We have a barrel type boiler feed pump installed in a 500 MW PC fired facility which has experienced intermittant vibration problems.
Suction pressure is from residual pressure of upstream booster pumps.
NPSHa was designed at 228 psia. We have checked pump nozzle loads and made minor pipe support adjustments. Piping does not appear to be overloading nozzles. Pump has double suction first stage with suction specific speed of 8250. Vibration tends to decrease as flow is reduced below design capacity.