The document summarizes a case study for maintenance planning and reliability centered failure analysis (RCFA) for a centrifugal fan in a dust removal system. Key points: 1) The fan experiences the highest monthly downtime (54.9 hours) which costs $250,000 in lost production monthly. 2) Vibration analysis revealed the fan blade is unbalanced and bearings are failing, which are the top two causes of downtime. 3) A preventive maintenance program is proposed including daily vibration monitoring, weekly balancing, and monthly bearing replacement to reduce downtime to 10.25 hours per month, saving $203,400 in production losses.

1. Real Case Study
MaintenancePlanning& RCFAfora centrifugalfan
ina de-dustingsystem
Eng.Mohammed Hamed Ahmed
Maintenance Planner
SID#700080583
1
Undersupervision: Prof.Dr.Attia Gomma
Industrial Engineering Professor & Consultant
American University in Cairo

2. 2
Maintenance Planning for Industrial Fan
1-System Overview.
Fan for de-dusting system in a Granulated Super Single Phosphate Plant.
Plant capacity: 500t/day.
Daily production value: 100,000$.
Feeding material: super fine powder.
De-Dusting Fan: Present 27% of the monthly breakdowns.
Working hrs/day: 22hrs/day.

3. 3
Equip code Equip
description
Downtime hrs
(average)
Downtime
frequesncy
Percentage
304K1 Centrifugal Fan 54.9 18 27%
304T1 Bucket Elevator 38.5 22 19%
304Z2 Granulator
Drum
35 22 17%
304WG1 Feed Belt
Conveyor
27 15 13.5
304N3 Recycle Belt
Conveyor
13.75 26 6.8%
304F1 Bag Filter 12.95 11 6.4%
304U1 Burner 6.5 7 3.2%
304N7 Belt Conveyor 3.75 3 1.8%
304N4 Belt Conveyor 3.5 3 1.7%
304T2 Bucket Elevator 2.25 2 1.2%
2-Problem Definition
(Monthly CM Downtime report for plant equipments)
Remark: the above table is only for equipments which has downtime more than 2 hrs.

4. 4
Chart Illustrate The Major Down Time Analysis By Equipment Break down

5. 5System Illustration Diagram
(1) Dryer Drum
(3) Fan
(4) Bag Filter
(2)
Cyclone
Dust settling
Suction

6. 6
Outlet
pipe
Cyclone
Bag Filter
Expansion
Joint
Fan
Cyclone

7. 7
Motor
Inspection
Window
V-Belts

8. 8
Shaft
Bearing 4
non-drive
end
Foundation
Bearing 3-
drive end
Pulleys
8 Qty of
V-belts

9. 9
Clean Fan
Blade!

10. 10
General components of centrifugal fan
Term Description
MDE Motor Drive End
MNDE Motor Non Drive End
FDE Fan Drive End
FNDE Fan Non Drive End

11. 11
4-System Description
Technical Data:
Fan Type= Centrifugal fan
Flow rate= 78,000m3/h
Motor Power= 200KW
Horse power= 268HP
Motor Speed= 1500RPM
Fan Speed= 1500RPM
Transmission type: V-belts

12. 12
Spare Parts Data:
FDE Bearing: 22222EK +H322
FNDE Bearing: 22222EK +H322
MDE Bearing: 6322
MNDE Bearing: 6322
Bearing Housing: SNH 522-619
Pulleys type: SPC335
V-belts type: SPC5300

13. 13
3-System Criticality

14. 14
Total monthly downtime caused by plant equipments=198hrs /
year (RTF Policy)
Total monthly CM downtime caused by fan K1=54.9hrs.
Total production loss caused by fan K1=54.9 x 22.7t/h
=1246 ton/ month x 200$
=Quarter Million Dollar Monthly Loss!

15. 15
Month Total Breakdown
Hours/Month
No of Failures
April 2009 64 20
May 2009 43.6 13
June 2009 47.5 15
July 2009 49.6 18
August 2009 54.7 17
Sept 2009 70 25
Average 54.9 18

16. 16
Downtime reason Hours Percentage No of Failures
V-belts damage 20.4 37.15% 6
High noise 12.25 22.3% 5
Motor damage 6.25 11.4% 1
High vibration 4.5 8.2% 1
Unblanace 3.75 6.% 1
Electric overload 2.75 5% 1
Bearing damage 2.5 4.5% 4
Crack in foundation 2.5 4.5% 1
Preventive
Maintenance
0 0 0
Total Downtime 54.9 100% 20

17. 17
Spare Parts Replacement
Frequency per
month
Monthly Cost
Bearing 4 300$x(4x2)=2400$
B.Housing 4 350$x(4x2)=2800$
B.Sleeves 4 40$x(4x2)=320$
V-belts 6 6x(8setx50$)=2400$
Total cost=7920$
Spare Parts Consumption Rate:
Current Maintenance Policy=Run To Failure

18. 18
General components of centrifugal fan
Term Description
MDE Motor Drive End
MNDE Motor Non Drive End
FDE Fan Drive End
FNDE Fan Non Drive End

19. 19
Fan Vibration Analysis
Standard acc to ISO 10816

20. 20
Machines less than 20HP.
Machines from 20-100HP without special foundations.
Machines with rigid foundations and over 100HP.
Machines with soft foundation and over 100HP.

21. 21

22. 22
POINT DESCRIPTION overall values LIMITS
1 H E-Motor non drive end horizontal 30.468 mm/s x x x
1 V E-Motor non drive end vertical 13.611 mm/s x x x
1 A E-Motor non drive end axial -
2 H E-Motor drive end horizontal 24.302 mm/s x x x
2 V E-Motor drive end vertical 23.217 mm/s x x x
2 A E-Motor drive end axial 22.827 mm/s x x x
3 H fan fixed bearing coupling side horizontal 35.610 mm/s x x x
3 V fan fixed bearing coupling side vertical 31.521 mm/s x x x
3 A fan fixed bearing coupling side axial -
4 H Fan free bearing fan side horizontal 29.609 mm/s x x x
4 V Fan free bearing fan side vertical 26.941 mm/s x x x
4 A Fan free bearing fan side axial 24.733 mm/s x x x
DANGEROUS x x x
ALARM x x
ACCEPTED x
Vibration Measurements

23. 23
Vibration Measurements:

24. 24

25. 25

26. 26
M/C type and
spindle
speed
Normal vibration level Damage
factor due
to
unbalance
(vib level
increase in
1st Band )
Damage
factor
due to
bearing
damage
(vib level
increase
in 2nd,
3rd, or 4th
Band)
1st
Band
(10hz-1khz)
2nd Band
(1khz-
3khz)
3rd Band
(3khz-
5khz)
4th
Band
(5khz-
10khz)
Overall
(10hz-
10khz)

27. 27

28. 28
Temp analysis
Camera Model: Flir i50
Emissivity: 0.96
Reflected Temp: 20C
Object distance: 1.0m
Bearing Temp: 108.4

29. 29
Camera Model: Flir i50
Emissivity: 0.96
Reflected Temp: 20C
Object distance: 1.0m
Bearing Temp:110.9

30. 30
Camera Model: Flir i50
Emissivity: 0.96
Reflected Temp: 20C
Object distance: 1.0m
Bearing Temp:108.4

31. 31

32. 32

33. 33
Target(smartobjectives):
•Minimize Fan K1 Breakdowns.
•Increase Availability & Reliability.
•Reduce Maintenance Cost.
•Reduce Mean Time Between Failures (MTBF).
•Improve PM & Reduce CM Downtimes.

34. 34
Problem Problem Cause Remedy
V-belts damage -Bad v-belts type
-Belt tensioning isn’t good.
-Bad pulleys
-Pulleys misalignment
Check belt tensioning &
pulleys alignment.
High noise -Unbalance issue
-Bearing failure
-Bearing housing failure
-Crack in foundation
Check for vibration & temp.
Motor damage -High vibration
-Electric overload
Check for vibration & electric
overload adjustable.
High vibration -Unbalance issue
-Crack in foundation
Check for vibration
Electric overload -Unbalance
-Blockage in fan suction or
discharge lines.
Check for vibration
Check for cleaning
Bearing damage -Unbalance
-Greasing problem
-Shaft misalignment
Check for vibration
Crack in foundation -High vibration level Check for vibration
Fan Troubleshooting:
Vibration is the most critical measurement for all industrial fans.

35. 35
Making a combinationbetweenthepreventive & predictive maintenance
programs to enhance the fanavailability & reliability.

36. 36
Main Items Job plan Frequency
(1) FAN Visual inspection Daily
Bearing greasing Daily
Vibration analysis Daily
Temp analysis Daily
Replace FDE & FNDE bearing Monthly
Replace bearing housing 6 Monthly
Pulleys laser alignment
check/perform
Weekly
V-belts change Monthly
Shaft laser alignment
check/perform
6 Monthly
Balance the blade When ever needed acc to
vibration monitoring
(2) Motor Vibration analysis Daily
Replace MDE & MNDE
bearing
Annually
Temp analysis Daily
PM & PDM program for centrifugal
fans:

37. 37
DailyMaintenance
•Visual Inspection (grease level, oil level, belt condition, bolts
tightening, expansion joints, foundation bolts, noise…etc).
•Vibration Monitoring (use simple vibration pin for measuring
vibration amplitude at the bearing points).
Vibra Pen Specs:
•Measurements velocity range: 7-
65mm/s, 0.04-3.6 in/s.
•Frequency range: 10-1000 HZ.
•Frequency band 3 (500-10000 HZ).

38. 38
•Temp Analysis (use infrared thermometer for measuring
bearing temperature).
Infrared Thermometer features:
•50:1 distance to spot size ratio
•Temp range: -60-1000º C, (-76-1832ºF).
•Accuracy: +-1º C
•Update freq=1.4Hz
•Wave length response=8-14µm

39. 39
Weekly Maintenance
Performing pulleys laser alignment using a specific instrument

40. 40

41. 41
MonthlyMaintenance
Certain spare parts used to avoid any breakdown caused by
fake parts.
•Replace bearing with reliable bearing type.
•Replace v-belts with reliable v-belts type.

42. 42
6 Monthly Maintenance
•Replace bearing housing with certain type.

43. 43
•Perform shaft laser alignment if necessary using a specific
professional tool.
Shaft Hog Laser Alignment system

44. 44
Annual Maintenance
•Replace Motor Bearing

45. 45
Balancing performance
We performed this on site when ever needed according to the
vibration measurements.
By performing the balancing on site you reduce the balancing
time by 90%! Even if you have a spare blade!

46. 46

47. 47
Cost of resources required to implement the above
maintenance plan.
•One vibration pen= 1500$.
•One infrared thermometer= 500$.
•One electrical technician to perform the daily analysis (labor from
the company).
•Two Mechanical technicians to perform the daily inspection &
other routine maintenance (labor from the company).
•Bonus for labors

48. 48
We used an outsourcing partner for balancing,
alignment, and other heavy services that required
expensive instruments:
•Balancing on site cost= 250$ (perform weekly).
•Laser pulley alignment cost= 50$ (perform weekly).
•Laser shaft alignment=300$ (perform 6 monthly).

49. 49
We foundafterintensivedailyvibrationmeasurementthatthisfanwill
requirebalancingweeklytoavoidbearingfailureandothercomponents
damage.

50. 50
Break-down type Hours Percentage Freq
Bearing damage 2 19.5% 1
High noise 2 19.5% 1
High vibration 0.75 7.3% 1
Total CM (unplanned) 4.75 46.3%
Total PM (Planned) 5.5 53.7%
1- Improved of Equip Availability & Production
(Monthly Downtimes report for fan K1)
Total downtime=10.25 hrs /month (Reduced from 54.9 to 10.25).
Loss in production=10.25hr/month * 22.7ton/hr=233ton/month
=233ton*200$=46,600$/monthly
Improvement in production (compared to previous status)
=250,000$-46,600$=203,400$ monthly.
Improvements & results (after 2 months from
applying the maintenance program).

51. 51
Spare Part Type Replacement
Frequency per
month
Was Now
Monthly Cost of Replacement
Bearing 4 1 300$x2=600$
B.Housing 4 1 350$x2=700$
B.Sleeves 4 1 40$x2=80$
V-belts 6 0 0
Total Spare parts cost=1380$
Total cost reduction=7920-1380=6540$
2-Spare parts cost reduction:

52. 52
3-Preventive Maintenance Improvenment Program for
Fan K1 (New Modified Program).
PM Levels PM Description Duration No of workers
Daily -Visual Inspection
-Vibration Test
-Temperature Test
-Greasing & Oiling
-Blade Cleaning
20 min
20 min
20 min
10 min
30min
1 worker
Weekly Perform Pulley Laser
Alignment & Belt
Tensioning
Perform Balancing on
Site
1 hr 1 worker
Monthly Replace Fan Bearing &
Bearing Housing
4hrs 2 workers
6 Monthly Check for Shaft
Alignment
30 min 1 worker
Annually Replace Motor Bearings 3 hrs 1 workers

53. 53

54. 54
Level I Level II Level III Level IV Level V Level VI
Fan operate with high
vibration level
Bearing fails Bearing seized Parts damage Aging Design life limit
Improper
lubricant
quantity
Housing wear High friction Bearing
damage
Bearing
seized
Parts damage
Unbalance fan
blade
High vibration Shaft wear Shaft
misalignm
ent
Fan damage
Looseness in
foundation bolts
High vibration Cracks in
foundation
Breaks Design life limit
Shaft wear Shaft
misalignment
Bearing
damage
Sleeve
looseness
Design life limit

55. 55
Failure mode Failure cause Source of
failure
Root cause Failure
chracteristics
Failure Effect
Fan operate with
high vibration
level
Bearing fails Bearing seized Poor Maint Wear in&out Unexpected
plant shutdown
Housing wear Deterioration Poor Maint Wear in&out Unexpected
plant shutdown
Unbalance fan
blade
Shaft wear Poor Maint Wear in&out Unexpected
plant shutdown
Looseness in
foundation
Poor Maint Wear in&out Unexpected
plant shutdown
Shaft wear Deterioration Poor Maint Wear in&out Unexpected
plant shutdown

56. 56
Centrifugal Fan
Dust
Temp 110º C
System control
Environment
Flowrate
78,000m3/h
Functional Block Diagram for the Fan
Temp 90-100ºC

57. 57
Recommendations for this fan acc to PDM
1-Due to high scale rate accumulation on the fan blade,
it’s very recommended to follow up the vibration
analysis on daily basis to avoid unbalance issue
High scale accumulation
require intensive daily
cleaning!

58. 58
2-Never perform balancing on a scaled blade

59. 59
Vibration
Limit
Equip
Condition
Root Cause Consequence Task
1-3 Good ----------------- ----------------- ------------------
3-6 Call for service High scale
accumulation
on the blade
Unbalance
issue
Perform
sandblasting &
balancing if
needed
6-10 Call for repair Fan left
without the
necessary
service
Looseness in
the foundation
and the
bearing
housing
Perform
balancing &
retighten all
components
10 and over Breakdown Fan left
without the
necessary
service
Damage to
mechanical
parts
Costly repair
3-Perform necessary maintenance acc to vibration measurements

60. 60
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