Centrifugal Pump Vibrations The Causes by Steven J

Centrifugal Pump Vibrations: The Causes by Steven J. Hrivnak, P. E. Associate Mechanical Engineer Tennessee 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

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

5 PUMPS - 6 YR. MTBF 8 PUMPS - 5 YR. MTBF 15 PUMPS - 4 YR. MTBF