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Volume 40 (2002)
- Issue 6 Pages 310-
- Issue 5 Pages 262-
- Issue 4 Pages 174-
- Issue 3 Pages 114-
- Issue 2 Pages 56-
- Issue 1 Pages 4-
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Volume 40, Issue 4
Special Issue
Displaying 1-8 of 8 articles from this issue
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Foreword
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Kazuyoshi SEKINESubject area: Others
2002 Volume 40 Issue 4 Pages 174-175
Published: 2002
Released on J-STAGE: April 25, 2003
JOURNAL FREE ACCESSDownload PDF (13K)
Technical Report
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Shigenori Yuyama, Minoru Yamada, Kazuyoshi SekineArticle type: Technical report
2002 Volume 40 Issue 4 Pages 176-184
Published: 2002
Released on J-STAGE: April 25, 2003
JOURNAL FREE ACCESSThe floor of an above ground storage tank is impossible to inspect using conventional methods with the tank still in-service. However, the cost of removing it from service is exceedingly high when cleaning and decontamination costs are taken into account. Since 1990 a database has been developed in Europe by opening and inspecting tanks after AE testing as an alternative in-service monitoring method to interpret tank floor condition. The method uses sensitive AE sensors on the outside of the tank to listen to the sound resulting from corrosion of the floor. It provides a very cost-effective maintenance planning tool for tank farm managers, proven by its use on more than 3, 000 tanks. This technique was introduced to the Japanese industry in 1999. Since then more than 20 field tests have been made on tanks with different diameters in Japan. Intensive laboratory tests on AE sources and AE wave propagation have been also made in order to demonstrate the effectiveness of the method. This article reviews current status of AE tank floor testing .View full abstractDownload PDF (186K) -
Atsuko MAIE, Minoru YAMADA, Shinsaku ZAMA, Ken HATAYAMA, Hiroaki MARUY ...Article type: Technical report
2002 Volume 40 Issue 4 Pages 185-193
Published: 2002
Released on J-STAGE: April 25, 2003
JOURNAL FREE ACCESSThe corrosion damage evaluation method using the AE is effective in the cost reduction in maintenance management of oil storage tanks. We measure AE wave transmitted through the contents of a tank, and obtain the information on AE, such as energy level, the number of source, and generating location. Further, corrosion damage evaluation is performed from the information. However, it is not clear that the propagation course, damping characteristic, etc.
Then, authors investigated the propagation characteristic and the damping characteristic of AE wave in a tank. This report introduces the result investigated about being shown below.
(1) The damping characteristic of AE wave, when various artificial AE generated on the shell plate of the empty tank.
(2) The damping characteristic of AE wave, when various artificial AE generated on the bottom plate of the empty tank.
(3) The difference in propagation and damping characteristic of AE wave by the difference in the existence of the contents of a tank
(4) The propagation characteristic of AE wave which transmitted through the contents of a tank.View full abstractDownload PDF (177K)
Original Paper
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Mikio TakemotoArticle type: Original paper
2002 Volume 40 Issue 4 Pages 194-202
Published: 2002
Released on J-STAGE: April 25, 2003
JOURNAL FREE ACCESSWith the aim of correctly estimating AE source locations in liquid-storage tanks, propagation behavior of AEs in water-loaded semi-spherical and cylindrical tanks were studied. Pressure profile or radiation pattern for semi-spherical tank indicated a complex profile with peak pressures and dead angles depending on both the source frequency and size. Experimental profile suggested the mode-converted P-wave in water to and from the Lamb wave (Ao-Lamb at 3000m⁄s) . Features of the radiation pattern agreed well with AE-peak profile measured for water-loaded cylindrical tank. The Lamb wave via bottom plate were converted to the large P-wave in water at the radiation angle of 30°. AEs with their sources on the bottom plate were found to arrive the AEs ensors on shell wall in the sequence of 1) Lamb wave with small amplitude, 2) Mode-converted P-wave with large amplitude, 3) direct P-wave in water. Source location method and accuracy of AEs were also discussed in relation to the propagating paths of AEs.View full abstractDownload PDF (225K) -
Ichiro MORITA, Takahiro ARAKAWA, Hiroaki HATANAKA, Minoru HAGIWARAArticle type: Original paper
2002 Volume 40 Issue 4 Pages 203-212
Published: 2002
Released on J-STAGE: April 25, 2003
JOURNAL FREE ACCESSPeriodic mandatory inspection with the inspection interval ranging from 8 to 10years is stipulated for Japanese large-scale crude oil storage tanks regardless of corrosion damage induced to the tanks. Tanks with small operational periods are usually free from any corrosion damage. Thus, opinions are raised for developing an inspection technology to be applied to such tanks without making any access to the inside surfaces of the tanks with utilizing acoustic emission (AE) related technology. Precise study has been scarcely reported so far on the generation mechanism of the AE for assessing corrosion incidents of oil storage tanks.
The present investigation has demonstrated acoustic emission from steel test specimens subjected to various corrosion rates in two kinds of accelerated corrosion tests registering the frequency at about 30 kHz. One of the accelerating corrosion tests is immersing test specimens in oxygenated aqueous solutions of 3. 5% NaCl, and the other is to pass electric current in the test specimens while immersed in the test solutions.
Furthermore, the propagation behavior of elastic waves in a mock-up tank of a diameter of 5 m and actual storage tanks has been discussed. Signal processing based on the wavelet analyses is conducted for improving S⁄N ratios, which shows wavelet analysis is effective in discriminating the AE signals from the noises. Some measuring test results of actual oil storage tanks are reporting with a comparison with AE measuring test results of corrosive tank after useless for long-period, and with discussion of noise features collaborated with such as wind.View full abstractDownload PDF (844K) -
-Application of Acoustic Emission Method to Field Tanks and Relationship between AE Signal Parameters and Plate-thickness Measurement Data-Shigeo KITSUKAWA, Minoru YAMADA, Shigenori YUYAMA, Hiroaki MARUYAMA, K ...Article type: Original paper
2002 Volume 40 Issue 4 Pages 213-221
Published: 2002
Released on J-STAGE: April 25, 2003
JOURNAL FREE ACCESSThis paper discusses some noise factors affecting the AE evaluation of external corrosion on bottom plate of real oil storage tanks, and also the relation of the AE parameters examined during in-operation to the current local corrosion state (statistical corrosion rate) estimated from thickness measurement data. The inner oil flows, oil or water drops from corn type roof and natural wind has been investigated as the typical and important sources of noise in in-operation real tank. In order to establish the diagnostics for degradation state due to corrosion on bottom plates, the measured AE signals have been compared with the parameters determined by the “risk curve for corrosion” derived from ultrasonic plate thickness measurement data as the current progress rate of corrosion in the much more corroded area. The result has shown the feasibility and applicability of the AE method for the in-operation evaluation of corrosion state in real oil storage tanks.View full abstractDownload PDF (148K) -
Minoru YAMADA, Shigeo KITSUKAWA, Shigenori YUYAMA, Atsushi KAMIYA, Kaz ...Article type: Original paper
2002 Volume 40 Issue 4 Pages 222-227
Published: 2002
Released on J-STAGE: April 25, 2003
JOURNAL FREE ACCESSA duty of an open inspection is imposed upon the oil storage tank of which volume is1000kl or more. This inspection opens the inside of a tank for every fixed period, and checks whether the welding line and thickness of a bottom plate to a technical standard. However, it has been thought that the “formation of performance regulation” which does not define an open cycle uniformly but defines the open cycle according to the degree of the healthiness of a tank from the contents of a design differing from the environment etc. greatly for every tank is more rational.
The AE method which is the technique of evaluating the corrosion damage on a bottom plate attracts attention, without opening a tank. This method was applied to the tank, comparison with AE measurement data and the plate thickness measurement data obtained by open inspection was performed, and that applicability was examined.
Consequently, it turned out that it is effective about correspondence with AE examination data and plate thickness measurement data as one of the standards for the number of hits per channel to judge corrosion damage evaluation of a tank bottom plate.View full abstractDownload PDF (168K) -
Atsushi KAMIYA, Koichi MOROFUJI, Kazushi ENUMA, Minoru YAMADA, Shigeno ...Article type: Original paper
2002 Volume 40 Issue 4 Pages 228-236
Published: 2002
Released on J-STAGE: April 25, 2003
JOURNAL FREE ACCESSThe leak from the floor of an above ground oil tank has a high possibility of bringing about environmental pollution or becoming the cause of the serious accident. For this reason, the AE method attracts attention as a method of inspecting in-service, without opening the inside of a tank. In domestic, although construction of the database about corrosion is performed, the data about leak hardly exists and the basic characteristic is not solved.
Then, in this report, AE wave generated in case water leaks from the small hole prepared in the floor using the water tank for fire extinguishing was measured. Consequently, the leak from a hole with a diameter of 1mm could be detected. Furthermore, even if it was the case of a large-sized tank, it is able to turn out that the leak from a hole with a diameter of 5-7mm or more is detectable, and the basic characteristic has been grasped. Furthermore, difference with AE by corrosion was clarified.View full abstractDownload PDF (302K)
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