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: Vibration: a measure of reliability!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 Three Basic Causes of Pump Vibrations:Vibrations:

• Mechanically Mechanically InducedInduced

• System InducedSystem Induced

• Operation InducedOperation Induced

Mechanically InducedMechanically Induced

• Bad bearingsBad bearings

• Bent ShaftBent Shaft

• Unbalanced RotorUnbalanced Rotor

• Check Valve Installed BackwardsCheck Valve Installed Backwards

• Mis-AlignmentMis-Alignment

• LoosenessLooseness

• Soft FootSoft Foot

• Maximum Size ImpellerMaximum Size Impeller

System InducedSystem Induced

• Partially/Plugged StrainerPartially/Plugged Strainer

• Clogged Impeller or Suction LineClogged Impeller or Suction Line

• InstallationInstallation

PIPING?

Foundations Foundations

andand

BaseplatesBaseplates

The mass ratio must be 3:1 to The mass ratio must be 3:1 to minimize vibrationminimize vibration

Operationally InducedOperationally Induced

• CavitationCavitation

• FlowFlow

• SpeedSpeed

• Insufficient Immersion of Suction Pipe or Insufficient Immersion of Suction Pipe or BellBell

Cavitation and FlowCavitation and Flow

Operating Off The B.E.P.

Flow

Hea

d

Hig

h T

emp

. Ris

e

Lo

w F

low

Cav

itat

ion

Lo

w B

eari

ng

an

d S

eal L

ife

Red

uce

d Im

pel

ler

Lif

e

Su

ctio

n R

ecir

cula

tio

n

Dis

char

ge

Rec

ircu

lati

on

B.E

.P.

Lo

w B

eari

ng

an

d

Sea

l Lif

e

Cav

atio

n

You can’t run a pump with suction You can’t run a pump with suction and discharge valves closed!and discharge valves closed!

Minimum FlowMinimum Flow

1750 rpm 15-20% BEP Flow1750 rpm 15-20% BEP Flow

3500 rpm 30-50% BEP Flow3500 rpm 30-50% BEP Flow

Maximum FlowMaximum Flow

110-115% BEP Flow110-115% BEP Flow

SpeedSpeed

Suction Pipe ImmersionSuction Pipe Immersion

EASTMAN

Avoid Max Size ImpellersAvoid Max Size ImpellersConclusionsConclusions

EASTMAN

Avoid Max Size ImpellersAvoid Max Size Impellers

Keep speed to 1750 max Keep speed to 1750 max

ConclusionsConclusions

EASTMAN

Avoid Max Size ImpellersAvoid Max Size Impellers

Keep speed to 1750 maxKeep speed to 1750 max

Keep flow in design rangeKeep flow in design range

ConclusionsConclusions

EASTMAN

Avoid Max Size ImpellersAvoid Max Size Impellers

Keep speed to 1750 maxKeep speed to 1750 max

Keep flow in design rangeKeep flow in design range

Grout your baseplatesGrout your baseplates

ConclusionsConclusions

EASTMAN

Avoid Max Size ImpellersAvoid Max Size Impellers

Keep speed to 1750 maxKeep speed to 1750 max

Keep flow in design rangeKeep flow in design range

Grout your baseplatesGrout your baseplates

Use proper pipingUse proper piping

ConclusionsConclusions

EASTMAN

Avoid Max Size ImpellersAvoid Max Size Impellers

Keep speed to 1750 maxKeep speed to 1750 max

Keep flow in design rangeKeep flow in design range

Grout your baseplatesGrout your baseplates

Use proper pipingUse proper piping

Avoid hydraulically induced problems like Avoid hydraulically induced problems like cavitation, and suction and discharge re-circulation, cavitation, and suction and discharge re-circulation, submergence.submergence.

ConclusionsConclusions

5 PUMPS - 6 YR. MTBF

8 PUMPS - 5 YR. MTBF

15 PUMPS - 4 YR. MTBF

5 PUMPS - 6 YR. MTBF

8 PUMPS - 5 YR. MTBF

15 PUMPS - 4 YR. MTBF