Assessing Circumferential Cracking in Non-Ferromagnetic Heat Exchanger Tubes
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The document discusses the challenges of detecting circumferential cracking in non-ferromagnetic heat exchanger tubes, particularly in power generation and petrochemical industries. It introduces a solution using a multiplexed eddy current array (ECA) probe and the Ectane testing instrument to accurately identify and characterize such defects. Key benefits include faster scanning times, enhanced sensitivity for defect detection, and improved visualization through advanced software.
Assessing Circumferential Cracking in Non-Ferromagnetic Heat Exchanger Tubes
- 1. Assessing Circumferential Cracking in Non-Ferromagnetic Heat Exchanger Tubes Application Note
- 2. Heat Exchangers Heat exchangers (HX) are used to heat and cool various fluids across a wide spectrum of industries. • HX are especially critical to: • Power generation • Oil, gas, and petrochemical • Tubes in HX are sometimes made from nonferromagnetic steels like: • Inconel™ • Austenitic stainless steel 2 © Eddyfi 2014
- 3. The Challenge Detecting, sizing, and positioning circumferential cracks in the vicinity of the tubesheet of non-ferromagnetic HX tubes. • Circumferential cracking is very difficult to detect and characterize with standard EC bobbin probes because: • They are very sensitive to tube expansion and ferromagnetic materials. • It is very difficult to isolate small-volume cracks from complex signals comprised of cracks, geometry changes, and added material. • The orientation of standard bobbin coils is not well suited to circumferential cracks because eddy currents flow parallel to indications. 3 © Eddyfi 2014
- 4. The Challenge Operators of such HX want to: • Identify leaking tubes affected by circumferential cracking. • Identify tubes showing signs of cracks that may grow to 100% through wall while the heat exchanger is in service. Sample scan data from calibration tube 4 © Eddyfi 2014
- 5. The Solution Using a multiplexed eddy current array (ECA) tubing probe to distinguish crack signals from tube sheet signals. Three-part solution: • • DefHi ® ECA tubing probe (patent pending) • 5 Ectane™ testing instrument Magnifi ® acquisition and analysis software © Eddyfi 2014
- 6. The Solution — Ectane Eddyfi’s workhorse testing instrument. • Can be configured for almost any type of inspection technique, including ECT and eddy current array (ECA). 6 © Eddyfi 2014
- 7. The Solution — DefHi Leverages ECA technology to accurately detect, size, and characterize circumferential cracking defects, differentiating them from other unwanted signals, e.g., from the tubesheet and roll transition. • • Coils working in transmitter-receiver mode • 7 Multiplexed coils Probe yields absolute signals with phase + amplitude information © Eddyfi 2014
- 8. The Solution — DefHi • Because of the coil configuration in the probe, eddy currents flowing in the inspected tube are perpendicular to circumferential defects, making them easier to identify. • ECA technology know-how has also made it possible to optimize the distance between the transmitter and the receiver coils so that the expansion signal detected by the probe is flat compared to others, making it extremely simple to isolate. 8 © Eddyfi 2014
- 9. The Solution — DefHi The DefHi also offers the following benefits: • Benefit 1 — Better Sensitivity The higher density of multiplexed coils in the DefHi enables you to estimate the circumferential length and position of defects. The DefHi’s highdefinition sensitivity is uniform to detect defects oriented in any direction. • Benefit 2 — Better Speed Scan tube ends in about an eighth the time it takes rotating probes. • Benefit 3 — Better Visualization The Magnifi software uses the DefHi’s inspection data to produce 2D and 3D C-scans with color palettes to distinguish between defects making defects easy to spot and characterize. 9 © Eddyfi 2014
- 10. The Solution — Magnifi Eddyfi’s cutting-edge acquisition and analysis software for graphical display (C-scan), record keeping, and reporting. Actual scan data 10 © Eddyfi 2014
- 11. The Solution — Magnifi Magnifi produces 2D and 3D C-scans. • Color patterns help distinguish between the tubesheet and the circumferential cracking defect. • Tubesheets yield angular responses compared to defects, so they appear clearly on the C-scans as having circumferential length and depth. 11 © Eddyfi 2014
- 12. The Benefits The main benefits of the solution are: • Unlike ECT, the solution can discriminate between the various complex geometries inside HX tubing to allow accurately detecting, sizing, and characterizing small-volume circumferential cracks. • Rotating probe technology scans tube ends at approximately 40 seconds per tube. Eddyfi’s solution can scan tube ends at 5 seconds per tube. • No need for a mechanical probe pushing device to accurately control the axial speed of the probe. 12 © Eddyfi 2014
- 13. The Benefits Additional benefits include: • Quantifying the circumferential extent of crack defects. • Accurate axial location and characterization of crack defects in the vicinity of the roll transition. • Standard ECT bobbin coils of the DefHi can serve as a reference point for typical ECT data signals. • The solution can be used for full-length tube examinations. • Personnel without extensive ECT data analysis experience can view the solution’s 3D data and be confident about the inspection results. • Actual testing demonstrates detection and sizing of circumferential cracks at the tubesheet as early as 50% wall loss and 30% in the free span area. 13 © Eddyfi 2014