Small Diameter Tube and Pipe Inspection with Phased Array

Small diameter tube and pipe inspection poses a particular set of challenges. A few difficulties inspectors face include limited access between pipes, the thinness of the pipe or tube wall, and the sheer number of required inspections. Historically, radiography has been the perferred method for this application, since scanner mechanics and relatively large sensor sizes excluded advanced ultrasonics from consideration. Now, however, ultrasonic phased array technology offers a fast, readily viable option for small diameter pipe and tube inspection. By using phased array, you can avoid all the inherent difficulties and disadvantages that accompany radiographic inspection, such as safety, speed, and regulatory issues, as well as the need to clear the inspection area.

The Olympus COBRA Solution, based on a COBRA scanner and accessories kit coupled with an OmniScan portable phased array flaw detector, is specifically designed to address small diameter inspections. The COBRA Solution kit is a complete scanning solution for the inspection of pipes and tubes ranging from 0.84 in. to 4.50 in. OD (21 mm to 114 mm). For the inspection of pipes and tubes situated in close proximity, the COBRA scanner operates within a 12 mm (0.5 in.) clearance. The scanner adheres to the pipe or tube by a spring mechanism, which permits 360-degree scanning, even when only one side of the pipe or tube is accessible. The spring mechanism also enables the COBRA to adhere to non-ferromagnetic materials. The versatile COBRA scanner has the capacity to simultaneously inspect from both sides of a weld, or it can be adapted to be used with a single phased array probe for welds with one-sided access, such as elbow and pipe-to-component welds.

The complete COBRA Solution portable kit provides you with all the necessary tools, including setup templates, probes, curved wedges, and all other accessories required to inspect throughout the usable range. The kit can be purchased as a complete or single probe system, depending on your needs. The COBRA Solution is a semiautomatic system that complies with ASME as well as other inspection codes requiring full data collection and encoding, including those addressing the use of ultrasonics in lieu of radiography.

To even further improve small diameter phased array inspections, the COBRA Solution features probes that have been specially designed for this particular application. Phased array probes can be electronically focused in the forward or active axis by controlling the pulse and reception of the elements. Without complex array construction (dual/matrix array, etc.), the passive axis has long been left to natural beam spread, which is determined by aperture and element dimensions and the frequency of the probe. CCEV (Concave Curvature in Elevation) probes were created by applying a curvature in the elevation axis (also known as the side-to-side, or passive axis) dimension of a phased array probe. The appropriate curvature was established through laboratory trials and beam simulations for the typical diameters and wall thicknesses of both pipeline construction welds and small diameter pipe and tube welds. Similar to applying a lens to an immersion probe, the result is a smaller beam spot width, which can lessen beam spread effects and increase length-sizing potential. An internal integrated lens allows the use of standard flat wedges and flat outside casing. Various probe frequencies and wedges (refracted longitudinal and sheer) are available to address different materials, such as austenitic pipe or tube. TOFD compatible ultrasonic wedges and probes are also available.

*Note: Longitudinal and TOFD wedges increase the required clearance needed for inspection.

Illustration of a flat array and an internally focused array showing reduced beam spot size.

The results of an inspection on a 2.75 in. (70 mm) OD pipe with an induced 6.9 mm x .5 mm OD notch. Note the significant sharpness of data and improved sizing using the CCEV probe. Sizing done via –6dB drop method.

Equipment Used

• OmniScan MX/MX2/SX (SX is limited to single probe/group acquisition files).
• COBRA Solution kit (standard with 7.5 MHz arrays):
  • Half scanner kit- U8775327/COBRA-K-ONESIDED
  • Complete dual probe kit-U8750055/COBRA-K-4.5
• U8775153/WTR-SPRAYER-4L or other suitable couplant delivery.
• OmniPC/NDT Setup Builder/TomoView (optional scan plan and analysis software programs).
• Other related and special applications (please contact for details/description):
  • Compatible phased array probes (1.5/2.225/2.5/5/10 MHz)
  • Ref. L-wave wedge complete kit (U8722168)
  • TOFD wedge complete kit (U8701348)
  • Spare part kits (various)

Summary of Key Benefits

• Covers standard pipes from 0.84 in. to 4.5 in. OD (21 mm to 114 mm).
• Operates within 12 mm (0.5 in.) clearance (on all standard pipes) permitting inspections in limited access areas.
• Can hold two phased array probes for complete weld coverage in one pass.
• Can be configured to make one-sided inspections for pipe-to-component evaluations.
• Design provides stable and constant pressure around the full circumference of the pipe.
• Urethane wheels provide smooth radial movement and limited axial drift.
• Encoder resolution of 32 steps/mm.
• Compact, lightweight, and portable.
• Wedges and probes can be quickly and easily changed.
• Distance between probes can be adjusted from 0 mm to 55 mm.
• Can be manipulated from one side of a pipe.
• Spring-loaded scanner can be used on ferromagnetic and non-ferromagnetic pipes.
• Waterproof, rust-free, and CE-compliant.
• Conforms to requirements of codes requiring encoded, full data collection.
• Available in complete or single probe configuration for compatibility with various instruments and budgets.
• Able to utilize phased array (shear or ref. longitudinal) or TOFD inspection strategies.