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State-of-the-Art RFT— Meeting the Ferromagnetic Tube Challenge
The document discusses the challenges of using remote-field testing (RFT) in inspecting ferromagnetic heat exchanger tubes in petrochemical plants, highlighting difficulties with tube permeability and thickness variations. It presents a solution through the use of Magnifi, an advanced software that improves RFT effectiveness by enabling precise defect characterization and automatic normalization of data. Ultimately, the software enhances inspection quality, providing valuable information to asset owners.
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State-of-the-Art RFT— Meeting the Ferromagnetic Tube Challenge
- 1. State-of-the-Art RFT —Meeting the Ferromagnetic Tube Challenge Application Note
- 2. Ferromagnetic HX Tubing Foundin petrochemical plants, it cannot be inspected with conventional ECT. Common inspection methods: • Internal Rotary Inspection System (IRIS) • Magnetic flux leakage (MFL) • Remote-field testing (RFT) RFT is usually preferred due to its defect sizing capabilities, decreased need for tube cleanliness, and high inspection speeds. 2 © Eddyfi 2014
- 3. The Challenge Overcome thedifficulties encountered when using RFT in ferromagnetic heat exchanger tubes. • The RFT technique is widely accepted, but difficult to master • Permeability of carbon steel tube material is unknown • Can change considerably from one heat exchanger to the next • At times, can vary significantly within the tubes of a single heat exchanger • Developing sets of calibration standards with different degrees of permeability is neither functional or financially sound 3 © Eddyfi 2014
- 4. The Challenge • Thethrough-transmission nature of RFT makes it sensitive to: • Nominal thickness variations • Permeability changes 4 © Eddyfi 2014
- 5. The Challenge The highsensitivity of RFT poses several challenges: 1. Typically, the manufacturing thickness tolerance of carbon steel tubes is approximately 10 % • Such a variation in thickness can represent a rotation of about 60 degrees on your channel, greatly affecting sizing interpretations 2. The magnetic permeability of carbon steel varies from grade to grade and according to processing history • Tubes processed at high temperatures do not have the same permeability as those processed at low temperatures • Variations in permeability have a considerable impact on RFT sensitivity and sizing 3. Calibration tubes matching the properties of tubes to inspect are extremely hard to come by. Differences in thickness and permeability almost always make calibrations inadequate without the proper tools to compensate. 5 © Eddyfi 2014
- 6. The Solution The shortcomingsof RFT can be worked around with software features, such as those found in Magnifi®, Eddyfi’s acquisition and analysis software. 6 © Eddyfi 2014
- 7. The Solution Magnifi usesa standard impedance plane and an absolute voltage plane. • The impedance plane has proven efficient to: • Detect and characterize small volumetric defects through standard techniques. • The absolute voltage plane: • Enables more precise characterization of large volumetric defects. Using both planes in concert allows improved detection, sizing, and characterizing a wider range of defects. 7 © Eddyfi 2014
- 8. The Solution 8 ©Eddyfi 2014 Magnifi is capable of saving the balanced, nominal operating point. • This stored value creates a reference point that enables tube-to-tube tracking of permeability variations.
- 9. The Solution Normalizations areautomatically applied to each channel in an effort to improve accurate defect sizing. 9 © Eddyfi 2014
- 10. The Solution • Magnifiissues warnings when the effects of magnetic permeability variations are too large to normalize. • Users can then adjust the inspection frequency to compensate for magnetic permeability differences between the calibration standard and the tubes in the bundle. • Magnifi can also detect landmarks automatically. • Allows accurately positioning defects without the need for an encoder. 10 © Eddyfi 2014
- 11. The Benefits The valueadded by software-enhanced RFT is easy to see: • One-click normalization of all channels • Automatically generated sizing curves • Normalization tracking for easier, faster, and more precise characterization of small and large volumetric defects • The result: higher quality inspections that provide much needed information to the asset owner 11 © Eddyfi 2014
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