Ending Excessive Vibration Response at a Nuclear Power Plant

摘要

Premature bearing and seal failures were occurring in a safety-related decay heat removal pump in a nuclear power plant. Plant management and the Nuclear Regulatory Commission asked Mechanical Solutions Inc (MSI) to verify that the resonance issue was the only reason for the increased vibration, and if so, to determine how best to eliminate the problem to end the chronic failures. MSI measured the pressure pulsation one pipe diameter downstream of the discharge nozzle. It then demonstrated with both manual calculations and finite element analysis that the pulsation level was close to that required to drive the discharge piping resonant response at the vibration level that had been detected. This verified it as the "problem source." After analysis and testing, the assembly was found to have quenched resonance at the vane pass acoustic frequency.