Pump fires at plants pose a severe and multifaceted threat, demanding immediate attention and preventative measures.
The safety of workers is of utmost importance in such situations, and the combustion of materials involved in pump operations can release hazardous substances, making it all the more critical to act fast. If not addressed promptly and accurately, a pump fire has the potential to jeopardize the overall integrity of the facility.
Recently, a plant in the Gulf Coast region experienced a fire at one of its centrifugal oil pumps. Although the fire was safely put out, the plant required a root cause failure analysis to determine the cause of the fire.
The team at KnightHawk Engineering (KHE) knew how to tackle the project precisely. KHE applied its integrated systems approach, in which the interaction of the process, the controls and instrumentation and the mechanical equipment were analyzed. For this specific case, KHE employed process, mechanical and metallurgical analyses.
Fire analysis
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 should not be present 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 determined that the failure of the thrust bearing, caused by rolling contact fatigue, led to the generation of heat through friction as the impeller face rubbed against the housing. This heat ignited the pumped medium, triggering the fire.
The metallurgical analysis also revealed indications that cavitation may have occurred in the pump. This corresponded well with the process and mechanical assessments, which 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.
Pump fire: Root cause failure analysis
Failed pump impeller with significant rubbing damage
Key proposals
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.
Integrated system excellence
Over the years, KHE has conducted comprehensive failure analyses on a diverse range of both rotating and static equipment. This extensive portfolio encompasses high-pressure and high-temperature vessels, reactors, turbines, compressors, pumps and piping systems.
Specifically, KHE’s integrated systems approach has proven to be one of the most effective methodologies for solving complex problems in the industry. Whether it is pressure vessel design, heat exchanger design, rotating equipment problems, heat and mass transfer, failure analysis or troubleshooting, KHE, with its multidiscipline approach, considers the mechanical, process, materials, controls, instrumentation and electrical sides of the problem.
As a "one-stop" solution provider, KHE’s highest priority is to address its customers’ problems sufficiently and efficiently. Packed with a personnel team displaying a plethora of knowledge and expertise, KHE is ready to get to the bottom of any complications.
For more information, visit knighthawk.com.
