Gunn, Kerry

Karban, Kevin

Texas A&amp;M Repository

Bearing Failure on a Boiler Feed Water PumpA Case Study by:Kevin KarbanKerry Gunn1522Background Information BB3 Between bearing multistage centrifugal pump. Ingersoll-Rand 5-HMTA-5 Service is Boiler Feed Water, 240F Operating Temperature, 10 PSIG Suction Pressure, 895 PSIG Discharge Pressure The pump was originally built for high pressure amine service at a different facility and was acquired in 1974 for use in the boiler feed water service.1533Pump Cross Section Drawing1544Failure Mode High outboard vibrations on the pump outboard bearing cause a shutdown for repair. Pump repair is attempted multiple times but continues to fail due to high outboard thrust bearing temperatures (250F+). 1555Maintenance Work Performed Problem started after the initial repair where the pump was sent offsite for a overhaul at a non-OEM shop.  The rotor assembly was replaced with a storehouse spare. After the initial repair failed a field repair (outboard bearing only), 2nd shop repair (non-OEM, case not split) and 3rd (OEM, case split) were attempted.  All failed with the same failure mode.1566Maintenance Work Performed On the 4th repair the pump was sent to the OEM shop again. The following modifications where made to the pump.1577Shaft Design Issue It was discovered that the installed shaft material was 410SS. The pump was originally designed with a 316SS shaft to match the 316SS casing. Thermal growth difference of 5.5 10-6 in/in F vs. 8.9 10-6 in/in F Delta L for 410SS = 5.5*(250F-80F)*12 in = 0.01122 in Delta L for 316SS = 8.9*(250F-80F)*12 in = 0.01815 Difference of 0.007 in1588Shaft Design IssueDirection of Case GrowthDirection of Shaft Growth1599Balance Drum Setting Existing design balance drum setting relied on a fairly tedious and vague thrust  A spring was added in the thrust bearing assembly which allowed the balance drum to close as needed to balance the load and not be constrained.16010Balance Drum and Balance Piston Pictures16111Existing Design Thrust bearing is contained on both ends in a traditional manner. A spacer is used between the bearings and inboard cover to set the balance piston gap at 0.002” to 0.005”.16212New Design Outboard bearing bracket was modified to install a wavy spring. This allows for the thrust force to close the gap to balance itself out rather than a fixed gap. Originally meant for use in pumps where the balance piston would wear and the spring will compensate for this wear.16313Pump Installation Issue One issue identified after the 2nd shop repair was possible thermal growth of the casing binding the pump.   The pump was not installed per the OEM recommendations for 200F and higher applications. On each repair after the 2nd shop repair the base bolts were loosened after heating with an indicator placed on the bearing housing. Thermal growth was found as high as 0.025”.16414OEM Recommended Mounting16515Field Results Before shaft material change and bearing housing redesign the thrust bearing was running over 200F.  Pump was taken out of service at less than a 24 hour run time. After modifications the bearing housing runs between 160F to 180F and has been in service for nearly one year without any repairs.16616Conclusions and Recommendations Recognize issues with material selection and changes during repairs Effects of thermal growth, especially with pumps that were not designed originally for the temperature Complications of using equipment that was not designed for the service API 610, 11th Edition, para 6.7.1 prohibits close axial clearance from being used to balance thrust.167

Bearing Failure On A Boiler Feed Water Pump

Texas A&M University

Bearing Failure on a 
Boiler Feed Water 
Pump
A Case Study by:
Kevin Karban
Kerry Gunn
152
2Background Information
 BB3 Between bearing multistage centrifugal pump.
 Ingersoll-Rand 5-HMTA-5
 Service is Boiler Feed Water, 240F Operating Temperature, 10 PSIG Suction 
Pressure, 895 PSIG Discharge Pressure
 The pump was originally built for high pressure amine service at a different 
facility and was acquired in 1974 for use in the boiler feed water service.
153
3Pump Cross Section Drawing
154
4Failure Mode
 High outboard vibrations on the pump outboard 
bearing cause a shutdown for repair.
 Pump repair is attempted multiple times but continues 
to fail due to high outboard thrust bearing temperatures 
(250F+). 
155
5Maintenance Work Performed
 Problem started after the initial repair where the pump 
was sent offsite for a overhaul at a non-OEM shop.  
The rotor assembly was replaced with a storehouse 
spare.
 After the initial repair failed a field repair (outboard 
bearing only), 2nd shop repair (non-OEM, case not 
split) and 3rd (OEM, case split) were attempted.  All 
failed with the same failure mode.
156
6Maintenance Work Performed
 On the 4th repair the pump was sent to the 
OEM shop again.
 The following modifications where made to the 
pump.
157
7Shaft Design Issue
 It was discovered that the installed shaft material was 410SS.
 The pump was originally designed with a 316SS shaft to match 
the 316SS casing.
 Thermal growth difference of 5.5 10-6 in/in F vs. 8.9 10-6 in/in F
 Delta L for 410SS = 5.5*(250F-80F)*12 in = 0.01122 in
 Delta L for 316SS = 8.9*(250F-80F)*12 in = 0.01815
 Difference of 0.007 in
158
8Shaft Design Issue
Direction of Case Growth
Direction of Shaft Growth
159
9Balance Drum Setting
 Existing design balance drum setting relied on a 
fairly tedious and vague thrust 
 A spring was added in the thrust bearing 
assembly which allowed the balance drum to 
close as needed to balance the load and not be 
constrained.
160
10
Balance Drum and Balance 
Piston Pictures
161
11
Existing Design
 Thrust bearing is contained 
on both ends in a traditional 
manner.
 A spacer is used between the 
bearings and inboard cover 
to set the balance piston gap 
at 0.002” to 0.005”.
162
12
New Design
 Outboard bearing bracket 
was modified to install a 
wavy spring.
 This allows for the thrust 
force to close the gap to 
balance itself out rather than 
a fixed gap.
 Originally meant for use in 
pumps where the balance 
piston would wear and the 
spring will compensate for 
this wear.
163
13
Pump Installation Issue
 One issue identified after the 2nd shop repair was 
possible thermal growth of the casing binding the 
pump.  
 The pump was not installed per the OEM 
recommendations for 200F and higher applications.
 On each repair after the 2nd shop repair the base bolts 
were loosened after heating with an indicator placed on 
the bearing housing.
 Thermal growth was found as high as 0.025”.
164
14
OEM Recommended Mounting
165
15
Field Results
 Before shaft material change and bearing housing 
redesign the thrust bearing was running over 200F.  
Pump was taken out of service at less than a 24 hour 
run time.
 After modifications the bearing housing runs between 
160F to 180F and has been in service for nearly one 
year without any repairs.
166
16
Conclusions and 
Recommendations
 Recognize issues with material selection and changes 
during repairs
 Effects of thermal growth, especially with pumps that 
were not designed originally for the temperature
 Complications of using equipment that was not 
designed for the service
 API 610, 11th Edition, para 6.7.1 prohibits close axial 
clearance from being used to balance thrust.
167


English

https://oaktrust.library.tamu.edu/bitstream/1969.1/162610/1/Bearing%20Failure%20on%20a%20Boiler%20Feed%20Water%20Pump.pdf

Bearing Failure On A Boiler Feed Water Pump

Abstract

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Texas A&M Repository

Texas A&M University

Bearing Failure On A Boiler Feed Water Pump

Abstract

Similar works

Full text

Available Versions

Texas A&amp;M Repository

Texas A&M University

Texas A&M Repository