Papermill in Virginia Uses Eagle 2000 RFET System

TesTex NDT Ltd carried out an Eddy Current Test (ECT) on a vertical heat exchanger at a Fertilizer plant. The unit tube bundle was manufactured from Stainless Steel 304 & therefore the preferred technique for this type of exchanger was ECT. No in-service failures or issues had been reported to TesTex prior to the inspection commencing. A sample of tubes (219 = 21% of total) were inspected using the TesTex developed TX4400 ECT system. On analysis of the data Row 1 Tube 21 (indicated by red arrow) displayed reportable wall loss (equal to or in excess of 20% Nominal Wall Thickness). The wall loss detected was to the external tube wall & measured by the ECT system at 34% loss of the NWT.

waveform diagram from an inspection of a papermill — A sample waveform collected from the inspection. The left most and right most circled areas show the Steam Drum and Mud Drum bends, respectively. The center circled area shows 180 degree soot blower thinning with 0.072″ wall remaining.

After consulting with the client a further inspection using an Internal Rotary Inspection System (IRIS) was carried out to establish the accuracy of the ECT results. As the IRIS system operates on an Ultrasonic principle a more accurate sizing of flaws would be expected. In comparison to the ECT result (34%) a wall loss of 39% was measured by the IRIS system. During the initial IRIS inspection sample it became evident that some large internal wall losses were present in the unit which had not been detected by the ECT system. Due to this a sample of tubes (239 = 23% of total) were inspected with IRIS with the results showing that 146 tubes displayed reportable wall loss indications. IRIS is more sensitive to flaw detection so the reportable threshold is set at 10% of NWT, however the largest wall loss was detected at 77% of NWT.

Conclusion

TesTex proved to the paper mill its ability to detect, size, and report indications along the entire length of the tube. Due to the speed, accuracy, and cost effectiveness, the Eagle 2000 System will be invited back to test the plants other boilers. In addition, the paper mills engineers are also interesting in inspected the swage region of the tubes with the TesTex developed Octavision 2000 System and inspecting D/A tanks with the TesTex Falcon 2000 Mark II Digital Tank System.