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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 PumpThree Basic Causes of PumpVibrations:Vibrations:
•• Mechanically InducedMechanically Induced
•• 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
•• MisMis-Alignment-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?
FoundationsFoundations
andand
BaseplatesBaseplates
The mass ratio must be 3:1 toThe mass ratio must be 3:1 tominimize vibrationminimize vibration
Operationally InducedOperationally Induced
•• CavitationCavitation
•• FlowFlow
•• SpeedSpeed
•• Insufficient Immersion of Suction Pipe orInsufficient Immersion of Suction Pipe orBellBell
Cavitation and FlowCavitation and Flow
Operating Off The B.E.P.
Flow
Hea
d
Hig
hT
emp
.Ris
e
Lo
wF
low
Cav
itat
ion
Lo
wB
eari
ng
and
Sea
lLif
e
Red
uce
dIm
pel
ler
Lif
e
Su
ctio
nR
ecir
cula
tio
n
Dis
char
ge
Rec
ircu
lati
on
B.E
.P.
Lo
wB
eari
ng
and
Sea
lLif
e
Cav
atio
n
You can’t run a pump with suctionYou can’t run a pump with suctionand 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 maxKeep 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 yourGrout your baseplatesbaseplates
Use proper pipingUse proper piping
Avoid hydraulically induced problems likeAvoid hydraulically induced problems likecavitation, 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
