In the case of E²G v. Ferrellgas, No. 2:22-cv-01234 (D. Utah Dec. 19, 2023), the testimony of a Vibration Analysis Expert Witness was pivotal in diagnosing and resolving issues related to high vibration levels in vertical pumps used in liquid natural gas (LNG) service.
Background of the Case
In October 2021, Ferrellgas installed vertical pumps with 25-stage impellers to handle LNG operations. Initially, the pumps produced higher pressure and flow than required, leading to operational adjustments that resulted in poor motor reliability. In January 2022, two stages were removed, reducing the impellers to 23 stages. A tuning plate was added between the motor base and discharge head to decrease the structural natural frequency of the motor-pump assembly. While vibration amplitudes decreased, in November 2023, one pump exhibited increased vibrations and noise, leading to inspections that revealed wear on the pump shaft and throat bushing.
Role of the Vibration Analysis Expert Witness
Ferrellgas engaged E²G, a firm specializing in vibration analysis, to identify the root cause of the increased vibrations. E²G’s expert conducted a comprehensive diagnostic evaluation, which included:
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Installation of Proximity Probes: Portable proximity probes were used to measure shaft vibration amplitudes, which were found to be as high as 6.15 mils peak-to-peak, exceeding acceptable limits per ISO 7919-3.
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Orbit Analysis: Orbit plots indicated non-synchronous vibration content, suggesting a rub-bounce condition between the shaft and throat bushing.
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Operating Deflection Shape (ODS) and Modal Testing: Accelerometer-based data and modal testing revealed significant deflection at the throat bushing area, with a structural natural frequency near the operating speed, contributing to high vibration levels.
Findings
The analysis identified excessive structural compliance in the discharge head and motor-adapter connection as the primary cause of high vibration levels and shaft-throat bushing rubs. The motor-to-discharge head stiffness was measured at 5,100 lbf/in, indicating a relatively flexible joint.
Recommendations
E²G recommended increasing the stiffness of the discharge head and motor-discharge head connection to reduce vibrations. This modification aimed to enhance the structural integrity of the pump assembly, minimize vibrations, and prevent further mechanical wear.
Legal Proceedings
Ferrellgas faced legal action due to the pump’s performance issues. The court considered expert testimony on vibration analysis to determine liability and appropriate remedies. The case underscored the importance of expert analysis in diagnosing technical issues and guiding corrective actions.
Conclusion
The involvement of a vibration analysis expert was crucial in identifying and addressing the causes of excessive vibrations in Ferrellgas’s vertical pumps. By applying specialized diagnostic techniques, the expert provided insights that led to effective solutions, highlighting the role of technical expertise in resolving complex engineering challenges within legal contexts.