Pump Fire Root Cause Failure Analysis
Problem: A plant experienced a fire at one of their centrifugal pumps that pumps oil. The fire was safely put out, but the plant required a root cause failure analysis to determine why the fire occurred.
Solution: KHE applied its Integrated Systems Approach to this project employing process, mechanical, and metallurgical analyses. While the failed pump parts displayed significant wear damage to the impeller and impeller housing, KHE metallurgical analysis was able to trace the failure to a defective bearing. Analysis of a bearing ball revealed the presence of aluminum oxide inclusions in the material, which are not expected in bearing material. The analysis also found significant signs of sub-surface cracking, and rolling contact fatigue in the bearing balls as a result of these inclusions. KHE concluded that once the thrust bearing failed, due to the rolling contact fatigue, the ensuing heat of friction that resulted from the rubbing of the impeller face on the housing ignited the pumped medium and caused the fire.
Solution: KHE applied its Integrated Systems Approach to this project employing process, mechanical, and metallurgical analyses. While the failed pump parts displayed significant wear damage to the impeller and impeller housing, KHE metallurgical analysis was able to trace the failure to a defective bearing. Analysis of a bearing ball revealed the presence of aluminum oxide inclusions in the material, which are not expected in bearing material. The analysis also found significant signs of sub-surface cracking, and rolling contact fatigue in the bearing balls as a result of these inclusions. KHE concluded that once the thrust bearing failed, due to the rolling contact fatigue, the ensuing heat of friction that resulted from the rubbing of the impeller face on the housing ignited the pumped medium and caused the fire.
Fig. 1: Failed Pump Impeller with Significant Rubbing Damage
The metallurgical analysis also found indication that cavitation may have occurred in the pump. This corresponded well with the process and mechanical assessments, which had found that under certain operating conditions the pump was permitted to operate with high flow and low head conditions, which would result in cavitation. Pump cavitation results in excessive loading of various pump components, including bearings. Such conditions may have contributed to the premature failure of the defective bearings.
Result: KHE recommended an investigation of the source of the defective bearings and implementation of improved quality control measures for pump bearings at the facility. KHE also recommended a plant wide process control review of centrifugal pumps, and implementation of process control measures to prevent pump cavitation.
Specialists in Design, Failure Analysis and Troubleshooting of Static and Rotating Equipment
Services
- Failure Investigation
- Field Service
- Rotordynamics
- Rotating Equipment Analysis
- Vibration Analysis
- Computational Fluid Dynamics (CFD)
- Finite Element Analysis (FEA)
- Acoustic Analysis
- Stress Analysis
- Metallurgical and Metrology Lab
- Fit for Service Analysis
- Expert Witness