Centrifugal Pump Vibrations: The Causes by Steven J. Hrivnak, P.E. Associate Mechanical Engineer Tennessee Eastman Eastman Chemical Company EASTMAN FAULTS REPORTED OVER 3 YEARS Vibration: a measure of reliability! Poorly installed and operated pumps average .178 in/sec overall vibration and have 6 months life. Properly installed pumps average .071 in/sec overall vibration and have 60 months life. EASTMAN Three Basic Causes of Pump Vibrations: • Mechanically Induced • System Induced • Operation Induced Mechanically Induced • Bad bearings • Bent Shaft • Unbalanced Rotor • Check Valve Installed Backwards • Mis-Alignment • Looseness • Soft Foot • Maximum Size Impeller System Induced • Partially/Plugged Strainer • Clogged Impeller or Suction Line • Installation PIPING? Foundations and Baseplates The mass ratio must be 3:1 to minimize vibration Operationally Induced • Cavitation • Flow • Speed • Insufficient Immersion of Suction Pipe or Bell Cavitation and Flow Flow Cavation Low Bearing and Seal Life B.E.P. Discharge Recirculation Suction Recirculation Reduced Impeller Life Low Bearing and Seal Life Low Flow Cavitation High Temp. Rise Head Operating Off The B.E.P. You can’t run a pump with suction and discharge valves closed! Minimum Flow 1750 rpm 15-20% BEP Flow 3500 rpm 30-50% BEP Flow Maximum Flow 110-115% BEP Flow Speed Suction Pipe Immersion Conclusions Avoid Max Size Impellers EASTMAN Conclusions Avoid Max Size Impellers Keep speed to 1750 max EASTMAN Conclusions Avoid Max Size Impellers Keep speed to 1750 max Keep flow in design range EASTMAN Conclusions Avoid Max Size Impellers Keep speed to 1750 max Keep flow in design range Grout your baseplates EASTMAN Conclusions Avoid Max Size Impellers Keep speed to 1750 max Keep flow in design range Grout your baseplates Use proper piping EASTMAN Conclusions Avoid Max Size Impellers Keep speed to 1750 max Keep flow in design range Grout your baseplates Use proper piping Avoid hydraulically induced problems like cavitation, and suction and discharge re-circulation, submergence. EASTMAN 55PUMPS PUMPS- -66YR. YR.MTBF MTBF 88PUMPS PUMPS- -55YR. YR.MTBF MTBF 15 15PUMPS PUMPS- -44YR. YR.MTBF MTBF
