Case StudyOutline: •Problem statement
 •Compressor service overview
 •Description of sealing system
 •Problem description
 •Troubleshooting
 •Findings
 •Remedial Actions
 •Result
 •Q & 

Kachu, Yoshimasa

Kikkawa, Fumitaka

Satoh, Hiroshi

English

Texas A&M University

 Yoshimasa Kachu*, Chief Engineer, Bearing Dept. at MIKASA 
Fumitaka Kikkawa, Ph.D., Director, Industrial Div. at MIKASA 
Hiroshi Satoh, Ph.D., P.E., Consultant, Professional Pump Engineer 
 
 
PTFE/Rubber Hybrid Bearings for     
Dry-Start Vertical Pumps 
MIKASA CORPORATION 
   
・Introduction of Pumps and Bearings 
・Bearing Failure Analysis 
・Statement of Problems & Countermeasures 
・PTFE/Rubber Hybrid Bearings 
・Verification & Results 
・Results of Field Application 
・Recommended Design 
・Conclusions 
 
Outline 
Plants with Vertical Pumps 
・ Thermal / Nuclear Power Plant 
・Sewage & Waterworks Plant ・Desalination Plant 
Wet 
M 
P 
Self-Feed Line 
Shaft 
Rubber    
Bearing 
Shaft Protection Tube 
Impeller 
Pump-Feed    
Line 
Typical Vertical Pumps             
＜When Using Rubber Bearings ＞ 
Advantages: 
Free from most forms  
of  shaft vibration 
・ 
Disadvantages: 
Requires feed-water  
line 
・ 
Maintenance for  
feed-water line is 
indispensible 
・ 
Stable and durable 
under normal use 
・ 
Typical Vertical Pumps             
＜When Using Bronze Bearings ＞ 
Advantages: 
・ 
Simple structure and 
low cost 
・ 
Disadvantages: 
Risk of shaft vibration ・ 
Risk of short life ・ 
No need for a feed-
water line 
Shaft 
Bronze Bearing 
Impeller 
Bearing Failure Analysis                              
＜Fishbone Diagram＞ 
Bearing 
Failure 
Tribology 
Lubric. Water  
Underestimated Quantity 
No-Replacement 
Operation Period in Air 
Friction Coefficients 
Wear Resistance 
Aggression on Shaft Sleeves 
Allowable PV-Values 
Bearing Structure 
Seawater Corrosion      
 Amount of Rubber Swell 
Structural Reliability 
Vibration Characteristics 
Undamping 
Risk of  Self-Excited Vibration 
Risk of Half-Speed Whirl 
Lubric. Water Auxiliary System Failure  
Valve
Strainer
Gland Packing
Upper Coupling
Shaft Coupling
Discharge Elbow
Pump Base
Bearing Spider
Pump Shaft
Column Pipe
Shaft Protection Tube
Submersible Bearing
Impeller
Suction Ball
Guide Vane
Discharge Bowl
From Outside Facility
Examples of Feed Water Defects     
＜When Using Rubber Bearings ＞ 
Seashells collect  
in the shaft 
protection tube.  
Seashells collect 
on the shelf-part. 
Statement of Problems & Countermeasures 
Eliminate feed water by adopting 
Dry-Start Bearings 
＜Problems＞ ＜Countermeasures＞ 
Corrosion of Shaft Protection 
Tubes and Feed Water Piping 
High Wear and Seizure 
High Shaft Vibration     
Eliminate Protection Tubes and 
Feed Water Piping by adopting 
Dry-Start Bearings 
Apply Low Friction Material 
as the Slide Member 
Use the Viscoelasticity of 
Rubber 
・ 
・ 
・ 
Maintenance trouble for 
feed-water line 
・ 
PTFE/Rubber Hybrid Bearings 
PTFE/Rubber Hybrid Bearings have a three-layer structure:        
strips of self-lubricating PTFE as a sliding material, elastic rubber, 
and a metal/resin shell.  
These bearings never burn out, even when used for short periods 
under dry conditions at pump start-up. They also minimize shaft 
vibration.  
PTFE 
Rubber 
Shell 
Brief History of Development 
1980 Start of the development Experimental Study of manufacturing method 
and material mixture ratio of PTFE/Rubber
Experimental study of wear using test bearings
1985 Application test to real pumps with full-scale bearing
Contributed ‘Turbomachinery of Society Japan’
Presentation at the 6th International Pump Users Symposium（1989）
1990 Improving of swelling rate
Experiments on grooves effect
Experiments on vibration absorption effect
1995
Friction coefficients were measured whenever any adjustment was necessary
2000 ：Means a comparatively long-term work to some extent.
：Means a short term marked work such as a contribution. etc…
2005
FEM analysis to see grooves effect
Friction coefficient comparison test with other bearings.
2010 Contributed to ‘World Pumps’（No.530 & 531, 2010）
Contributed to Journal of The Japan Institute of Marine Engineering
Presented at METSⅡ in Doha, Qatar
Contributed two papers to JSME
Measurement of Friction Coefficients 
Cooler
MotorTorque
Transducer
Thermometer
Temperature
Controller
Solenoid
Valve
Water
Air Cylinder
Bearing
Water Tank
Direction of
  Shaft Rotation
Shaft
Water Temp. kept (20～22℃）
Shaft Bracket
Load Direction
Shaft Sleeve
Bearing Pressure = 0.25MPa
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0 0.5 1 1.5 2 2.5 3 3.5 4
Shaft Peripheral Speed （m/s）
F
ri
ct
io
n
 C
o
ef
fi
ci
en
ts
PTFE/Rubber
PTFE monolithic
Rubber
Bearing Size:φ60×60L 
Comparison of Friction Coefficients 
The PTFE/Rubber Hybrid bearing is more ‘self-alignable’ than   
the monolithic PTFE bearing. 
 
Danger of Seizure 
Seals were installed after the test bearing was merged into  
the tank to interrupt the inflow/outflow of water. 
Cooler
MotorTorque
Transducer
Thermometer
Temperature
Controller
Solenoid
Valve
Cooling
Water
Air Cylinder Teasted Bearing
（φ66×246mm）
Water Tank
Direction of
　 Shaft Rotation
Shaft
Water Temp. kept 32℃
Shaft Bracket
Load Direction
Shaft Sleeve
Seal
A B C
D
Results 
Temp. points A, B, and 
C were measured near 
the slide surface. The 
real temp. of the rubber 
surface was higher.                
Seizure occurred. 
The PTFE/Rubber 
Hybrid Bearing 
temperature rose by 
only about 10 deg. C 
and stayed almost 
constant throughout 
the test. 
 
stable  
Point A 
Point B 
Point C 
Point D 
Point C Point A Point B 
Rubber Bearing 
1 2 3 
Test stopped. 
Point D 
Water Temp.=32℃ 
90 
80 
70 
60 
50 
40 
30 
20 
T
em
p
er
at
u
re
 (
℃
) 
PTFE/Rubber Hybrid Bearing 
60 20 10 
Test Time (min.) 
Test Time (min.) 
T
em
p
er
at
u
re
 (
℃
) 
20 
30 
40 
50 
Test Condition 
(1) Bearing Pressure = 0.25MPa 
(2)  Shaft Peripheral Speed = 8m/s 
seizure  
Water Temp.=32℃ 
Vibration Characteristics of Bearings 
The bearings apparently vibrate as long as a cylindrical bearing material like bronze 
is used. Distributed rubber doesn’t stop the vibration.   
Cylindrical SiC/Rubber 
PTFE/Rubber 
Rubber 
Revolution/min 
A
m
p
li
tu
d
e 
(μ
m
) 
Test Apparatus 
Motor
Strain Gauge
Ball Brg.
1
4
5
0
Fly Whool
6
0
0
0
2
2
4
5
2
0
0
0
2
0
0
0
200
Coupling
Shaft
Bearing
Allowable Operation Time in Air 
 
0
0.1
0.2
0.3
0.4
0.5
0.6
0 20 40 60 80 100 120 140
RUNNING TIME (sec)
B
E
A
R
IN
G
 P
R
E
S
S
U
R
E
 (
M
P
a
)
7.5 m/s
6.0 m/s
5.0 m/s
Shaft Peripheral Speed 
Allowable Operation Time in Air (sec) 
B
ea
ri
n
g
 P
re
ss
u
re
 (
M
P
a)
 
Under a normal bearing load, this PTFE/rubber hybrid bearing        
can be applied to all vertical pumps. 
Result of Slide Materials Examination                                
Aggression on Shaft Sleeves 
Ratio of                          
Bearing Wear 
PTFE/Rubber 
PEEK/Rubber 
Polyurethane          
/Rubber 
1.0 
1.1 
3.5 
Results of Field Application 
・Bearing exchange interval 
・The lifetime of PTFE/Rubber Hybrid Bearings was confirmed                   
to be 1.5 to 2 times higher than the lifetime of conventional Rubber                         
Bearings.  
Rubber PTFE/Rubber
φ110～φ240 4～6 years ～10 years
φ250 and over 4～6 years ～9 years
Bearing Type
Bearing I.D.
Recommended Design 
M 
P 
Self-Feed Line 
Shaft 
Pump-Feed    
Line 
Shaft Protection Tube 
Shaft 
Rubber        
Bearing 
Rubber Bearing 
PTFE/Rubber 
Hybrid Bearing 
Conclusions 
Merits of using the PTFE/Rubber Hybrid Bearing, a component 
usable with almost all vertical pumps when aiming at ‘dry-start’: 
Lower cost and lower risk at operation 
 
 No need for a lubrication water system or shaft protection 
tubes 
 No need for corrosion-prone piping   
 Simple maintenance: no bearing lubrication control required 
 Hardly any vibration 
 
 
This bearing became the De Facto Standard in Japan.  
(1200 pieces/year are produced).  


PTFE/Rubber Hybrid Bearings for Dry-Start Vertical Pumps

Texas A&amp;M Repository

 Yoshimasa Kachu*, Chief Engineer, Bearing Dept. at MIKASA Fumitaka Kikkawa, Ph.D., Director, Industrial Div. at MIKASA Hiroshi Satoh, Ph.D., P.E., Consultant, Professional Pump Engineer   PTFE/Rubber Hybrid Bearings for     Dry-Start Vertical Pumps MIKASA CORPORATION    ・Introduction of Pumps and Bearings ・Bearing Failure Analysis ・Statement of Problems & Countermeasures ・PTFE/Rubber Hybrid Bearings ・Verification & Results ・Results of Field Application ・Recommended Design ・Conclusions  Outline Plants with Vertical Pumps ・ Thermal / Nuclear Power Plant ・Sewage & Waterworks Plant ・Desalination Plant Wet M P Self-Feed Line Shaft Rubber    Bearing Shaft Protection Tube Impeller Pump-Feed    Line Typical Vertical Pumps             ＜When Using Rubber Bearings ＞ Advantages: Free from most forms  of  shaft vibration ・ Disadvantages: Requires feed-water  line ・ Maintenance for  feed-water line is indispensible ・ Stable and durable under normal use ・ Typical Vertical Pumps             ＜When Using Bronze Bearings ＞ Advantages: ・ Simple structure and low cost ・ Disadvantages: Risk of shaft vibration ・ Risk of short life ・ No need for a feed-water line Shaft Bronze Bearing Impeller Bearing Failure Analysis                              ＜Fishbone Diagram＞ Bearing Failure Tribology Lubric. Water  Underestimated Quantity No-Replacement Operation Period in Air Friction Coefficients Wear Resistance Aggression on Shaft Sleeves Allowable PV-Values Bearing Structure Seawater Corrosion       Amount of Rubber Swell Structural Reliability Vibration Characteristics Undamping Risk of  Self-Excited Vibration Risk of Half-Speed Whirl Lubric. Water Auxiliary System Failure  ValveStrainerGland PackingUpper CouplingShaft CouplingDischarge ElbowPump BaseBearing SpiderPump ShaftColumn PipeShaft Protection TubeSubmersible BearingImpellerSuction BallGuide VaneDischarge BowlFrom Outside FacilityExamples of Feed Water Defects     ＜When Using Rubber Bearings ＞ Seashells collect  in the shaft protection tube.  Seashells collect on the shelf-part. Statement of Problems & Countermeasures Eliminate feed water by adopting Dry-Start Bearings ＜Problems＞ ＜Countermeasures＞ Corrosion of Shaft Protection Tubes and Feed Water Piping High Wear and Seizure High Shaft Vibration     Eliminate Protection Tubes and Feed Water Piping by adopting Dry-Start Bearings Apply Low Friction Material as the Slide Member Use the Viscoelasticity of Rubber ・ ・ ・ Maintenance trouble for feed-water line ・ PTFE/Rubber Hybrid Bearings PTFE/Rubber Hybrid Bearings have a three-layer structure:        strips of self-lubricating PTFE as a sliding material, elastic rubber, and a metal/resin shell.  These bearings never burn out, even when used for short periods under dry conditions at pump start-up. They also minimize shaft vibration.  PTFE Rubber Shell Brief History of Development 1980 Start of the development Experimental Study of manufacturing method and material mixture ratio of PTFE/RubberExperimental study of wear using test bearings1985 Application test to real pumps with full-scale bearingContributed ‘Turbomachinery of Society Japan’Presentation at the 6th International Pump Users Symposium（1989）1990 Improving of swelling rateExperiments on grooves effectExperiments on vibration absorption effect1995Friction coefficients were measured whenever any adjustment was necessary2000 ：Means a comparatively long-term work to some extent.：Means a short term marked work such as a contribution. etc…2005FEM analysis to see grooves effectFriction coefficient comparison test with other bearings.2010 Contributed to ‘World Pumps’（No.530 & 531, 2010）Contributed to Journal of The Japan Institute of Marine EngineeringPresented at METSⅡ in Doha, QatarContributed two papers to JSMEMeasurement of Friction Coefficients CoolerMotorTorqueTransducerThermometerTemperatureControllerSolenoidValveWaterAir CylinderBearingWater TankDirection of  Shaft RotationShaftWater Temp. kept (20～22℃）Shaft BracketLoad DirectionShaft SleeveBearing Pressure = 0.25MPa0.000.050.100.150.200.250.300.350 0.5 1 1.5 2 2.5 3 3.5 4Shaft Peripheral Speed （m/s）Friction CoefficientsPTFE/RubberPTFE monolithicRubberBearing Size:φ60×60L Comparison of Friction Coefficients The PTFE/Rubber Hybrid bearing is more ‘self-alignable’ than   the monolithic PTFE bearing.  Danger of Seizure Seals were installed after the test bearing was merged into  the tank to interrupt the inflow/outflow of water. CoolerMotorTorqueTransducerThermometerTemperatureControllerSolenoidValveCoolingWaterAir Cylinder Teasted Bearing（φ66×246mm）Water TankDirection of　 Shaft RotationShaftWater Temp. kept 32℃Shaft BracketLoad DirectionShaft SleeveSealA B CDResults Temp. points A, B, and C were measured near the slide surface. The real temp. of the rubber surface was higher.                Seizure occurred. The PTFE/Rubber Hybrid Bearing temperature rose by only about 10 deg. C and stayed almost constant throughout the test.  stable  Point A Point B Point C Point D Point C Point A Point B Rubber Bearing 1 2 3 Test stopped. Point D Water Temp.=32℃ 90 80 70 60 50 40 30 20 Temperature (℃) PTFE/Rubber Hybrid Bearing 60 20 10 Test Time (min.) Test Time (min.) Temperature (℃) 20 30 40 50 Test Condition (1) Bearing Pressure = 0.25MPa (2)  Shaft Peripheral Speed = 8m/s seizure  Water Temp.=32℃ Vibration Characteristics of Bearings The bearings apparently vibrate as long as a cylindrical bearing material like bronze is used. Distributed rubber doesn’t stop the vibration.   Cylindrical SiC/Rubber PTFE/Rubber Rubber Revolution/min Amplitude (μm) Test Apparatus MotorStrain GaugeBall Brg.1450Fly Whool6000224520002000200CouplingShaftBearingAllowable Operation Time in Air  00.10.20.30.40.50.60 20 40 60 80 100 120 140RUNNING TIME (sec)BEARING PRESSURE (MPa)7.5 m/s6.0 m/s5.0 m/sShaft Peripheral Speed Allowable Operation Time in Air (sec) Bearing Pressure (MPa) Under a normal bearing load, this PTFE/rubber hybrid bearing        can be applied to all vertical pumps. Result of Slide Materials Examination                                Aggression on Shaft Sleeves Ratio of                          Bearing Wear PTFE/Rubber PEEK/Rubber Polyurethane          /Rubber 1.0 1.1 3.5 Results of Field Application ・Bearing exchange interval ・The lifetime of PTFE/Rubber Hybrid Bearings was confirmed                   to be 1.5 to 2 times higher than the lifetime of conventional Rubber                         Bearings.  Rubber PTFE/Rubberφ110～φ240 4～6 years ～10 yearsφ250 and over 4～6 years ～9 yearsBearing TypeBearing I.D.Recommended Design M P Self-Feed Line Shaft Pump-Feed    Line Shaft Protection Tube Shaft Rubber        Bearing Rubber Bearing PTFE/Rubber Hybrid Bearing Conclusions Merits of using the PTFE/Rubber Hybrid Bearing, a component usable with almost all vertical pumps when aiming at ‘dry-start’: Lower cost and lower risk at operation   No need for a lubrication water system or shaft protection tubes  No need for corrosion-prone piping    Simple maintenance: no bearing lubrication control required  Hardly any vibration   This bearing became the De Facto Standard in Japan.  (1200 pieces/year are produced).  

https://oaktrust.library.tamu.edu/bitstream/1969.1/172600/1/METS2CaseStudy18.pdf

PTFE/Rubber Hybrid Bearings for Dry-Start Vertical Pumps

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Texas A&M University

Texas A&M Repository

PTFE/Rubber Hybrid Bearings for Dry-Start Vertical Pumps

Abstract

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Full text

Available Versions

Texas A&M University

Texas A&amp;M Repository

Texas A&M Repository