Field Demonstration of a Boiler Feedwater Pump Upgraded to Reduce Vibration and Acoustic Emissions Without Compromising Performance

Abstract

The high-energy boiler feedwater pump is the heart of the steam-generation cycle in modern high-pressure boiler systems. These multi-stage centrifugal pumps are engineered to produce system pressures from 12 MPa (1800 lb/in2) to 45 MPa (6500 lb/in2) at temperatures ranging from 150°C (300°F) to 312°C (600°F). To optimize pump hydraulic performance, pump designers have focused on impeller and diffuser vane angles, hydraulic passageway shapes and minimized impeller-to-diffuser vane clearances to maximize performance within a narrow range of operation. This was the approach that had been applied successfully on lower energy pump design of an earlier era. However, in the mid-1980s, in response to market forces, operators began to cycle and operate plants over a wide range of loads, which was contrary to the original plant designs. This new operating paradigm has resulted in unacceptable vibration and acoustic emissions that are often attributable to impeller-to-diffuser vane interaction (a result of the minimized clearances referenced previously). Efforts to reduce these emissions by changing the design must always be balanced with the potential impact on hydraulic performance. This paper uses operating field data taken from boiler feedwater pumps to prove that by: • optimizing hydraulic passageways and • changing the internal geometry, specifically, impeller-to-diffuser vane combinations, vibration and acoustic emissions are reduced without compromising hydraulic performance.