Case Studies Cetntrifugal Pumps

1. Reliability Case Studies
• Reza Emami, P.Eng, PMP
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2. Reza Emami
P. Eng, PMP
Currently, Engineering Specialist – Oil & Gas Industry, North America
12 years with Flowserve in various aftermarket roles: Applications
Engineer, Project Engineer, Service & Repair Engineer, Senior Technical
Services Engineer and Engineering Manager
3 years with Bartar Pumps company, Involved in re-engineering and
applications engineering.
2 years with Tarh Negasht company, Design engineer involved in
Computational Fluid Dynamics (CFD) for 3D simulation of flow in
Automotive torque convertors
MSc from Tehran University (Mechanical Engineering)
Presenter
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3. Presentation Content
• Failures (they happen…)
• Maintenance Practice Strategies
• Case Studies
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• RCA for Reliability Based Maintenance

4. Failures (they happen …)
Key Parameters:
Maintenance
Design
Installation
Manufacturing
Upset Condition
…..
Failures can affect:
Safety
Production
Additional Damages
Additional Spare Parts Cost
Unnecessary Overtime
……
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5. Maintenance Practice Strategies
Graph Source: http://www.maintenanceonline.co.uk/article.asp?id=10286
Reliability based
maintenance
RCA (Root cause
analysis) &
appropriate upgrade
solutions to eliminate
the issue
OEE (Overall Equipment Effectiveness) Improvement
OEE Availability x Performance x Quality
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6. RCA for Reliability Based Maintenance
RCA (Root cause analysis) & appropriate upgrade solutions for defect elimination
5 Why Concept
https://www.qualitydigest.com/inside/health-care-column/dig-5-whys.html
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7. Case Studies
• Case 1 - High Vibration issue – Shipping pump
• Case 2 - Material Upgrade for Erosive Service
• Case 3 - Bearing Upgrade (CH design)
• Case 4 - Multi Stage pump in Amine Service
• Case 5 - Vertical Can Pump –Hydrocarbon Condensate
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8. Case 1 - Shipping Pump Vibration
BB3 pump – 10 stages
- Butane / Propane Shipping
Problem:
- High vibration at vane passing
frequency (5X)
- Frequent failures due to
inconsistent abnormal high
vibration.
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9. Shipping propane/butane pumps:
- Feed from GL1K ( “cryogenic” LNG)
- Feed from RA1K (refinery GPL )
Two pumps installed
- Pump was sent to factory for repair & tests then shipped back to site & restarted
showing high thrust & radial bearing vibrations at 5X (250 hz) when pumping
butane ~1 hour (colder product) from successful start-up
Case 1 - Shipping Pump Vibration
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10. Pump B. tests in Factory (Water Ambient )
Vibration level at 5X (250hz) was very
low in the full operation range
(including minimum flow and minimum
suction pressure).
Case 1 - Shipping Pump Vibration
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11. Test on site
Case 1 - Shipping Pump Vibration
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12. Test on site
Case 1 - Shipping Pump Vibration
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13. Influence of process temperature on Vibration
Possible Causes?
Case 1 - Shipping Pump Vibration
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14. 5 Vanes
Impellers
Long Cross-Over
All other impellers are 3 Vanes
Case 1 - Shipping Pump Vibration
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15. Hz (Acoustic Frequency) =
C (Speed of sound) / WL
(wavelength)
C depends of Fluid property, Passage
dimensions / material
Acoustic Resonance?
Acoustic resonance data are calculated
basis cross over length and speed of sound
in various products:
Acoustic Frequency
- Water 20° 331 Hz
- Butane 20° 221 Hz
- Butane 10° 232 Hz
- Butane 4° 240 Hz
5 vanes x 50 Hz running = 250
Case 1 - Shipping Pump Vibration
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16. Conclusions:
- In water (on test platform), the 5X component did not exist.
- In butane
• At start-up, pumping hot product with a critical acoustic frequency below 5X,
no amplification occurs
• As soon as the product becomes colder, the critical acoustic frequency
increases and reaches the 5X frequency causing the measured high pump
vibration by amplification
It was proposed to change to 7 vanes impellers
It was also recommended to change the source of product to RA1K (LPG from
refinery at higher temperature) if possible
Case 1 - Shipping Pump Vibration
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17. Re-test with butane at 25°C
Source = RA1K
Half day after start-up
Butane temperature = 25 ̊ C
Vibrations are around 1 mm/s !!!!
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Case 1 - Shipping Pump Vibration

18. Site Test Results
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Case 1 - Shipping Pump Vibration

19. Case 2 - Erosive Service
Single stage OH pump
- FCC bottom
Problem:
- Existing casing needs replacement every month due
to severe erosion
Possible Causes?
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20. EXISTING NEW
Flow (gpm) 790 980
Differential Head (ft) 200 232
Suction pressure
(psig)
27 (29 max) 27 (29 max)
NPSH available (ft) 15 15
Liquid FCC Main Fractionator Bottoms
Oper Temp (°F) 675 (690 max) 675 (690 max)
Viscosity <0.5 cSt <0.5 cSt
Originally Rated Condition
(3x50%)
New Condition (2x100%)
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Case 2 - Erosive Service

21. Operating range reviewed and noted
pumps are running toward left of the
curve due to increased demand
Half Flow
Non modified impeller
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Case 2 - Erosive Service
Generally wear rate is proportional to
the increase of the particle velocity
cubed

22. Hydraulic Re-rate (Diffuser
Design) proposed along with
material upgrade
Drop-in replacement upgraded
with:
- The casing will not be subject
to high velocities However was
coated with HVOF line of sight
- Future repairs will be limited to
replacement of the wear kit
Upgraded Hydraulics
Upgraded Bearing Frame
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Case 2 - Erosive Service

23. Case 3 - Bearing Upgrade
Coker Charge Pump
Problem:
- Ball thrust bearing
failure
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Root Cause:
- Transient upset
condition could not
be avoided

24. 24
Case 3 - Bearing Upgrade

25. Self contained CH bearing assembly (Thrust)
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Case 3 - Bearing Upgrade

26. C bearing assembly (Radial)
- Not required for this case
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Case 3 - Bearing Upgrade

27. Self contained (C & CH) bearing operation
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Case 3 - Bearing Upgrade

28. Upgraded pump
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Case 3 - Bearing Upgrade

29. Another example
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Case 3 - Bearing Upgrade

30. Case 4 - Pump in Amine Service
BB3 Pump – 5 stages
- Amine Service
Problem:
- Unable to reach
the duty point
- Lower Head /
Higher Power
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31. Materials:
- 316 SS Impellers
- 410 SS Shaft
- CS casing (Meeting API Specs…)
Inspection notes:
- Casing parting flange eroded
- Casing bores eroded
- Casing volute lips heavily eroded
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Case 4 - Pump in Amine Service

32. Upgrades:
- Recommended for replacement
casing in SS material. Not
implemented.
- Casing weld with SS material
- Re-boring & facing
- 316 SS volute lip welds
- Complete performance test and field
test (Successful)
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Case 4 - Pump in Amine Service

33. Notes for Services with dissolved gases:
Gas scrubbing, by chemical
absorption process.
- MEA, DEA,TEA, DGA, DIPA, MDEA
….
- Benfield, Potassium, Carbonate, …
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Case 4 - Pump in Amine Service

34. Notes for Services with dissolved gases:
- NPSH margin (Could be a factor in loss of performance)
NPSHA/NPSHR ratio 1.3 – 2.0
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Case 4 - Pump in Amine Service

35. Notes for Services with dissolved gases:
- Range of operations
Off Range operation
Recirculation
Gas Release
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Case 4 - Pump in Amine Service

36. Notes for Services with dissolved gases:
- Materials
CA6NM Impellers in good condition
C.S. Diffusers severely pitted
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Case 4 - Pump in Amine Service
Recommended:
- API class A-7 or A-8
- API class C-6 conforming to NACE requirements

37. Case 5 - Vertical Can Pump
VS6 Pump– 10 stage
- Hydrocarbon Condensate
- Vapor Pressure at PT =61 bar = 896 Psi
Problem:
- Frequent seal & bearing failure with
excessive vibration & bearing wear
- Failure every 6 month
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38. Observations (Venting)
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Case 5 - Vertical Can Pump

39. Observations (Duty)
Re rate needed
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Case 5 - Vertical Can Pump

40. Upgrade (Re-bowling)
Replaced with smaller
hydraulics
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Case 5 - Vertical Can Pump

41. Last test Nov. 2011
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Case 5 - Vertical Can Pump

42. Questions ?
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