May I inquire regarding high vibration of Feedwater Pump at a partial load range only. At partial load range, the vibration could reach up to 8 mm/s-rms, the alarm is set at 7.1 mm/s-rms. Vibration is normal at low load - when Automatic Recirculation Valve (ARV) is close and at full load - when ARV is fully open. We suspected that this was due to the actuation of the ARV (we assumed of a worn out valve internals). We replaced the valve with new, but did not solve the issue.
The ARV is on the discharge side (NDE) of the pump but the high vibration is on the suction side (DE).
I would like to hear if anyone has experience on this.
I can provide more information. Please let me know what information is needed that can lead to the cause of this.