7 สัญญาณเตือน Varnish ก่อนเกิด Turbine Trip

Technical Explanation

1. Slower servo valve response - The commanded and actual positions begin to diverge, or the valve takes longer to respond.
2. Rapid increase in filter differential pressure - Filter life becomes shorter without unusually high particle contamination, or sticky deposits are found on the filter media.
3. Rising bearing temperature - This is especially significant when load, supply oil temperature, and cooling conditions have not changed materially.
4. Sawtooth temperature pattern - Temperature rises gradually, then falls and rises again in a cycle. This pattern may be associated with deposits accumulating on and detaching from bearing surfaces.
5. Change in rotor position - Deposits around a bearing can affect oil-film geometry and rotor position.
6. Reduced cooler efficiency - Oil outlet temperature increases even though cooling-water conditions have changed very little.
7. Routine oil analysis still appears normal - Viscosity, TAN, or demulsibility may not yet reflect the severity of varnish. Specific tests and trends must therefore be evaluated together with machine condition.

Impact on Machinery

• Evaluating warning signs separately may miss the opportunity to act before a trip
• Control-system response may deteriorate without an identified cause
• Heat and wear may accumulate until operating limits are exceeded
• Greater risk of unplanned shutdown and production loss

Points to Consider

• Trend MPC, bearing temperature, filter differential pressure, valve response, and vibration
• Compare results with machine and new-oil baselines
• Establish triggers for in-depth investigation when trends begin to change
• Give more weight to sustained changes than to a single sample result

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