Problems Encountered In Boiler Feed Pump Operation

Abstract

Although mechanical and hydraulic instabilities in centrifugal pumps caused a considerable amount of problems for large Nuclear and Fossil Generating Stations influencing "Power Plant Availability," a relatively limited amount of res Parch work was clone in this area. The author makes an attempt to outline problems in general, gives definitions for hydraulic and dynamic "Instabilities," outlines the "Mechanisms" that create them, establishes safe operating speed and flow ranges for large pumps, and discusses how to treat the above subjects when Held failures occurred. Interaction between hydraulically induced forces and bearing design parameters, and their influence on rotor vibration characteristics is emphasized. Friction induced partial frequency modes are also discussed. These forces are sizable and can influence rotor and bearing design requirements, can change rotor stability and the appearance of the pump rotor critical speeds. Comparison is made between vertically and horizontally oriented pumps and between volute and diffuser types. The author also outlines the minimum instrumentation necessary to identify problem areas before and after failure occurs and supports this with actual field failure cases. It is outlined how a simple factory (witness) test can uncover potential future Held problems. Areas where systematic future research and development work is necessary are pointed out.