在新近的非破壞檢測技術中，導波法可在不去除管線上包覆層
的狀態下，快速地作長距離管線檢測工作。導波中的T(0,1)模態，因具有寬廣的非頻散區域，故常被激發入射於管線中以偵測管線中的缺陷及其位置。然而，在煉油與石化工業中，許多管線為了製程上的需要，或於管內注滿流體予以輸送；或在管線外部被覆材料作為保溫、防蝕功用；抑或以夾持式支撐固定管線。這些因應現場所需之作業環境，對導波執行管線檢測時，其傳播於管線中的能量會分別受到管內流體、包覆層材料及夾持式支撐之鬆緊度等因素而產生不同程度的洩漏，影響其靈敏度與傳播距離。本論文乃利用模擬與實驗方式，分別探討管內各式流體、各種被覆材料及不同夾持扭力等參數，對導波於管中傳播時所造成之變化情形。於研究中，利用DISPERSE 軟體，模擬分析T(0,1)模態於各種狀況下之波形結構，並估算其衰減率。本研究又以導波檢測管線系統，分別實際量測上述各條件下之管線回波訊號，計算其衰減特性，並與模擬結果比對，發現其實驗值與理論預估趨勢匹配吻合。管線中若注滿水、柴油及潤滑油等低黏度之液體，其對導波在管中之傳播並無影響。然而，當管內流體為黏滯性較高的重油時，會嚴重地衰減導波的回波訊號。另於管中流體之研究中，亦探討注入半滿流體與全滿流體間之影響差異。結果顯示，管中流體不論是半滿或全滿，其對管中缺陷之影響皆相同。本論文中，就管線被覆不同材料之研究而言，發現若被覆材料對管線具較強黏著力，如瀝青及聚乙烯等材質時，其對導波之能量衰減較大，檢測之傳播距離相形地較短。反之，若管線被覆材料不具黏著性，如石棉材質時，其幾乎不會造成導波在檢測上之衰減。就不同夾持方式對導波衰減之研究而言，發現附有橡膠墊之夾持式支撐，其導波衰減遠大於直接挾持於管線之支撐；其施加扭力愈大，其回波訊號愈強；管線導波之入射頻率愈低，其回波訊號愈大。此外，在挾持扭力之實驗量測中，亦發現導波對夾持式支撐之橡膠墊產生共振現象，若與理論計算結果比較，則得到共振頻率一致之印證。

The guided wave technique is commonly used for rapidly long-range pipeline inspection without removing the insulation of pipes. The torsional mode T(0,1) of the
guided waves is usually generated to detect the defects in pipelines, since it has the advantage of being non-dispersive across the whole frequency range. However, a
large number of pipelines are carrying fluid, wrapped with the coating material, and supported with clamp for the necessary manufacturing process in refinery and petro-chemical industrials. When these works are employed on the pipeline, the propagating guided waves may vary with the contents of material and how well the material compact on the pipe. Some energy of the incident guided wave in the pipe wall may leak into inside of contents or outside of wrapped materials and reduce the wave propagation distance. The effect of the fluid-filled pipe, the wrapped pipe, and the clamp support mounted on the pipe for guided wave propagation is investigated by both simulative and experimental methods. The wave structure of the T(0,1) mode
in the pipes is analyzed by using the DISPERSE software for various cases to evaluate its influence to the guided wave propagation on the pipe. The amplitudes of the reflected signals from various features on the pipe are also measured using pipe screening system for calculating the attenuation of guided waves due to the features.
The trend for the results is in good agreement between the experiments andpredictions for all cases of researches in this dissertation. It is found that the low viscosity liquid deposited in the pipe, such as water, diesel oil, and lubricant, has no effect on the torsional mode; while the high viscous of the fuel oil deposited in the
pipe attenuates the reflection signal heavily for the pipe carrying fluid. In addition, both the full-filled and half-filled contents in the pipe are also studied in this case. The effects of the half-filled are the same as the full-filled results obtained. For the pipe wrapped with the coated material, the adhesive strength of the coated material is strong, such as bitumen and polyethylene; the attenuation of the guided waves is high; and there is almost no effect for mineral wool coating. Furthermore, the traveling distance of the guided waves in the pipe is also evaluated for various cases of the coated materials. The results indicate that the higher attenuation of the guided waves for the coated material, the shorter of the traveling distance in the pipe. For the clamp support mounted on pipe, the attenuation of the guided waves for the clamp support with a rubber gasket in between the pipe and the clamp is heavier than the case of clamp support without the rubber gasket is. Furthermore, the higher torque setting on the clamp (with or without the rubber gasket), the higher amplitude of the reflected
signal is measured for the guided wave propagation. The effect of the frequency excitation is additionally demonstrated in this dissertation. It is noted that the higher amplitude of the reflected signal, the lower frequency excitation; moreover, theresonant effect is observed in the case of the clamp support with rubber gasket during the torque setting in the experiments. Good agreement has been obtained between the experiments and theoretical calculations of this effect.

LIST OF TABLES…………………………………………………………………..iii
LIST OF FIGURES…………………………………………………………………..iv
ABSTRACT (CHINESE)…………………………………………………………… vi
ABSTRACT (ENGLISH)…………………………………………………………...viii
NOMENCLATURE………………………………………………………………….xii
CHAPTER 1 INTRODUCTION……………………………………………………1
1.1 Background……………………………………………………………………1
1.2 Application of Guided Waves in Pipes………………………………………...2
1.3 Motivation……………………………………………………………………..6
CHAPTER 2 THEORY OF GUIDED WAVES IN A PIPE………………………..10
2.1 Basic Concepts of Guided Waves…………………………………………….10
2.2 Equation of Motion…………………………………………………………..12
2.3 Dispersion Curves……………………………………………………………17
2.4 Waves Structure………………………………………………………………20
2.5 DAC Curve…………………………………………………………………...21
CHAPTER 3 THEORETICAL PREDICTIONS IN THE ATTENUATION OF
GUIDED WAVE PROPAGATING ON THE PIPE…………………………….25
3.1 The attenuation of fluid-filled Pipe…………………………………………..25
3.1.1 Background…………………………………………………………….25
3.1.2 Theoretical Analysis……………………………………………………26
3.1.3 Wave Structure Analysis………………………………………………..28
3.1.4 Predictions……………………………………………………………...29
3.2 The Wrapped Pipe……………………………………………………………30
3.2.1 Background…………………………………………………………….30
3.2.2 Theoretical Analysis……………………………………………………31
3.2.3 Wave Structure Analysis………………………………………………..34
3.2.4 Predictions……………………………………………………………...35
3.3 The Clamp Support Mounted on the Pipe……………………………………36
3.3.1 Background…………………………………………………………….36
3.3.2 Theoretical Analysis……………………………………………………37
CHAPTER 4 EXPERIMENTAL SETUP………………………………………….45
4.1 Fluid-filled Pipe………………………………………………………………45
4.2 The Wrapped Pipe……………………………………………………………46
4.3 The Clamp Support Mounted on the Pipe……………………………………51
CHAPTER 5 RESULTS AND DISCUSSION…………………………………….61
5.1 The Fluid-filled Pipe…………………………………………………………61
5.1.1 Predictions……………………………………………………………..61
5.1.2 Air-filled Pipe………………………………………………………….63
5.2 The Wrapped Pipe……………………………………………………………65
5.3 The Clamp Support Mounted on the Pipe……………………………………67
CHAPTER 6 CONCLUSION AND FUTURE WORK……………………………89
6.1 Conclusion…………………………………………………………………..89
6.2 Future Work…………………………………………………………………..91
BIBLIOGRAPHY……………………………………………………………………93
Appendix A…………………………………………………………………………..98
Table page
3.1 The kinematics viscosity of various fluid……………………………………..40
3.2 The acoustic properties of various coated materials………………………….40
5.1 The measurement results of the guided wave attenuation for various coated
materials………………………………………………………………………74
5.2 The amplitude of the reflected measurement of the clamp support without the
rubber gasket and the attenuation calculation for various torque settings from
18 to 32 kHz…………………………………………………………………..75
5.3 The amplitude of the reflected measurement of the clamp support with the
rubber gasket and the attenuation calculation for various torque settings from
18 to 32 kHz ………………………………………………………………….76
5.4 The normal modes for the rubber gasket at frequency band of 18 to 22 kHz...77
Figure page
1.1 Conventional ultrasonic testing measures region below the transducer. Guided
waves propagate the waves many tens of meters in pipe………………………..9
2.1 A traction free infinitely long hollow cylinder with the inner radius a and outer
radiusb………………………………………………………………………….23
2.2 The phase velocity dispersion curve for a 6 inch schedule 40 steel pipe in
vacuum………………………………………………………………………….23
2.3 The group velocity dispersion curve for 6 inch schedule 40 steel pipe in
vacuum………………………………………………………………………….24
2.4 The wave structure of T(0,1) mode in a 6 inch pipe at 28 kHz. This profile shows
the relative displacements from inside wall 76 mm to the outside wall 82 mm. The
radial displacement r u and axial displacement z u are zero…………………...24
3.1 The wave structures for (a) diesel oil, (b) lubricant, and (c) fuel oil filled pipe. The
figures represent the amplitude of circumferential displacement from the center
line (position 0 mm) to the outer half space (position 76 mm). The amplitude of
circumferential is left 1.91645×10-8m to the pipe for diesel, 1.90478×10-8m to the
pipe for lubricant and 1.178608×10-8 m to the pipe for fuel oil…………………41
3.2 Prediction of the attenuation of guided wave for (a) diesel oil, (b) lubricant, and (c)
fuel oil filled pipe. The attenuation is nearly zero for diesel oil (a) and lubricant (b),
and there are significantly attenuation values for fuel oil (c)…………………… 42
3.3 The wave structures of various coated material at frequency 28 kHz; (a) for
bitumen coated, the amplitude of circumferential displacement is vary from the
inside wall (position 76 mm) to outside wall (position 83.2 mm) and then through
the coated material. The relative displacement changes significantly high in the
viscous layer; (b) for polyethylene coated, the variation of the relative
displacement is slightly high in the viscous layer; (c) for mineral wool coated, its
relative displacement is near the same as in the viscous layer…………………...43
3.4 Prediction of the attenuation of guided wave for (a) polyethylene and (b)
bitumen………………..……………………………….………………………..44
4.1 The test pipe with an artificial defect and the transducer.....................................55
4.2 An 6 cycles Hanning-windowed tone burst signal..............................................55
4.3 The transducer elements are equally spaced around the pipe…………………...56
4.4 The profile of the test pipe and measuring system...............................................56
4.5 The reflected signal of the test pipe at 28 kHz (unwrapped)...............................57
4.6 An 10 cycles Hanning-windowed tone burst signal.............................................58
4.7 The reflected signal of the experimental measurement. (a) bitumen (b)
polyethylene (c) mineral wool..............................................................................59
4.8 The profile of the test pipe and the transducer.....................................................60
4.9 The reflected signals of various features on the test pipe at 28 kHz. Notice that the
pipe is not loaded, i.e., the torque setting is 0 in-lb……………………………. 60
4.10 The U-type clamp support with the rubber gasket is mounted on the test pipe and
the clamp is screwed on the pipe by four screws……………………………… 61
5.1 The reflected signal of the air-filled pipe for experimental measurement..........78
5.2 The results of the fluid-filled pipes in comparison with the air-filled pipe: (a)
water-filled, (b) diesel oil-filled, and (c) lubricant-filled.………………… ...79
5.3 The reflection signal for fuel oil-filled pipe (case (b)) in comparison with the
air-filled pipe (case (a)). In case (a), the amplitude of the reflected signal is 7.4 mV
for flange (+F2) and 0.51 mV for defect (+F1). In case (b), the amplitude of the
reflected signal is 5.5 mV for flange (+F2) and 0.38 mV for defect (+F1)...........80
5.4 The results of the half-filled pipes: (a) diesel oil, (b) lubricant, and (c) fuel oil.
They have the same effects with the full-filled pipe.............................................81
5.5 The attenuation of guided wave for various coated materials…………………..82
5.6 Comparison of the ratio of the reflected amplitude of the clamp support and the
flange feature between the case of clamp support with the rubber gasket and
without the rubber gasket at 28 kHz…………………………………………….82
5.7 Ratio of the amplitude of the support/flange for various torque settings from 18 to
32 kHz. (a) Clamp support without the rubber gasket, (b) clamp support with the
rubber gasket.……………………………………………………….83
5.8 Amplitude of the reflected signal of the clamp support for various torque settings
from 18 to 32 kHz. (a) Clamp support without the rubber gasket, (b) clamp support
with the rubber gasket. The peak at frequency band of 18 to 22 kHz is the
resonance effect on the rubber material................................................................84
5.9 The resonant effect of the clamp support with the rubber gasket. (a) is enlarged
from Figure 5.7b, (b) is enlarged from Figure 5.8b.…………………………….85
5.10 The frequency bandwidth of transducer, the nominal frequency is the center of
frequency………………………………………………………………………..86
5.11 Comparison of the ratio of the reflected amplitude of the artificial defect and the
weld feature between the case of clamp support with the rubber gasket and without
the rubber gasket at 28 kHz...................................................................................86
5.12 Ratio of the amplitude of the +F3/+F4 for various torque settings from 18 to 32
kHz. (a) Clamp support without the rubber gasket, (b) clamp support with the
rubber gasket........................................................................................................87
5.13 Ratio of the amplitude of the +F5/+F4 for various torque settings from 18 to 32
kHz. (a) Clamp support without the rubber gasket, (b) clamp support with the
rubber gasket........................................................................................................88

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