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

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

RECOMMENDATIONS AND CONCLUSION JOH-KGN001-20071212-JvW-X1 OUTLINE RECOMMENDATIONS AND CONCLUSION RESULTS METHODOLOGY INTRODUCTION

INTRODUCTION Is electricity reliable in Kenya? JOH-KGN001-20071212-JvW-X1 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.

JOH-KGN001-20071212-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.

HOTWELL SYSTEM

BUTTERFLY VALVE OPERATION JOH-KGN001-20071212-JvW-X1 BUTTERFLY VALVE OPERATION The function of the MBFV is to control and regulate condensate flow from the condenser to the cooling tower.

MBFV COMPONENTS GEARBOX MOTOR BUTTERFLY VALVE ACTUATOR

Failure Mode And Effect Analysis (FMEA) METHODOLOGY JOH-KGN001-20071212-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.

Reliability Priority Number (RPN) METHODOLOGY JOH-KGN001-20071212-JvW-X1 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)

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

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

HIGH RISK COMPONENTS

TORN EPDM VALVE SEAT GOOD SEAT TORN SEAT JOH-KGN001-20071212-JvW-X1 TORN EPDM VALVE SEAT EPDM rubber – ethylene propylene diene monomer TORN SEAT GOOD SEAT

HIGH RISK COMPONENTS SHAFT WORM GEAR JOH-KGN001-20071212-JvW-X1 HIGH RISK COMPONENTS The price of these parts is small relatively to the price of the valve SHAFT WORM GEAR PINS

HIGH RISK COMPONENTS Circuit Board Electrical connections Bearings O-Rings

JOH-KGN001-20071212-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.

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

REDUCED RPN VALUES EPDM rubber – ethelene propylene diene monomer JOH-KGN001-20071212-JvW-X1 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

FINANCIAL EVALUATION Assumptions JOH-KGN001-20071212-JvW-X1 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.

59.5% Reduction in Loss of Revenue JOH-KGN001-20071212-JvW-X1 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

A similar failure occurred in April 2018. JOH-KGN001-20071212-JvW-X1 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

JOH-KGN001-20071212-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.

CONCLUSION The MBFVs high risk components were identified. JOH-KGN001-20071212-JvW-X1 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.

JOH-KGN001-20071212-JvW-X1 OLKARIA IV POWER PLANT