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