Root Cause Analysis of Instability in a High-Speed Turbomachinery using VIB360 Studio
Customer Profile
- Sector : Land based Oil Gas exploration field
- Asset : K8-401B, Re-Injection Compressor
- Compressor Type : 6 Stage Centrifugal Compressor (Dresser-Rand D6R6S)
- Rated Speed : 10,700 RPM
- Driver : 5002C Turbine via Lufkin NF1919C Gearbox
- Monitoring System : Portable Vib360 studio ( linear Vibration solution)
Context
A re-injection compressor at the customer site experienced repeated trips triggered by high vibration levels. The maintenance team required a deeper understanding of the rotor behaviour and the underlying cause of the instability. Using VIB360 Studio, the engineer analysed rotor dynamics, phase behaviour, and spectral patterns to identify the mechanism behind the trips and support corrective decisions. Following the successful diagnosis and confirmation of the findings, the customer voluntarily reached out to us to share how the system enabled him to perform a root cause analysis of this chronic issue and express his appreciation for the support and capability of the VIB360 platform.
Problem Statement
The compressor suffered repeated high-vibration trips, but the root cause of the instability was unclear. The maintenance team needed a reliable analytical method to interpret vibration behaviour, distinguish between possible causes such as unbalance, aerodynamic stall, or rotor rubbing, and determine the mechanical factors driving the instability. Vib360 Studio enabled detailed vibration and phase analysis to diagnose the rotor-bearing system behaviour and guide corrective actions.
Vib360 Measurement Setup
To investigate the repeated vibration trips of the re-injection compressor, the Vib360 system was used as the primary diagnostic platform to analyse the rotor–bearing dynamic behaviour during operation.
Signal Inputs from multiple accelerometers and existing Displacement probes were used to measure the shaft displacement and vibration amplitude.
Physics-Based Diagnostics
- Vibration spectrum showed dominant 1X rotational frequency, confirming the presence of rotor dynamic unbalance forces.
- Emergence of sub-synchronous components (0.27X and 0.7X) indicated aerodynamic instability such as compressor stall or internal recirculation.
- Phase analysis between DE and NDE bearings revealed large phase shifts (~120°), confirming poor rotor guidance and asymmetric bearing stiffness.
- Orbit behaviour and truncated waveform peaks indicated intermittent rotor-to-stator rubbing during instability events.
Action Taken
- Detailed vibration investigation performed using VIB360 Studio analysis tools.
- Rotor-bearing dynamics evaluated through spectral, phase, orbit, and waveform analysis.
- Mechanical inspection, verification of journal bearing clearances and damping system components were recommended.
- Corrective actions included replacement of balancing checks and verification of the spring-damping system configuration to restore rotor stability.
Outcome and Value
- Root cause of repeated compressor trips was clearly diagnosed rather than assumed
- Enabled targeted maintenance instead of trial-and-error troubleshooting
- Reduced risk of progressive rotor damage and unexpected shutdowns
- Strengthened engineer confidence in data-driven vibration diagnostics
- The Customer Representative voluntarily shared a positive feedback acknowledging the accuracy of the analysis and the value of VIB360 in solving the problem.
Technical Significance
- Demonstrates the capability of VIB360 Studio to perform advanced rotor dynamic diagnostics.
- Identified complex fault mechanisms including dynamic unbalance, aerodynamic stall, and rotor instability.
- Showcases how vibration analytics can support engineering decisions in high-speed turbomachinery.