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Procedia Engineering 43 (2012) 459 463

1877-7058 2012 Published by Elsevier Ltd.

doi:10.1016/j.proeng.2012.08.079

International Symposium on Safety Science and Engineering in China, 2012

(ISSSE-2012)

Ultrasonic Phased Array for the Circumferential Welds Safety Inspection

of Urea Reactor

Dong Hua, Qiang Wang

a,*, Kun Xiao

a, Yehao Ma

a

aDepartment of Quality and Safety Engineering, China Jiliang University, Hangzhou 310018, China

Abstract

Due to the multi-layer thick wall structure and coarse grain materials of inside liner, the circumferential welds safety inspection of urea

reactor is usually not easy. The paper analyzes the problems and difficulties of NDT techniques used for circumferential welds of urea

reactor and overviews the theory and advanced point of UPA technology. Then two related test blocks (RB-2/20 and Austenitic stainless

steel butt joint test block) with artificial defects are selected to simulate the outer and inner layer. Experiments by UPA are carried out onthe test blocks and results are analyzed. It is proved that UPA is effective and efficient in solving the circumferential welds safety

inspection.

2012 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the Capital University of Economicsand Business, China Academy of Safety Science and Technology.

Keywords: Urea reactor, Circumferential welds, Ultrasonic phased array testing, Multi-layer thick wall structure, Coarse grain material

1.IntroductionMulti-layer structure, widely used in high pressure and ultra-high pressure vessels such as urea reactor, is a common

structural style for pressure vessel. But in recent years, several safety accidents of urea reactor have caused concern in the

community [1]. In order to avoid such catastrophic accidents, timely inspection should be carried out, especially the

inspection of circumferential welds that is easier to be corroded.

Non-destructive testing (NDT), which is based on techniques that rely on the application of physical principles to

determine the characteristics of materials, always contributes to detect and assess flaws or harmful defects without changing

the serviceability or usefulness of said materials [2]. Multiple NDT techniques have been used together in the inspection of

circumferential welds of urea reactor such as RT (Radiographic Testing) and UT (Ultrasonic Testing), which not only

increases the cost of detection but also reduces the detection efficiency. Deep weldsRT detection could only get very poor

sensitivity, and traditional UT system has only fixed focus, which is burdensome for layer inspection of welds [3]. In

addition, coarse grain materials, which lead to attenuation losses and scattering noise, also bring difficulty to UT inspection

[4].

Ultrasonic phased array (UPA) has excellent abilities of electronic steering, deflection and focusing [5]. As the rapid

development of electronic and computer technology, it has been widely employed in industry NDT, the nuclear industry [6]

*Qiang Wang. Tel.: +86-571-87676301; fax: +86-571-87676301.

E-mail address: [email protected], [email protected]

Available online at www.sciencedirect.com


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460 Dong Hu et al. / Procedia Engineering 43 (2012) 459 463

and chemical industry in particular. In the past few years, UPA inspection of coarse grain materials [7] and UPA imaging

technology [8,9] have made great progress.

In this paper, the structure of urea reactor and the superiorities of UPA are analyzed firstly. Then, UPA is employed to

inspect the defects on two test blocks. The defects are located at RB-2/20 test blocks 80mm depth and Austenitic stainless

steel butt joint test blocks 10mm depth. Finally, conclusions are presented.

2.Structure of urea reactorUrea reactor belongs to pressure equipment, design pressure of which is usually above 20MPa and usually uses multi-

layer structure. The structure of circumferential welds of urea reactor is as Fig.1, It is clear that the welds are divided into

outer and inter layers. The material parameter of each layer is as Table.1

Fig. 1.Structure of circumferential welds of urea reactor

Table 1.Material parameter of welds

Name Material Thickness

(mm)

Inside Liner 316L 8~12

Laminate panel 15MnVR 90~100

3.Mathematic model of ultrasonic phased arraySeen from Fig.2, UPA testing instrument can electronically steer and focus the transmission ultrasonic beams. These

features provide a new testing approach for circumferential welds.


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461Dong Hu et al. / Procedia Engineering 43 (2012) 459 463

Fig. 2.Beam focusing and beam deflection of liner UPA

In order to keep good directivity and depress energy leakage of the ultrasonic beam, the shape of the focus sound fieldand the location of the focus area must be controlled. Therefore, precision control of transmission delay for each element is

demanded. The object of delay computation is to find the delay differencent between an arbitrary element ( n the element)

and the first element.

Take linear UPA for example, if the deflection angle of the ultrasound beam is , the delay time of random adjacentelements

0 satisfies [10]:

0 sin /d c

(1)

where c is the ultrasound velocity in the medium, d is the center distance between two adjacent elements.

Supposing the ultrasonic beam focuses along the line that has an angle of with the normal line. The line is called thebeam direction. There are N elements are excited. Relative to the middle element, the delay of element is (1 )n n N [9]:

2

0

1 11 1 ( ) 2sin ( )

2 2n

f d N d Nt t n n

c f f

(2)

4. Experimental procedureInner and outer layer defects of circumferential welds in urea reactor are simulated through related test blocks. Table.2

presents the introduction of experiments

Table 2.Introduction of the Experiments

Number 1# 2#

Name Inspection experiment of

Laminate defect

Inspection experiment of

Inside Liner defectInstrument OmniScan MX OmniScan MX

Probe 5L64-A2 5L64-A2

Test block RB-2/20 Austenitic stainless steel

butt joint test block

Depth of the simulated defects 80mm 10mm

Fig.3 and fig.4 show the specific information of the test blocks:


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462 Dong Hu et al. / Procedia Engineering 43 (2012) 459 463

Fig. 3.RB-2/20

Fig. 4.Austenitic stainless steel butt joint test block

5.Results and discussion

(a) (b)

Fig. 5. Austenitic stainless steel butt joint test block


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463Dong Hu et al. / Procedia Engineering 43 (2012) 459 463

Figure.4 shows that inspection of simulated defects in both inner and outer layer by UPA technology get nice effects, the

imaging results is intuitive. High SNR UPA images are obtained through one time parallel inspection, which improve the

inspection efficiency. In addition, UPA technology has good effects on the coarse-grained material.

6.ConclusionsUPA technology has the advantages of convertible beam direction and focus, the results is easy imaging and thedetection has better accessibility and applicability. Therefore, it can solve the problems and difficulties of NDT inspection

in over-lapped pack structure and coarse grain materials testing. The technology can improve the accuracy of ultrasonic

testing and the reliability of test results, ensure the safe and economic operation of urea reactor.

Acknowledgements

This work is supported by Key Program of Science and Technology Planning Project of Zhejiang Province, China underGrant 2011C11079.

References

[1] Wu Junfei, Zhu Xiaochen, Zhang Yanfei, Yu Benliang, Gao Wei, 2010. Theoretical research & numerical simulation on the effect of urea-reactor

layer plate gap on stress distribution.Mechanic Automation and Control Engineering (MACE), International Conference on, pp. 2419 2422.

[2] Raj B., Jayakumar T., Thavasimuthu, 2002. Practical Non-destructivetesting, Woodhead Publishing.New Delhi ,INDIA.

[3] Shili Chen, Xianglin Zhan, Shijiu Jin, 2006. Design of Ultrasonic Phased Array System on Pipeline Girth Weld Inspection. Journal of Tianjin Univ 39,

p. 235.[4] Xianglin Zhan, Shijiu Jin,2005.Ultrasonic Inspection of Stainless Steel Welds.Journal of Nondestructive Inspection 29, p.12.[5] Zheng Zhongxing, 2009. A Fractal-Based Flaw Feature Extraction Method for Ultrasonic Phased Array Nondestructive Testing. Proceedings of the

2009 IEEE International Conference on Mechatronics and Automation August 9 - 12, Changchun, China.

[6] Abittan Elie, 2000. Inspection of thermal barriers of primary pumps with phased array probe and piezocomposite technology. Journal of Nondestructive

Testing 5.

[7] Mahauts, Godefroit J. L., Roy O., 2004. Application of Phased Array Techniques to Coarse Grain Components Inspection. Journal of Ultrasonic 42,p. 791.

[8] Steve Mahaut, Olivier Roy, Sylvain Chatillon, et al, 2001.Application of the Simulation to the Conception of Phased Array Mathods, 8th ECNDT,

Barcelone.[9] Austeng A.,Holm S.,2002.Sparse 2-D Arrays for 3-D Phased Array Imaging: Design Methods, Journal of IEEE Trans. Ultrason. Ferro. Freq. Contr. 49,

p. 1073.[10] Azar L., Shi Y., Wooh S.C., 2000. Beam Focusing Behavi or of Linear Phased Array. Journal of NDT & E Intern 33,p.189.

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