POWER PLANT HEAT EXCHANGER CONDITION ASSESSMENT SEMINAR - 2 DAYS
Presentation Time: Seven sessions totaling 2 days
The text material that will serve as a guide and will minimize the need for note taking. Background information, copies of diagrams, and relevant papers will be included in the text. The text is supplemented by EPRI report GS-6724, Condition Assessment Guidelines for Fossil Fuel Power Plant Components.
Lecture Abstract: Power Plant Heat Exchanger Condition Assessment is a slide assisted lecture/discussion seminar that is presented by an experienced power plant heat exchanger engineer/nondestructive testing technician. It is directed towards engineers, and plant operations/main-tenance supervisors.
The intent of the seminar is to provide the participants with the necessary background information that is required to identify and evaluate heat exchanger condition. This information includes a review of feedwater heater and steam surface condenser design and operation.
Half of the seminar is devoted to identifying heat exchanger failure mechanisms and the other half is devoted to examination techniques. Eddy current testing (ET) is the principle examination technique discussed. ET's capabilities and limitations are identified. The role of the analyst is emphasized.
SESSION 1 - Operating and Design Features of Steam Surface Condensers and Feedwater Heaters
An overview of alternate designs and design features pertinents to inspection practices. Also included is overview of principles of operations. Includes subjects such as steam flow, high velocity zones and the detrimental affects of abnormal operation.
SESSION 2 - Condenser Failure Causes
An overview of the most frequent tube problems both on the steamside, (impingement attack, flow induced vibration, condensate corrosion and stress corrosion cracking) and on the waterside, (galvanic corrosion, dealloying, pitting, and sulfide attack) is presented. Proper design, operation and maintenance methods are also identified.
SESSION 3 - Feedwater Heater Failure Causes
An overview of the most frequent tube failure causes such as impingement erosion is presented. The relationship between feedwater design, feedwater heater normal and abnormal modes of operation and other component failures such as impingement plates are discussed.
SESSION 4 - Visual Examination
Visual examination techniques and key components to be examined are identified. Surface preparation, lighting, level of detection and re-according methods and equipment are identified.
SESSION 5 - Principles of Eddy Current Testing Non-Ferromagnetic Tubes
Included is an explanation of how the technique works and an overview of signal analysis, various modes of operation, test frequencies and test sensitivity are discussed. The alternate equipment and probe designs are identified. The advantages and limitation of the technique are discussed.
SESSION 6 - Electromagnetic Examination of Slightly Ferritic (i.e. monel) and Highly Ferritic (i.e. ferritic stainless steel and carbon steel), Tubing.
The following techniques are presented and their advantage and limitation are discussed:
Saturation Eddy Current Testing
Partial Saturation Eddy Current Testing
Flux Leakage Testing
Remote Field Eddy Current Testing
SESSION 7 - Condition Assessment Techniques
The EPRI three level approach is:
Level I Assessment
- Records Review/Interviews
- Historical Data Comparison
Level II Assessment
- Visual Examination
- Magnetic Particle Testing
- Electromagnetic Examination
- Eddy Current Testing
- Flux leakage Testing
- Remote Field Eddy Current Testing
- Ultrasonic Testing
- Shells, Waterboxes and Channels
Level III Assessment
- Failure Analysis
- Corrosion Monitoring
The advantages and limitations of each technique are discussed. Eddy Current Testing is described in more detail, being the principle form of tube testing. The technique is demonstrated using tube samples removed from power plant heat exchangers.
Eddy current testing is as much an art as it is a science. Erroneous results are often obtained because of the examiner's lack of knowledge of power plant heat exchanger failure mechanisms and because of the use of poorly qualified technicians. Techniques for assuring accurate eddy current testing are identified.
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