When Structure Becomes the Problem: Vib360 Reveals Hidden Instability in a Steam Turbine
- Customer: Energy (Biomass Power Generation)
- Asset: 7.5 MW Steam Turbine and gearbox assembly (GTA)
- Location: Monthyon, France
Initial Condition & Challenge
- No clear fault detected under standard operating conditions
- At higher loads, the machine exhibited increasing instability
- The issue was difficult to diagnose due to its load-dependent nature
Traditional monitoring methods did not clearly explain the root cause, making repair planning complex and uncertain.
Limitations of Convential Monitoring
All turbines at the site were also equipped with the Conventional Monitoring System..
- The system detected increased vibration levels only when thresholds were exceeded
- However, it did not provide insight into the source or mechanism of the instability
The load-dependent behavior remained unidentified and unexplained
As a result, the problem was visible in terms of vibration levels, but no actionable diagnosis could be made
Detection through Vib360
With Vib360 deployment, detailed dynamic analysis revealed:
- Significant structural deformation at higher loads
- Variation in angular behavior and vibration response with load changes
- Non-linear system response indicating support structure weakness
This made it clear that the issue was not originating from rotating components alone, but from the supporting structure itself.
Diagnosis & Insight
Vib360 enabled the team to understand that:
➡️ The structural support of the turbine was insufficiently rigid
As load increased:
- Structural elements deformed
- Alignment conditions changed dynamically
- Additional forces were introduced into the rotating system
- Resulting in amplified vibration and instability
This created a load-dependent mechanical behavior, which is often difficult to capture with conventional techniques.
Why this was Critical
- The intermittent, load-driven nature of the problem made it difficult to capture using conventional monitoring approaches
- Repairs targeting only bearings or alignment would have missed the real issue
- Structural deformation meant that standard fixes would not be effective
Outcome & Impact
- Vib360 provided clear visibility into how the machine behaved under different loads
- Enabled identification of a non-obvious structural root cause
- Allowed the team to approach the issue with correct engineering focus
If the issue had not been diagnosed, the consequences could have been severe.
At higher loads, the weak gearbox structural support led to increased deformation, which in turn affected the alignment of rotating components. This created conditions where the blade wheel could come into contact with stationary parts (rubbing)—a phenomenon that was later confirmed during maintenance.
Such contact would have:
- Accelerated mechanical wear
- Increased vibration and thermal stress
- Potentially led to catastrophic failure of the turbine
Without early identification, the issue could have progressed unnoticed, resulting in unplanned shutdown, significant damage, and costly downtime.