LCC Quick Notes, Turbine Balancing
Since most turbine supervisory vibration monitors do not accurately detect true rotor deflection (The LCC ALERT System is the exception), temporary instrumentation is necessary to determine the need for balancing. Temporary sensors and analyzers should always be scheduled following repair work on turbine rotors which affects the rotor mass balance like blade and shroud repairs or replacements. Likewise, the following preparatory tasks are recommended:
◘ Maintain balance hole location maps for each turbine balance plane. Include installed mass and polar phase location with respect to a rotating protractor reference. Knowing what is in the turbine prior to a new weight installation can save hours of down time.
◘ Verify that all bearing metal temperature sensors are properly functioning... these are needed to project bearing loads.
◘ Leave lagging and insulation off of balance plane access locations until balancing is completed.
◘ Never trust an X-Y Proximity Probe system to represent accurate rotor deflections... many systems have happily reported "2-mil" levels as rotors were wrecked.
◘ Never permit a balance weight move based upon changing or instable data.
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