1. Presented by: VICTOR OUMA
FAILURE MODES AND EFFECTS ANALYSIS OF HOTWELL SYSTEM MOTOR OPERATED BUTTERFLY VALVE
Presented by: VICTOR OUMA
2018 G2G INNOVATION SEMINAR, PRIDE INN SPA & RESORT
18TH JUNE - 22ND JUNE 2018

2. M.Sc. Nuclear Engineering (NPP) B.Sc. Mechanical Engineering
Graduate Engineer Member ERB and IEK
Maintenance Engineer at Olkaria IV GPP.
Involved with operations and maintenance of Olkaria IV GPP
Previously worked as a Mechanical Engineer (Building Services)
Participated in Olkaria I & IV Unit Major Maintenance Activities.
Click to add Photo

3. RECOMMENDATIONS AND CONCLUSION
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OUTLINE
RECOMMENDATIONS AND CONCLUSION
RESULTS
METHODOLOGY
INTRODUCTION

4. INTRODUCTION Is electricity reliable in Kenya?
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INTRODUCTION
Is electricity reliable in Kenya?
The cumulative time of power outage in South Korea was 58 minutes (2005).
FMEA is a tool used in Reliability Centered Maintenance (RCM) to identify and eliminate weaknesses in engineering designs.
It is used in Aeronautical, Nuclear and Weapons Engineering
( esp. US Army).
Depends on maintenance data.

5. JOH-KGN JvW-X1
PROBLEM STATEMENT
The Olkaria 280 MW Geothermal Power Plants have been experiencing breakdowns of the Motor operated Butterfly Valves (MBFVs).
The revenues from Olkaria IV & 1 AU are 13.4 M and 12.4 M respectively.
These failures have adversely impacted on Safety, Availability & Revenue.
This work will demonstrate how to predict, plan, eliminate or reduce the IMPACT of failure of the MBFV.

6. HOTWELL SYSTEM

7. BUTTERFLY VALVE OPERATION
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BUTTERFLY VALVE OPERATION
The function of the MBFV is to control and regulate condensate flow from the condenser to the cooling tower.

8. MBFV COMPONENTS
GEARBOX
MOTOR
BUTTERFLY VALVE
ACTUATOR

9. Failure Mode And Effect Analysis (FMEA)
METHODOLOGY
JOH-KGN JvW-X1
It identifies failure modes it effects
Failure Mode And Effect Analysis (FMEA)
A tool that combines technology and experience of people in identifying fore-seeable failure modes
The main goal is to identify a failure risk and eliminate risk within a design.

10. Reliability Priority Number (RPN)
METHODOLOGY
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A tool to quantify failure risk
Reliability Priority Number (RPN)
An analysis to identify which component failures which bears the highest risk to the operation of the power plant.
It is a product of numerical values to Severity (S), Occurrence (O) and Detection (D).
RPN = (S) x (O) x (D)

11. FMEA AND RPN ANALYSIS Valve Seat RPN Value 8 x 8 x 8 = 512
Component
Function
Failure Mode
Failure Effect
Root Cause
Seat
Ensure disc complete shut
Leakage
Incomplete closure, Plant cannot start up
Foreign material, silica deposit, Wear, poor material, poor seat design,
Tear, Permanent deformation, Swelling
Loss of flow control, Plant cannot start up
Wear, Excessive force/ pressure
Disc not fitting, Poor material selection
Valve Seat RPN Value
8 x 8 x 8 = 512

12. RISK MATRIX The risk matrix helps in prioritizing of component failure
The valve seat with an RPN of 512 is a Critical A component

13. HIGH RISK COMPONENTS

14. TORN EPDM VALVE SEAT GOOD SEAT TORN SEAT
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TORN EPDM VALVE SEAT
EPDM rubber – ethylene propylene diene monomer
TORN SEAT
GOOD SEAT

15. HIGH RISK COMPONENTS SHAFT WORM GEAR
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HIGH RISK COMPONENTS
The price of these parts is small relatively to the price of the valve
SHAFT
WORM GEAR
PINS

16. HIGH RISK COMPONENTS Circuit Board Electrical connections Bearings
O-Rings

17. JOH-KGN JvW-X1
TASK SELECTION
EPDM rubber – ethelene propylene diene monomer
Seat replacement program of 4 years during ovehauls
Failure of pins is fatigue break- We need to increase the strength of the pins but should not wear disc shaft
Current material of the driven gear is mild steel
Valve Seat (EPDM) - Annual inspection; Develop seat replacement capabilities on site; Have adequate seat spares.
Valve to have major overhauls after 3 years of service.
Disc Pins - Material testing, redesign with a tough material, locking wires and use high strength thread lock.
Worm Gear - Adequate spares, Leakage inspection and annual inspections.

18. TASKS STATUS UNDERTAKEN PENDING
Spares of critical spares have been procured e.g. worm gears.
Pins material tests and re-design
Maintenance plan developed
Capacity development for seat replacement
Quality issues of seat discussed with manufacturer
Locking wires & high strength thread lock to fasten the pins
Overhaul of 1 valves has been done

19. REDUCED RPN VALUES EPDM rubber – ethelene propylene diene monomer
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REDUCED RPN VALUES
EPDM rubber – ethelene propylene diene monomer
Seat replacement program of 4 years during ovehauls
Failure of pins is fatigue break- We need to increase the strength of the pins but should not wear disc shaft
Current material of the driven gear is mild steel

20. FINANCIAL EVALUATION Assumptions
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FINANCIAL EVALUATION
EPDM rubber – ethelene propylene diene monomer
Seat replacement program of 4 years during ovehauls
Failure of pins is fatigue break- We need to increase the strength of the pins but should not wear disc shaft
Current material of the driven gear is mild steel
Assumptions
Reduced total number of outages from 5 (in 2016), to 2 annually for both 280MW plants.
Failures have led to unit trips that took 2 days to repair.
Labour, spares and materials costs vary with the number of outage days.

21. 59.5% Reduction in Loss of Revenue
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FINANCIAL EVALUATION
EPDM rubber – ethelene propylene diene monomer
Seat replacement program of 4 years during ovehauls
Failure of pins is fatigue break- We need to increase the strength of the pins but should not wear disc shaft
Current material of the driven gear is mild steel
Cost Item
Cost (KShs.)
Loss of Revenue
65,000,000
Spares
710,000
labour
1,380,000
Materials
134,000
Total
67,224,000
Cost Item
Cost (KShs.)
Loss of Revenue
26,000,000
Spares
610,000
labour
552,280
Materials
80,000
Total
27,242,200
Financial Saving = KSH. 39,981,800.00
59.5% Reduction in Loss of Revenue

22. A similar failure occurred in April 2018.
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CASE STUDY
Find out if the machine had to run on half load on the 24th of April 2018
Saved more than 24 hours which is about 6.7 Million
Sept. 2017, Olkaria IV. MBFV breakdown caused a 32 hours plant outage. This was caused by worm gear failure.
A similar failure occurred in April 2018.
This outage took 8.48 hours to repair.
Prod. Cost of KSH 5000

23. JOH-KGN JvW-X1
RECOMMENDATION
EPDM rubber – ethelene propylene diene monomer
Seat replacement program of 4 years during overhauls
Failure of pins is fatigue break- We need to increase the strength of the pins but should not wear disc shaft
Current material of the driven gear is mild steel
Mention the there was no maintenance plan by the manufacturer
Spares of risk significant components should be readily available in stores.
Apply maintenance tasks in the plans.
Adopt RCM strategies and teams to look into the frequent systems and component failures.
Liaise with data management resources within the company.
An investment cost of KSH. 1.8 Million for pilot study for 280 MW.

24. CONCLUSION The MBFVs high risk components were identified.
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CONCLUSION
EPDM rubber – ethelene propylene diene monomer
Seat replacement program of 4 years during ovehauls
Failure of pins is fatigue break- We need to increase the strength of the pins but should not wear disc shaft
Current material of the driven gear is mild steel
The MBFVs high risk components were identified.
This strategy will increase availability.
An investment cost of KSH. 14,000,000 is saved. The cost would have been used to replace 2 valves after 5 years.
Saving of KSH. 39,981,800 annually.

25. JOH-KGN JvW-X1
OLKARIA IV POWER PLANT