Hot Gas Path - Condition Based Maintenance (CBM): Condition Monitoring (Part 3/7)

What is Condition monitoring?

Condition monitoring can be described as ‘assessing the current state and estimating the future state of a system by means of measurements and calculations’. The results of condition monitoring can be used to take corrective actions, to plan the availability and maintenance, and to optimize the plant’s performance.

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Why apply Condition Monitoring?

The main reasons to apply condition monitoring are:

• Prevention of damage.
• Increasing availability.
• Increasing reliability.
• Increasing time between outages (TBO).
• Changing from periodic maintenance to condition dependent maintenance.
• Fuel savings, by optimizing the process continuously.
• Reduction of production loss.
• Better operator process knowledge through more information and insight.

The condition monitoring level uses data from the data fusion platform and compares these data with expected values or operational limits and generates alerts based on these limits.

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What are functions of Condition Monitoring?

The primary function of the condition monitor is to compare features against expected values or operational limits and output enumerated condition indicators (e.g. level low, level normal, level high, etc.). The condition monitor may also generate alerts based on defined operational limits and when appropriate data are available the condition monitor may generate assessments of operational context (current operational state or operational environment).

Component life monitoring

Through direct or indirect monitoring of component properties:

On-line monitoring of component life would allow some assessment of when the next shutdown might occur.

On-line indication of component degradation could alert operators to failures that could propagate through the unit. For example, on- line monitoring of the combustor status or blade coating integrity.

On-line risk assessment of extending the outage schedule would also be useful to determine whether it is possible to operate for extended periods.

On-line monitoring of exhaust gases for metal particles.

Off-line non-destructive evaluation (NDE) of component life would help to determine if component replacements are needed before the next scheduled shutdown.

• Eddy-current metallic coating life (Al depletion vs conductivity).
• TBC integrity (NDE methods).
• Component physical condition referenced to baseline.
• Component cyclic fatigue status.
• Component coating wear and integrity status.