NDLI: Detailed Finite Element Analysis of Darlington NGS Feeder Pipes With Locally Thinned Regions Below Pressure Minimum Thickness

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Haq, Irfan Stojakovic, Mike Fabbri, Sandy
Copyright Year	2012
Abstract	Feeder Pipes in CANDU nuclear stations are experiencing wall thinning due to flow accelerated corrosion (FAC) resulting in locally thinned regions in addition to general thinning. In Darlington NGS these locally thinned regions can be below pressure based minimum thickness (tmin) in the straight pipe region (STR1) between Grayloc and Bend 1. The (tmin) is required as per ASME Code Section III NB-3600 Equation (1). A methodology is presented to qualify the locally thinned regions under NB-3200 (NB-3213 & NB-3221) using internal pressure loading only. Detailed finite element models are used for internal pressure analysis using ANSYS v11.0. All other loadings such as deadweight, thermal and seismic loadings are separately qualified under NB-3600 using a general purpose piping stress analysis software. The piping stress analysis is based on average thickness equal to tmin along with maximum values of ASME Code stress indices (Table NB-3681(a)-1). The requirement for the use of this methodology is that the average thickness of each cross-section with the locally thinned region shall be at least tmin. In contrast, the finite element analysis models are thinned to 0.75 tmin (in increments of 0.05 tmin) all-around the circumference in the straight section region allowing for flexible inspection requirements. In Darlington NGS there are 22 different types of feeder pipes which have been grouped into 6 types based on similarities in pipe size, straight section length, bend angle and orientation. Thickness versus the allowable axial extent curves were developed for 6 representative feeder types. The stress analysis results show that all Darlington NGS outlet feeder pipes are fit for service with locally thinned regions in STR1 with down to 75% of the pressure based minimum thickness. This paper demonstrates the methodology and effectiveness of finite element analysis in extending the useful life of degraded piping components.
Sponsorship	Pressure Vessels and Piping Division
Starting Page	167
Ending Page	177
Page Count	11
File Format	PDF
ISBN	9780791855027
DOI	10.1115/PVP2012-78800
Volume Number	Volume 3: Design and Analysis
Conference Proceedings	ASME 2012 Pressure Vessels and Piping Conference
Language	English
Publisher Date	2012-07-15
Publisher Place	Toronto, Ontario, Canada
Access Restriction	Subscribed
Subject Keyword	Computer software Stress analysis (engineering) Service life (equipment) Inspection Pressure Flow (dynamics) Stress Finite element model Corrosion Finite element analysis Pipes Asme standards Pipe sizes
Content Type	Text
Resource Type	Article

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