ND T Abstracts

CARP practice. A new procedure was developed for these "noisy" structures. The method is based on a fixed sequence of six repeated loading cycles. The AE count activity from cycle to cycle is recorded, and normalized with respect to activity during the first cycle.

44293 Miller, R.K. T a n k - b o t t o m leak detect ion in above-ground storage tanks by using acoustic emission Materials Evaluation, Vol. 48, No. 6, pp. 822-829 (Jun. 1990)

Technology of acoustic emission, which has commonly been used to detect and assess leaks in pipelines and valves is applied, in this paper, to the external monitoring of tank bottoms on above-ground storage tanks. Using laboratory tests, studies of tanks with known leaks and actual field tests, a set of procedures and equipment for tank-bottom leak detection has been assembled. Data analysis is important in preventing false positives and to locate real leaks accurately. This in-service inspection technique provides economic nondestructive evaluation of tank conditions and can outline which tanks require repair or future reinspection.

43788 Scruby, C.B.; Beesley, M,I.; Stacey, K.A.; Buttle. D.I. Continuous monitoring by acoustic emission measurements United Kingdom Atomic Energy Authority, Harweli, AERE-R- 13644, 24pp. (Oct 1989)

Advanced acoustic emission technique have been applied to the monitoring of the first hydrotest and the subsequent pressure cycling of a l/5-scale experimental PWR vessel. The same techniques have also been applied to a laboratory specimens in a comprehensive series of tests designed to simulate the behaviour of weld fabrication defects under more extreme conditions of tensile loading and cyclic fatigue than could by applied to the vessel. It was concluded that fabrication defects such as slag inclusions and hot cracks generate detectable emission provided tensile loading is sufficiently high to initiate defect growth.

43546 Green, A.T.; Lauben, R.W. Nondestructive examination of above ground storage tanks for leak detection Nondestructive Evaluation: NDE Planning and Application, The 1989 ASME Pressure Vessels and Piping Conference, Honolulu, (United States), 23- 27 Jul. 1989. pp. 99-105. Edited by R.D. Streit. The American Society of Mechanical Engineers

For the past six years, we have been developing and using acoustic emission inspection methods to detect which above ground tanks are leaking. In 89% of the tests, our analysis concluded the tank was not leaking. In the I 1% where our analysis showed leakage to exist, a follow-up internal inspection confirmed our call to he correct better than 91% of the time. This paper presents the background details of the procedures used and the results obtained.

43545 Takahashi, H.; Jeong, H.D.; Murakami, Y. On-l ine eva lua t ion procedure for s t ruc tura l integri ty by acoustic emission frequency analysis - weld defect containing pressure vessel Nondestructive Evaluation: NDE Planning and Application, The 1989 ASME Pressure Vessels and Piping Conference, Honolulu, (United States), 23- 27 Jul. 1989. pp. 107-112. Edited by R.D. Streit. The American Society of Mechanical Engineers

The aim of this paper is to apply the acoustic emission technique as the on-line evaluation method to pressure vessel integrity assessment. Hydrostatic tests, AE measurement and ultrasonic inspection have been achieved for pressure vessels having the weld flaw. AE frequency analysis was simultaneously carried out using the high speed frequency analyzer system.

43544 Carlyle, J.M.; Evans, R.S.; Sherlock, T.P. Acoustic emission characterization of a hot reheat line rupture Nondestructive Evaluation: NDE Planning and Application, The 1989 ASME Pressure Vessels and Piping Conference, Honolulu, (United States), 23- 27 Jul. 1989. pp. 113-119. Edited by R.D. Streit. The American Society of Mechanical Engineers

The Electric Power Research Institute funded on an acoustic emission investigation in which a hot reheat line was destroyed in a controlled manner. Acoustic emission data, of both the burst and continous type, clearly tracked the initiation and growth of the cracks which lead to the high pressure steam leak. The acoustic emission instrumentation also showed that the leak, once established, changed its character in a manner which was consistent with the growth of the leak from a small length to the full 6 inch notch length. Finally, the acoustic emission data gave no evidence that further crack propagation was continuing once the full 6 inch leak path was established.

43543 Stulen, F.B. Improved accuracy and reliability of est imates of defect locations by detailed analysis of acoustic emission waveforms Nondestructive Evaluation: NDE Planning and Application, The 1989 ASME Pressure Vessels and Piping Conference, Honolulu, (United States), 23- 27 Jul. 1989. pp. 121-127. Edited by R.D. Streit. The American Society of Mechanical Engineers

A location algorithm based on detailed analysis of individual acoustic emission waveforms has been developed. Estimates for both axial and circumferential positions are obtained from a single waveform obtained from a single transducer. The detailed-analysis location algorithm is presented, and its use in conjunction with conventional systems is discussed. The combined approach greatly improves the accuracy and confidence obtained by acoustic emission monitoring.

43539 Rogers, C.B.; Clayton, J.Q. Stable microcracking in br i t t le f r ac tu re ini t ia t ion Scripta Metallurgica, Vol. 23, No. 10, pp. 1785-1789 (Oct. 1989)

Advanced nondestructive testing methods are used to identify events such as microcracking, that precede final failure in large steel structures. Consequences of rapid brittle fracture in items like nuclear pressure vessels have potentially catastrophic consequencies. Acoustic emission (AE) sources and their relation to crack growth processes in ferrous materials are studied in this paper. Fracture tests at temperatures below the ductile-brittle transition temperature ensures that all cracking is by the brittle cleavage mode. AE monitoring can reliably detect the initiation of cleavage microcracks. Observations of microcracking and fracture in 1.0 mm thick spheroidized steels are discussed.

43296 Jones, R.M. Acoustic monitoring of nuclear plant operating valves for leakage Materials Evaluation, Vol. 47, No. l l , pp. 1278-1280 (Nov. 1989)

This paper describes two uses of high frequency acoustic emission (AE) as a method of leak detection testing (LT) for valves in use in the nuclear industry, A high frequency AE transducer on the valve body. Spectra are taken with the valve open, dosed and open again. Each valve is then examined with a portable high-frequency portable analog analyzer to identify the leaking valves. Test tests are easy to perform, but complicated to interpret and operator experience is essential to their success.

43295 Lucia, A.C.; Tonolini, F. General review of recent activit ies in acoustic emission technology in Italy Centro Informazioni Studi Esperienze, Milan, (Italy), N89- 19601/8/GAR, 18pp. (1987)

Instrumentation development for acoustic emission studies; pressure vessel examination during hydrotest; fatigue tests on experimental structures; leak monitoring; loose part monitoring; materials characterization; and standards and procedures are summarized.

43293 Nordstrom, R. Direct tank bottom leak monitoring with acoustic emission Materials Evaluation, Vol. 48, No. 2, pp. 251-254 (Feb. 1990)

As the nation's estimated 20 000 above-ground petrochemical storage tanks age, the need for cost-effe, ctive tank maintenance procedures increases. Acoustic energy from leaks has been studied for the past two decades. AE instruments, built to detect either continuous or burst emission, have been used to perform acoustic leak detection for almost as long. In view of this, it should not be surprising that the current standard in AE instruments could be adopted for directly monitoring acoustic energy generated from leaks. It is the transient acoustic behavior that is most easily detectable and discernible as noise generated from the leakage. In a singular liquid, the onset of turbulence is associated with high liquid velocities, indicated by high Reynolds numbers. In this case, the properties of petroleum products in large storage tanks would not produce detectable turbulence until large leakage rates were experienced, That acoustic bursts are detectable below a strict calculation of turbulence can he explained in one of two ways. First, turbulence can occur below the single-liquid model when nonideai conditions are present (such as large liquid density gradients, which are present in the bottom of crude oil storage tanks) and particles can interfere with the leak. Second, liquid movement away from the orifice can generate noise.

43042 Fowler, T,I.; Blessing, J.A.; Conlisk, P,I.; Swanson, T.L. The MONPAC system Journal of Acoustic Emission, Vol. 8, No. 3, pp. 1-8 (1989)

The MONPAC acoustic emission system is established as an important global nondestructive test for examining the structural integrity of metal

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chemical process equipment. Extensive field test experience has led to codes and standards and to development of improved test procedures and load schedules. Improvements in post-test analysis methods, such as use of correlation plots, standard filters, and intensity analysis have led to a more accurate assessment of the nature, location, and severity of defects. MARSE has emerged as the primary acoustic emission panm~ter. Correlation plots are used to evaluate the validity of the data and preprngrammed filters are used to eliminate spurious events. Instrumentation has become much simpler, less cosily, and outputs and displays are readily understood by individuals not trained in acoustic emission technology.

43041 Peacock, M.I. Acoust ic emission mon i to r ing of a large pressure vessel du r ing a pneumat i c re-qual i f icat ion test Journal of Acoustic Emission, Vol. 8, No. 3, pp. 11-19 (1989)

This paper describes the use of Acoustic Emission (AE) to monitor a regenerator vessel during a proof test following an extensive program to refurbish and modify the forty year old vessel. The MONPAC procedure was used with special attention given to the need for real- time data evaluation. A set of raw data classification roles allowed system operators to assess incoming data according to numeric criteria. Off-line computers were updated with data from the four AE systems. Of the active areas detected none were judged critical enough to stop the test for immediate follow-up inspection. The vessel was pressurized a second time and the primary AE source became active at about 90% of previous test pressure.

43040 Hewerdine, S. I C I ' s perspect ive on acoustic emission moni tor ing Journal of Acoustic Emission, VoI. 8, No. 3, pp. 21-24 (1989)

ICI was one of the earliest members of the MONPAC User's Club and has been using MONPAC technology for acoustic emission monitoring of process plant equipment for some three years. The paper lists factors to be taken into account in planning and execution of monitoring and in interpretation of results to obtain optimum information on the future integrity of the vessel. It also gives examples of AE monitoring of equipment in each of the categories described above. Finally, some views are given on the future role of AE monitoring within ICI.

43039 Miller, R.K.; Tobin, R.G.; Gross, D.I.; Tran, D.T. A s u m m a r y of experiences with M O N P A C test ing by the M Q S / D u n e g a n Test ing G r o u p Journal of Acoustic Emission, Vol. 8, No. 3, pp. 25-29 (1989)

MONPAC testing and analysis has been applied by Dunegan testing to several types of metal pressure vessels. A review of four tests, the results and follow-up recommendations is presented. In particular is a discussion of the testing of an insulated hotadiene storage sphere, a phosgene recovery tower, an ammonia storage bullet and an insulated hydrocracker reactor.

43038 Cole, P.T. M O N P A C - condi t ion moni to r ing for stat ic p lant - case his tor ies Journal of Acoustic Emission, Vol. 8, No. 3, pp. 31-33 (1989)

MONPAC is a standardized method of condition monitoring for pressure vessels and storage tanks. It provides management with an indication of the condition of vessels often without the need for their removal from service. Several case histories are covered in this paper to illustrate the applications and benefits of the technology.

43027 Holler, P.; Waschkies, E. Advanced methods and equ ipmen t for acoustic emission test ing Acoustic Emission, Edited by J. Eisenblather, pp. 3-23. Pubi. DGM Informationsgesellschaft, Verlag, 321 pp. (1988) ISBN 3883551317

This paper looks at advances in measurement and evaluation techniques used in acoustic emission (AE) testing at pressurized steel components with thermally activated AE, involving cyclic loading at 240C. The theoretical basics of AE testing is discussed and experimental work described. Crack growth was detected well under hot and cold conditions, but where flaws had not grown during pressure tests, flaws were not detected.

43023 Tscheliesnig, P. Acoust ic emission test ing (AET) of spherical s torage tanks Acoustic Emission, Edited by J. Eisenblatter; pp. 247-257. Publ. DGM Informationsgesellschaft, Verlag, 321pp. (1988) ISBN 3883551317

Acoustic emission testing (AET) has a number of advantages when assessing the spherical pressure vessels, used in the petrochemical, chemical and power industries to store hazardous gases and liquids. If AET is

ND T Abstracts

performed during the first pressure test, it can predict failure by detecting crack formation at an early stage. It also allows the structure integrity of the entire structure to be assessed at one time offering convenience and economic benefits. This paper looks at several possible nondestructive methods for examining these large vessels hot concludes that AET is best suited to the test.

43021 Bartholome, G.; Bazant, E.; Schopper, A.; Schucktanz, G. Evalua t ion of reac tor componen t s by means of f rac tu re mechanics and acoustic emission Acoustic Emission, Edited by J. Eisenblatter; pp. 215-226. Pubi. DGM lnformationsgesellsehaft, Verlag, 321pp. (1988) ISBN 3883551317

This paper discusses the use of acoustic emission (AE) techniques to study macroscopic crack initiation and propagation with reference to fracture mechanics. The components tested are from the coolant system of a pressurized water reactor and consequently critical and allowable flaw sizes are defined. While fault initiation is good with this AE technique, other methods must be used to determine flaw size, orientation, depth and geometry. However, AE can be used for testing components in areas inaccessible to other methods.

43020 Janoschek, E.; Keller, H.P.; Runow, P. Determinat ion of surface work c rack growth applying a new acoustic emission cr i ter ion based on m e a s u r e m e n t s on compact specimens Acoustic Emission, Edited by J. Eisenblatter; pp. 227-234. Publ. DGM Informationsgesellschaft, Verlag, 321pp. (1988) ISBN 3883551317

Specimens of pipework, from the same steel melt, and later manufactured into high pressure gas transport vessels were pre-stressed. These and the presstu~ vessels were investigated with acoustic emission (AE) techniques, so that surface crack growth on compact specimens could be assessed. AE is particularly suited to the detection and location of such faults from their earliest stages. Results compared favourably with standard values for the compact specimens and the pressure vessels.

43019 Waschkies, E. Results of in terpre t ive acoustic emission test ing of mechanical ly a n d thermal ly loaded reac tor pressure vessels Acoustic Emission, Edited by J. Eisenblatter; pp. 203-214. Publ. DGM Informationsgesellschaft, Verlag, 321pp. (1988) ISBN 3883551317

Using a number of examples from tests on reactor pressure vessels under mechanical and thermal loading, this paper examines the effectiveness and reliability of acoustic emission (hE) tests using modem equipment and signal analysis techniques. Tests included thermal shock experiments on a reactor pressure vessel, and cyclic pressure loading and hydrotests on larger pressure vessels. Crack growth was reliably detected using AE. Fatigue and corrosion (non-growing and growing) flaws were detected through crack border friction in the .thermal shock experiments. Non-growing flaws were not well detected in the hydretests as crack border friction does not occur.

43017 Jax, P.; Streicher, V. Acoustic emission analysis - an in tegra ted m e t h o d o f plant survei l lance Acoustic Emission, Edited by J. Eisenblatter; pp. 167-188. Publ. DGM lnformationsgesellschaft, Verlag, 321pp. (1988) ISBN 3883551317

This paper provides an assessment of acoustic emission (AE) as a method of plant surveillance using the tanks, pipes and vessels of a nuclear power plant as for in-line inspection purposes. AE is shown to provide approximate fault location and initial classification of defects for the entire volume of the component with few sensors. Defects must then be precisely located and quantified using other nondestructive examination methods.

43013 Mori, Y.; Obata, Y.; Aoki, K. Acoustic emission from fatigue crack of 304 stainless steel Acoustic Emission, Edited by J. Eisenblatter; pp. 109-I 16. Publ. DGM Informationsgescllschaft, Verlag, 321pp. (1988) ISBN 3883551317

This paper reports on laboratory and field tests of acoustic emission (AE) as a non-destructive evaluation method for metal pressure vessels. such as reactor pipework. Fatigue crack propagation studies in type 304 austenitic stainless steel are described. The effect of temperature, stress and thickness are studied. Results tentatively suggest criteria for recognizing incipient fatigue damage.

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