Limit Analysis of a Pipe Section With Non-Uniform Wall Thinning

2002 ◽  
Author(s):  
Keshab K. Dwivedy
Keyword(s):  
Limit Analysis ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Structural Integrity ◽  
Pipe Wall ◽  
Limit Load ◽  
Pipe Section ◽  
Wall Thinning ◽  
Uniform Wall

Certain process piping in nuclear and non-nuclear power plants undergo pipe wall thinning due to flow assisted corrosion (FAC). This localized mechanism of corrosion combined with erosion is complex. The potential degradation of the pipe wall depends upon the water chemistry, operating temperature and pressure, flow velocity, piping material and piping configuration. The management of FAC in a power plant is performed in the following basic steps: Identification of potential locations, UT inspection of locations and characterization of pipe wall thinning, and evaluation of wall thinning to establish structural integrity and/or repair/replacement. The section of the pipe is repaired or replaced if the structural integrity cannot be established until next scheduled inspection. In the past 15 years, FAC programs have been established in nuclear power plants. Structural integrity evaluation is a part of the program. Simplified methods and rules are established in ASME Section XI code and in several code cases for verifying structural integrity. Pressure design methods are formalized for uniform and non-uniform wall thinning. However, the limit analysis methods for moment loading in the code rules are formulated for uniform thinning of the wall for simplicity. FAC related wall thinning is truly non-uniform, and treating it as non-uniform in the analysis can show additional structural margin compared to analysis conservatively assuming a uniformly thinned wall. This paper has developed simple analytical formulation of limit load carrying capability of a pipe section with non-uniform thinning. The method of analysis is illustrated with examples of actual plant situations. The formulation developed here can be used with the ASME code method to extend remaining life of FAC degraded components until the plant can plan for repair or replacement. Thus the analytical tool can help the plant owners to save resources by performing repair and replacement in a planned manner.

Load Factor for Evaluating Non-Planar Flaws in Carbon Steel Piping Using Limit Load Methodology

2016 ◽  
Author(s):  
Phuong H. Hoang
Keyword(s):  
Carbon Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Pipe Wall ◽  
Local Strain ◽  
Limit Load ◽  
Evaluation Methodology ◽  
Load Factor ◽  
Wall Thinning ◽  
Steel Piping

Non-planar flaw such as local wall thinning flaw is a major piping degradation in nuclear power plants. Hundreds of piping components are inspected and evaluated for pipe wall loss due to flow accelerated corrosion and microbiological corrosion during a typical scheduled refueling outage. The evaluation is typically based on the original code rules for design and construction, and so often that uniformly thin pipe cross section is conservatively assumed. Code Case N-597-2 of ASME B&PV, Section XI Code provides a simplified methodology for local pipe wall thinning evaluation to meet the construction Code requirements for pressure and moment loading. However, it is desirable to develop a methodology for evaluating non-planar flaws that consistent with the Section XI flaw evaluation methodology for operating plants. From the results of recent studies and experimental data, it is reasonable to suggest that the Section XI, Appendix C net section collapse load approach can be used for non-planar flaws in carbon steel piping with an appropriate load multiplier factor. Local strain at non-planar flaws in carbon steel piping may reach a strain instability prior to net section collapse. As load increase, necking starting at onset strain instability leads to crack initiation, coalescence and fracture. Thus, by limiting local strain to material onset strain instability, a load multiplier factor can be developed for evaluating non-planar flaws in carbon steel piping using limit load methodology. In this paper, onset strain instability, which is material strain at the ultimate stress from available tensile test data, is correlated with the material minimum specified elongation for developing a load factor of non-planar flaws in various carbon steel piping subjected to multiaxial loading.

309 High Temperature Impact-Fretting Wear Experiments for Evaluation of Pipe Wall Thinning Phenomena in Nuclear Power Plants

2013 ◽  
Vol 2013.49 (0) ◽  
pp. 87-88
Author(s):  
Yoshiki SATO ◽  
Akira IWABUCHI ◽  
Michimasa UCHIDATE ◽  
Hitoshi YASHIRO ◽  
Akito OYAKAMA ◽  
...  
Keyword(s):  
High Temperature ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Pipe Wall ◽  
Fretting Wear ◽  
Wall Thinning ◽  
Temperature Impact

FSI-Based Assessment of FAC-Caused Wall Thinned Piping

2009 ◽  
Author(s):  
Sun-Hye Kim ◽  
Yoon-Suk Chang ◽  
Young-Jin Kim
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Flow Characteristics ◽  
Limit Load ◽  
Bend Angle ◽  
Piping System ◽  
Integrity Assessment ◽  
Wall Thinning ◽  
Analysis Scheme

Lots of investigations on failures of wall thinned piping have been carried out since the accident of Surry unit 2 in USA. From these preceding efforts, flow accelerated corrosion (FAC) which is a kind of wall thinning phenomenon is revealed main factor of failure of pipes in nuclear power plants. However, there are a few researches which directly take into account of flow characteristics and geometric changes for stress assessment of FAC-caused wall thinned piping. In this paper, structural integrity assessment employing a fluid-structure interaction (FSI) analysis scheme is performed on pipes representing secondary piping system of PWR which consists of straight pipes and elbows of various bend angles. Prior to the assessment, CFD analyses are conducted to predict plausible wall thinning location by considering flow and geometric parameters such as bend angle and radius of elbow. Then, for typical pipe geometry, detailed limit load analyses are performed to calculate maximum stress caused by turbulence and velocity of flow near the wall thinned part. Through these kinds of detailed parametric analyses, effects of FSI were observed, which should be considered for assessment of FAC-caused wall thinned piping.

scholarly journals Development of ToSPACE for Pipe Wall Thinning Management in Nuclear Power Plants

2019 ◽  
Vol 09 (01) ◽  
pp. 1-15
Author(s):  
Kyeong Mo Hwang ◽  
Hun Yun ◽  
Hyeok Ki Seo ◽  
Geun Young Lee ◽  
Kyung Woo Kim
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Pipe Wall ◽  
Wall Thinning

scholarly journals A non-contact ultrasonic sensor for pipe-wall thinning inspection of nuclear power plants

2019 ◽  
Author(s):  
A. Tamura ◽  
M. Endo ◽  
N. Kono ◽  
H. Okazawa ◽  
S. Okido ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Pipe Wall ◽  
Ultrasonic Sensor ◽  
Wall Thinning

The Comprehensive Discussion of the Pipe Wall Thinning of Secondary System in BWR and PWR Nuclear Power Plants

2006 ◽  
Author(s):  
Taku Ohira ◽  
Tomohiko Hoshino
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Single Phase ◽  
Pipe Wall ◽  
Secondary System ◽  
Power Company ◽  
Wall Thinning ◽  
Secondary Systems ◽  
Pipe Bending

The behaviors of pipe wall thinning of secondary systems in The Japan Atomic Power Company (JAPC)’s BWR and PWR nuclear power plants were compared in this paper, to discuss the effects of respective factors contributing to corrosion protection of pipe. The rates of pipe wall thinning in single-phase flow environment, in both BWR and PWR, depend on temperature. Nevertheless, the rate of pipe wall thinning in PWR is more than that in BWR. The rates of pipe wall thinning at elbow of pipe, bending of pipe, straight run of pipe and reducer areas are mutually different, although they are located in the same line. Especially, the rates of pipe wall thinning at elbows of pipes, bendings of pipes, straight runs of pipes and reducers, which are located closely downstreams of the pumps discharge nozzles, elbows, orifices or bent pipes, depend on not the temperature but the pipe configuration.

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