Remote-Field Examination Using Array Sensors

Transcription

1 ECT This image cannot currently be displayed. Remote-Field Examination Using Sensors Presented by: Brian K. Beresford TechCorr &. Manager Tubular Integrity Services Presented at: The International Chemical and Petroleum Industry Technology (ICPIIT) X Conference in Houston, Texas, June 2007.

2 Acknowledgements Dennis O'Quinn Chevron, Cedar Bayou, Texas Max Kidd Equistar Chemical, Channelview, Texas Will Rettman Petro Canada Oil & Gas Fort McMurray, Alberta ECT

3 Overview Introduction Analysis Technique Detection Method Remote Field Bobbin Probe Technology Disadvantages Remote Field Probe Technology Advantages Chevron Vs. Bobbin Test Bundle Results Vs. Bobbin Equistar C-Scan Results Petro Canada Oil & Gas Vs. Bobbin Results Conclusions ECT

4 Introduction This paper presents the results from a remote field array examination and demonstration of SA-214, ¾ X.072 exchanger tubing. The exchanger was found to be fouled due to product build-up. Tube cleanliness was a concern and two cleaning methods were employed to compare the effects of the acquisition and analysis of the data. All tubes were examined with a remote field bobbin probe and an array probe to compare the averaging effect of the bobbin. ECT

5 Introduction (Cont d) Tubes sections from the same exchanger had been found to have leaked or corroded in the past and the failure mechanisms had been attributed to multiple inside diameter pitting located in the same circumference of the tube. TechCorr developed a remote field eddy current array inspection and analysis procedure for detecting and sizing corrosion pits on the internal surface. ECT

6 Analysis Technique The remote field eddy current array sensitivity was required to detect multiple inside diameter pits in the same circumference using a voltage curve for multiple pitting and a phase curve for single pitting. The probe chosen was a remote field eddy current array probe built by Carbon Steel. Carbon Steel s EZ- analysis software played a big part in the ease (EZ) in which the speed of the analysis was done. This was accomplished by employing the Auto Normalization buttons. This analysis was tried with other competitors software and was found to take 3-4 times longer to complete the analysis. ECT

7 Detection Method With considerations of the material and the size of the tube as well as the type of the defects to be inspected, an remote field eddy current inspection technique was considered to be the best choice. IRIS was tried with no success even after water blasting eight (8) tubes and grit blasting six (6) tubes. ECT

8 Remote Field Bobbin Technology Probe Disadvantages Averages over the circumference 360 Vector addition of multiple defects Limited to no defect morphology circumferential extent ECT

9 Remote Field Probe Technology Advantages Segmented coils decreases affects of averaging Increased signal to noise ratio Limits vector addition of multiple defects Provides more detailed information on defect morphology ECT

10 Remote Field Probe C-scan Technology A C-Scan Presentation of the data is now possible using the array probe technology. This presentation is extremely useful during the analysis phases of the programs. Metal loss can be attributed to specific quadrants within the tube being inspected. The below image shows metal wall loss in the third quadrant, where as the other sections of the tube are near nominal. ECT

11 Chevron VS Bobbin There was a difference between the bobbin and array percent wall loss. The array data appears to be more accurate in sizing small volume pitting compared to the bobbin data based on the pulled tube results. The tube was then longitudinally split in half and the internal surface cleaned using a wire brush for examination of the internal surface. ECT

12 Chevron Results Tube cleanliness was a concern only for the water blast tubes. The Grit blast tubes produced better RFT data. Less noise. ECT

13 Chevron Defect Bar Chart ECT

14 Chevron Bobbin Defect Bar Chart As per the pulled tube results bobbin data overcalled the pitting depth. ECT

15 VS Bobbin in Test Bundle Raw data from a specific tube was released to TechCorr from a customers test bundle to show the sensitivity and accuracy of technology. The tube specifications were SA-214, ¾ X.109 exchanger tubing. This tube had a large volume 360º flaw, a 180º flaw and a small pin hole drilled in the tube. The bobbin data from the test bundle revealed that the pin hole was so small in volume and because of the averaging affect the pin hole only revealed a 34% wall 137º. The array data revealed that the pin hole in the test bundle matched the TWH in the calibration standard. As revealed in the array defect printout below its much easier to identify the defect mythology. ECT

16 Bobbin Test Bundle Result The bobbin data revealed a 137º 34% wall loss (The TWH in calibration standard 90º) ECT

17 Test Bundle Result The array data revealed a 112º on coil #5 100% wall loss (The TWH in calibration standard 112º) 100% TWH (Pin Hole) 360º Flaw all 6 coils hit TWH 180º Flaw 3 coils hit ECT

18 Test Bundle Calibration Standard ¾ X The calibration standard 112º and the 20% 155º TWH ECT

19 Equistar Exchanger Results Equistar requested that TehhCorr perform a reexamination on a specific exchanger that was examined by another company to compare the sensitivity and accuracy of technology. The tube specifications were SA-214, ¾ X.083, 20 feet in length. The array examination revealed mostly outside diameter 360º corrosion and some isolated pitting. The bobbin data and array data were compared and it concluded that the array data was more accurate than the bobbin data. The pin hole was so small in volume and because of the averaging affect the pin hole only revealed a 34% wall 137º. The defects were visually noticeable. As revealed in the array defect printout below its much easier to identify the defect morphology. ECT

20 Pitting & Corrosion Defect Distribution Map ECT

21 Side View Drawing of Exchanger Showing Damage Location ECT

22 Equistar of SA-214 ¾ x.083 C-Scan Voltage Curve ECT

23 Equistar Calibration Standard 100% Thru Wall Hole 60% Single Flat Bottom Hole 20% Outside Diameter Groove ECT 60% 270º Fret

24 Equistar Calibration Standard Continued ECT 360º Tapered Flaw

25 E-3706-A Exchanger 360º Corrosion Stationary End Floating End ECT Notice all 6 channels hitting and the response from the C-scan Plot

26 Petro Canada Oil & Gas of Exchanger E-112. Vs. Bobbin Petro Canada requested TechCorr to examine 100% of their exchanger utilizing remote field eddy current utilizing and Bobbin probes. The tube material specification was ¾ x.083 SA-214. The array in this case was more sensitive to pitting located on the near and far side of the tube support. After the initial calibration setup we than rotated the tube support horizontal. By rotating the tube support horizontal it makes strip chart review easier. ECT

27 Petro Canada Oil & Gas Vs. Bobbin Defect Count Bobbin Probe Inspected 129 Tubes Total Defects 97 Probe Inspected 129 Tubes Total Defects 240 ECT

28 Row 27 Tube 1 (100% Through Wall Hole) The array probe Row 27 Tube 1 Through Wall Hole ECT

29 Vs. Bobbin Indication Defect on back side of tube support Percent wall loss with 32% ECT Defect on back side of tube support Percent wall loss with Bobbin 4%

30 Conclusions technology is more sensitive and accurate than bobbin. More sensitive to defects near tube supports. Utilizing the proper software increase the speed of the analysis. Auto normalization is a key ingredient to the analysis. provides more detailed information on defect morphology Segmented coils decreases affects of averaging ECT

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