The Closed Feedwater Heater is an essential component in fossil and nuclear fueled power generating stations. Feedwater heaters have significant influence on plant availability and performance and, if neglected, can contribute to long-term unit load reductions. This course concentrates on their design, operation and maintenance aspects.

Participants are provided with the background information required to identify, evaluate, and correct feedwater heater operation and maintenance problems. This information includes a review of related heat transfer principles, feedwater heater design, and construction principles. Techniques for identifying failures and heat transfer deficiencies are identified. The multiple choices of possible corrective actions that can be taken in each given situation are presented. This course segment is followed by a discussion of the methods that are employed to select the optimum technical corrective action among all of the choices that were previously described.

Feedwater heater failure causes are identified and related to design features, corrosion mechanisms, and modes of operation. Methods of failure prevention and failure rate reduction are also identified. Available maintenance methods and the various types of tube plugs are discussed. Methods of prolonging life are reviewed. The practical aspects of electromagnetic testing (i.e. eddy current testing) and ultrasonic testing of tubes are identified. The advantages and limitations of each method are discussed and the optimum methods for different tube materials are presented.

Upon completion of this course, the participants will understand the principles of closed feedwater heater operation and will be able to develop strategies for performance improvement and increased availability. Participants will also gain knowledge of closed feedwater heater design; failure mechanisms; performance monitoring; and non-destructive examination of heat exchanger tubes.

Robert J. Bell, P.E., is President of Heat Exchanger Systems, Inc., a consulting engineering firm in Boston, Massachusetts. He specializes in the analysis and specification of feedwater heaters, steam surface condensers and associated systems. Mr. Bell's experience includes performance testing, performance monitoring, corrosion failure analysis, vendor surveillance, materials selection, consultation on operation and maintenance, condenser retubing and troubleshooting.   l

The seminar material builds upon simple conduction through a solid plate of a homogeneous material and adds the complexity of evaluating heat transfer through a series of plates of different materials to demonstrate analysis of multiple heat transfer resistances. The effects of non-uniform geometries inducing circular geometry are discussed. This leads to the analysis of heat transfer in a heat exchanger tube. Temperature duty diagrams for counter flow, parallel flow and condensing phase are reviewed. The five resistances to heat transfer are identified and related to feedwater heater rating.

Feedwater heater rating is reviewed. Methods of determining heat transfer resistances or limits of resistance are identified. The method of determining feedwater heater heat balance is presented.

The functions of a feedwater heater are discussed. Each zone is treated separately and the effects of multiple zones are reviewed. The effects of cascading drains are also discussed. Feedwater heater temperature duty diagrams are reviewed and, related to measured performance parameters. The feedwater heaters place in the cycle is also discussed.

Terminology is reviewed. Specific information regarding tube material selection, tube fabrication and tube mill quality control is provided. Channel and tubesheet design and construction is reviewed. Alternate methods of tube joint design and tube joint fabrication are discussed. Key component designs, such as the drain cooler end plate, are also discussed.

An overview of the most frequent failure causes, such as impingement erosion, is presented. The relationship between feedwater design, feedwater heater normal and abnormal modes of operation, alternate tube materials and other component failures, such as impingement plates, are discussed.

Level maintenance, the effects of heaters out of service, leak detection, record keeping, visual examination, lay up, selected repair technologies including tube plugging are discussed.

Review of instrumentation types and application, parameters to be monitored on an operator level, TTD and DCA monitoring, performance testing, and alternate cleaning techniques are discussed. Some guidance for feedwater heater trouble shooting analysis also is presented.

Principles of various techniques including eddy current testing and ultrasonic testing will be discussed and their application to feedwater heaters will be identified.

This course is intended for those engineers and support staff concerned with specification, operation, maintenance and repair of closed feedwater heaters. The program should be of special value to personnel who are required to evaluate the condition and operation of existing equipment, make "repair or replace" decisions, and resolve operating problems.