanner can be configured to perform one-sided inspections using a single probe. Olympus also offers a more affordable COBRA package that can be used with the single-group OmniScan SX flaw detector. This package requires two passes to inspect a weld.
|
