Potential Difference Distribution on Flat Plate Around Semi-Ellipsoidal Thinning on the Back Surface

2014 ◽  
Author(s):  
Naoya Tada ◽  
Makoto Uchida ◽  
Manabu Nohara
Keyword(s):  
Flat Plate ◽  
Liquid Droplet ◽  
Potential Difference ◽  
Back Surface ◽  
Analysis Method ◽  
Droplet Impingement ◽  
Accelerated Corrosion ◽  
Flow Accelerated Corrosion ◽  
Non Destructive ◽  
Local Wall Thinning

Local wall thinning is one of serious problems in aged power generating plants and is known to occur mainly by Flow Accelerated Corrosion (FAC) and Liquid Droplet Impingement (LDI) erosion. As the thinning grows inside the pipes, it is difficult to detect and evaluate it from the outer surface of pipe. The direct-current potential difference method (DC-PDM) is thought to be a suitable non-destructive technique to monitor the initiation and growth of these damages. In this study, an approximate analysis method of the potential difference around a semi-ellipsoidal thinning on the back surface of flat plate is presented and the accuracy is discussed based on the results obtained by the finite element analyses.

Studies on Flow and Pipe Wall Thinning and the Reduction in the Downstream of Orifice Nozzle

2011 ◽  
Author(s):  
Toshihiko Shakouchi ◽  
Takayuki Suzuki ◽  
Hideki Yuya ◽  
Masaki Naruse ◽  
Koichi Tsujimoto ◽  
...  
Keyword(s):  
Cavitation Erosion ◽  
Pipe Wall ◽  
Liquid Droplet ◽  
Piping System ◽  
Droplet Impingement ◽  
Accelerated Corrosion ◽  
Wall Thinning ◽  
System 1 ◽  
Flow Accelerated Corrosion ◽  
Droplet Impingement Erosion

In a piping system of power plant, pipe wall thinning by Flow Accelerated Corrosion, FAC, Liquid Droplet Impingement Erosion, LDI, and Cavitation Erosion, C/E, are very serious problems because they give a damage and lead to the destructtion of the piping system[1]–[6]. In this study, the pipe wall thinning by FAC in the downstream of orifice nozzle, flow meter, is examined. Namely, the characteristics of FAC, generation mechanism, and prediction of the thinning and the reduction are made clear by experimental analysis. As a results, it was made clear that (1) the thinning is occurred mainly according to the size of the pressure fluctuation p′ on the pipe wall and the thinning can be estimated by it, and (2) the suppression of p′ can be realized by replacing the orifice to a taper shaped one having an angle to the upstream.

Assessment of Piping Field Failures and Burst Tests on Carbon Steel Pipes With Local Wall Thinning Using ASME Section XI Code Case N-597-2

2009 ◽  
Author(s):  
Kunio Hasegawa ◽  
Toshiyuki Meshii ◽  
Douglas A. Scarth
Keyword(s):  
Carbon Steel ◽  
Accelerated Corrosion ◽  
Steel Pipes ◽  
Pipe Burst ◽  
Evaluation Procedures ◽  
Wall Thinning ◽  
American Society ◽  
Corrosion Mechanisms ◽  
Flow Accelerated Corrosion ◽  
Local Wall Thinning

One of the more common modes of degradation in power plant piping has been wall thinning due to erosion-corrosion or flow-accelerated corrosion. Extensive work has been performed to understand flow-accelerated corrosion mechanisms and develop fracture criteria of locally thinned pipes, since the tragic events at Surry Unit 2 and Mihama Unit 3. A large number of tests have been performed on carbon steel pipes, elbows and tees with local wall thinning. In addition, the American Society of Mechanical Engineers Boiler and Pressure Vessel Code provides procedures in Code Case N-597-2 for evaluation of wall thinning in pipes. This paper provides validation of the evaluation procedures in Code Case N-597-2 by comparing with the field rupture data and pipe burst test data. The allowable wall thinning from the Code Case N-597-2 procedures is shown to maintain adequate margins against rupture.

Study on Pipe Wastage Mechanism by Liquid Droplet Impingement Erosion

2009 ◽  
Author(s):  
Yuma Higashi ◽  
Tadashi Narabayashi ◽  
Yoichiro Shimazu ◽  
Masashi Tsuji ◽  
Syuichi Ohmori ◽  
...  
Keyword(s):  
Test Piece ◽  
High Speed ◽  
Nuclear Power ◽  
Mass Measurement ◽  
Liquid Droplet ◽  
Mass Difference ◽  
Rotating Disk ◽  
Droplet Impingement ◽  
Accelerated Corrosion ◽  
Droplet Impingement Erosion

Evaluation of wastage speed for nuclear power plant maintains plant reliability and power up rating is important. There are two main cause of wastage flow accelerated corrosion (FAC) and mechanical erosion. This study is to develop evaluating the wastage speed by liquid droplet impingement erosion (LDIE). LDIE often occurs at downstream of corner of pipe or orifice. In this study, the liquid drop impinging tests were conducted with the test pieces mounted on a high speed rotating disk that cross thin water down jet and produced LDIE phenomena. The amount of the wastage by LDIE was evaluated by changing the rotational speed, the impingement frequency, and test piece materials. In addition, the generation mechanism of erosion was investigated by observing the surface of the test piece with a microscope. There is a method of evaluating by the mass difference before and after experiments. But this method is not correct because error becomes larger for mass measurement in the experiment, for the lost mass by LDIE is very little amount. Therefore, the method was developed to measure the volume in the erosion part. In this method, depth of LDIE was measured by the accuracy of ±0.01μm; therefore accurate measurement of the wastage can be improved.

Tackling Erosion in Nuclear Piping Systems

2007 ◽  
Author(s):  
Harold M. Crockett ◽  
Jeffrey S. Horowitz
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Training Module ◽  
Droplet Impingement ◽  
Damage Mechanisms ◽  
Accelerated Corrosion ◽  
Computerized Training ◽  
Piping Systems ◽  
Research Plan ◽  
Flow Accelerated Corrosion

Various mechanisms degrade power piping in nuclear power plants. The most important mechanism has been flow-accelerated corrosion (FAC). FAC has caused ruptures and leaks and has led to numerous piping replacements. U.S. utilities are using a combination of EPRI software and aggressive inspection programs to deal with FAC. However, current technology does not deal with erosive forms of attack including, cavitation erosion, flashing erosion, droplet impingement, and solid particle erosion. These forms of degradation have caused shutdowns and leaks have become a maintenance issue. To deal with these problems EPRI has begun a series of projects in this area. The first of these was a comprehensive report on erosion in piping systems. This work was followed with a computerized training module designed to educate utility engineers about erosive attack. Further steps are planned to deal with these forms of degradation. The first will be a meeting with knowledgeable EPRI and utility engineers to prioritize the damage mechanisms. From this meeting a research plan will be developed. This paper will present a description of erosive damage mechanisms and describe the planned R&D to deal with these mechanisms.

Assessment of Piping Field Failures and Burst Tests on Carbon Steel Pipes With Local Wall Thinning Using ASME Section XI Code Case N-597-2

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Kunio Hasegawa ◽  
Toshiyuki Meshii ◽  
Douglas A. Scarth
Keyword(s):  
Carbon Steel ◽  
Accelerated Corrosion ◽  
Steel Pipes ◽  
Pipe Burst ◽  
Evaluation Procedures ◽  
Wall Thinning ◽  
American Society ◽  
Corrosion Mechanisms ◽  
Flow Accelerated Corrosion ◽  
Local Wall Thinning

One of the more common modes of degradation in power plant piping has been wall thinning due to erosion-corrosion or flow-accelerated corrosion. Extensive work has been performed to understand flow-accelerated corrosion mechanisms and develop fracture criteria of locally thinned pipes since the tragic events at Surry Unit 2 and Mihama Unit 3. A large number of tests have been performed on carbon steel pipes, elbows, and tees with local wall thinning. In addition, the American Society of Mechanical Engineers Boiler and Pressure Vessel Code provides procedures in Code Case N-597-2 for the evaluation of wall thinning in pipes. This paper provides validation of the evaluation procedures in Code Case N-597-2 by comparing with the field rupture data and pipe burst test data. The allowable wall thinning from the Code Case N-597-2 procedures is shown to maintain adequate margins against rupture.

Erosion in Nuclear Piping Systems

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Harold M. Crockett ◽  
Jeffrey S. Horowitz
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Cavitation Erosion ◽  
Solid Particle Erosion ◽  
Particle Erosion ◽  
Droplet Impingement ◽  
Accelerated Corrosion ◽  
Piping Systems ◽  
Flow Accelerated Corrosion

Various mechanisms degrade components and power piping in nuclear power plants. The mechanism with the greatest consequence has been flow-accelerated corrosion (FAC). FAC has caused ruptures and leaks and has led to numerous piping replacements. United States utilities use a combination of EPRI guidance, software, and aggressive inspection programs to deal with FAC. However, current technology does not detail guidance for erosive forms of attack including, cavitation erosion, flashing erosion, droplet impingement, and solid particle erosion. These forms of degradation have caused shutdowns, and leaks have become a maintenance issue. This brief will present a description of erosive damage mechanisms found in nuclear power plants.

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