RCFA Case Study: Infant Mortality: Lean Solvent Centrifugal Pump Motor
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Qadeer Ahmed Sr. Reliability Engineer, Integrity & Reliability Engineering
Qatargas Operating Company Limited, Qatar
The 1st Middle East Turbomachinery Symposium (METS)February 13 - 16, 2011
Sheraton Resort and Convention Center - Doha, Qatar
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Agenda:
• Introduction:
• Qatargas Operating Company Limited
• Refresher: Bathtub Curve & Failure Regions (i.e. Infant Mortality)
• Root Cause & Failure Analysis
• Brief Introduction – Incident and Action Plan
• Simplified System Diagram
• Basic Data – Pump & Motor
• Event Diagram (Timeline)
• Pictures of Failed Parts
• PROACT Logic Tree & Vibration Data
• Root Cause(s)
• Recommendations & Lesson Learned
• Q&A / Thanks
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Introduction
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• Qatargas is pioneer in Qatar’s LNG production and will be the largest producer of LNG in the world by 2010 with total production of 77 MTPA.
• Qatargas existing LNG capacity is approx 25.6 MTPA of LNG
• Qatargas is going through phenomenal expansion and capacity will be
42 MTPA of LNG by end of 2010
• Qatargas Expansion Projects – 4 new Mega Trains (7.8 MTPA) : TR4&5 in production – Largest LNG Trains
– Laffan Refinery (150K BPD): Naphta, Kerosene, Gasoil
– Common Sulfur Project (12K TPD) – Granulated Sulfur
– Q-Max & Q- Flex LNG Ships (Q-Flex:210,000 m3 and Q-Max:266,000 m3)
• High Availability & Reliability is a vital to meet global demand– Asset Management is key to achieve desired Reliability & Availability
Introduction:
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A Glimpse - Qatargas Offshore:
LNG TRAIN 5
QATARGAS NFBCOMPLEX
LNG TRAIN 4
PU
WH4 - 64 m
(12 Slots)
QatargasRas Laffan Industrial City
PL4
34”
(91 km)
Power/Comm
5-6 Power/Comm5-4
QATARGAS NFB COMPLEX
WH6 - 56 m
(15 Slots)
WH5 - 46 m
(15 Slots)
PL5-6
16”
(800 m)
PL5-4
16”
(300 m)
Power/Comm
Main
FOC
to
Shore
PL6
38”
(81 km)
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A Glimpse - Qatargas Onshore:
LNG Tanks
CSP
Liquids Loading
Berths
QG2 TR4 & 5
QG3TR6 &
QG4TR7
Laffan Refinery
QG1
Liquid Storage
LNG Loading Berths
~150,000 BPD
12,000 TPD
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Basics: Refresher!!
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What is Bathtub Curve?
• Bathtub Curve– It is a Reliability Engineering tool which describe the particular form of
Hazard Rate. Lifetime of a population of product in graphical representation. The bathtub curve mainly consist of three regions:
– Infant Mortality/Early Failure:
• It is a decreasing failure rate region in the curve mainly constitutes of early failures.
– Random Failures Region (Useful Life):
• It is a constant failure rate region in the curve mainly constitutes of random failures
– Wear Out / Aging :
• It is a increasing failure rate region in the curve mainly constitutes of wear out / aged failures
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Bathtub Curve:
Source: http://en.wikipedia.org
Most Critical Region
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RCFA
(Root Cause Failure Analysis)
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Incident Description:
• Description:
• During the early stage of plant service, Two out of two motors failed within a
short duration and caused disruption in normal operations and other
consequential damages (pump, production etc..)
• Action Plan:
• RCFA investigation was requested using Meridium PROACT
• RCFA team was established (SMEs, Vendor, EPC invited)
• RCFA Charter & Critical Success Factors were developed
• All the events were collected in Meridium Event Manager
• All the evidences and required data collected
• All pictures, failure data, Trends and failed parts were analyzed
• PROACT Logic Tree was developed with Failure Modes and Hypotheses
• Root Cause Identified & Issued Recommendations
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Simplified System Diagram:
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Pump & Motor Basic Data:
Driver: Motor
• Type: Induction Motor
• Voltage: 6.6 KV
• Rated Output: 185 KW
• Rated Torque: 593 NM
• Speed: 3000 RPM
• Bearings
– Radial: Ball
• Lubrication: Grease
Driven: Pump
• Type: Centrifugal
• No. of Stages: 2
• Rated Capacity: 257 M3/HR
• Liquid: Lean Solvent
• Bearings
– Radial: Sleeve
– Thrust: Ball
• Lubrication: Oil Ring
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Event Diagram (Timeline):
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Motor B Tripped
16/02
Motor A Started
Unit was running
at 87% load
23/02
Vibration Alarm
Appeared &
Attended
23/02
23/02
Motor A tripped on
Thermal O/L Protection
Low Flow Alarm &
Unit Tripped on
Level Protection
23/02
Noticed smoke in
the area (motor),
EMS notified
23/02
23/02
Called Electrical
Mtce to check
motor
Motor was checked, found
shaft jammed – Winding
Resistance /Insulation
Resistance Satisfactory
Motors Inspected :
Found Bearings &
Shaft Damaged
23/0223/02
Incident
Incident
1
2 3
4
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Pictures - Failed Bearings:
Motor Drive End
Motor Non Drive End
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Pictures - Burnt Rotor Shaft:
Motor Burnt Shaft
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Pictures - Burnt Stator / Rotor:
Cage - Drive End
Stator - Drive End
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Consequential Damage:
• Internal Coating Peeled Off
• Lube Oil Contamination
Pump BearingPeeled Off Coating
• Bearing Damage (Replaced)
• Excessive Clearance
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PROACT Logic Tree:
Failure Modes
Incident
Hypotheses
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Verifications - Vibration Trends
Motor & Pump
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Vibration Trend – Overall:
Overall Vibration Trends
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Spectrum – Pump:
Pump Drive End
Pump Non Drive End
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Spectrum – Motor Drive End:
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Leading & Contributing Cause(s):
Leading Cause:
Lack of lubrication is the leading root cause of this failure. No grease was
found during inspection and bearing showed the clear signs of overheating.
Vibration data supports and confirms the failure initiating point was bearing
(BPFO -Ball Pass Frequency Outer Race).
Contributors:
PMs to lubricate the bearings were not active in CMMS.
Grease was not checked/replaced during commissioning (built in 2006).
Greasing procedure was not available for such motors
Vendor Recommendation were not followed about greasing.
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Recommendations & Lessons Learned:
Recommendations:
1. Activate the all PM plans in CMMS. Ensure to set the initial PM startup date
manually. Revisit the equipment strategies to include vendor recommendations.
2. Create area based lubrication work orders and release for maintenance execution.
3. Develop greasing procedure for Motors (based on type of bearing).
4. Inspect the pump and accessories prior to installation of new motor.
Lessons Learned:
1. The Project Maintenance & Engineering was informed immediately to take
appropriate measures to address similar potential issues.
2. The new project practices were issued. Check sheets were developed to ensure
proper lubrication before the mechanical run test to avoid such failures. (No reported
bearing failure)
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Q & A ….
Thanks!!!
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