309 Highland Terrace
Prince Frederick, MD 20678
USA
Phone: (410) 535-6851
Fax: (410) 535-6846
Email:
Specializing in Sampling and Instrumentation, Corrosion,
Water and Steam Chemistry, and Failure Analysis
Serving the power industry since 1983
Evaluation for Flow-Accelerated Corrosion (Erosion-Corrosion) for Nuclear, Fossil, and Industrial Steam Generation
Copyright (c) 2009 Jonas, Inc. All Rights Reserved
- Preliminary assessment (drawings, flow velocities, cycle design, experience)
- Component details and actual installation
(walkdown, assembly, past history)
- Final system and/or component description and operating and inspection/maintenance history
- Computer modeling, calculation of erosion-corrosion rates, contributions of individual effects
- Monitoring of wall
thinning rate
- Report with conclusions and recommendations
- Implementation of engineering solutions
- Follow-up
Project Tasks (one or more)
On December 9, 1986, a rupture occurred in an 18-inch diameter elbow in the feedwater pipe leading to the main feed pump "A" of Virginia
Power Surry Unit #2. The "break before leak" demonstrated itself as the separation of a large piece of the carbon steel elbow,
which was found to have been significantly weakened by wall thinning caused by flow-accelerated corrosion (FAC, E-C).
In 1995, a fatal
pipe break at the economizer inlet occurred at a Wisconsin utility and in 1996 at a Wisconsin paper mill. An industry survey
revealed that wall thinning by flow-accelerated corrosion, as well as formation of excessive amounts of corrosion products in the
steam cycle is a widespread problem. Almost 100% of PWR unit wet steam and 50% of preboiler systems, 30% of fossil, and 40%
of industrial units in the U.S. are affected. Flow-accelerated corrosion is also very common in the combined cycle units in piping
and HRSGs. It can lead to catastrophic failures, leaks in feedwater, wet steam, and condensate piping, interference with proper
cycle chemistry control, and accumulation of corrosion products in steam generators, turbines, and on heat transfer surfaces.
Using
various sources of field and laboratory data, Jonas, Inc. has developed an evaluation procedure as described below.
Figure 1. Example of Failure due to Flow-Accelerated Corrosion
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Evaluation of Combined Effects:
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Objectives of the Evaluation:
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- Component Geometry
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- Find and Select
Components to be Inspected
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-
Flow Velocity
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- Interpret NDT Results
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- Water and Steam Properties
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- Find Root Causes of
Wall Thinning
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- Material Composition
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- Determine Inspection Interval
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- Water Chemistry
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Determine Effects on Cycle Iron Transport
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- Operating Experience
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- Recommend Engineering Solutions
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